Sciencemadness Discussion Board

aromatic sidechainchlorinations - Toluene - Benzylchloride, Benzalchloride, Benzotrichloride and followup reactions yielding...

Organikum - 26-3-2004 at 12:31

Long title, short post.

Wellknown are the usual methods to chlorinate the sidechain of toluene by Cl2 and light, by Cl2 and PCl3 and by bleaching powder (hypochlorite, Loomis patent).
Wellknown are also the methods for producing benzaldehyde and benzoic acid from benylchloride, benzalchloride and benzotrichloride.
Wellknown are also the problems regarding ringchlorination as these ringchlorinated compounds are almost not to remove from endproducts in completeness - this being a problem in special in the case of benzaldehyde.

Now I pick up the case of benzaldehyde and present a way to produce this compound from toluene via the sidechainchlorinated compounds benzyl and benzalchloride whereby ringchlorination is avoided and up to no benzoic acid is formed as byproduct.

Reference: US2817632

This patent claims that a small amount of hexamine added to the reaction avoids ringchlorination and deactivates eventually present catalysts which would promote this ring-chlorination, Fe and other heavy metal ions etc. The amount of hexamine to add comes from 0,1% w/w to 10% w/w.

Nice. Use toluene from the paintthinnercan as is.....

Better even: If chlorinating toluene you unavoidable end up with a mixture of mono-di-and-tri-chlorinated compounds. Temperature control helps but the best way is control of temperature and a large excess of toluene. Keep it on the lower side you will end up with a mixture of mono and di-chlorinated toluene - benzylchloride and benzalchloride. Now you want to get benzaldehyde - what to do?

Ullmann 2002:
Boiling a mixture of benzyl and benzalchloride in an aqueous solution of hexamine yields - benzaldehyde.

And here the ring closes - add hexamine to avoid ringchlorination and add more hexamine in water to get benzaldehyde which is to be called free from ringchlorinated impurities, good enough to be used in biosynthesises or similar.

And the Polverone special:

Benzalchloride and acetic acid plus tin(II) or tin(IV) chloride yields benzaldehyde and chloroacetic acid.

[Edited on 8-11-2004 by vulture]


Polverone - 26-3-2004 at 13:14

What a marvelous aid to the DIY production of benzaldehyde, benzyl alcohol, and chloroacetic acid! Now I just need to see who I can find to sell me a cylinder of Cl2 :D

Nick F - 26-3-2004 at 13:20

I think we should all stop for a moment and just consider how wonderful hexamine is.

Thanks Organikum :).

Organikum - 26-3-2004 at 14:10

One big advantage of the described way to benzaldehyde is in my eyes that the synthesis avoids the distillation of the chlorinated compounds - benzylchloride at least is an evil lachrymator worse than chloroacetone for example.

The suggested way to do this would be:
- gently chlorinate the toluene at low temperatures - I actually would try to stay below the boiling point of the reaction mixture, using a 500W halogen as lightsource and a thin walled flask. The chlorine has to be as free from oxygen as possible. Also the tolune should be gently boiled before use to remove dissolved O2. Minimal amounts of red phosphorus are told to to drive the reaction forward - even some matchbox striking pads will work.
(dont forget the hexamine - yep)
- after a certain amount of chlorine was taken up - what can be determined by weighing the flask, bubble air through the reaction mixture to remove/destroy the excess Cl2 present, then distill out most of the toluene (a short column is favorable but by no way a must have here) and add a good excess of hexamine in water solution and boil the shit outa the soup under reflux.
- After some time shut down the reflux and collect what comes over with the steam - this will be benzaldehyde and toluene.
(benzylchloride can be steamdistilled too I was told, but after my best of knowledge this wont happen as long as toluene and benzaldehyde are present, at least those will come first.

It should be easy to determine when the reaction hexamine-benzyl/benzalchloride is completed: As soon the vapors stop to make you cry and sick it´s done. ;)

Organikum - 12-5-2004 at 01:54

The good Ullmanns was a little short in explanaition of the Sommelet procedure.

Just boiling the benzyl/benzalchloride mixture with aqueous hexamine is not right.

Here is it right:


EXAMPLE 1,050.1 g of chlorinated p-xylene, consisting of 47.61% of p-xylyl chloride, 43.76% of p-xylene, 3.6% of nuclear-chlorinated p-xylene and 5.03% of polychlorinated p-xylenes, the mixture containing exactly 500 g (3.55 moles) of p-xylyl chloride, are stirred with 546.7 g (3.9 moles) of urotropin for 15 minutes, under nitrogen, in a 4 liter three-necked flask equipped with a reflux condenser and stirrer. 1,000 g of water are then added and the mixture is refluxed for 3 hours. It is then allowed to cool, brought to a pH of 3-4 at room temperature with 170 ml of concentrated HCl, and then refluxed for a further 15 minutes. Thereafter, the mixture is allowed to cool again and the aqueous phase is separated off. The organic phase is distilled after addition of 0.01 g of hydroquinone.

The other patent describing the addition of hexamine to prevent ringchlorination is US2817632

[Edited on 12-5-2004 by Organikum]

gently chlorinate?

cavgdad - 13-5-2004 at 08:57

which method of chlorination are you suggesting? or do you prefer?

Chlorination of toluene

Prince_Lucifer - 14-5-2004 at 18:41

Organikum is clearly and obviously stating that the Photo-Catalyzed Chlorination of toluene be utilised, hence the 500W halogen light! :D
Right, now that is settled:
Organikum my friend, how are you?
I am well, i am also intrigued by the information you have just posted.
Swim has recently decided to shun the Ca(OCl)2 chlorination due to safety concerns and by-product formation that the reaction is unfortunately notorious for!
Swim would like to pursue the method you have outlined, however he needs clarity.
Now, swim is clear on the chlorination aspect of things, however he is unsure of the amount of hexamine to use.
In the example provided, i assume the amount of hexamine used is in relation to the amount of by-products in the flask.
Since swim does not have the means to analyze the contents of a flask, he considers it difficult to measure the amount of by-products as a percentage.
Say for example, 100g of toluene was chlorinated thouroughly.
Now in theory, after the necessary distillations have been completed, then the final yield of Benzyl Chloride should be around 100g. Now this example is just to demonstrate how much Benzyl Chloride should be available.
Seeing as swim have never performed this reaction, he havs no idea as to how much Benzal Chloride or other by-products are in the solution. Anyways:
What amount of hexamine would you suggest to add to a solution of this calibre?
You say benzaldehyde and toluene will come over with the steam after reflux is stopped.
After initial distillation to seperate these two compounds, would you suggest redistillation, perhaps under vaccuum to purify the benzaldehyde, or would it be suitable for a bio-synth as is?
Org, can you suggest a 'safer' way to estimate when the initial reaction with hexamine is completed?
Swim may wear a tactical gas mask so unfortunately he wont be able to sample the delightful aromas of Benzal/Benzyl Chloride!
:D:P Thankyou.

[Edited on 15-5-2004 by Prince_Lucifer]

Answers and a goodie....

Organikum - 19-5-2004 at 07:34

Actually it has shown that it makes no sense to go for a mixture of benzyl and benzalchloride, but it is better to chlorinate the toluene until mostly benzalchloride is formed with benzotrichloride as impurity.
This point of chlorination can be determined either by weighing the receiving flask or easier by the boiling point. When the thermometer shows the refluxing solution has reachewd 185°C it is done. The mixture should contain now about 80% benzalchloride.
Basic hydrolysis with sodium carbonate will transform the benzalchloride into benzaldehyde and the benzzotrichloride into benzoic acid which can easily separated as its salt.

The addition of 0.1% to 0,3% hexamine to the toluene inhibiting ringchlorination is a winner. The Sommelet - BzCl to b-dehyde by hexamine - works well but is uneconomical because of the amounts hexamine needed.

And the goodie:

Toluene can be chlorinated by TCCA, trichloroisocyanuric acid (swimming pool supply) and a radical initiator under acidic conditions. The radical initiator named in the article was benzoylperoxide, red phosphorus or UV might work too. Without radical initiator mainly ringsubstituted compounds are formed.

This reminds on a experiment on the chlorination of toluene by TCCA and light I read about but never got it working although I tried it several times..

But lets fuse things together now:
- What about either using benzoylperoxide in the usual chlorination, instead of red phosphorus in addition to the light?
- What about adding a dash of hexamine to the toluene and doing the chlorination with TCCA and benzoylperoxide to avoid the ringchlorination (bright light wont hurt for sure) ?

I will give it a try.

ADDOON: benzoylperoxide (or dibenzoylperoxide whats interchangeable here) is found as activator for polyester resin in every automobile supply shop. You will have to buy it together with the polyester resin probably, this contains at least 40% styrene - not bad too, isnt it?

Mendeleev - 12-6-2004 at 18:18

I am sort of new to synthesizing chloroaromatics, but the benzyl chloride synthesis interests me. I was looking at the article on rhodium and the two methods that interest me are the photo-catalyzed chlorination of toluene, and the calcium hypochlorite method. I had some question about the photo-chlorination procedure, namely how important is the calcium chloride tunnel described in the article, and what is the deal with the sodium hydroxide wash bottles? I was thinking, could you just boil the toluene while a gas generator pumps Cl2 under a 2 million candle power bulb? Also it says to distill under reduced pressure, will normal pressure not work or is it too slow? As far as the calcium hypochlorite method goes, their description was very vague. It says mix equal volumes of toluene and hypochlorite and heat to 105 C, but it gives no details for extraction, and I'm not sure about measuring solids by volume. Would you just distill it for extraction? What is the reaction anyway: 2C7H8 + 1Ca(ClO)2 ---> 2C7H7Cl + 1Ca(OH)2?

[Edited on 13-6-2004 by Mendeleev]

[Edited on 13-6-2004 by Mendeleev]

Organikum - 13-6-2004 at 04:32

Download Vogels 3rd from our ftp or from Rhodiums page and look for the sidechainchlorination of toluene there. You should find it under "aromatic chlorinations" I think.
There is everything better explained as any of us probably can do.


For the hypochlorite method go to the HIVE
and do a search for "loomis" and one for "benzylchloride toluene" and you will find what you want to know.

Mendeleev - 13-6-2004 at 09:22

What is the ftp address, I couldn't find a link or the actaul address anywhere on the forum despite searching for half an hour. The info on the hive was good though, thanks.

Mendeleev - 15-6-2004 at 06:59

Just to clarify my earlier post, I found out that equal masses of toluene and calcium hypochlorite are used. This means the reaction doesn't go to completion, but the main product is benzyl chloride, by about 30% and the rest is unreacted toluene. The reaction has to be heated but can't be heated above 105 degrees C or it will explode, so a boiling water bath is perfect to keep the reaction about 95-100 degrees C. Once the reaction finishes the toluene bp (108-112) is distilled off and the benzyl chloride (bp 179) is distilled after all the toluene is distilled off. A vacuum is not necessary for distillation, but helps. As no one has told me the address of the ftp, I have one question left, were the wash bottles described in rhodium's page just for keeping the mixture dry or what?

[Edited on 15-6-2004 by Mendeleev]

Organikum - 15-6-2004 at 08:24

You might consider to look in "Forum Matters" for information about the forum-ftp.

If you dont provide better information or a direct link you wont get any answers. I am not going to invest my time to search through Rhodiums page for the tidbit of information you hinted at.

Please dont regard me as inpolite but try to see it from my point of view. Altough I CAN read other peoples thoughts I RARELY do so as it hurts me always badly - its so damned messy and often conflicts with my own mental diseases, ya know? ;)


Mendeleev - 15-6-2004 at 17:18

I did provide a direct link, see my first post in this thread :).

Organikum - 16-6-2004 at 02:58

Huhh, I overlooked it.

The washbottles refer to the photocatalyzed chlorination of toluene by Cl2 and are necessary for cases of suckback.
And: Yes they ARE necessary.

Look in the Vogels 3rd. thats a much better source for information than any webpages. This book can be dl from Rhodiums page or from the forums ftp as OCR-pdf whats preferable. Thanks Polverone and Mephisto.

[Edited on 16-6-2004 by Organikum]

Mendeleev - 18-6-2004 at 20:55

I downloaded Vogel's Third Edition in pdf, it is my holy book now. I also realized the passage in Rhodium on photochlorination is directly from Vogel's Third Edition. The photochlorination method interests me in the long run, but for starters I would like to try the calcium hypochlorite method.

In the loomis thread on the hive, somebody began to doubt the safety of the reaction because it required anhydrous or nearly anhydrous products. However after a bit of searching I found that calcium hypochlorite is non-hygroscopic and decomposes readily to hypochlorous acid in water. So you should have no problem with water absorption and even if some gets in it will not stay for long, but will decompose into hypochlorous acid. The toluene I get at the store is labeled as 100% so that takes care of that.

Also the pool calcium hypochlorite says it has 65% available chlorine. Hoping this does not mean it is 65% I did a few calculations and found that calcium hypochlorite is % chlorine by mass, but that the decomposition product, calcium hypochlorite, which is more relevant to pools, is 67% chlorine. So hopefully 65% available chlorine means its >97% calcium hypochlorite, right? Oh and I'm hoping that this site that says the 65% available chlorine calcium hypochlorite is only 67% is just a typo.

[Edited on 19-6-2004 by Mendeleev]

[Edited on 19-6-2004 by Mendeleev]

Organikum - 19-6-2004 at 06:45

Pool-Shock is pure calcium hypochlorite. Important is that it contains no water. The "available chlorine" is not on the point here, just forget it.

I would suggest to use the chlorination though. The hypochlorite method is not so good for making benzalchloride as it is for making benzylchloride. This is based on the amounts of hypochlorite needed. If the toluene doesnt cover the hypochlorite completely you will get an explosion.
I tried this lately and I will not do it again although I had no explosion. At least no big one.

If you want to use the hypochlorite pathway you should only chlorinate to benzylchloride and use the Sommelet with hexamine to convert this to benzaldehyde as described in my first post.

If you want benzalchloride which is more easy converted to benzaldehyde by just running it into a slurry of chalk in water whilst stirring strongly you should use the chlorination as described in Vogels 3rd.

Mendeleev - 19-6-2004 at 09:31

My goal is neither benzal chloride nor benzaldehyde, at the moment, right now I am trying to get benzyl chloride so I guess I am fine for now. Is this the pool shock stuff you mentioned Organikum?

The pool shock says its 68% calcium hypochlorite and the super pool shock says just calcium hypochlorite, I gues you were talking about the super stuff?

Also is this brand reasonably pure?

[Edited on 19-6-2004 by Mendeleev]

Organikum - 20-6-2004 at 07:00

I dont know this, I dont live in the US and never tried these brands.
The Super-Pool-Shock sounds best to me though.

Try to get the MSDS data sheet.

Mendeleev - 20-6-2004 at 15:25

This is a nightmare, I went through 15 US pool suppliers and 3 UK suppliers, and the highest they have 65-73% calcium hypochlorite. The rest they say is soluble salts. Will the reaction work with 73% material, provided its anhydrous? After all as the reaction goes along, the calcium hypochlorite is converted into the chloride, hydroxide, and etc.

Edit: Even the goddamn science supplier sells it as 65% and they have a very good selection.

[Edited on 20-6-2004 by Mendeleev]

[Edited on 21-6-2004 by Mendeleev]

Organikum - 21-6-2004 at 03:20

I guess it will work, but guessing says not knowing for sure......

a possible safety consideration

Polverone - 21-6-2004 at 10:37

I wish I could check the Hive for that patent, but I never do that while at work (even on lunch). Wasn't the patent from, say, before 1940? I believe high-test-hypochlorite was rare or unkown as a commercial product at the time of the patent's writing. The "bleaching powder" referred to probably had a considerably lower chlorine content than modern pool shock treatments. For example, a JACS article from 1933, "Action of Bleaching Powder on Ketones," begins the experimental section with "Three hundred grams of commercial bleaching powder (24% available chlorine) was made into a paste with 750 cc of water at 15 degrees C." Also, from Ullman's, referring to more modern products: "The following qualities of solid hypochlorites are available (content of available chlorine, wt %, in parentheses): tropical bleach (34 – 35), bleaching powder (35 – 37), and high-percentage hypochlorite (70)."

I'm a bit alarmed at the idea of heating toluene with the most potent calcium hypochlorite available, given the exothermic nature of the reaction.

Mendeleev - 21-6-2004 at 12:38

Here's the patent, straight from the hive.

Be it known that I, CHAUNCEY C. Loomis, a citizen of the United States, residing at Syracuse, in the county of Onondaga and State of New York, have invented a new and Improved Process of Chlorinating Toluene, of which the following is a specification.
My invention relates to the chlorination of toluene with consequent production of benzyl chlorid and its related products, benzal chlorid and benzo trichlorid. This has heretofore been accomplished by passing chlorin gas through boiling toluene and also by admitting to a mixture of toluene and bleaching powder an acid gas to decompose the bleach with liberation of nascent chlorin.
Both these processes are subject to objections, the former because of the difficulties incident to handling the chlorin and the production of by-products of little value which are not readily separable from the product desired and the latter by reason of the inconvenience of generating and applying the acid gas and the gumming up caused by its reaction with the bleaching powder in the toluene. I have discovered, however, and my invention broadly stated consists in the application of the fact, that by heating to a high temperature an anhydrous mixture of toluene and bleaching powder, with thorough commingling, and without the use of any acid, the chlorination of the toluene is effected without any of the disadvantages incident to the processes above referred to. In the absence of any added water the chlorin from the bleaching powder seems to go directly to produce benzyl chlorid in the side chain without attacking the nucleus, even though the process is carried on in the presence of iron, as in an iron vessel.
   In carrying my invention into effect, dry bleaching powder (calcium hypochlorite, or other equivalent hypochlorite,) and toluene are mixed in proportions varying according to the extent of chlorination desired. For example, 200 kilograms of toluene are heated, as in a steam jacketed iron mixing kettle to a high temperature, say 90°. Dry bleaching powder is then slowly added to this, the temperature being gradually raised until it approximates the boiling point of toluene, which, of course, cannot be exceeded. When 200 kilograms of bleaching powder have been added the mixture is held at the high temperature attained, (i. e., to secure the best results, from 100° C. to 105° C.) for about one hour, or, until the reaction is effected, with continuous thorough mixing. The escape of toluene vapor during the operation may be prevented by means of a reflux condenser fitted to the mixing vessel.
   The resulting mixture is then cooled down and allowed to settle and as much oil as possible is siphoned off from the top. The oil left adhering to the lime residue is then removed by steam distillation and added to that siphoned off. In this way 200 to 210 kilos of oil are obtained, having a specific gravity of .910 to .960 at 20° C. and containing from 30 to 35 per cent. of benzyl chlorid and from 70 to 65 per cent. of toluene. These can then be separated by fractional distillation. A higher percentage of chlorinated product can be obtained by using a greater proportion of the bleaching powder. In this case, however, some benzal chlorid and benzo trichlorid will be formed. Or, if desired, sufficient bleaching powder may be added to convert all the toluene directly to benzal chlorid and benzo-trichlorid and the resulting mixture of lime and the chlorids can be converted into benzaldehyde and benzoic acid by boiling with water.
Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:
1. The process of chlorinating toluene which consists in heating together an anhydrous mixture of toluene and bleaching powder without other admixture.
2. The process of chlorinating toluene which consists in heating together toluene and dry bleaching powder in the absence of acid.
3. The process of chlorinating toluene which consists in heating together toluene and dry bleaching powder in the absence of acid or other agent for decomposing the bleaching powder.
 In testimony whereof I have affixed my signature, this 15 day of October, 1917.

You're right it does say bleaching powder! So I might even have to use a lower mass of pool hypochlorite? If you could find out for sure what percent was available in those days, that would be awesome.

[Edited on 21-6-2004 by Mendeleev]

Mendeleev - 22-6-2004 at 12:11

According to this link:

bleaching powder is 35-37% hypochlorite and that the commercial 65-70% product is the dihydrate thus unfit for chlorination of toluene. However it says that it is also available as 75-80%, would this be anhydrous? If so the 73% super pool shock on the "in the swim" link I posted earlier would be good for the reaction.

Polverone - 22-6-2004 at 14:10

Ullmann says:

"High-Percentage Hypochlorite. Solid hypochlorites with 70 % and higher available chlorine contents can be prepared by chlorinating slurries of such calcium compounds as calcium hydroxide, or bleaching powder. Initially, hemibasic calcium hypochlorite, Ca(OCl)2· 1/2 Ca(OH)2, is formed. When further chlorinated, this gives neutral calcium hypochlorite dihydrate, Ca(OCl)2 · 2 H2O, which is then dried to the desired high-percentage hypochlorite."

It sounds like the water should already be gone from the hypochlorite, and that cheminfo page is confusing an intermediate with a final product. But if you want to be sure, put 200 mg or so of calcium hypochlorite pool shock in the bottom of a test tube, heat strongly, and see if you get water droplets in the cool portion of the tube. A dihydrate should be easy to distinguish from anhydrous or almost-anhydrous material.

Edit: from perusing old JACS articles, I would say that bleaching powder circa 1917 probably contained between 25 and 35 percent available chlorine. I don't know if it is better to simply use less high-strength hypochlorite, or to add an inert solid to dilute it.

[Edited on 6-22-2004 by Polverone]

Mendeleev - 2-7-2004 at 06:21

Could benzyl chloride be effectively dried by mixing with calcium chloride and distilling? I am going to try this synthesis sometime next week and will post my results.

[Edited on 2-7-2004 by Mendeleev]

Mendeleev - 14-7-2004 at 14:30

I tried the benzyl chloride synthesis today. I heated 500 mL toluene on a 95-98 degreee boiling water bath, then 210 grams of calcium hypochlorite, a little less than half the mass of toluene. The loomis patent instructs one to use equal masses of bleaching powder, but it is only 35 % and super pool shock from one of the links I posted earlier is 73%. My magnetic stirrer failed at this point because all the hypochlorite sunk to the bottom as predicted, so I manually stirred it for several minutes. I then proceeded to relux the beaker by covering it with saran wrap and filling it the indentation with ice, a la brainfever. The reaction proceeded for 4 hours and 40 minutes. I opened the apparatus halfway through to stir the contents for several minutes.

Everything seems fine except for one thing, when I opened it, I did not notice any of the tear gas effects everyone has described. This means one of 4 things.

1. The temperature was too low and chlorobenzene was formed instead.

2. The high boiling point of benzyl chloride means there wasn't to much of it in the air.

3. The claim that leaving an open container of benzyl chloride for five minutes outside of a fume hood will cause one to cry for half an hour is false.

4. I am somehow resistant to tear gas. Unlikely.

So, any input/tips? What is the minimum temperature which will prevent significant chlorination of the ring and the formation of chlorobenzene?

Marvin - 14-7-2004 at 16:13

Chemistry does not work on faith. Buy some glassware, do some fractional distilling, find out what youve made if anything.

You are using hypochlorite instead of bleaching powder, maybe this will cause the reaction to fail, after all it wont produce chlorine when acidified, you need chloride as well to do that. Maybe what you have is hydrated, did the patent say anhydrous? Maybe that will cause the reaction to fail.

Altering a reaction and then doing it very badly could do anything, might do nothing, its not a question for chemists, try ringing a psychic hotline.

Mendeleev - 14-7-2004 at 18:35

Jeez man, I was just asking for some advice, you didn't have to be so mean :(. Just kidding. I didn't alter the reaction that much. I put it on a water bath instead of 105 C because I would rather have a failed reaction than a lost limb. As far as bleaching powder vs. purer hypochlorite goes, the reaction calls for calcium hypochlorite, not bleaching powder, its just that in the early 1900's, when the patent was written bleaching powder was the main form of calcium hypochlorite available, the other 65% are inert calcium salts that have no effect on the reaction. Is a beaker not glassware? Furthermore, my method is based on previous attempts by other people. There is a good thread in the hive called benzyl chloride from hypochlorite salts in which a glass coffe pot, pool chlorinator tablets, and paint can toluene are used on a water bath for around four hours without drying any of the ingredients. The reaction time is lengthened to compensate for the lower temeprature. This is not that different from the way I did it. The importan tquestion still stands, what is the minimum temperature which will prevent significant ring chlorination? I searched google and could find nothing useful.

[Edited on 15-7-2004 by Mendeleev]

Organikum - 15-7-2004 at 05:59

1. Calcium hypochlorite so dry works better than bleaching powder. This is even mentioned in the patent.

2. In UV catalyzed chlorinations using Cl2 85°C is named as the lower limit for temperature. There is no defined borderline though. At 40°C you have lots of ringchlorination.

You should have realized when the reaction kicked in, if you are not sure on this, it didnt happen. The Loomis procedure gets VERY exothermic and this happens VERY sudden.
You had no reaction taking place. Not enough temperature to kickstart it.
I would say after what you told at least.


Mendeleev - 17-7-2004 at 14:49

I tried this on a smaller scale, one fourth of what I attempted and this time kept it on the hot plate directly, so temperature was 103 to 104. However it was a pain in the ass, the toluene fumes made me dizzy, and constantly manipulating the hot plate knob was a pain in the ass. I did get some benzyl chloride this time, my eyes were red and itchy and kept sneezing. So, I want to try photo chlorination, I already have a mercury vapor lamp and a chlorine generator connected to a U-tube filled with calcium chloride. Basically, I was wondering before I try this, will the U-tube sufficiently dry the chlorine, and what precautions would I have to go through with the touene. It is klean strip brand in a metal paint can labeled "100% pure toluene". It still probably has to many metal contaminants and water, no? I am currently drying it with calcium chloride, and distilling it through a calcium chloride tube. Will this give me toluene of sufficient purity? Furthermore I would probably be able to use it straight from the paint-can using the hexamine method? :) Thanks everyone for your help, you especially Organikum.

Edit: Will CaCl2 screw up the photochlorination reaction?

[Edited on 18-7-2004 by Mendeleev]

Organikum - 17-7-2004 at 19:15

To dry toluene you can boil away 1/10 of the volume and done. Any whe water will be removed azeotropically then. Thats a common labaoratory method. :D

For all this you need a powerful condensor and an exhaust line ending over lye. Look in the Vogel´s 3rd (best version available is to find on our ftp, its the OCR-pdf made by mephisto - recommended) and you may also take a look in the old "Gattermann" from 1909 available here from the sciencemadness library ( then go to "library";).
Read at least the Vogel´s 3rd on this, its written in fairly a understandable language and a "must read" here.

After my experience it is possible to substitute/improvise parts of the setup recommended in the book, but it is not possible to omit anyone. Say, you can improvise washbottles/security-anti-suckback bottles/condensor/exhaust-gas-scrubber, but dont leave one away.

The reaction spits huge amounts of HCl (and some Cl2 escapes). The lye-scrubber is ESSENTIAL. This CANNOT be done open pot, no way.

Mendeleev - 15-9-2004 at 17:07

Don't use platic bottles out of the recycling as sulfuric acid wash bottles for chlorine, for chlorinating toluene. I had a bad experience with that today. It made me realize I like fresh air. I moving back to the easier if more dangerous hypochlorite method, meanwhile I ordered some benzoyl peroxide for the TTT method, which is neithre explosive nor toxic, but it is not clear yet whether it will work without carbon tetrachloride. I believe it will, but the important thing is to have benzoyl peroxide as the promoter.

[Edited on 16-9-2004 by Mendeleev]

Mendeleev - 26-10-2004 at 19:41

Queer things happened with this reaction as of late. I performed the calcium hypochlorite toluene reaction using 275 g of toluene to 275 g of pool Ca(OCl)2. The toluene was redistilled from the paint can and boiled to anhydrousness. The glassware was clean and oven dried. The toluene was heated to 95 C before the hypochlorite was added and the reaction was refluxed for 5-6 h at 100-110 C. Protection from moisture was afforded by sodium hydroxide.

The problem is that when I got a whiff of the contents of the flask, no tear gas effects, but there was an organic odor, very different from toluene or calcium hypochlorite, sort of smelled like industrial cleaning agents. The odor is very persistent too. After the hypochlorite was wrapped in 15 sets of platic bags, it's presence in the trashcan for 1 day caused the trash can to smell for weeks afterward.

I am guessing I have either benzal chloride or benzotrichloride from using too much hypochlorite or benzaldehyde because I didn't dry the hypochlorite, the water may have caused the benzyl chloride to decompose into benzaldehyde.

Has anyone ever smelled benzal chloride or benzaldehyde, who could verify what I have? I have not fractioned the mix yet because my vacuum pump has a leak which I am currently fixing. Thanks.

[Edited on 27-10-2004 by Mendeleev]

Esplosivo - 27-10-2004 at 01:54

Benzaldehyde (phenylmethanal) smells of almonds, a smell similar to, but stronger than, phenylmethanol. But I have heard many friends describing the smell differently, therefore the smell is subjective.

Mendeleev - 7-11-2004 at 14:32

I believe that what I have as a result of my last attempt to make benzyl chloride is actually benzaldehyde because after almost a month now, the solution has turned yellow, and I have read benzaldehyde is clear to yellow.

Organikum - 7-11-2004 at 17:21

Benzaldehyde has an distinctive smell. The color says nuthing here.
How does it smell?

Mendeleev - 10-11-2004 at 19:31

I can't really describe it, but it does smell, sort of like some cleaning agent or something, but no chlorine like odor and no burning/tears. I guess its not too bad, since I've also been working on various syntheses for benzaldehyde.

Mephisto - 11-11-2004 at 04:52

Can really everybody smell Benzaldehyde? It's the same smell like HCN and a certain part of people can't smell HCN. Maybe they can't smell Benzaldehyde too, because of the missing receptor, which is generally responsible for this certain smell?

Sure a far theory. Anyway, those, who mistrust their own olfactoric abilities could at least count on chemistry. The presence of Benzaldeyhde (as it's the only aldehyde in the described product) can be checked with the Schiff reagent (fuchsine and a sulfit-source).

Organikum - 11-11-2004 at 06:43

The problem with HCN can be overcome by smoking a cigarette, its the traditional method to avoid HCN poisoning in the lab. Cigarette + HCN gives a certain bad taste, and then its time to leave.

Everybody else may ask himself if he knows the smell of bitter-almonds.

But for sure benzaldehyde has no "sharp" smell. Tinkering with unidentified reaction products is a waste of time IMHO, its always easier to discard the stuff and to run a new reaction. After the third or forth time one starts to get product, after some more runs good yields. At least thats how it works for me :)

Mendeleev - 19-11-2004 at 23:08

If chlorinating toluene to benzal chloride, with the purpose of hydrolyzing to benzaldehyde, would you be able to avoid using sulfuric acid wash bottles, since you are going to hydrolyze your product, what difference would it make if it is hydrolyzed as it is formed by wet Cl2?

[Edited on 20-11-2004 by Mendeleev]

Organikum - 20-11-2004 at 05:05

The hydrolysis being the second, independent step, this is no argument that wet chlorine can be used.
All literature speaks of dry chlorine to be used. H2SO4 is probably best, but I would say that two not to small drying stages with CaCl2 will suffice.
It is important to use not too strong a base for the hydrolysis, calcium carbonate for example.
Or use the Sommelet as describe above.
Or use acidid hydrolysis with HCl and ZnCl, but I would have to look the details up.

It is important though to have a security bottle before the reaction flask as the reaction can get quite violent and is prone to drive toluene backwards, not filling the reaction flask to more than 1/2 is recommended.

Cold , Wet Sidechain chlorination

ballzofsteel - 7-12-2004 at 06:09

This is the simplest route to benzyl chloride Ive found so-far.


4,250. Levinstein, Ltd., Levinstein, H., and Bader, W. July 27, 1918. Chlorhydrocarbons. - Benzyl chloride, benzal chloride, and similar side-chain chlor-substituted aromatic hydrocarbons are prepared by treating toluene or its homologues at a low temperature with aqueous hypochlorous acid (hypochlorite and acid). The process can also be applied to the treatment of the chlor-derivatives of these hvdro- carbons containing one or two chlorine atoms in the nucleus or one chlorine atom in the side chain, e.g. monochlortoluenes, 2 : 4-dichlorto- luene, or benzyl chloride. Examples are given of the preparation of benzyl chloride from toluene and benzal chloride from benzyl chloride; m- xylene gives m-tolyl chloride and m-tolal chloride

Obviously Benzyl/benzal;chloride mixtures can be obtained by increasing the amount of hypochlorite.

Calcium hypochlorite works.

HCL works fine.

Strong mixing seems to help somewhat.

Slow addition of acid.

Can I link this patent directly?sorry.

Hope this helps.

alcohol chlorination

antibond - 7-12-2004 at 11:35

Don't believe this has been discussed.

A very simple way of making benzyl chloride :
1 mol benzyl alcohol
1-3 moles aqueous HCl
add stirbar, and stir for sufficient time (follow on TLC if you want), add heat to speed up the reaction (not necessary though). Fractionally distill the benzyl choride. Yields are high.
Raffike from the Hive used to swear by this method and has been confirmed.

Ref: Synthesis of benzylchloride

solo - 7-12-2004 at 13:33

I have always thought that the Lucas test , i.e. clorination of alcohols the tertiary>secondary> primary were chlorianted in that order. While it's true that tertiary alcohols can be chlorinated with just HCl , the secondary , benzyl alcohols included, would need the ZnCl in order to get chlorinated, but ZnCl is cheap and that 's easy to get ......solo

Organikum - 8-12-2004 at 06:27

Thanks Ballz!

I guess this will be my new method of choice so it works with TCCA.

preliminary results - better than sliced bread

Organikum - 21-12-2004 at 10:21

The method of the patent as posted by Ballzofsteel was tried with TCCA and seems not to work when done as described. :(
A yellow compound is produced which is probably something highly ringchlorinated.

.....when one omitts the addition of HCl completely it works.

Say: Grinded TCCA tablets + water + excess toluene (in the cold, time, shaking) = Benzylchloride

As told, these are PRELIMINARY, unchecked results, but I thought this so goil that I couldnt resist to post it ASAP.

I am not going to fuck around with the lachrymatoric BzCl, I will run a Sommelet and post the final amount of Benzaldehyde yielded, as this is what I want.

The explanaition is easy:
toluene + HOCl (cold) = BzCl
TCCA + H2O = HOCl + isocyanuric acid
(this is an equilibrium! No Cl2, no HCl in the cold!)


ballzofsteel - 21-12-2004 at 15:12

Great work:D

Use Ice instead of water,in an insulated container
This seemed to help yeilds a little,I reason due to the localised formation of HOCL,and thus a lesser chance of polychlorination.
This also avoids the need for external cooling to some degree.
That is if you are aiming for plain benzyl chloride,otherwise it dont matter.

Tip,form an Ice stirrer by freezing some water around a paint stirrer.
still,this may be of no advantage whatsoever when using tcca.

ORG.Thanks for trying this.
Roughly what ratios did you use?
Did you aim for benzyl chloride,or a mix of benyl/benzal/benzo?

[Edited on 21-12-2004 by ballzofsteel]

Organikum - 22-12-2004 at 06:49

You can use a metal-stirrer when adding 0,1% to 1% w/w hexamine to the toluene. This binds the metal ions and prevents them from catalyzing ring-chlorination.

I thought about using ice and did in involuntarily by letting the broth ouside over nicht without stirring.
I would say the ice just provides a higher concentration of HOCl - using less water might do the same trick.

I didnt try it up to now with bleaching powder.



ballzofsteel - 23-12-2004 at 05:13

Tried today with Tcca.

Added a couple of kilo ice to 1l toluene
and roughly 500gm TCCA.
Stirred only occasionally.
Maybe overshot with to much chlorine,because I ended up with the deep yellow product you described when hcl was added.

For some reason I didnt have this trouble when roughly the same amount of Hypochlorite was used(chlorine content wise)
In both cases I was aiming to favour the formation of benzalchloride.
After christmas I will try again with tcca using ratios closer to those proposed in the patent.

Merry Christmas you mad scientists.

Organikum - 23-12-2004 at 06:02


favour the formation of benzalchloride
Your ratios are wrong then. This favors benzylchloride I might say.

TCCA = 232g/mol
500g TCCA is roughly 2 mol, is 3 mol Cl2 is theoretically enough to chlorinate 6 mol toluene to benzylchloride or 3 mol toluene to benzalchloride.
1000 ml toluene is about 10 mol.

I didnt do the workup by now, but somethings sketchy it seems.

We will see.

ballzofsteel - 23-12-2004 at 14:00

Yes you are right.

So sorry,Wasnt thinking right.

I made a mistake when writting that post,thinking that 1 pool tab=100g when they are in fact 200g,and I used 5 of the suckers = 6mol cl2.

Ill still work this up,as it should contain at lleast a portion of benzal/benzyl chloride.
After sitting over night the yellow seems less intence leading me to believe it may just be the mix I was after.

[Edited on 23-12-2004 by ballzofsteel]

to good to be true - for me

Organikum - 25-12-2004 at 04:56

The workup of the TCCA/water/toluene via Sommelet produced zero/nada/nothing on benzaldehyde.

It might be
- fucked up Sommelet (not very likely)
- hydrolysis of BzCl to BzOH because I waited too long and/or because this happens anyways.

I guess that hydrolysis is the main problem of this reaction.
Will try this with hypochlorite next time, maybe that works better.
Adding sodium carbonate might help though, or using the di-chloroisocyanuric acid sodium salt, this would be better soluble too.

what a fucking christmas

IPN - 22-1-2005 at 03:59


...or using the di-chloroisocyanuric acid sodium salt, this would be better soluble too.

I was organizing my chems and found a 1kg box of granulated sodium dichloroisocyanuric acid and remembered this thread. :)
So now I have 80g of toluene, 50ml saturated solution of SCCA in water and 1g of hexamine refluxing in a water bath. I'll let it be there for 3h or so and then add sodium carbonate and reflux that. I hope I get something. :)

Heres a vid of the mix refluxing: :P

garage chemist - 3-4-2005 at 02:32

Sorry for bringing up old threads... but its better than opening a new one.
I hope that this hasn't been posted before.

In "The war gases", I found something interesting about benzylchloride:

"Under the influence of weak oxidisers, like calcium nitrate, barium nitrate etc., the benzylchloride is converted to benzaldehyde after the following equation:

2 C6H5-CH2Cl + Ba(NO3)2 -----> BaCl2 + C6H5-CHO + NO + NO2 + H2O

With strong oxidisers, like chromic acid, it is converted to benzoic acid."

Also, in this book, benzylchloride is prepared by bubbling chlorine through 100g toluene with 5g PCl5 as the catalyst (until the weight has increased by 35g). The PCl5 could likely be replaced with the same molar amount of red P, as it reacts with chlorine rapidly to form PCl5.

I planned to chlorinate toluene to benzylchloride, hydrolyse this to benzyl alcohol and oxidise this to benzaldehyde, since benzyl alcohol is oxidised to the aldehyde much easier than straight toluene.
But the hydrolysis apparently isn't necessary, just adding some barium nitrate seems to produce benzaldehyde.
Reactions conditions aren't named, but if you see red nitrogen oxides evolving from the reaction, you know that it is working.

garage chemist - 11-4-2005 at 14:08

Will adding red P (gets converted to PCl5 rapidly) as a sidechain chlorination catalyst interfere with the added hexamine?
I don't know too much of the chemistry of hexamine... and if there's a chance that bis(chloromethyl)ether forms, hexamine is out of the question. Bis(chloromethyl)ether is ultra carcinogenic and as toxic as phosgene.
Drying + distilling the toluene before chlorination, heating and lighting the flask with a halogen lamp should prevent ringchlorination as far as possible, even without hexamine.

S.C. Wack - 24-7-2005 at 19:51

On a slightly less than 1 gram scale:

Attachment: jacs_105_7672_1983.pdf (208kB)
This file has been downloaded 1567 times

The_Davster - 27-2-2006 at 20:27

Originally posted by Organikum


Benzalchloride and acetic acid plus tin(II) or tin(IV) chloride yields benzaldehyde and chloroacetic acid.

I just read through that patent and saw nothing even mentioning chloroacetic acid, the reactions there produce the acid chlorides, nothing on the chloroacids. Did I miss something there or did you mean to say acetyl chloride instead of chloroacetic acid?

[Edited on 28-2-2006 by rogue chemist]

Organikum - 27-2-2006 at 20:50

Hell thats so long ago I hardly can remember it. But I remember all the pain this chlorinations gave me.

Sorry, I won´t look it up, I am completly into non-toxic transformations now, I had my share of lachrymators and more then I ever wanted. Passing out under seizures from cleaning a flask with chloroacetone did it for me. Cost me expensive glassware (don´t give a shit) and braincells (thats bad).


ordenblitz - 13-7-2006 at 17:45

I have had some success using TCCA.

A 250 ml. flask was equipped with overhead stirring, a reflux condenser, thermometer and a free neck with a stopper. Therein was placed toluene, H2SO4/H2O 50/50 mix and a pinch of hexamine.

Heat was applied and when the temperature reached ~80º, large chunks of TCCA was added one at a time through the free neck of the flask. The TCCA chunks were broken from a large pool chlorinating tablet sized to just barely fit through the 24/40 neck. It was easy enough to add the chlorinator by momentarily pulling the stopper in the neck; quickly dropping said chunk, then replacing the plug. I had nothing resembling a run away and it was no problem to control the foaming with good stirring. The additions continued periodically, about every 8 to 10 minutes, as the temperature rose through 100º. I was going to wait until 100º to begin additions but was nervous about what might happen upon the first drop. I have to say that in retrospect it wasn't as hard as one would expect. I had plenty of time for the additions as the foaming never made it up into the reflux condenser. Remember though.. big chunks.
The final temperature was roughly 130. After the requisite amount of TCCA was added and the reaction ceased, the contents were cooled, suction filtered and distilled. The result was an equal mixture of ring chlorinated product as well as the side chain chlorinated specimen coming over at 176º
I do think that if the first additions are commenced after reaching 100º, a good deal more of the desired product could be had.

I did repeat the process deciding to skip the filtration step, opting to separate the products directly by distillation. Not a good idea. Upon heating the combined material began to rapidly darken and get viscous. Eventually it turned into a tarry mass of black crap that nothing distilled from until the temperature was well over 200. What came over was a lovely maroon oil. What it was I have no clue.

Some pictures:
This picture was from a previous attempt where the plan was to drop powdered TCCA down the condenser where upon it could be gradually reflux washed into the reaction. It did not go as planned as was abandoned.
The first picture was immediately after the first TCCA addition, the second two or three chunks in and the third picture from about 40 minutes into the reaction.
This is how it looked not long before the foaming subsided and the cooling was begun.

JohnWW - 14-7-2006 at 18:18

Can benzyl chloride be used as an intermediate in the preparation of DDT? I would think so.

Nicodem - 15-7-2006 at 00:45

No, you need chlorobenzene.
But if you do have benzene you can chlorinate it with TCCA under electrophilic conditions (H2SO4 catalisys). Actually I don't know how Ordenblitz obtained so much benzyl chloride at all since the conditions he used were for electrophilic substitution mostly (except for the higher T and the part of toluene that got chlorinated in the vapor phase). Yet it seams he was after benzyl chloride and not ortho/para chlorotoluene.
I would never do something like he did though. TCCA in dilluted H2SO4 hydrolises to HClO which in highly acidic media easily dehydrates to Cl2O. Vapors of toluene and Cl2O are a highly instable mix that can explode any time, especialy by the presence of light. Anyway, you certainly don't want to heat the reaction mixture if you want to chlorinate benzene. The reaction procceds at room temperature if left stirring for two days or is done in 5 hours at 65-80°C (see the original paper J. Org. Chem, 1970, 56(3), 719-722).

ordenblitz - 15-7-2006 at 07:41

Some time ago, working from said reference for the production of chlorotoluene, I was not paying close enough attention to temperature control and inadvertently let it climb over 100°. Upon filtration and distillation I was surprised to collect a small amount of benzyl which I did not think was probable from this reaction.
The above was done simply to see if the conditions could be altered slightly to increase the production of side chain chlorinated product, for which incidentally I have no use. This was done for curiosity sake and was posted here merely for discussion purposes.

Do you think that changing the reaction conditions by raising the temperature from 80° to 100° increases the danger of this reaction substantially over that of the published procedure?

Nicodem - 15-7-2006 at 08:41

I know from the equilibrium constants of TCCA hydrolysis to HClO (0,00067 mol/L) and HClO dehydration to Cl2O (0,00357 mol-1L-1 at 20°C) that substantial amounts of Cl2O is formed under your reaction conditions (especially under the acidic and reflux condition). I also know that a correct vapor mixture of Cl2O and toluene explodes violently and unpredictively without the need of a spark. So, my answer is: Yes, it is potentially very dangerous, especially if working with such large amounts. Going from 80°C to reflux is an enormous difference for what regards the composition of the gases above the liquid phase.

This is what I think about why you got some benzyl chloride:
Cl2O and HClO are capable of benzylic side chain chlorinations in the vapor phase even if barely any or no light is present. So I guess the reason why you got some benzyl chloride besides the normal products is because you used reflux conditions. I would assume a similar thing happens when using the famous "Loomis patent" method (and that's probably why it is so prone to dangerous runaways) only that no ring chlorination can happen there since the hypochlorite is insoluble in toluene and the reaction probably proceeds only in the vapor phase between the solid and liquid boundary (Cl2O, Cl2 and HClO vapors being reversibly formed in an equilibrium from “calcium hypochlorite” at that temperature while at the same time these vapors are prevented from dissolving/reacting in liquid toluene by the reversible process – reaction with the left over calcium hydroxide).

The reaction conditions for side chain chlorination of toluene with TCCA are published in that same JOC paper. No strong acids must be present to avoid ring chlorination and a radical initiator is used to start the radical chain reaction. The authors used dibenzoyl peroxide as radical initiator which is also the most common initiator used for radical polymerizations. Hence it is available OTC, at least in my country, as a solution in methyl ethyl ketone (MEK). You can leave the MEK solution to evaporate at room temperature on a plate (benzoyl peroxide explodes when heated!) and dissolve what remains in the toluene that will be used for the reaction. That is all you need to get benzyl chloride in a safe and clean way.

[Edited on 15-7-2006 by Nicodem]

Ephoton - 28-12-2006 at 00:31

I have never had a single prob with chlorinating toluene with hypochlorite ions.
they key to a safe reaction of course is to stay under 105C this is very easy to do.
just use a boiling water bath. as for dryness of hypochlorite and toluene this does
play a major factor. but if you put more toluene in the mix than needed then distill a small amount out. the water will go with it as an azeotrope :) too easy why not just do it the old fashioned way. every time it works. never a prob its the easiest one in the book.
personaly ive tried many ways to benzylchloride and this one has never failed. and for keeping the hypo ion covered with toluene to keep it from detonating. this is not true its the temperature that the reaction is done at. I have done many of these going for many different products trying to play with baker light like substances. (wondered if benzyl alcohol would work instead of phenol which it does not in my books) the only problem that I can see with this synthesis is the fact you have to filter the product before distillation very nasty for the eyes and nose. make sure the filtration is fully enclosed so as not to let out fumes. and if you have to sniff it to notice the sting you have done some thing wrong (which I can not see as its so dam easy to do)
psycho kitty was the one who first suggested the use of red phosphorus for the initiator of the chlorination I believe on the hive. She gave patent refs too but I don't have the time to dig them up. she swore by it and I have never had a problem with her posts working. still to try the TCCA and I will one day but not for a bit.

evil_lurker - 29-5-2007 at 22:30

Tonight I attempted to chlorinate some toluene using chlorine gas generated by the reaction between MnO2 and HCl. The MnO2 was pottery grade, and the HCl was off the shelf hardware store 31%, and the Toluene was "Ace Hardware" brand, once distilled.

The equipment used was a 2L addition funnel, 3L flask, Claison adapter, and gas inlet adapter (outlet in this case). The gas generator was hooked onto a 500ml pyrex gas wash bottle loaded with "liquid lightning" sulfuric acid drain cleaner, a trap flask, check valve, and finally into the chlorinator. The chlorinator consisted of a 3 neck 1L flask with inlet adapter, gas dispersion tube, thermometer, 200mm reflux condensor, and finally another inlet adapter for discharging HCl.

Heat was provided by an embossing tool that looks like a hair dryer and light by a 500watt halogen bulb minus the glass shielding.

Total charge, 1400ml of muriatic acid, 3.5 moles of MnO2, and 552g (approx 6 moles) of Toluene. The heat tool was only able to get the flask up to around 100ºC, however once the light was turned on it quickly refluxed, and did so at a rate that the heat tool was turned off and all heat provided by the halogen light for the rest of the reaction (amazing... refluxing a damn 1L flask with a freaking LIGHT of all things).

Once the flask was brought up to temp, the muriatic acid was allowed to drip onto the pre-moistened MnO2. Nothing! I was like WTF, that asshole ripped me off, this ain't MnO2! So I said F-it and pretty much added in about 1000ml into the reactor. After a minute or two, some Cl2 gas began began to be formed. I instantly thought "oh crap, massive runaway time" but amazingly the gas generation never did really get out of hand... in fact it never really did much of anything. So I added in the rest of the muriatic acid. Still no increase inflow with only a small stream of Cl2 being produced. Flow slackend after about an hour and a half, and magnetic stirring was begun to compensate for the reduced flow.

After 3 hours the chlorine gas flow was barely going, and so the reaction was terminated. The contents of the flask were still clear and almost colorless, even though no Hexamine was added as a catalyst/iron sequesterant. The contents of the flask were then transferred to a 1L flask for distillation and weighed.

Then the crapper. Total weight increase of crude product 8 freaking grams!!!! ARRRGH! I was hoping for at least 1-2 moles worth, but the yield of crude product was pathetic.

Last time I attempted to add HCl to MnO2 massive clouds of chlorine gas were emitted, but this stuff was crappy to say the least. Even on the outside of the building there was barely any flow coming out of the discharge hose... swim was expecting massive clouds of HCl but there really wasn't squat coming out.

I think I got ahold of some bad MnO2 if there is such a thing. Going to try tomorrow with some TCCA as a chlorine source and see what happens.

garage chemist - 29-5-2007 at 22:51

Its strange that you even got a good chlorine production from MnO2/HCl once, because the very slow reaction you described is what usually happens.

HEAT man! MnO2/HCl wants to be heated to near boiling temperature before it outputs chlorine with any usable speed!
TCCA/HCl also needs to be heated well in order to produce the theoretical amount of chlorine. Also finely powder the TCCA before using it, coarse granules will coat themselves with cyanuric acid and not react fully.

evil_lurker - 29-5-2007 at 23:29

Well... your right... went outside to clean up and in the flask was lots of unreacted MnO2.

I got a sneaking suspicion after a few minutes that one might have to heat the stuff up to get decent Cl2 production... but didn't want to set back up my water bath since I was using a RBF and a rather large bulky setup.

All I can say after cleaning up is thank god for respirators... chlorine is hell to work with, especially on a large scale.

garage chemist - 30-5-2007 at 00:52

Your procedure wasnt a failure, you just found out that chlorine is not produced at room temperature. Your chemicals are still fine, they just havent reacted. Your synthesis hasnt begun yet.
All you have to do is heat the toluene to reflux again and then heat the chlorine generator.

I hope you didnt throw out the chemicals! It would be a shame if you didnt continue the synthesis.

Magpie - 30-5-2007 at 11:25

FYI, from Laboratory Studies in Chemistry by Bradbury (1923):

1. Prefered method of Cl2 generation:

Place crystals of KMnO4 1 cm deep in a 300mL flask supported by a ringstand with a wire gauze. Place a small flame 8cm below the flask. Using a dropping funnel allow HCl to fall drop by drop into the flask.

"...the production of gas is under perfect control, and the method is greatly superior to the use of hydrochloric acid and manganese dioxide."

2. Alternate method:

"On account of historical interest of the reaction, some teachers may prefer to use manganese dioxide. In that case the dropping funnel is replaced by a thistle tube running to the bottom of the flask. Enough concentrated hydrochloric acid is added at once to cover the manganese dioxide, and a gentle heat is applied."

[Edited on by Magpie]

evil_lurker - 30-5-2007 at 15:20

Bah. I switched over to TCCA and HCl... still using the 12 theoretical mole amount of chlorine... all it takes with the TCCA put out massive amounts of chlorine is to just slooowly drip in the HCl and then heat when the flow slackens..

This time the reaction ran much more smoothly, albeit there were a few hiccups when a check valve I was using stopped up... that was messy to say the least... thank god for ventilation fans.

Only other problem I ran into was that the sulfuric acid washing bottle however creates significant back pressure on the generator and slows down the generation of Cl2.

Total time of chlorine generation was approx 4 hours.

Its distilling now so hopefully I'll know the yield in about 2-3 hours.

evil_lurker - 30-5-2007 at 17:26

Well it got distilled. Total for a 6 mole run boiling over a 5ºC range = 108g

I distilled at atmospheric and there was quite bit of dark liquid in the flask. I estimate with fractionation that over a mole could be had as the mix I distilled off had quite a bit of benzyl chloride smell to it.

Anyways, my yields suck. :(

For now anyways.

bio2 - 30-5-2007 at 19:55

.......Only other problem I ran into was that the sulfuric acid washing bottle however creates significant back pressure on the generator and slows down the generation of Cl2...........

To dry your gas with H2SO4 it is not necessary
to put the dip tube to the bottom of the wash bottle.

An inch submerged is enough. This makes a good flow estimating device also by counting the bubbles.. You can swirl the bottle ocassionally if you like...

When doing a procedure for the first time it is always
best to do it on a small scale to identify the pitfalls.

evil_lurker - 30-5-2007 at 21:52

Yeah I heard that... but there ain't much smaller I can go using the equipment that I have.

I think my biggest problem, is the fact that I was using the wrong kind of light (halogen lamp).

From the website for chlorine molecules to disassociate the light must have a wavelength shorter than 488nm. Any higher wavelength than that just does not carry sufficiant energy to break the bond.

From what I could find, a typical halogen spectrum looks like this:

If one notices, the spectral output barely reaches into the sub 500 range... so even though there is a shitload of light put out by a 500watt halogen bulb, the light just ain't got enough energy to work.

The ideal solution would be a 20,000K metal halide light fixture, somewhere around 400watts. That should work quite well, and probably require sunglasses while chlorinating.

Initial setup, minus hoses. 2nd run gas dryer was omitted and only wash bottle used.

Reaction vessel, up close:

Chlorine generator setup:

Chlorine generator, closeup:

not_important - 30-5-2007 at 22:43

Better than a metal halide lamp, which is intended to give moderately good colour rendition and thus puts out a fair amount in the green through red, would be a plain uncoated (clear) mercury lamp. These have peaks at 365, 404, 436, 546, and 578 nm, mostly in the range you want, and are cheaper than metal halide.

Organikum - 31-5-2007 at 05:16

I used a 150W halogen (about 7€ or so) with the glass removed and it worked just fine (toluene/TCCA).

I believe the cheapest lamps work best for they offer no kind of inbuildt UV protection.

[Edited on 31-5-2007 by Organikum]

evil_lurker - 11-6-2007 at 20:07

Toluene run #3

I had to abort this run after about 1/3rd a mole of TCCA was converted into CL2.

In it I used 600g of toluene and a 20K light w/ 1 g of hexamine added.

The result?

Fucking SNOW!!!!

I'm guessing that the hexamine absorbed the HCl formed, which became insoluble, and well the rest is history.

So, it would seem that hexamine is NOT a good catalyst and does not need to be used... or at least if it is used, in tiny tiny amounts.

[Edited on 11-6-2007 by evil_lurker]

evil_lurker - 11-6-2007 at 21:50

After a complete tear down, rinsing, and oven drying cycle of all flask equipment Run #4 has begun.

The metal halide lamp is inufficiant to heat and react the flask at the same time. Therfore the floodlight was used as a heat source. I figure there is in the neighborhood of some 40,000 lumens hitting the flask with about 20,000 being the correct spectrum to initiate the reaction you can see the blue tint above.

Chlorine production seems to have stabilized for the moment, all the leaks are out of the system, and clouds of HCl are coming out the exhaust tube and being blown off into the night by the exhaust fan.

All in all this run is looking very promising.

evil_lurker - 12-6-2007 at 02:06

Success... the light works!!!

Run #3 started off with a standard 12 mole theoretical load. Using a 50-50 solution of HCl and water, approx 200mls was put into the reaction flask so estimate that there was 10 moles of Cl2 left in the chlorine generator when run #4 was begun.

Run #4 initial charge was 613 grams of toluene and the weight of the contents of the flask had increased by a whopping 154g over the last run.

Provided that a mole of chlorine gas weighs in at @ about 35.5g, that means approx 4 moles of chlorine were absorbed and reacted...

Since I am unable to determine how much chlorine was in the initial charge, I am guessing that yields are in the 80% plus range based on chlorine input.

The crude product will be distilled later today after I get a nap and the fraction boiling over the 170-180ºC range will be collected.

jimmyboy - 12-6-2007 at 15:48

nice - i hope the yield was high..

garage chemist - 12-6-2007 at 15:55

I hope the toluene was distilled before use.

evil_lurker - 12-6-2007 at 18:33

Originally posted by garage chemist
I hope the toluene was distilled before use.

It was straight out the freaking can. :D I've distilled some out of the can before, and its indeed 99%+ pure.

I'll probably break down start using distilled in the future, but I'm rather short on reagent storage bottles at the moment so it will just have to wait till a later time.

Anyways, I distilled the crude reaction product. There was significant darkening which resulted in quite a bit of high boiling tarry material left in the flask.

Total isolated yield was 374g of cystal clear material boiling between 174-182Cº or roughly 2.95 moles.

garage chemist - 12-6-2007 at 19:57

Distillation is not necessary because the toluene is not pure enough, it is necessary because the can is made of iron. When iron is present in the reaction, the aromatic nucleus will be chlorinated instead of the side chain, no matter if you irradiate with light or heat to boiling.
Lets hope there wasnt enough iron in there to completely screw up the reaction.

evil_lurker - 13-6-2007 at 02:35

There was definately some iron contamination due to darkening of the reaction mix and decomposition of the reaction product in the distilling flask.. however, this could be at least partially caused by the ceramic packing and reflux (I used a 250mm vacuum fractionating column) and large amounts of residual HCl dissolved in the crude RP... I'm sure that distilling at atmospheric did not help things one bit either.

I do believe that I have benzyl chloride in rather decent purity as only about 30-40 ml or so came over between 150-174ºC (chlorotolune b.p. 160-162ºC, benzyl chloride b.p 179ºC).

The next batch I run will definatly be distilled prior to running, but as I said before I need some new reagent storage bottles.

Any suggestions for glassware cleaning?