Sciencemadness Discussion Board

The synthesis of 1 and 2-naphthols from Napththalene

benzylchloride1 - 4-1-2009 at 14:56

Theory behind the synthesis
1 and 2 naphthols are interesting phenolic compounds that can be produced in 2 steps from naphthalene which is readilly available in the form of moth balls. These 2 isomeric phenols are useful intermediates for the synthesis of catalysts, dyestuffs and quinone derivatives. The synthesis involves the sulfonation of naphthalene, isolation of the sulfonic acid as the sodium salt, fusion of the sodium sulfonate with potassium hydroxide and acidification of the fusion product to produce the crude product. The 2 isomers of the sulfonic acid can be produced by varying the temperature of the sulfonation reaction. Below 60 degrees celsius, the 1-sulfonic acid predominates, while at higher temperatures the 2-sulfonic acid predominates. This is an example of kinetic versus thermodynamic control of a chemical reaction. The 1-isomer is the kinetic product, it forms quicker at lower temperatures, while the 2-isomer is the thermodynamically more stable product and forms quickly at high temperatures. To produce sodium 1-naphthalene sulfonate, the naphthalene is stirred with the sulfuric acid at about 50 degrees celsius until all of the naphthalene dissolves forming the sulfonic acid. The solution of sulfonic acid is then diluted with water, partially neutralized with sodium bicarbonate and salted out with sodium chloride at the boiling point, this causes fine crystals of the product to seperate. The product is then filterd off and dried in a drying oven at 100 degrees celsius. To produce the 2-isomer, the napthalene is heated to 160 degrees celsius and the sulfuric acid rapidly added. After the mixture is homogenous, the solution is poured into water and worked up in the same fashion as the 1-isomer. To produce the 1 or 2 naphthol, the sodium naphthalene sulfonate is fused in a copper crucible with potassium hydroxide at about 300 celsius. Sodium hydroxide can be used, but potassium hydroxide produces a cleaner product and the fusion reaction works better. A larger quantity of sodium hydroxide would have to be used to get the mixture to fuse properly. The use of potassium hydroxide results in a more fluid melt that is easier to stirr and the reaction is less violent then that of the sodium hydroxide. A safety warning is appropriate at this point: Caustic alkali at 300 celsius is extremly dangerous; the fusion step must be conducted in a fume hood with the sash pulled down to protect the chemist. a laboratory coat, safety goggles and gloves must be worn at all times!


sodium 1-naphthalene sulfonate

A 1000 mL 3-necked flask was placed in a Buchi rotovapor water bath. A mechanical stirrer was attached to the flask and a thermometer placed in one of the necks. 50g of powdered naphthalene was placed into the flask through the open neck using a powder funnel. A addition funnel was then placed in neck of the flask. The stirrer was started and 50 mL of 92% sulfuric acid was poured into the flask. Water was placed in the water bath and the water bath was heated to about 45 celsius. The naphthalene slowly dissolved, forming a light purple colored solution. The temperature was regulated to keep the reaction mixture from going above 60 celsius. After the naphthalene had dissolved, 4 hours, the mixture was poured into 400 mL of waterin a 1L beaker. The flask was then washed with water and the washings added to the solution in the beaker. The solution was then filtered to remove a small amount of unreacted naphthalene. 20 g of sodium bicarbonate was then added in small portions to the mixture which was rapidly stirred by hand. The mixture was then heated to boiling and about 35g of finely powdered sodium chloride was added to the mixture with rapid stirring. The sodium 1-naphthalene sulfonate crystallizes out of the solution at the boiling point. The mixture was then allowed to crystallize for several hours in a ice bath. The mixture than consists of a thick mass of crystals that fills the solution. The crystals are then filtered off using vacuum filtration to speed the process. The product can be recrystallized from a sodium chloride solution using the same salting out process with a much smaller amount of sodium chloride. I did not recrystallize my product to save time. The product was then broken out of the filter and allowed to air dry for about a day. Then it was dried in a drying oven set at 100 celsius for several hours or until the product was bone dry. The product was than ground up and placed in a tared bottle. In my experiment the product weighed over the theoretical (90g) because of occluded salts in the product from not recrystallizing.

I am currently working on the fusion of the sodium 1-naphthalene sulfonate, more to come in the next month.

[Edited on 4-1-2009 by benzylchloride1]

not_important - 4-1-2009 at 18:19

Just a quick note that a mix of KOH/NaOH sometimes works even better, and fuses ay a lower temperature while being less costly. There are some liquid drain clearer productions that are a concentrated solution of NaOH+KOH, and make a decent starting point.

benzylchloride1 - 4-1-2009 at 20:27

The alkali fusion of the sodium sulfonates:

The procedure I used came from Vogels practical Organic Chemistry, which called for a 250 mL copper crucible. I only had a 2 inch copper end cap to use as a crucible for this reaction, so the required chemicals where divided by 1/10 and ten fusion runs were made. 12 grams of potassium hydroxide obtained off of Ebay were placed in the crucible and 0.5 mL of water was then added. 5.0g of sodium 1-naphthalene sulfonate was than weighed out. The cruicible was then heated in the fume hood with the sash pulled pown with a propane torch. Once the potassium hydroxide had melted, the sulfonate was added in one portion and rapidly stirred by hand with a spiral copper wire attached to a metal shaft. The melt was initially light grey, but the colored turned green over a peroid of about a minute or two. The mixture was heated with stirring until the mixture began to froth up. The heating was removed and the mixture was stirred until the reaction subsided. The mixture was then cautiously heated until the frothing ceased and a brown oil had separated on top of the alkali. The mixture was then heated for an addition 2 minutes before being poured on to a piece of sheet metal to harden and cool. This was repeated ten times which equaled 50 g of sodium 1-naphthalene sulfonate, 120g of potassium hydroxide and 5 mL of water. This procedure can also be conducted all at once in a 250 mL copper crucible.The fusion product was than added to 300 mL of water in a 1000 mL beaker. The fusion product was than dissolved with stirring for about 15 to 20 minutes. Concentrated hydrochloric acid was then slowly added with stirring. The mixture must be kept from boiling which would cause the lost of some of the product during the addition of the acid. The heat produced from the neutralization assists in consolidating the product making it easier to filter. The acid is added until the pH is around 4 or 5 which is around the point that large quantities of sulfur dioxide are produced from the reaction of the sodium sulfite produced in the reaction with the hydrochloric acid. The 1-naphthol precipitates during this process as a brown crystalline solid. The mixture is than cooled in an ice bath for several hours and the filtered. The wet 1-naphthol is then placed in a 1 L beaker and covered with about 300 mL of water. Enough 50% sodium hydroxide solution is then added to dissolve the naphthol; do not use an excess. The solution is now very dark in color. The solution is then filterd into a 500 mL flask and hydrochloric acid is now slowly added until the solution is acidic and the napthol precipitates as a finely divided white precipitate. The solution is than allowed to cool and is filtered off with a vacuum filtration apparatus. The product is than pressed with a piece of saran wrap until it is fairly compacted and most of the water is forced out. The product is than removed from the funnel, broken up and allowed to dry on several paper towels for about 2 days. My product is currently drying in my fume hood. I will report back as soon as the product is dry with a melting point and percentage yield.

kclo4 - 5-1-2009 at 20:06

You'd have a pretty good procedure if you had some pictures I think. :) Also if you converted a file into a PDF so we can all keep a copy! Great job on making the naphthols. I would be a little bit worried of their carcinogenicity though, I know one isomer of naphthylamine is a known human carcinogen, and the naphthols may be as well.
Anyways, thanks I like how easy this procedure is.

UnintentionalChaos - 5-1-2009 at 20:32

Originally posted by kclo4
You'd have a pretty good procedure if you had some pictures I think. :) Also if you converted a file into a PDF so we can all keep a copy! Great job on making the naphthols. I would be a little bit worried of their carcinogenicity though, I know one isomer of naphthylamine is a known human carcinogen, and the naphthols may be as well.
Anyways, thanks I like how easy this procedure is.

Phenol and aniline aren't exactly health products either (nor are most things we consider interesting on this site), but phenol is still used as an antiseptic. Google Chloraseptic.

Food dyes of the azo variety sometimes have a naphthol moiety, and they don't seem to be too toxic. Not to mention that the azo bond gets cut somewhere in your body, releasing in the case of say, red 40, a 2-naphthol sulfonic acid.

benzylchloride1 - 11-1-2009 at 20:48

The 1-naphthol was obtained as a off white solid in a yield of 70% that melted at 90 celsius which is slightly blow the literature value. The naphthols are toxic and may be carcinogenic which most interesting and not interesting chemicals are. The naphthylamines are carcinogenic, especially the 2-isomer which is a known human carcinogen from way back. 1-naphthol can also be produced by nitrating naphthalene, reducing to 1-naphthylamine and running a reverse Bucherer reaction with sodium bisulfite to produce the 1-naphthol. I would not advise this method unless you are working in a out building with a suitable fume hood. I am currently trying to improve my ventilation system for my 4-foot Kewaunee fume hood so that I can conduct chlorination reactions. The interior of the fume hood is stainless steel and hydrochloric acid is not to friendly to it. When I conduct the 2-naphthol synthesis, I will post some picture of the procedure. I recently synthesized some ammonium 2,4-dinitronaphthol from the 1-naphthol. This is the first intermediate in the Maritius Yellow series of synthesises in Fieser's textbook.

benzylchloride1 - 10-4-2009 at 21:55

I conducted the synthesis of sodium 2-naphthalene sulfonate today. I used the procedure in Vogels. I forgot to take pictures again. 100g of naphthalene was placed in a 500ml 3-neck flask. The flask was heated with a heating mantle. The mixture was mechanically stirred with a stirring motor using the home made stirring bearing described in Fiesers textbook. A addition funnel and thermometer was placed in the other two necks of the flask. The naphthalene was melted and the stirrer was started. Glascol mantles are wonderful, beats heating with a hot plate or burner. The liquid naphthalene was heated to 160 Celsius. 90ml of 92% sulfuric acid was run in over a peroid of 10 minutes. The mixture turned to a purple color and then almost black. The mixture was stirred for an additional 5 minutes after the additon of the sulfuric acid. The apparatus was disassembled and the sulfonated naphthalene was then carefully poured with stirring into 750ml of water in a 1000ml beaker. A fine precipitate formed. 4 grams of decolorizing charcoal was added and the solution was heated to boiling and filtered. The dark solution was partially neutralized by adding 40 grams of sodium bicarbonate in small portions with stirring. The solution was heated to boiling and 70 grams of finely powdered sodium chloride was added with stirring. the sodium salt precipitated instantaneously. upon cooling, the contents of the beaker completely solidified. The solid was then filtered and pressed to remove most of the mother liquer. The crude product was then recrystallized from 700ml of water. The product crystallized as small plates. The crystallizing salt is being left over night at room temperature to complete the crystallization.

Paddywhacker - 11-4-2009 at 03:46

I am tempted to try this out, as I have been thinking of buying the two naphthols, but don't like the asking price.

A quick internet search shows that a mixture of 41% NaOH and 59% KOH melts at 170 Celsius, or maybe lower if commercial water content is taken into account.

benzylchloride1 - 11-4-2009 at 20:48

Some alkali fusions can be conducted with mixtures of potassium and sodium hydroxides. I have had consistently bad results when using pure sodium hydroxide. After filtering, pressing, drying the product over a wood burning stove and then powdering and further drying the product at 80 Celsius a fine off white powder was obtained. The product weighed 98 grams which gives a percentage yield of 54%. The fairly low percentage yield was due to not salting out the product druing the recrystallization. I have enough sodium 2-naphthalene sulfonate to make 2 batchs of 2-naphthol according to the procedure in Vogel. I may trying synthesizing p-cresol from toluene using the method provided in Vogel for this compound using a mixed alkali fusion in the near future.

[Edited on 12-4-2009 by benzylchloride1]

[Edited on 12-4-2009 by benzylchloride1]

16MillionEyes - 12-4-2009 at 17:07

I agree with others that pictures would be nice. In addition--not that I'm the best writer or anything--I think it would be easier to read what you wrote if you broke down your sentences into paragraphs.

As for the chemistry, I'm actually disheartened to know that most naphthalene seems to be slowly being replaced by p-dichlorobenzene. I have tried to think of something interesting and easy to do with this compound but all I can think of is out of my league. For the napththalene reaction it seems like it is relatively easy to do. I'd figured it would be in the ranks of benzene, but apparently it isn't so and it's much friendlier in terms of reaction conditions.


Paddywhacker - 12-4-2009 at 17:53

Before Christmas, I sealed up 0.1 mole of p-dichlorobenzene (PDCB) in a jar with 0.25 moles of potassium iodide and about 150 ml of acetone.

The idea was that I'd get p-diiodobenzene out of it, but my lab is in transition while I install subzero cooling for my rotovap, and I haven't done anything for months.

I did open the jar at one stage but got frustrated trying to work out a TLC protocol for checking the reaction.

But that begs the question .... what to do with p-diiodobenzene.

At one stage last year I tried to nitrate PDCB by prolonged reflux, but during workup I pulled the tap out of the separating funnel and the product soaked into my carpet.... but there was some yellowish goodness there.... I think.

[Edited on 13-4-2009 by Paddywhacker]

UnintentionalChaos - 12-4-2009 at 19:23

Feel free to delete my useless contribution if you see fit.

thread direction.gif - 6kB

nitric - 13-4-2009 at 07:24

i attempted this with the first part of the sythesis, and the sulfonic acid crystalizes out of the sulfuric acid if left for about 24 hours with a perfect 1:1 (grams:ml) ratio of reacted naphthalene and sulfuric acid.

benzylchloride1 - 13-4-2009 at 21:16

Sulfonic acids can usually be recrystallized from concentrated hydrochloric acid. A glass fritted funnel is needed to filter of the product because the sulfonic acid and solvent will quickly destroy any filter paper.

nitric - 14-4-2009 at 06:25

I can usually filter conc. HCl but not conc. H2SO4. The fusion part can be done with a glass vessel if you don't care about it, i cant see the copper catalyzing any reactions since its often just done in a iron or ceramic vessel in literature as far as I've heard

len1 - 14-4-2009 at 06:48

Quote: Originally posted by Paddywhacker  
I am tempted to try this out, as I have been thinking of buying the two naphthols, but don't like the asking price.

A quick internet search shows that a mixture of 41% NaOH and 59% KOH melts at 170 Celsius, or maybe lower if commercial water content is taken into account.

This can't be right. Where on the internet did you find this info?

nitric - 14-4-2009 at 07:26

Quote: Originally posted by Paddywhacker  

A quick internet search shows that a mixture of 41% NaOH and 59% KOH melts at 170 Celsius, or maybe lower if commercial water content is taken into account.

I have heard simialar information about KOH and NaOH mixtures that melt at lower temperatures than both, it may have been on Bromic's book project and wiki

not_important - 14-4-2009 at 21:27

Abstract A eutectic etchant consisting of 50 mole percent KOH and 50 mole percent NaOH has been developed having a melting point of 170°C.

The mixture of NaOH and KOH preferably contains NaOH and KOH in the molar range ratio of 70:30 to 30:70. It is particularly preferred to use mixtures whose composition is close to that of the eutectic mixtures, e.g. 65:35 to 57:42 and 45:55 to 55:45 (NaOH:KOH).

A mixture of NaOH and KOH in a molar ratio of 1:1 form an eutectic mixture melting at 170° C., which has a low viscosity.

US Patent 4769359

In the molten hydroxide fluxes 20 g of the equimolar eutectic NaOH (8.32g) / KOH (11.68g) were fused at 185ºC (the theoretical melting point of the mixture is 170ºC) in a Teflon crucible exposed to the atmosphere in a sand bath.

The mixture of NaOH and KOH melts at and is the lowest melting binary mixture among the alkali and alkaline earth hydroxides.

Magpie - 8-12-2012 at 11:53

Here's my recent experience at making sodium 2-napthalene sulfonate (SNS). This will be used later as a precursor in making 2-naphthol.

My first attempt was a half-batch (32g naphthalene charge) using the procedure in Gattermann (1937), forum library. This was a complete failure yielding no product. I attribute this to the requirement for a 4-hr cook at 170-180C which resulted in virtually all of the naphthalene evaporating. This occurred despite my attempt to restrict evaporation by using an Erlenmeyer flask.

Seeing upthread that benzylchloride1 had successfully made SNS using the procedure in Vogel's 3rd, this was tried. This only required a 10 minute cook at 160C, and was done at a larger scale (100g naphthalene charge). This was successful and yielded 124g of SNS compared to Vogel's predicted 140g.

SNS is very soluble in water and is therefore salted out using a 10% solution of NaCl. I found that it took 600g of the boiling salt solution to dissolve 30g of SNS. The picture below shows the recrystallization (overnight) in the 10% NaCl for 1/2 of the batch.

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Recrystallization in 10% NaCl

The crystals were then sucked dry and pressed using a Buchner funnel, then dryed overnight in a 100C oven. I used regular filter paper in the Buchner funnel but it had to be replaced regularly due to acid attack. The picture below shows the lustrous flake crystals for 1/2 of the batch.

SNS crystals.JPG - 102kB

sodium 2-naphthalene sulfonate crystals


My guess is that the 4-hr cook in the Gattermann (and Fierz-David) procedure was taken from a large scale industrial procedure. In that case surface/volume ratio and equipment provisions were such that excessive evaporation of the naphthalene was not a problem. Anybody else have an opinion on this?

It is interesting to me that the Vogel procedure (as did Fierz-David, but not Gattermann) only calls for partial neutralization of the 2-naphthalene sulfonic acid initially produced. NaHCO3 is used for this. My resulting pH was about 2 using pH paper. My question is why only partial neutralization?

Incidentally, I made a mistake and used 40g of Na2CO3 instead of 40g of NaHCO3. Since I was still carrying an acidic product I went ahead and finished up the synthesis. Unfortunately I really have no way of determining the purity of my product. All I can say at this point is that it looks good.

[Edited on 8-12-2012 by Magpie]

[Edited on 8-12-2012 by Magpie]

[Edited on 9-12-2012 by Magpie]

[Edited on 9-12-2012 by Magpie]

Magpie - 14-12-2012 at 16:31

Using the procedure in Vogel’s 3rd I have prepared 2-naphthol using recently prepared sodium 2-naphthalene sulfonate (SNS). This was a high temperature caustic fusion using KOH.

A. Equipment
Vogel specifies a 250mL metal crucible mounted in a piece of asbestos sheet for the fusion. Not having any asbestos I substituted an 8” square x ¼” sheet of Hardie board, a fireproof, cement-like siding material. For the crucible I used a ½ pint ss measuring cup. See picture below:

ss crucible in Hardie board.JPG - 109kB
ss crucible in Hardie board

A 3/8” copper tube was used to protect the thermometer which was also used to stir the reactants during the fusion.

B. Fusion
The 50g of SNS was first ground to a fine powder in a coffee grinder. 120g of flake KOH and 5mL of water were then heated to 250°C in the crucible using a Meker burner on propane. The SNS was then added and stirred into the liquid KOH. There was barely enough room in the crucible.

As the temperature reached 310°C the fused mass produced a brown oil that floated on the molten KOH. The mass also began spitting. I wore 2 heavy shirts, a lab apron, and a pair of leather gloves. The hood window was down to protect my face and the fan was on. I regard these safety measures as essential. After heating was completed the fused mass was ladled into a 1-liter beaker half filled with crushed ice using the spoon end of a spatula. Results can be seen in the picture below which was taken after the fusion was completed

fusion to 2-naphthol completed.JPG - 117kB
aftermath of the fusion to 2-naphthol

C. Precipitation
Following the melting of the ice ~170mL of con HCl was added to the beaker to precipitate the 2-napthol. The picture below shows this precipitation in progress:

2-napthol and Na 2-naphtholate.JPG - 100kB
precipitation of 2-naphthol from sodium 2-naphtholate

Then just enough 5% NaOH was added to redissolve the 2-naphthol (~110mL). 1g of sodium dithionite was added to prevent oxidation, per Vogel. The dissolved sodium 2-naphtholate was then filtered using a Buchner funnel to remove a fair amount of fine, dark brown, insoluble char-like material. Then finally the 2-naphthol was reprecipitated using acetic acid (~50mL of 65% acetic acid). The 2-naphthol was then filtered again using a Buchner funnel. The cake was then transferred, with filter paper, to a dinner plate and left to dry for 3 days at room temperature. The picture below shows the dried product:

dried 2-naphthol.JPG - 134kB
dried 2-naphthol

D. Results
The yield of 2-naphthol was 24.5g, vs the 25g predicted by Vogel. The melting point (sealed tube) was 110°C vs the literature value of 122°C . Since this melting point indicated impure product I tested recrystallization of a sample in dilute (33%) alcohol. However the sample turned brown and “oiled-out.” So, for now, I will leave the remainder “as is.”

E. Discussion
This is my 2nd caustic fusion to produce a member of the phenol family. The first was that for the synthesis of resorcinol. Although maintaining safety during the time-temperature control of the fusion was again a challenge, overall, making 2-naphthol was much easier. This is due to two facts, primarily: (1) oleum is not required in producing the sulfonate, as only a single sulfonic acid group is added, and (2) 2-naphthol is insoluble in water, greatly simplifying the workup.

If I ever make 2-naphthol again I will wash the somewhat gummy product well with water before drying. This wasn’t called for by Vogel. Perhaps it is just assumed to be part of good technique.

Questions, comments, and suggestions are welcomed.

[Edited on 15-12-2012 by Magpie]

UnintentionalChaos - 14-12-2012 at 16:48

Nice work, as always, Magpie.

I'll probably be replicating this shortly since 2-ethoxynaphthalene is supposed to have an interesting fragrance.

Magpie - 14-12-2012 at 16:51

Quote: Originally posted by UnintentionalChaos  
Nice work, as always, Magpie.

I'll probably be replicating this shortly since 2-ethoxynaphthalene is supposed to have an interesting fragrance.

Thank you. That's exactly what I was going to make, also called Nerolin. ;)

Magpie - 15-12-2012 at 16:34

My recrystallization of a sample of crude 2-naphthol in 33% aqueous ethanol was partially successful. The lustrous appearance and color was much improved. Here's a picture - sorry for the out-of-focus:

recrystallized 2-naphthol.JPG - 67kB

After drying at room temperature for 7 hours I determined the melting point. It was a much improved 120°C vs the lit value of 122°C.

UnintentionalChaos - 16-12-2012 at 10:58

Quote: Originally posted by Magpie  
Quote: Originally posted by UnintentionalChaos  
Nice work, as always, Magpie.

I'll probably be replicating this shortly since 2-ethoxynaphthalene is supposed to have an interesting fragrance.

Thank you. That's exactly what I was going to make, also called Nerolin. ;)

Man, any time I try to do something original, someone has me beat to the punch! You say that the recrystallization was partially successful? Did you get a low recovery? I would call a 10C raise in mp a success. :cool:

Magpie - 16-12-2012 at 12:40

Quote: Originally posted by UnintentionalChaos  
You say that the recrystallization was partially successful? Did you get a low recovery? I would call a 10C raise in mp a success. :cool:

Yes, I agree. That was a poor choice of words. What I meant was that some of the 2-naphthol remained as a solid clump from the "oil-out" after thoroughly cooling, but much of it recrystallized nicely.

I used food grade ethanol (from Everclear) for the recrystallization. I'm going to try it with solvent grade alcohol. Otherwise I may have to buy a 5th of cheap vodka to recrystallize the whole 24.5g. :(

Boiling 33v/v% ethanol dissolves 3.4g 2-naphthol/100mL. But a significant fraction turned to oil.

In reference to the making of Nerolin, do you have a facile way of making ethyl iodide?

UnintentionalChaos - 16-12-2012 at 14:30

Quote: Originally posted by Magpie  

In reference to the making of Nerolin, do you have a facile way of making ethyl iodide?

Crud, I hadn't thought about that. EtBr might be too low boiling to work, though I have quite a bit of that. My supply of iodides is limited.

Do you think that this procedure could be modified for ethyl iodide? I don't really see why not, to be honest.

I have prepared some MeI with it, and got 70% yield, but I think I know where I lost the 10%.

Magpie - 16-12-2012 at 16:42

Quote: Originally posted by UnintentionalChaos  

Do you think that this procedure could be modified for ethyl iodide? I don't really see why not, to be honest.

I have prepared some MeI with it, and got 70% yield....

That's a good question. I would like to make this a general discussion so will take it up in the existing "Ethyl Iodide" thread:

Magpie - 19-12-2012 at 10:28

I recrystallized the 24.5g of crude 2-naphthol using 33v/v% Ace denatured alcohol. There was some oil-out but not much. This was discarded. The crystals were caught on a Buchner funnel then dried overnight at room temperature. The melting point was 121°C vs the lit value of 122°C. The recovered yield was 17.8g. This is a 56.8% yield based on the 50g of Na 2-naphthalene sulfonate charged.

recrystallization of 2-napthol.JPG - 106kB

Nicodem - 19-12-2012 at 12:23

Quote: Originally posted by UnintentionalChaos  
EtBr might be too low boiling to work, though I have quite a bit of that. My supply of iodides is limited.

Alkylation of naphthols with ethyl bromide should work just fine. Ethyl bromide is quite reactive and 24-48 h at 50 °C in acetone with K2CO3 as the base is usually good enough for this reagent. Alternatively, for alkylations of phenols with alkyl bromides, KOH or NaOH in ethanol often works even better.

Magpie - 19-12-2012 at 14:03

Quote: Originally posted by Nicodem  

Alkylation of naphthols with ethyl bromide should work just fine. Ethyl bromide is quite reactive and 24-48 h at 50 °C in acetone with K2CO3 as the base is usually good enough for this reagent. Alternatively, for alkylations of phenols with alkyl bromides, KOH or NaOH in ethanol often works even better.

For comparison, my college handout recipe specifies the use of ethyl iodide in methanol, and KOH. Reflux time is 1.5-2 h.

Nicodem - 20-12-2012 at 11:31

As alternatives to ethyl halides/sulfates/sulfonates/etc., there are several reports that nerolin can be prepared by heating 2-naphthol and ethanol in the presence of various acid catalysts (NaHSO4, H2SO4, FeCl3, CuCl2, Al2(SO4)3, and so on). Unfortunately most of these publications are in Chinese and in some difficult to get journals. There are some older and easily accessible references, for example:
Ber. 1882, 15, 1427 (probably the first report on this reaction)
J. Am. Chem. Soc. 1935, 57, 1459–1464. DOI: 10.1021/ja01311a025
J. Chem. Soc. 1900, 77, 33.

It was proposed the reaction proceeds trough the hemiacetalysation of the keto tautomer of naphthols, followed by the rearomatization by water elimination. If so, and experiments indicate this, it is only useful for 2-naphthols and higher benzophenols where the tautomerization is possible at all.

An interesting article describes that refluxing 2-naphthol in ethyl acetate in the presence of catalytic amounts of sulfuric acid for 4 h gives nerolin in 40-45% yields. The mechanism is probably similar. See J. Am. Chem. Soc. 1952, 74, 6118. DOI: 10.1021/ja01143a516

nezza - 3-1-2013 at 03:51

:DThanks for the post benzylchloride. I have not been able to get hold of naphthol so I had a go at your synthetic route. It worked perfectly. I have a beige coloured product which gives the expected red dye with diazotised sulfanilic acid. I used a low temperature sulfonation so my product is mainly 1-naphthol.

smaerd - 3-1-2013 at 07:33

Another method could be nitration, reduction, and hydrolysis?

Probably don't need to go this route for the nitration but I found it reading about other transformations and thought it was neat.

Title: Silica Gel-Mediated Organic Reactions under Organic Solvent-Free Conditions
Authors: Satoaki Onitsuka, Yong Zhi Jin, Ajam C. Shaikh, Hiroshi Furuno and Junji Inanaga
Molecules 2012, 17, 11469-11483

As for the hydrolysis I guess the information is in this collection
Title: Naphthalene Derivatives
Author: Gerald Booth
DOI: 10.1002/14356007.a17_009
I don't have access so I can't really tell if it's viable or not.

DJF90 - 3-1-2013 at 07:47

The problem with going via the amines is that its difficult to get regiopure nitronaphthalene and the 2-naphthylamine is a potent carcinogen (carinogenity of the 1-naphthylamine was attributed to the presence of small amounts of the 2-isomer). If this is a route you intend on taking please ensure you're equipped to work with such materials.

White Yeti - 31-1-2013 at 14:25

I'm interested in making the 2-isomer of tetralone. I found one synthesis that started from a 2-naphthol-ethyl ether, but this synthesis called for sodium to reduce the second aromatic ring, and that's simply not up my alley.

I was wondering if one could potentially start from tetralin and oxidize the positions along the non-aromatic ring to give a mixture of 1-tetralinol and 2-tetralinol. The alcohol can then be reduced to a ketone with hypochlorite relatively easily.

Is there an oxidation reaction that will effect oxidation upon a non-aromatic ring while leaving the aromatic ring untouched?

Magpie - 13-3-2013 at 15:00

I recently made 7.7g of 1-naphthol from naphthalene (Enoz "old-fashioned" mothballs). Not finding a procedure in the literature I used that by benzylchloride1 in this thread for the precursor Na 1-naphthalene sulfonate and that in Vogel for 2-naphthol to make the 1-napthol.

Making the Na 1-naphthalene sulfonate using con sulfuric acid at 55°C was uneventful. 50g of naphthalene was charged to a 3-neck 1000mL RBF w/mechanical stirring. I would use a 500mL RBF next time. I used a silicone oil bath controlled to 57°C with a PID controller. % yield was 50.9%.

The precursor was fused to 1-napthol using KOH per the procedure in Vogel's for 2-naphthol. There was a lot of spitting of the molten reactants and my temperature/time was a little out of control. I have some remedies for this situation for my next fusion: 1) a 1" deeper all-copper crucible, and 2) a Bi/Sn eutectic heat transfer fluid for the thermometer-stirrer. The first crystallization gave 16.1g of crude 1-naphthol (mp = 75-87°C vs lit value of 96°C). Then followed several batches of recrystallizations in 33v/v% solvent grade alcohol, none of which gave good melting points, ie, 90-92°C, 88-90°C, and 76-80°C. There was also significant oil-out. The oil was distilled at atmospheric pressure at 278°C. Upon taking a melting point of the solidified distillate it was 86-88°C. Altogether my yield was just a hard-won 7.7g for a % yield of 25.1%. Next time I would distill the whole batch to avoid the recrystallizations/oil-out scenario. It is interesting to note that 1-naphthol has a strong phenol smell. I don't remember my 2-naphthol having much of a smell.

Comments, recommendations, or questions?

[Edited on 13-3-2013 by Magpie]

[Edited on 14-3-2013 by Magpie]

Synthesis of sodium 1-naphthalene sulfonate

Blue Matter - 29-7-2013 at 15:16

These are some pictures I took during the synthesis of sodium 1-naphthalene sulfonate, I know that this thread has been inactive for a while but figured someone might be interested in the pictures I took while making the sulfonate.

The pictures should be in order
The first picture was Sulfuric acid and naphthalene reacting in a 3 neck 250ml flask with overhead stirrer and water bath.

Second picture is the solution of water and product from he first picture.

third and fourth picture is Sodium bicarbonate being added into the flask.

fifth picture is the solution after boiling and adding sodium chloride leaving it in ice bath to crystallize.

The sixth and seventh pictures are the final product after around a hour in a ice bath.

I hope you found these pictures interesting, I will be attempting synthesis of 2-napthol soon and will have pictures of it also.

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hyfalcon - 29-7-2013 at 15:24

You chasing a synthesis on Tetralin, Blue?

Blue Matter - 29-7-2013 at 15:50

Quote: Originally posted by hyfalcon  
You chasing a synthesis on Tetralin, Blue?

Actually Parared dye, 2-napthol is one of the ingredients in synthesizing it.

Tetralin sound interesting thought I will look into it.

Why am I getting so much (grey) precipitate (and no crystals)?

bob800 - 9-8-2013 at 09:50

I used the procedure by Fieser for sodium 2-naphthalene sulfonate:

For this sulfonation at an elevated temperature it is convenient to use a 200-cc. three-necked round-bottomed flask. This is supported in a position convenient for heating with a free flame and a mechanically driven stirrer is fitted into the middle open- ing, the shaft turning in a bearing consisting of a glass tube inserted in a cork stopper of suitable size. The bearing may be lubricated with glycerol. The best form of stirrer is a glass rod bent through an angle of 45 0 about 2 cm. from the end. A ther- mometer is inserted with a cork in one of the side tubulatures in such a way that the bulb will be immersed when the flask is one-third filled. The sulfuric acid is to be run in from a dropping funnel which should be clamped in such a position that it will deliver into the third tubulature of the flask.

In the flask melt 50 g. of naphthalene, start the stirrer, and adjust the flame until a steady temperature of 160° is maintained. In the course of 3 minutes run in from the dropping funnel 45 cc. of c.p. concentrated sulfuric acid, keeping the temperature at 160° (the flame may be removed). After stirring for 3 minutes longer pour the solution into 400 cc. of water. In a well con- ducted operation there will be no precipitate of naphthalene, but there may be 1-2 g. of the water-insoluble di-^-naphthyl sulfone, formed thus: C10H7SO3H -\- CIOHS ^- C10H7SO2C10H7 -f" H2O To remove it boil the solution with animal charcoal and filter by suction.

Partially neutralize the clarified solution by adding cautiously 20 g. of sodium bicarbonate in small portions. Saturate the solution at the boiling point by adding sodium chloride (30-35 g.) until crystals persist in the hot solution, and then allow crystallization to take place. Recrystallize the material, using this time only a small amount of sodium chloride. Test the purity of the product by examining a sample of the />-toluidine salt which, when pure, melts at 217-218 0 . (See page 140.) The yield is 70-75 g.

Only 48.84g of naphthalene made it in my flask (after powdering moth balls), but I thought that would be fine as I was using Rooto drain opener which certainly contained some water.

Initially, the naphthalene was melted in a 250 mL round bottom flask; however, I was unable to get the temperature hot enough with this setup (using a free flame). I let the flask cool, then some time later remelted the naphthalene and transferred it to a 250 mL Erlenmeyer, which I then heated directly on my hotplate.

Somehow I misread my thermometer and began adding the H2SO4 at 180*C instead of 160*, though I soon realized this and lowered the temperature to ~160*C. The mixture turned dark purple and quickly black. Magnetic stirring was begun and the acid dripped in for roughly 3-4 minutes with somewhat poor temperature control (but maintained within +/- 10*). After complete addition of the acid, the mixture was allowed to stir for an additional 3 minutes.

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The mixture was poured into 400 mL RT water, with the formation of a greyish precipitate in black solution. The solution was boilied with a generous heaping of activated charcoal and vacuum filtered to yield a clear, very very very dark purple solution.

20g of NaHCO3 were added with stirring, causing the formation of a creamy layer1 on top of the solution. Most of this dissolved with stirring, but the solution was gravity filtered just in case.

Next the solution (IIRC there it was 350 mL in volume) was boiled and saturated with 24.3g NaCl. The solution was allowed to cool with the formation of a precipiate:

resized-IMG_1270.JPG - 14kB

The grey precipiate was vacuum filtered/dried for about 20-30 minutes. It weighed 137.82g at this point, which I do not understand... the estimated yield was 70-75g, and there could only be a maximum of 24.3g NaCl mixed in, along with residual water, though I have a hard time believing that there was at least 50.7g of water in there.

Anyway I thought the recrystallization step might "fix" things so I dissolved the precipiate in 400 mL of boiling 10% NaCl solution. Shortly after I set it down (5 min?), however, a huge mass of similar-looking grey precipiate formed!

I haven't massed it yet but I'm sure it's way over 70g... and still quite dull and grey

resized-IMG_1279.JPG - 14kB

The solution remained quite acidic after the NaHCO3 was added so I don't think there is any excess precipitating out...

1Interestingly enough this was bright-white unlike the my main yield...
--Also, I used Kosher Salt for my sodium chloride.

Any suggestions would be greatly appreciated!

[Edited on 9-8-2013 by bob800]

[Edited on 9-8-2013 by bob800]

Blue Matter - 9-8-2013 at 12:35

When I made it there was a lot of residual moisture even after filtration and it looked like much more than it actually was, once it was totally dry I ended up with 67g. I don't think that it would be a big problem but maybe try using a different brand of drain cleaner or pure H2SO4. The really white crystals are made from really pure chemicals I feel like any contaminants will change the color?

Also see what your density is g/cm

UnintentionalChaos - 25-10-2013 at 20:14

I too, did the preparation of 2-naphthol from naphthalene and sulfuric acid, followed by alkali fusion per Vogel 3rd edition. I don't have much to add, and my yields were pretty in-line with others in this thread. During the prep of the sodium 2-naphthalenesulfonate, you can squeeze a few extra grams of product out of the recrystallization liquor after filtering off the first crop by adding 15 more grams of NaCl per 100ml of filtrate, heating up to dissolve everything, and allowing to cool undisturbed.

I started out with 50g of naphthalene and got 52.98g of sodium naphthalenesulfonate after the first recrystallization. The second crop gained by adding additional NaCl weighed 7.64g for a total of 60.62g.

For the fusion DO NOT add any water. Instead of 120g KOH, use 60g of KOH and 40g of NaOH prills with no added water. This is a roughly equimolar mixture that forms a low melting eutectic. I found that my melt spit very little, though I would still advise some sort of heat resistant gloves and probably a lab jacket. I think the problem is that as hydroxide is consumed in reaction and turned into sulfite, the capacity to hold onto superheated water vanishes and it suddenly turns into steam. It is absurdly hard to dry KOH and it clings to water in surprising amounts even when molten, including what you added deliberately. I had only what few % of water came in the technical KOH.

Zephyr - 10-2-2014 at 16:52

I preformed a procedure fro vogels, that is very similar to the one done by bob800. After recrystallization, i too was left with this grayish gunk. I may have gone slightly over the recomended tempature, but otherwise the experiment went perfect. Any idea what this goop is?

<img src="" width="800" />

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced image size(s)]

[Edited on 11.2.14 by bfesser]

Mailinmypocket - 11-2-2014 at 05:09

Mine looked just like that (except pinkish because I didn't bother to recrystallize and some of the dye from the acid must have made it through). It proved quite annoying to dry this stuff well though.

benzylchloride1 - 11-2-2014 at 23:52

The sulfonate salt tenaciously hangs on to water, it is often advisable to dissolve in boiling water and add finely ground NaCl, slowly until the product begins to crystallize and then slowly cool to room temperature. The product is a pain to dry, I would press the filter cake under vacuum and allow all the water to drain out, probably about 30 minutes. I would then dry in a warm place in a glass dish for several days after breaking the material up. Remove the filter paper before this final drying. Be patient, it can take longer then a week if the drying vessel it not gently heated, 50 to 60 C.

BOD513 - 18-6-2016 at 08:12

I know this thread has been inactive for a while, but I'm experiencing something weird running the sulfonation reaction and I wonder if anyone has had the same thing- the reaction starts off in the usual way, with the light pink/purple slowly giving way to a dark purple/black solution, but at some point a couple hours in, the reaction mixture solidifies as a blueish grey concrete-like mass. This is strange because it happens extremely rapidly; from the time it begins thickening to the time it hardens completely is usually less than five seconds. This not only results in no yield, but is a real pain to clean out of glassware. I've been using enoz moth flakes that claim to be 99%+ naphthalene, but I'm wondering if this might be false. I haven't found anything in the literature that would indicate what could be happening here (there doesn't seem to be much out there in general about synthesizing the 1-naphthalene sulfonate salt), has anyone had this happen to them?

Edit: On further examination I've found what may be the strangest part of this- it only happens when being stirred. When I've used a thermometer (the first attempt) or a jury-rigged mechanical stirrer (the second and third attempts) it solidifies. When I covered the beaker with Saran Wrap and just left it in the sun all day, the reaction proceeded pretty much as it did for previous people in this thread, albeit with a low yield. Strange

[Edited on 18-6-2016 by BOD513]

[Edited on 18-6-2016 by BOD513]