Sciencemadness Discussion Board - The short questions thread (1)

The short questions thread (1)

Pages: 1 2 3 .. 7

Nicodem - 11-9-2008 at 23:57

This is a thread where you can post all those short questions you always wanted to ask but did not consider them worthy of a new thread. You can ask amateur science related questions of all kind as long as you think they are simple enough to be answered by other forum members in a preferably single post.
Consequently, self discipline in avoiding off topic replies is expected.

Panache - 12-9-2008 at 01:02

Does anyone have any relevant data on the polymer PPP, or poly(p-phenylene), things like glass transition temperature, % crystallinity, solvent resistances etc. My old crc handbook is too outdated (1972) and the infinet gave me nothing except derivatives of said polymer.

[Edited on 12-9-2008 by Panache]

Nicodem - 12-9-2008 at 06:06

You can find some data here: http://xxx.lanl.gov/PS_cache/cond-mat/pdf/0507/0507515v1.pdf
(Probably useless but check also http://dx.doi.org/10.1002/macp.1995.021961110)

kclo4 - 12-9-2008 at 22:56

This is a great idea Nicodem!

I've have been wondering what would happen (although I haven't searched, so I really guess I shouldn't be asking it here) if acetic acid were dripped into hot concentrated. H2SO4 in a setup analogues to the Diethyl ether setup? I know it probably wouldn't make Acetic anhydride, but probably something interesting?

[Edited on 13-9-2008 by kclo4]

Per - 13-9-2008 at 09:34

I heated once concentrated sulphuric acid with 80% acetic acid, after a while it a few black particles were observed, but this could also have been just impurities.
And I don´t think that something new is formed, the acetic acid just would distil over I think.

And I´ve also a questin, everybody knows triphenylmathane and it´s preparation step.
I asked myself if it would also be possible to prepare trinaphthalenemethane out of naphthaline and chloroform catalyzed by AlCl3?
I wanted to attempt this but the first problem I couldn´t solve was finding a solvent for the reaction which wouldn´t react.
Until now I couldn´t find anything about this stuff.
And it doesn´t matters which isomer would be formed, if the naphthalene is attached at the 1 or the 2 position. Also many other things will be formed because naphthalene and AlCl3 are reacting at their own, so the desired stuff must be isolated from this other stuff and the reaction must be brought to a way in which the formation of trinaphthalenemethane is preferred.

And does anybody know if it could be from interest for chemiluminescence?

Picric-A - 13-9-2008 at 10:02

@ the acetic acid question- nothing new is formed however considerably stronger acetic acid distills off.
i am pretty certain this was acetic acid as it passed all the salt tests...

kclo4 - 13-9-2008 at 13:56

Well, I was thinking of doing it like the ether synthesis where you heat up the sulfuric acid to 140*C and then drip Glacial Acetic acid in.
If you got it hotter, say 200*C and then dripped in the GAA maybe something would form if not from the first experiment. I assume at some point methane would be produced.

panziandi - 13-9-2008 at 15:18

I treated sodium chloroacetate with conc H2SO4 and it fizzed... any ideas?

kclo4 - 13-9-2008 at 15:55

Could you have perhaps had some impurities such as carbonates etc?
I noticed my Sodium acetate that I made from vinegar and baking soda fizzed, It had sat on a shelf with out a lid for a few months. I believe I made sure to use an excess of Vinegar at the time of producing it.

Could you explain how you obtained your Sodium Chloroacetate? This may help.

panziandi - 13-9-2008 at 16:12

Its GPR grade from BDH

... so probably 97% - 99%. I suppose it could be carbonate impurities, that did not occur to me at the time.

I did it at the start of summer. I will try it again and pass the gasses into lime water etc.

[Edited on 14-9-2008 by panziandi]

kclo4 - 13-9-2008 at 18:26

Another thought, if chloroacetic acid is produced from chlorine, and HCl is a byproduct perhaps their were very small amounts of HCl that got to react with the Sodium base to form Sodium chloride. The gas would then obviously be Hydrogen Chloride when it was reacted with the Sulfuric acid.

I assume gases couldn't be dissolved in your Sulfuric acid, right?
If for some reason gases even dissolve in concentrated sulfuric acid, the possibly of it dissolving more of one gas then Chloroacetic acid + Sodium Bisulfate could, may perhaps cause the gas to evolve and fizz away leaving the allusion that you have impurities. This only seems like a very slight possibility to me, and I'd say that it was probably a carbonate or a chloride impurity.

solo - 14-9-2008 at 09:04

I have been unable to locate the refractive index of l,psudoephedrine HCL ....does anyone have this information handy....as I searched and have not been able to find it....many thanks.....solo

What is Refractive index....?

http://en.wikipedia.org/wiki/List_of_refractive_indices

[Edited on 14-9-2008 by solo]

Ragnarok - 14-9-2008 at 10:06

http://www.erowid.org/archive/rhodium/chemistry/comparison.e...

Bottom of the page, hope it helps

solo - 14-9-2008 at 12:06

I think i found some information in pages 634-648 in the book of Alkoloids found here.....thanks...java

http://www.sciencemadness.org/library/books/the_plant_alkalo...

Picric-A - 17-9-2008 at 11:32

Kinda random, is the fillament of a sodium lamp made of mettalic sodium?

DJF90 - 17-9-2008 at 13:42

I beleive there is a small piece of sodium metal that needs to vaporise before the characteristic yellow light is observed.

solo - 17-9-2008 at 17:40

I found a neat way to test for ketones using...p-nitrophenylhydrazone, however I can't seem to find it's CAS# or much about it .......solo

Quote:

...1 Phenylacetone forms a beautifully crystalline paranitrophenylhydra-
zone melting after crystallization from alcohol or pyridin at 145’ to 145.5’.
It usually crystallizes in rosettes of platelets which are only moderately
soluble, even in hot alcohol. The substance serves well for the identi-
fication of phenylacetone.

....................source,

FURTHER STUDIES OF THE MODE OF OXIDATION OF PHENYL DERIVATIVES OF FATTY ACIDS IN THE ANIMAL ORGANISM. III. SYNTHESIS OF SOME DERIVATIVES OF PHENYLPROPIONIC ACID
H. D. Dakin
J. Biol. Chem., Oct 1908; 5: 303 - 309

[Edited on 17-9-2008 by solo]

Attachment: 173.pdf (735kB)
This file has been downloaded 1293 times

Drying glassware using solvents, does it work?

Panache - 18-9-2008 at 07:12

i have always had this technique for when if i needed a piece of glass dry but i didn't have time for the oven and if absolutely super dry wasn't in need. Everytime i do it i wonder if i'm completely delusional. Its fairly simple i just swirl the flask in the dry solvent i will be using in the flask, then discard that solvent to recycle and proceed with the glass as if it were dry. it always plays on my mind because it is reasonable theory but i know i have little evidence of its efficacy
How long would it take say a 250mL round bottom to dry out effectively at 140 C, how long would it take if you immersed it in dry ether or dry toluene at RT.

[Edited on 18-9-2008 by Panache]

Nicodem - 18-9-2008 at 08:10

To Solo:

I'm not sure you are asking for the CAS number of p-nitrophenylhydrazine or the p-nitrophenylhydrazone of phenylacetone, but here are the numbers of both:
p-nitrophenylhydrazine, CAS 100-16-3, 158°C dec.
phenylacetone p-nitrophenylhydrazone, CAS 70063-29-5

More commonly than p-nitrophenylhydrazine the 2,4-dinitrophenylhydrazine (CAS 119-26-6) is used for the derivatisation of ketones (actually I should say that it used to be used since nearly no one does characterisation based on derivatisation any more). The melting points reported for phenylacetone 2,4-dinitrophenylhydrazone (CAS 19072-92-5) are 157-158°C, 153-155°C and 149.5°C.

To Panache:

Since the hardest to remove water from glass is the one that is chemisorbed on the silicate surface I think just washing your glasware with a dry solvent does not do much. Generally in the lab one would let the flask stay at 120-150°C for at least five hours and let it cool in a desiccator or under dry argon or nitrogen flow. However, myself being too lazy, I just heat the flask under the argon flow with a heat gun (max air temperature of 400°C) for some 15 min and let it cool while still being purged with argon. Works well for organolithiums and Grignards.

[Edited on 18/9/2008 by Nicodem]

Picric-A - 18-9-2008 at 10:50

Has anyone got any info on Aluminium carbonate? eg, decomp temp?
cheers!

solo - 18-9-2008 at 19:20

In a rearrangement of a well known aldehyde poured into a very cold H2SO4 (-16C) rearrangement of the aldehyde occurs and a ketone is produced .......along with a large amount of water with a distinctive rooten egg smell......my question is what can i treat this water with to salt out the sulfur and rid of the smell as it makes for a very uncomfortable reaction waste product that I don't want to pour down the drain.....solo

12AX7 - 19-9-2008 at 06:39

Quote:

Originally posted by Picric-A
Has anyone got any info on Aluminium carbonate? eg, decomp temp?
cheers!

Aluminum is too acidic in solution. There isn't even a bicarbonate. In fact, aluminum is acidic enough that it might displace the carbonate, turning sodium carbonate, at least in part, into sodium aluminate. Sodium aluminate solution is stable in air.

Tim

panziandi - 19-9-2008 at 09:08

It will form the hydroxide. Aluminium hydroxide decomposes to aluminium oxide at 300*C according to my CRC handbook (I just got the 75th edition from the chemistry library they sold it for £5 woo)

sonogashira - 19-9-2008 at 16:31

Could I please ask for a little assistance in translating this German sentence:

dann wurde unter Feuchtigkeitsabschluß trockner Chlorwasserstoff eingeleitet.

babelfish gives me: then under humidity conclusion dry hydrogen chloride was introduced.

So the problem is with "Feuchtigkeitsabschluß," does it just mean a dry atmosphere (drying tube) or does it imply heating of some kind?

(I think it's a really nice idea for a thread by the way Nicodem

)

garage chemist - 19-9-2008 at 16:44

Feuchtigkeitsabschluß simply means exclusion of moisture, anhydrous conditions. So use a drying tube or something like that to keep atmospheric moisture away, and, of course, dry the HCl gas as good as possible.

sonogashira - 19-9-2008 at 17:00

Ah, thanks very much

Could I also bother you to ask what 2-stdg or 4.5-stdg means, as in the sentence:
"Nach kurzem Einleiten trat eine Trübung auf, dann kam es zur Abscheidung eines tief dunkelrot gefärbten Öles, das nach 2-stdg."

garage chemist - 20-9-2008 at 04:16

The sentence is incomplete. 2-stdg. is an abbreviation for 2-stündig, meaning 2 hours long. Post the complete sentence, or better, the complete procedure so that there are no dangerous misunderstandings.

sonogashira - 20-9-2008 at 05:55

Thanks again! Very kind of you

It's not a procedure I'm thinking of doing so I won't bother you with the whole text. I know the sentence was incomplete but I just wanted to put the abbreviation into some sort of context for you. Thanks again, I can make much more sense of it now.

solo - 20-9-2008 at 15:03

Quote:

Originally posted by solo
In a rearrangement of a well known aldehyde poured into a very cold H2SO4 (-16C) rearrangement of the aldehyde occurs and a ketone is produced .......along with a large amount of water with a distinctive rooten egg smell......my question is what can i treat this water with to salt out the sulfur and rid of the smell as it makes for a very uncomfortable reaction waste product that I don't want to pour down the drain.....solo

...........in this same reaction there is a yield of a ketone and unreacted aldehyde...but both distillation point is too close hence oxidation is recommened........i used Potassium permanganate in water....but since water and the ketone don't mix i just got a mess.....the ketone doesn't seem to solvate in either methanol or ethanol ....any suggestion as to what trans phase solvent to use to be able to oxidise the aldehyde to propionic acid, and remove my ketone .......solo

Klute - 20-9-2008 at 16:11

Solo, you might want to try acetone as a solvent, it will surely dissolve your ketone, and if 5-10% water is added, sufficent permanganate will dissolve.

By rotten eggs smell, do you mean H2S is present? In that case NaOCl is a effective treatment to neutralize it, forming some sulfur and sulfides presumably.

Regarding the drying glassware with solvents: I routinely use acetone to dry glassware for any type of reaction where an aqueous is not going to be present, or for drying erlen/beakers etc in which I am going to transfert organic solutions and dry them for example.
Of course this doesn't suffice for water-sensitive reactions, but is a very quick and efficient way of getting surface-dry glassware... using a hair drier speeds things up.

the used acetone can be kept and recycled by simple distn to relatively dry (not anhydrous) acetone, or used to wash out organics from glassware for example.

For those who know

franklyn - 20-9-2008 at 20:52

maybe you can clue me in
What's the meaning of a CAS number when the same compound can have many
different ones referring only to it's state of hydration.

Cupric dinitrate ( anhydrous ) . . . . . . . .Cu(NO3)2 . . . . . . . . . . . .CAS 10402-29-6
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .CAS 3251-23-8

Cupric dinitrate Basic ( double salt ) . Cu(NO3)2•3Cu(OH)2 . . CAS 12158-75-7

Cupric dinitrate hydrate . . . . . . . . . . . . .Cu(NO3)2•H2O . . . . . . . CAS 13778-31-9

Cupric dinitrate hemipentahydrate . . . Cu(NO3)2•2.5 H2O. . . . CAS 19004-19-4
dicopper tetranitrate pentahydrate . . . [Cu(NO3)2]2•5 H2O. . . . ( same thing of course)

Cupric dinitrate trihydrate . . . . . . . . . . .Cu(NO3)2•3H2O . . . . . . . CAS 10031-43-3
Copper trihydroxy dinitrate ( also known as )

Systematic and trivial naming adds further confusion. The term Cupric can instead be
called Copper II or just Copper nitrate as well as dinitrate.

.

not_important - 20-9-2008 at 21:40

Well, the basic nitrate is a rather different compound so I don't see why you included it.

Anhydrous compounds can have quite different properties than their hydrated forms, Cu(NO3)2 is an example as is AlCl3 vs AlCl3.6H2O - which would you want to deal with a spill of?

CAS numbers are supposed to serve as a unique identifier of a compound or substance, and the various hydration states are different compounds. If you buying a nickel compound for its nickel content and you were quoted a price per kg, whould you want to know the hydration state? How about mixing benzene, acetyl chloride, and aluminium chloride, might not hydration state be important - and all the opaque container is labeled with is "aluminium chloride".

CAS numbers also get around the various naming conventions, you use whatever naming is standard for where you are, find the CAS number, and everyone will know exactly which substance you are referring to. Is copper chloride CuCl, CuCl2, or CuCl2.2H2O? How about vanadium fluoride - give me the formula for which one I mean.

Naming has a lot of historical baggage involved, especially in industry where trivial names and abbreviations are not that infrequently used - some of which have been used for a century and a half or more.

Not even formula are a perfect solution, for several reasons. The symbols for some elements vary in different countries; ask the European members how they'd write the chemical name and formula for cobalt iodide, if they weren't writing for an international audience.

So CAS reduces confusion, a given compound has but one CAS number and a CAS number refers to a single compound, not one of several possible compounds.

kclo4 - 20-9-2008 at 21:41

How could one turn a Ketone into an alcohol?
For example Benzophenone to Diphenylmethanol, also known as benzhydrol?

solo - 20-9-2008 at 21:49

Formula: NaBH4

Content 99.5~~99%

Mol. Vt: 37.85

Chemical properties:

Physical state: White crystalline powder particle

Melting point: 400C(slowly decomposes above 400C, completely decompose at higher temperature)

Specific gravity: 1.07-1.08

Solubility in water: Reactive(insoluble in ether and hydrocarbons)

Description and usage.

Sodium borohydride is a milder reducing agent, can be used in aqueous solution. It converts selectively aldehydes and ketones the corresponding alcohols in the manufacture of pharmaceuticals and other fine chemicals. It will not react with esters, amides, or carboxylic acids, the more powerful reducing agent lithium aluminum hydride(LAH) is used to reduce these compounds. LAH is the more powerful reducing agent than sodium borohydride due to the weaker Al-H bond compared to the B-H bond. The reactivity of sodium borohydride can be modified by addition of iodine or methanol in BH3-THF to reduce esters into the corresponding alcohols like the reaction of benzyl benzoate to benzyl alcohol. Sodium borohydride is used as a hydrogen source for fuel cell systems and a foaming agent for rubbers. Sodium cyanoborohydride converts certain alcohol groups to methylene groups. Sodium Cyanoborohydride is used as a selective amination reductant. It converts aldehydes (chemoselective), ketones (stereoselective) to the corresponding alcohols in the manufacture of pharmaceuticals and other fine chemicals. It is used in the reductive alkylation of amines, novel metals and oximes. Some examples of reducing agents are: PHYSICAL STATE white crystalline powder particle

kclo4 - 21-9-2008 at 04:56

Sorry, One that isn't so pricey. I really should have specified.
Isn't there some easy reduction similar to a clemmensen reduction that can turn a ketone/aldehyde into an alcohol?

Thanks for your response

panziandi - 21-9-2008 at 05:05

Aluminium isopropoxide in isopropanol is an excellent way of reducing ketones to alcohols.

In fact this method is used for Benzhydrol on page 885 of Vogel 3rd edition

[Edited on 21-9-2008 by panziandi]

S.C. Wack - 21-9-2008 at 06:17

If you bought or found in the library a later edition, say the fifth, you would find a different method for benzhydrol involving zinc. Someone should scan that edition sometime.

EDIT: It's also in OS CV1, page 90.

[Edited on 21-9-2008 by S.C. Wack]

Klute - 21-9-2008 at 06:21

Clemmensen? You prefer working with marge amounts of HgCl2 than NaBH4?

Atmospheric hydrogeantion over Cu/SiO2, very easily prepared from Cu(NO3)2.xH2O, 30% NH3 and silica gel, is a very cheap alternative. Aromatic ketones are desoxygenated to the alkanes with higher catalyst loadings.

sonogashira - 21-9-2008 at 09:03

I attach the procedure using zinc reduction from Vogel's 5th... Kindly provided by S.C. Wack

Attachment: Benzophenone to Benzohydrol with Zn.pdf (73kB)
This file has been downloaded 942 times

kclo4 - 21-9-2008 at 14:20

Klute, What happens if you don't use any mercury compounds? Wouldn't it still work, but just not as well? I'd like to know why it would matter.
I never clemmensen would work or that i've done it, I just said was wondering if there was something similiar to it. However, I do have a decent amount of Mercury, while I don't have any NaBH4

Thank you for the PDF file, and the other options guys

I'll look into all of them.

solo - 21-9-2008 at 18:23

Quote:

Originally posted by Klute
Solo, you might want to try acetone as a solvent, it will surely dissolve your ketone, and if 5-10% water is added, sufficent permanganate will dissolve.

....acetone does not dissolve the ketone and the micellaneous sticky stuff....tried DMC and although it dissolves the ketone, the water and the current oxidising agent , Potassium Permangenate , will not mix, hence I need some help finding another oxidant that will be soluble in DMC......although not sure what to use.......perhaps I will need some phase transfer material.........solo

Klute - 21-9-2008 at 22:39

I think a clemmensen without Hg will only give the alcohol in some case. i remeber seeing something like that when looking into the Zn reduction of unsaturated ketone to the ketones...

Solo, maybe try AcOEt and TCCA? TCCA is very soluble in AcOEt... Or use DCM and TCCA with a PTC (I always use TBAB), this worked well enough for oxidation of various alcohols into aldheydes with TEMPO. You could try KMnO4 with TBAB or similar in DCM..
Sounds like a tricky ketone, not soluble in acetone!

Nicodem - 22-9-2008 at 00:52

Quote:

Originally posted by solo
....acetone does not dissolve the ketone and the micellaneous sticky stuff....tried DMC and although it dissolves the ketone, the water and the current oxidising agent , Potassium Permangenate , will not mix, hence I need some help finding another oxidant that will be soluble in DMC......although not sure what to use.......perhaps I will need some phase transfer material.........solo

Then the obvious conclusion is that what you have is not the ketone you think it is. I have a very hard time imagining a ketone containing only H2SO4 resistant functional groups and not being soluble in acetone. What you have is most probably some polymeric goo. Was it vacuum distilled? What kind of analysis have you performed?
KMnO4 is soluble in acetone and this is the solvent commonly used for KMnO4 in organic oxidations. If your KMnO4 does not dissolve in acetone than it is not KMnO4 or perhaps your acetone is not acetone.

Edit: Sorry, I misunderstood the post which only mentions the insolubility of the crude ketone in acetone and not KMnO4.

[Edited on 22/9/2008 by Nicodem]

panziandi - 22-9-2008 at 02:36

KMnO4 often contains some MnO2 as a contaminant even in lab grade samples also you can buy KMnO4 as powdered or as larger crystalized material. The later dissolves very slowly even in water, takes a lot of stirring to get a complete solution. Perhaps if your KMnO4 is in crystals you could grind it to a powder?

I too am very surprised that your ketone/aldehyde mixture does not dissolve in acetone

Many aldehydes do polymerize in highly acidic conditions, how long did you let the reaction go for? I would imagine what is happening is the aldehyde and ketone ARE dissolving in the acetone but what is left is the high molecular weight crap.

Perhaps remove as much acetone as possible after the goo has settled and evaporate this off to see if anything has dissolved in the acetone (very likely it has)... If so then isolate all of the acetone extration and treat with KMnO4 powder...

Just had a shocking brainwave (doesn't explain your KMnO4 not dissolving but may explain organics not dissolving...) perhaps your acetone is not dry or has been diluted with quite a few % of water? Perhaps distil before use and/or try drying with CaCl2 / Na2SO4 / K2CO3 and another distillation

[Edited on 22-9-2008 by panziandi]

vulture - 23-9-2008 at 12:51

Quote:

Does anyone have any relevant data on the polymer PPP, or poly(p-phenylene), things like glass transition temperature, % crystallinity, solvent resistances etc. My old crc handbook is too outdated (1972) and the infinet gave me nothing except derivatives of said polymer.

Try the handbook of conducting polymers, it's on gigapedia.

Does anybody know a solvent for triphenylphosphine, excluding the following: hexane, pentane, THF, diethylether, toluene?

DJF90 - 23-9-2008 at 13:14

How about benzene?

kclo4 - 23-9-2008 at 20:25

Can Propionaldehyde be produced by dehydrogenating N-Propyl alcohol over Copper catalyst much like how formaldehyde or acetaldehyde is produced?

I have read that Zinc oxides and other weird oxides can be used, but that's about all i could find.

If not, How would I produce it on the lab scale?

Dang, I thought my reagents for organic synthesis book would help me out more then it does

not_important - 23-9-2008 at 21:28

Quote:

Originally posted by kclo4
Can Propionaldehyde be produced by dehydrogenating N-Propyl alcohol over Copper catalyst much like how formaldehyde or acetaldehyde is produced?
...
Dang, I thought my reagents for organic synthesis book would help me out more then it does

Yes, although you get some condensation products too. If not adding air/O2, which is tricky to control, the conversion is incomplete; you'll want to fractionate the product and recycle the n-propanol.

Pre-WW2 books are the best bet for this sort of method, pre-Depression a even better bet.

Klute - 23-9-2008 at 21:38

I would go for TEMPO-catalyzed oxidation, with NaOCl or TCCA as a secondary oxidant..... Good yields on butanol to the aldehdye have been reported!

4-oxo-TEMPO is easy to prepare, and you need very little.

Ephoton - 23-9-2008 at 22:08

I would like to know if it is possible to swap alkyl chains on alkoxides and how it is done if
it is possible.

eg.

sodium ethoxide + ?????????? ----> sodium methoxide.

I also have second question that I would truly love answered.

what is the best way to extract pure vanillan from the brown
vanilla extract in suppermarkets.
bisulfite sucks

we are dealing with ethanol and vanilla bean extract.
maby sometimes some glycerol at worst.

[Edited on 24-9-2008 by Ephoton]

chemrox - 23-9-2008 at 22:45

Hey not_, why is this so?
"Pre-WW2 books are the best bet for this sort of method, pre-Depression a even better bet. "
Any particular books in mind?

Nicodem - 23-9-2008 at 23:03

Quote:

Originally posted by Ephoton
I would like to know if it is possible to swap alkyl chains on alkoxides and how it is done if
it is possible.

eg.

sodium ethoxide + ?????????? ----> sodium methoxide.

You can not literally "swap alkyl chains on alkoxides" but you can do an normal proton exchange to get the same result. If you dissolve your NaOEt in a large excess of dried methanol, rotavap the solvent, add again some methanol and rotavap again you should obtain a fairly pure NaOMe (depending on what you want to use it for). In theory, if in addition to methanol you add a solvent that forms an azeotrope with ethanol (but not methanol) and distil to half volume using a distillation column, followed up by completely drying on a rotavapor, you should be able to obtain very pure NaOMe in one go, yet I don't know what kind of solvent would fit such a requirement.

Obviously, all this even if efficient is actually pointless as it easier to prepare NaOMe from NaOH and MeOH trough azeotropic removal of water or simply by drying the NaOH/MeOH solution with 3A molecular sieves. There was quite some discussion on the forum about the many possibilities. (Disregarding the fact that NaOMe is commercially available, not regulated and almost as cheap as NaOH).

Care should be taken in rotavaping sodium alkoxides to dryness. Always remember that heat, sodium alkoxides and oxygen is a good recipe for ending up in flames.

Ephoton - 23-9-2008 at 23:23

a lot of older books chemrox are easier to use in our case as they were well
before some of the more technical industrial methods.

Nicodem exactly what i NEEDED thanx dude as always.

a thought depending on the size of your pocket the azeotropic
solvent realy only needs to absorb more ethanol than methanol.
not that hard realy. ethyl acetate I belive will do this.

[Edited on 24-9-2008 by Ephoton]

Klute - 24-9-2008 at 10:30

Refluxing sodium ethoxide and ethyl acetate will get you ethyl acetoacetate... Not a recommended solvent. I woul duse toluene and large excess of MeOH. Even better, I would use NaOEt in the first place. Unless this is for some kind of Ar-X --> Ar-OMe swap?

Maybe making Mg(OCH3)2 from Mg metal and anhydrous MeOH, and then performing a metathesis with NaOH (insoluble Mg(OH)2 should drive the equilibrium far to right)? Just an idea.

EDIT: Ephoton, IIRC Unionised posted a good method for extracting vanillin from vanilla extarct in the Raspberry Ketone thread, check it out. But I'm sure if youlook enough you cna find synthetic vanilla flavouring composed of pur vanillin... And vanillin is the kind of chemical that a company that doesn't normally sell to individuals will feel confortable selling...

[Edited on 24-9-2008 by Klute]

kclo4 - 24-9-2008 at 15:33

Quote:

Originally posted by not_important

Quote:

All right, that is cool.
Do you have any reference for this? patents, etc?
I've been looking but I guess my searching skills are a tad poor.

Actually, for what I am doing and for what I have, can KMnO4 oxidize N-propanol to Propionaldehyde? KMnO4 always goes to the carboxlic acid doesn't it? so I'd need a dichromite, which I hear as only about a 37% yield.

Yeah.. My Reagants for Organic Synthesis book is 1967.

[Edited on 24-9-2008 by kclo4]

DJF90 - 25-9-2008 at 03:56

Not sure about the permanganate, but you'd dichromAte. I'm sure its just a typo though

Supposedly (according to an article on rhodium), Silica gel supported Jones reagent can be used to oxidise alcohols to aldehydes in fairly high yeilds and doesnt allow any of the chromium compounds to leach out into your reactant (using DCM as a solvent). Here's the link:
http://designer-drugs.com/pte/12.162.180.114/dcd/chemistry/a...

Edit: Although on more careful reading, "except oxidation of primary alcohols to aldhydes, produce excellent results"
[Edited on 25-9-2008 by DJF90]

[Edited on 25-9-2008 by DJF90]

sonogashira - 25-9-2008 at 12:06

Quote:

Originally posted by kclo4
All right, that is cool.
Do you have any reference for this? patents, etc?
I've been looking but I guess my searching skills are a tad poor.

Actually, for what I am doing and for what I have, can KMnO4 oxidize N-propanol to Propionaldehyde? KMnO4 always goes to the carboxlic acid doesn't it? so I'd need a dichromite, which I hear as only about a 37% yield.

Yeah.. My Reagants for Organic Synthesis book is 1967.

[Edited on 24-9-2008 by kclo4]

You can use dichromate in solvent-free conditions (see attached paper, in djvu format). I suggest you download Larock's Comprehensive Organic Transformations from the References section. It might make your searching a little easier

Attachment: Solvent Free Oxidation of Alcohols to Aldehydes with Potassium Dichromate.djvu (170kB)
This file has been downloaded 763 times

not_important - 25-9-2008 at 20:03

Quote:

Originally posted by chemrox
Hey not_, why is this so?
"Pre-WW2 books are the best bet for this sort of method, pre-Depression a even better bet. "
Any particular books in mind?

The laboratory supply houses really expanded their lines of organics and unusual inorganics starting in the mid-1930s and especially after WW-II. As a result most researchers just purchased most of the simpler reagents instead of making them; lab methods textbooks dropped those synthesis as a result.

No particular book, I don't remember which books I've seen that in and most of my books are boxed and warehoused.

separating funnel with long stem

Panache - 26-9-2008 at 15:25

I noticed in one of Klutes pictures a sep funnel that after the bulb had a long tube section before the tap. What are these sep funnels and what are they good for?

not_important - 26-9-2008 at 15:43

It can make separation easier. First, the narrow tube gives good visibility of the boundary. Second, in some cases the tube can help break up blobs of one liquid in the other; it can even help speed up the separation of emulsions a bit. Third, when being used as an addition funnel, it gets the bulb away from the crowded flask top; this was more common back before ground glass joints were common.

starman - 26-9-2008 at 19:16

Also they are handy for introducing additions to the bottom of rxn miture eg. ethanol introduction in ether synthesis.

Available from an ebay supplier in your neck of the woods if interested Panache.

Klute - 26-9-2008 at 20:25

Funny, because I have nearly always seen these kind of seperating funnels, and wondered what the point was of having an inverted-pear shape one, as the seperation can be less precise/easy. I find the ones I have very practical to remove those last drops hanging around. Some somewhat viscous solutions can cling to sides though, a good rubbing/shaking is then required to get them off, otherwise they fall off when the top layer is withdrawn and the surface ring "pulls" them off.

vulture - 27-9-2008 at 04:29

Quote:

You can not literally "swap alkyl chains on alkoxides" but you can do an normal proton exchange to get the same result.

As a sidenote, with 3-methoxythiophenes it's possible to do this using NaHSO4 and the corresponding alcohol or thiol. I don't know if it's generally applicable to aromatics though, because it involves addition of a proton in the 2-position of thiophene.

[Edited on 27-9-2008 by vulture]

desiccant

texaspete - 27-9-2008 at 07:06

Which of the following is a stronger desiccant than powdered ammonium nitrate: copper sulfate, magnesium sulfate, calcium chloride, or sodium hydroxide. Are there any other desiccants that will keep ammonium nitrate dry and are readily available?

Thanks!

kclo4 - 27-9-2008 at 10:40

texaspete, I would think any of those mentioned would keep ammonium nitrate dry or would dry it. Magnesium Sulfate, Calcium Chloride, and the others are all good desiccants from what I know.

-----------------------------------------------------------------------------

I've been trying to make chlorophenol lately via NaOH and an excess P-dichlorobenzene in methanol + a small amount of sulfur, since I thought the sulfur might work as some sort of catalyst. I believe I have succeeded in making approximately 20grams of chlorophenol, but I need a way to test if it is Hydroquinone because I fear that might be a significant side reaction. I doubt it but I'm not to sure if 4-chlorophenol would more willingly replace its chlorine for a hydroxyl group more easily then P-dichlorobenzene would.

I was thinking of getting enough water to dissolve all of my product, as if it were Hydroquinone, and then what would be left would be chlorophenol. However, I fear I would lose a decent amount of chlorophenol this way, if most of the product was chlorophenol.

A test for hydroquinone would tell me if i even needed to worry about it, but I seem to be unable to find a method to test for it.

It has a phenolic smell at least.

Ephoton - 27-9-2008 at 23:50

that sounds excellent kclo4

so many tried to convert the halide on
thouse toilet lollies.

my self to test for hydroquinone I would try percipitating gold with it.
phenol will not do this from my experiance.
(the phenol I used was 4methoxy phenol)

were as hydroquinone will leave either a red or violet percipitate (or collodial
solution if only small amounts of gold is used.)

I would love to try this

either the chlorophenol or the hydroquinone would make me say goodbye to a supplier

[Edited on 28-9-2008 by Ephoton]

raiden - 28-9-2008 at 00:22

Does anybody have any info regarding sesamol to piperonal/safrole?

Cheers.

not_important - 28-9-2008 at 00:43

Adding strong aqueous NaOH to the cooled reaction mix, then distilling off the MeOH, cooling to 30-40 C, and filtering will separate unreacted dichlorobenzene. Saturating the filtrate with CO2, or dropping the pH to around 6, and chilling should precipitate most of any p-chlorophenol out, leaving hydroquinone in solution. Note that alkaline solutions of hydroquinone are easily oxidised by air.

kclo4 - 28-9-2008 at 01:17

Quote:

Originally posted by raiden
Does anybody have any info regarding sesamol to piperonal/safrole?

Cheers.

no clue, but I do know of some other ways to Piperonal/safrole if you're interested.

Perhaps oxidize the OH with oxone into a ketone, if thats even possible?

____________________________________________

err, my solution of "chlorophenol" has crystals in it, and more form when it gets colder, but it only increases a very very slight amount. Perhaps I have it to acidic with HCl? Does anyone have a solubility chart for 4-Chlorophenol? I've been looking but I have been unable to find anything on it.

Not_Important, that is almost exactly what I did, except for my pH is probably a lot lower - would this explain my crystallization problem?

Ephoton - 28-9-2008 at 03:11

why bother going to md when mmd -2 is better and stronger anyway.

what about if you used the gold solution to reduce the hydroquinone to
quinone then used an organic solvent to extract both the chlorophenol and
the quinone. then use a base in water to turn the phenol into a salt leaving the
quinone in the organic solvent.

the gold will percipitate all you need to do is the normal disolve then clean of
oxidizing agent to get it ready to clean the chlorophenol again.

you would probably loose very little gold each time you did this too so it would
be very very recyclable.

crystals hmmm hydroquinone from water makes thin needles if that helps.

[Edited on 28-9-2008 by Ephoton]

kclo4 - 28-9-2008 at 11:30

Quote:

Originally posted by Ephoton
why bother going to md when mmd -2 is better and stronger anyway.

What do you mean by md and mmd -2?

Quote:

what about if you used the gold solution to reduce the hydroquinone to
quinone then used an organic solvent to extract both the chlorophenol and
the quinone.

I don't have gold, and its pretty expensive

Quote:

then use a base in water to turn the phenol into a salt leaving the
quinone in the organic solvent.

I do like this idea however! Quinone could probably be produced another way with out gold and also with out destroying the chlorophenol.

Quote:

crystals hmmm hydroquinone from water makes thin needles if that helps.

But do you know if chlorophenol does also?
I know phenol crystals are thin needles also.

Thanks for the idea!

Nicodem - 29-9-2008 at 00:53

Quote:

Originally posted by kclo4
I've been trying to make chlorophenol lately via NaOH and an excess P-dichlorobenzene in methanol + a small amount of sulfur, since I thought the sulfur might work as some sort of catalyst. I believe I have succeeded in making approximately 20grams of chlorophenol, but I need a way to test if it is Hydroquinone because I fear that might be a significant side reaction. I doubt it but I'm not to sure if 4-chlorophenol would more willingly replace its chlorine for a hydroxyl group more easily then P-dichlorobenzene would.

Obviously there can be no reaction between p-dichlorobenzene and NaOH in methanol unless you heat to >200°C which requires an autoclave. Such a benzyne mediated reaction would however give you a mixture of 3- and 4-chloroanisole as well as 1,2-, 1,3- and 1,4-dimethoxybenzene (and a bunch of minor side products including the toxic chlorophenolic crap). If you ever make any 4-chlorophenol or other chlorophenols even in trace amounts, you will immediately know as it is has annoyingly insidious smell that sticks on you and your clothes for months. It is also quite toxic!

Panache: Avoid abusing this thread for your "jokes".
Ephoton: Reply in line of the question and do not diverge the topic.

starman - 29-9-2008 at 17:28

Quote:

Originally posted by raiden
Does anybody have any info regarding sesamol to piperonal/safrole?

Cheers.

Your serious? Phenolic group to unsaturated allyl group.Well some of the members may be knowledgable enough to come up with that in a home lab,although the robustness of the MD grouping to survive would be suspect.
I think you are probably more interested in the ketone derivative,try wetdreams,they have an entire forum dedicated to the subject.You may also want to research penalties for listed pecursors in your region.

kclo4 - 29-9-2008 at 20:29

Nicodem, your right. I had mistaken some weird solution of "stuff" that formed for chlorophenol. I wasn't to sure what was happening, but Sodium Chloride did precipitate and that's why i wanted to test for things. Thanks for letting me know!

Penalties for precursors?
Do you have a reliable source for that sort of information regarding people in the US?

starman - 29-9-2008 at 20:54

Penalties for precursors?
Do you have a reliable source for that sort of information regarding people in the US?

The US...no.

My part of the world .... Possession of a small quantity of safrole "without lawful excuse"
(= assumed guilty of a crime regadless of legitimate explanation) punishable by up to 5 years jail and/or $25 000 fine.

Nicodem - 30-9-2008 at 01:20

Quote:

Originally posted by starman

Quote:

Originally posted by raiden
Does anybody have any info regarding sesamol to piperonal/safrole?

Cheers.

Aryl triflates can be used in the Heck and Sonogashira couplings (quite possibly also for the Neigishi and Kumada couplings, but I'm not sure). Obviously 1,3-benzodioxol-5-yl triflate can be prepared from sesamol just like any other phenyl triflate. It is only a question of choosing a proper substrate to couple this triflate with, so that the cleavage/modification to safrol or piperonal is possible in a simple way. However, anybody who bothered checking the price of sesamol and the reagents required will realize it is a pretty stupid idea to use such a route for preparing a substrate such as piperonal which is relatively cheap and/or can be prepared by much simpler means.

Jor - 30-9-2008 at 02:55

I have 3 containers of zinc chloride here. They are supposed to be all anhydrous. One is still sealed, 250g p.A Merck. Two are from an eBay supplier, who repacks his chems. Now, Im donating one of the containers from eBay supplier to another hobby chemist in uni. But I'm not really sure if the stuff from eBay is really anhydrous. It does not fume, does not react with room temperature water, and does look crystaline. When dropped into heated water in a test tube, it bubbles vigorously, but maybe this is just because the water is already above the boiling point, but can't boil due to the smooth test tube.
I do not want to open the Merck container, it's still sealed, and it would reduce the quality.
Is there any way to quickly determine whether it's anhydrous or not, with a 100% certain outcome?

Klute - 30-9-2008 at 04:52

You could try dissolving it in a aprotic solvent such dioxane or toluene (not sur eof the solubilities though). I guess if it's sufficently hydrated, it will not dissolve at all where as the anhydrous would be soluble (just a guess though).

I think anhydrous ZnCl2 is a cristallin solid anyway, so that should be a criteria for judging it's water content. Try heating a small sample in a tube with a flamme, and see if water condenses on the sides (even if you ahev decomposition to the oxychlorie or similar)

or just throw some SOCl2 onto it, as for oxalic acid

EDIT:

BTW, I would build myself a cheap dry box, and repack the ZnCl2 in small 2-10g containers as to not waste the whole container after opening it a few times. A sealed dry box is very easy to build, and is really practical to weigh/handle moisture sensitive products with no concern (I even use it for NaBH4 etc because it's easy to use and make your reagents last longer).

use some CaCl2 or NaOH (depending on the sensibility of the reagent) to dry the box for a few hours (I just leave 200-300g CaCl2 in it at all times), with your containers spatula etc inside, and then do your repackaging/weighing safely.

I can post a pic of the dry box if you want, cost me under 10e to make, and a couple hours work.

[Edited on 30-9-2008 by Klute]

Jor - 30-9-2008 at 05:28

Yes sure, post a picture, that'd be nice

. I was thinking of building some sort of dry box before, my idea was a small box, with CaCl2 in it, the leave the spatula and container of chemical in the box for few hours, then open the container with gloves integrated in the box (like a glovebox, but then much more simple).
I will try dissolving it in some solvent. I have at hand methanol, ethanol, acetone, benzene, DCM, ethyl acetate, Ligroin (high boiling hydrocarbons), diethyl ether, GAA.
I think the hydrate will dissolve in methanol, ethanol and GAA, but I will try AcOEt, DCM, and acetone. Benzene I'm not so sure, I rather only use it when my hood is finally done.
I don't have toluene :O. Well I do have 'Thinner' but it other crap as well like xylenes. Dioxane, I don't see a single reason why I would ever buy that stuff, Ive hardly ever yet seen a synthesis involving it. Besides it probably carcinogenic.

SOCl2. Well I could try that in a few days when my thionyl chloride arrives. But still ZnCl2 will always contain SOME water, so there will be a reaction anyway.

[Edited on 30-9-2008 by Jor]

DJF90 - 30-9-2008 at 05:28

Pictures are always good. What materials did you build it from? And what did you used to seal the joints?

Klute - 30-9-2008 at 06:01

I used a cheap transparent platic box, some PVC tubing, some washing gloves, and silicon to seal all the connection. The lid/box seal was improved by applying a layer of "elastic" silicon , and letting it dry without the lid on, so that when the lid is on the silicon is pressed down and the box is sealed properly.

I will post some pictures in the Tour my lab thread.

Jor - 30-9-2008 at 08:12

Ok, I'm quite convenient that it is anhydrous ZnCl2 now.

-Heating in a test tube results is melting, and a slightly yellow liquid is formed. The temperature in the tube is far above 100C, I think at least 200C (used alcohol burner, with absolute alcohol technical grade as the fuel). No fumes or condensing water are observed whatsoever.
Adding water after the liquid has solidified results in complete dissolution and formation of clear liquid.
-Adding about 100mg of the material to 2mL p.a. Acros acetone (wich is thus very dry, so hardly any formation of possible hydrate). Solid completely dissolves and forms clear solution wich appears a little turbid but if you look good it is completely clear.
-Adding 2mL of very pure diethyl ether to about 100mg results in partial dissolution, however most of the ZnCl2 does not dissolve.

http://www.acros.be/DesktopModules/Acros_Search_Results/Acro...

It should be soluble in ether, however it is not mentioned how much dissolves.

Based of the 1st experiment I assume I have the anhydrous material. Im not sure if hydrated zinc chloride dissolves in acetone, so the 1nd is unsure.

Klute - 30-9-2008 at 15:09

Has anyone used sodium isopropoxide in IPA for b-ketoester alkylations (AcAcOEt to be precise)? Or do you see any reasons why it would work as well as EtONA/EtOH? I would prefer using IPA to ethanol, as it is less of a pain to dry than the latter (and I have anhydrous IPA, but only 96% EtOH at hand).

Or could I just stick to acetone/K2CO3, using quite reactive benzyl halides?

Panache - 30-9-2008 at 20:04

I can't remember if the pKa of organic acids that are solids at RT is quoted at their melting point or is it some standard solution of, thats the first question.
Secondly if someone could bash out for me how much of an excess of malic acid over sodium propionate i would require to effectively completely protonate all of the propionate. I must go and buy a scientific calculator, i started using the log tables in the crc but quickly decided fuck that. I will love you forever.
Relevant data,
Malic acid, MW=134, pKa1=3.4, pKa2=5.13
Propanoic acid,MW=74, pKa=4.88, inverse log is the dissocation constant for sodium propionate.

If it turns out too great an excess could you quickly check the numbers for
citric acid,
MW=192 pKa1=3.15, pKa2=4.77, pKa3=6.40,
this may be a better option.

Loving you in advance!!!! Thanks!!!!

Nicodem - 30-9-2008 at 23:22

Panache, the pKa of solid acids has nothing to do with their state when pure. All pKa values are always reported for a specific solvent since the acidity is highly dependent on solvent. If no solvent is reported then it is assumed the pKa value stands for a water solution as the standard solvent.
The pKa stands for the negative decadic logarithm of the (de)protonation equilibrium constant. So, if you need the equilibrium equation of a mixture of an acid (malic acid) and base (propionate anions) in water solution, it is simply the difference of the two constants "deloged". Unfortunately malic acid has two pKa values which complicates things a lot and you will need someone with some knowledge in mathematics to solve the problem (I'm clueless when it comes to mathematics). You could ignore the pKa2 of malic acid if c(malic acid)>>c(propionate), but this would be a source of (potentially big) error:

Ka1(malic acid) = -([malonate][H3O+] / [malic acid])
Ka(propionic acid) = -([propionate][H3O+] / [propionic acid])
K = [malonate][propionic acid] / [malic acid][propionate] = 10^(pKa(propionic acid)-pKa1(malic acid)) = 30.2

So an quimolar mixture of malic acid and propionate would consist of a malonate : malic acid = propionic acid : propionate in a ratio of ~30 (when ignoring the pKa2 of malic acid). The ratio would be even slightly higher when not ignoring the pKa2. Obviously it is not possible to fully protonate the propionate to form only propionic acid since this would require an infinite concentration of malic acid. Therefore, essentially the answer to your question is that it is impossible to completely protonate the propionate anion using malic acid, but you can reach an approximately 97% protonation just by mixing your propionate with an equivalent molar amount of malic acid.

Quote:

Originally posted by Klute
Has anyone used sodium isopropoxide in IPA for b-ketoester alkylations (AcAcOEt to be precise)? Or do you see any reasons why it would work as well as EtONA/EtOH? I would prefer using IPA to ethanol, as it is less of a pain to dry than the latter (and I have anhydrous IPA, but only 96% EtOH at hand).

Or could I just stick to acetone/K2CO3, using quite reactive benzyl halides?

I have used both NaOH/EtOH, NaOEt/MeOH, NaOEt/MeOH/PhMe for C-benzylating ethyl acetoacetate or diethyl malonate (the reason why I did not used EtOH as solvent, like usually done, was because I had no absolute ethanol). NaOH/EtOH worked well on ethyl acetate even when the ethanol used was 96% (but fails miserably on diethyl malonate). NaOEt/MeOH gives poor yields (I don't remember if I used it for the acetylacetate or malonate), perhaps due to the low reflux temperature. A mixture of MeOH/PhMe with a longer reflux worked a better. This is from memory - I should check my lab notes to be sure. But in essence I think isopropanol will work just fine, though you might end up with some transesterification (which I guess is irrelevant since you will probably hydrolyse/decarboxylate your product anyway).

K2CO3/acetone is unlikely to work.

Klute - 1-10-2008 at 08:23

Well, I have an old patent (US 1 094 417) where AcAcOEt is C-benzylated with 4-MeOBnCl in moderate yields (~50%) using acetone and K2CO3, but they don't specify the amount of K2CO3 used and reflux for 12h...

But indeed i better stick to more conventional reaction conditons.

If you find you notes or remember more details, I'd love to hear them.

I have solid NaOMe and NaH, so might try the methoxid'e in MeOH and toluene at first, and then jump to NaH/IPA if it doresn work as well as I would like it to. Thanks for tips.

12AX7 - 1-10-2008 at 09:15

Quote:

Originally posted by Panache
I must go and buy a scientific calculator

Windows+R
"calc"
<ENTER>
View, Scientific

Tim

solo - 1-10-2008 at 11:15

In a reduction amination reaction when the ketone isn't soluble in methanol but soluble in ethylacetate, and ethyl acetate has a solubility of 8.3gr/100ml H2O ...my question is can the reaction be run in this solvent as a transition solvent without running the risk of any side reactions.............solo

Klute - 1-10-2008 at 12:39

What reducting agent will be used? NaBH4? catalytic hydrogenation?

Will the amine be used anhydrous or as an aqueous solution? have you tested the solubility of the ketone in other alcohols, like IPA or even EtOH?

solo - 1-10-2008 at 13:09

The reducing agent ill be through Pd/C via catalytic hydrogenation and the amine will be in water....will try the iso propanol alcohol, however since ethylacetate is soluble in alcohol and there is some solubility of water in ethyl acetate and in alcohol It may be enough to allow the reaction to go forward.....solo

querjek - 1-10-2008 at 18:24

I was reading this the other day:

http://orgsyn.org/orgsyn/prep.asp?prep=cv4p0866

And was hoping to find anything more about the same/similar reactions on aldehydation of aromatic rings; I've tried numerous Google searches and searches here but haven't come up with anything (and I can't find the fourth reference in that article, which is supposed to be the original procedure).

Also, can anyone tell me why/under what conditions phenols polymerize?

Thanks!

12AX7 - 1-10-2008 at 20:47

The word is "formylation".

Interesting synthesis, a bit perplexing. I suppose the glycerol is a polar solvent to help deal with the ammonia and substitution? An odd choice as a solvent, it's often quite reactive. Maybe that's part of the reason it turns black. I don't get the boric acid, and just about enough is added to take up the ammonia, but ammonia still bubbles out of it (that must be a foamy mess!). The tight temperatures and exothermy looks tricky as hell to get to work first time. Maybe even second time.

The textbook addition consists of aromatic substitution, which in analogy to any other acylation, means using formyl chloride, CHOCl, which doesn't exist in a bottle so is created in situ using formylating agents.

Phenol polymerizes under conditions of formaldahyde, for instance. That makes bakelite. Methylene bridges substitute the ring at the ortho/para positions, eliminating H2O. This is the most connective reaction (a potential of three links per phenol -- now that's a rigid plastic), but others take place, such as monosubstitution (leaving a -CH2OH on a ring) and linking the hydroxyls and even some ether bridges.

Phenols in general? Depends. Phenols in general are strongly activated at the ortho/para locations, so unless substituents are blocking those positions, whatever can happen, will. Even if blocked, the substituents might be reasonable substrate, carbonyls (at or adjecent to the ring) for instance. Benzylic carbons are somewhat acidic as is.

Tim

Klute - 1-10-2008 at 22:25

Better look at Mg methoxide/paraformaldehdye formylation of phenols, the conditions are much less ahrsh and the reaction is very selective and high yielding with sufficently activated substrates. There a thread on this in the Prepublication forum

Nicodem - 1-10-2008 at 23:00

Quote:

Originally posted by querjek
I was reading this the other day:

http://orgsyn.org/orgsyn/prep.asp?prep=cv4p0866

And was hoping to find anything more about the same/similar reactions on aldehydation of aromatic rings; I've tried numerous Google searches and searches here but haven't come up with anything (and I can't find the fourth reference in that article, which is supposed to be the original procedure).

You probably did not use the correct search terms. Actually it is obvious you did not, since you call the reaction "aldehydation". The reaction is a formylation and is called the Duff reaction. The electrophile is the protonated hexamine and the intermediate the same as in the Sommelet reaction (the N-benzyl-hexaminium cation). The original version used glyceroboric acid as catalyst (made in situ from glycerol and boric acid), but the new or so called modified Duff reaction uses carboxylic acids as both solvent and catalyst. It only work on reactive phenols. There are versions using AcOH or mixtures of HCOOH/AcOH, while the use of trifluoroacetic acid allows for the formylation of even less nucleophilic aromatic systems than phenols.

Quote:

Also, can anyone tell me why/under what conditions phenols polymerize?

Simple phenols do not polymerize unless they have a polymerizable double bond or other such functional groups. They can polymerize by condensation with some electrophiles like formaldehyde, glyoxal, etc. In such case the intermediate o,p-hydroxybenzyl alcohols condense with other phenolic moieties (via acid catalysed Friedel-Crafts benzylation) yielding a crossed polymer. The classical such polymer is bakelite which can be prepared by condensing phenol with formaldehyde under acidic conditions (for example using H2SO4 as catalyst).

solo - 2-10-2008 at 06:54

In a recent experiment with aldehyde rearrangement the conversion to the desired ketone results in a thick emulsion which has all the properties of a polymerized failed reaction......during the process all the experimental instructions were followed ....however after the reaction and prior to the distillation of the ketone from the non polar solution containing the ketone the mixture was washed with both brine solution and a carbonate solution ....which in fact might have just contributed to the polymerization of the unreacted aldehyde as all was fine till the last wash with plain water where all the solution turn to milk.....left alone for two days at which time the non polar has separated from the water and of course once the non polar was distilled off at 25mm the remaining material refused to give forth the ketone at the indicated temp at 25mmm and only a honey remained.......so is it possible that the aldehyde might have gone through some base catalyzed aldol condensation which would polymerize the material........

Quote:

These oxygen containing compounds,particularly acetaldehyde, will undergo polymerization in the presence ofthe basic wash or scrubbing conditions.

..................source,

US Patent 5160425 - Method of inhibiting formation of fouling materials during basic washing of hydrocarbons contaminated with oxygen compounds

Klute - 2-10-2008 at 08:20

But if the workup described a basic wash, the compound can't be that sensible? Perhaps alot of unreacted aldehdye was left for what ever reason, and a aldol was caused by the washes, but I'm surprised it would happen so quick.. Maybe using a very dilute, cold NaHCO3 wash next time might minimze things. But I don't think that wash is responsible for the faimure of the reaction, i guess it's something to to with the recation conditiosn properly spoken off.

solo - 2-10-2008 at 08:52

Quote:

Originally posted by Klute
But if the workup described a basic wash, the compound can't be that sensible? Perhaps alot of unreacted aldehdye was left for what ever reason, and a aldol was caused by the washes, but I'm surprised it would happen so quick.. Maybe using a very dilute, cold NaHCO3 wash next time might minimze things. But I don't think that wash is responsible for the faimure of the reaction, i guess it's something to to with the recation conditiosn properly spoken off.

....

......the original russian study never mentioned any washes it's the later efforts reported where they go into the washes many with similar failures while others has success....will try the reaction without the wash as all the temps were carefully monitored....Danilov's rearrangement has been tried by many with only two reported success stories ....one with the wash and the other without , at lest it wasn't mentioned....the material does have the ketone scent but it's chained up in a monster polymer that won't let go ....may also try to cross the barrier with the material in ethylacetate and adding the bisulfite in alcohol and water, to see if it can pull it out......solo

ssdd - 3-10-2008 at 15:07

How large must a molecule containing an amine in the form of an HCL salt be to not be soluble in water.

I know as a general rule most HCl salts of amines are soluble in water, but when does the molecule become to large if at all? Are there any exceptions to the above rule?

-ssdd

Klute - 4-10-2008 at 05:27

I don't have the precise examples in head, but yes I am sure some HCl salts are sparingly soluble, or even not at all. I will try to find some examples. I think it has soemthing to do with the gloabl polarity of the molecule and stearic hindrance of the ammonium function, and the size obviously. I don't know if there is a universal rule though.

kclo4 - 5-10-2008 at 13:31

I am unable to find a synthesis for Benzoic acid from Toluene via KMnO4.

I imagine its just add a solution of KMnO4 to Toluene and reflux/stir a lot, or something like that, but I'd rather take the guess work out of it do something that works.

Do I add an excess of toluene or just stoichiometric amounts, etc?

3 C6H4CH3 + 2 KMnO4 + KOH = 3 C6H4COOK + 2 MnO2 + H2O
Is its reaction, right?

[Edited on 5-10-2008 by kclo4]

Pages: 1 2 3 .. 7