Sciencemadness Discussion Board

Wittig Reaction

Sriraman - 5-9-2006 at 00:00

I am carrying out the Wittig reaction of 3-methoxy benzyl chloride with Triphenyl phosphine to give the salt and reacting with Salicylaldehyde in presence of DBU to give 2-(3-methoxystyryl)phenol. In this process lot of Triphenylphosphine oxide is formed, which is carried along with the product. The publications recommend column chromatography for separation of Thriphenylphosphine oxide. I want to carry out this as a large scale proess.
Can some one suggest how this Triphenylphosphine oxide be separated with out chromatography, either based on solubility or adduct formation.


Dr Sriraman

solo - 5-9-2006 at 07:04

Going through my files I found some articles of solubility separation and adduct information, that may be of some assistance.........solo

http://rapidshare.de/files/32046058/help_files.zip.html

triphenylphosphineoxide - 6-9-2006 at 08:45

Is your product being held in an oil?
If so and based on a wild arsed guess at 2-(3-methoxystyryl)phenol's solubility try dissolving some of the oil in toluene and allow to sit open and slowly evaporate. Do this slowly as the line between fully dissolved oil, seperated product, and regeneration of the original mess(now with added Toluene), is extremely fine.
In practice I have found that Column Chromatography really is the best way to seperate TPPO on a laboratory scale.

May you have better luck with this horrendous compound than I have had.
Post a description of your reaction product, whilst i take a look at 2-(3-methoxystyryl)phenol, something that failed for oxazines and thioureas may work for you.

Edit
Actually I have a few questions here, but sleep must come first Ican't work out what is bugging me.

[Edited on 6-9-2006 by triphenylphosphineoxide]

Wittig Reaction

Sriraman - 8-9-2006 at 19:26

Thank you very much for the references. The impurities present are mainly DBU and Triphenylphosphine oxide.
Basically I need to separate themon an industrial scale.

I shall be grateful if you can suggest something.

Sriraman

Sandmeyer - 9-9-2006 at 04:24

Quote:
Originally posted by Sriraman
Thank you very much for the references. The impurities present are mainly DBU and Triphenylphosphine oxide.
Basically I need to separate themon an industrial scale.

I shall be grateful if you can suggest something.

Sriraman


Why don't your corporation hire professional personel to work on the problem, as allready stated - this place not about increasing your profit margins but about amateur chemistry.

[Edited on 9-9-2006 by Sandmeyer]

Sriraman - 21-9-2006 at 18:56

In this reaction I also observe that there is unreated Salicyl aldehyde and the benzyl chloride which is formed back from the phosphonium chloride salt.

I feel Triphenylphosphine oxide can be separated only by solubility means. Can some one help me to get the solubility data.

Sriraman

solo - 22-9-2006 at 02:41

Ylid Intermediate in the Reaction of Triphenylphosphine with Carbon Tetrachloride
Rabinowitz
Journal of the American Chemical Society yr:1962 vol:84 iss:7 pg:1312


Excerp
...........The reaction mixture was conveniently worked up taking advantage
of the insolubility of triphenylphosphine oxide in ethyl ether and the much greater solubility of benzophenone in methanol than that of 1,l-diphenyldichloroethylene. The latter, m.p. 78.0- 78.5' was identified by comparison with an authentic sample.

Attachment: Ylid Intermediate in the Reaction of Triphenylphosphine with Carbon Tetrachloride.pdf (272kB)
This file has been downloaded 996 times

not_important - 22-9-2006 at 09:31

Solubility only works well when the products are fairly non-polar, allowing selective extract of or from the more polar triphenylphosphane oxide (and DBU salts). Too often the unreacted materials, product, and triphenylphosphane compounds drag some of each other along into whatever is being used as a solvent; countercurrent extraction might work to salvage some of those cases.

In some cases complex formation with d-block metal ions can facilitate separation, or at least it is claimed so.

Using polymer bound triphenylphosphane is a good method, this allows simple filtration to recover the product. This also allows for easier recovery of the oxide for regeneration of the 'triphenylphosphane' with chlorosilane.

I think there was a good idea given above - hire some industrial chemists in a backwards country like the US, where according to posts elsewhere they don't have access to sulfur or methane and need the work, and let them come up with solutions to the problem. Asking a bunch of hobbists might get you answers, but also might send you down paths that waste a good deal of time and money. It's one thing to take a chance using a homebrew method for making 50 cc of acetic anhydride using only OTC materials, another to bet a large scale industrial process on such information sources.


Edit - Nice reference there, solo



[Edited on 22-9-2006 by not_important]

Sandmeyer - 23-9-2006 at 12:52

Quote:
Originally posted by not_importantI think there was a good idea given above - hire some industrial chemists in a backwards country like the US, where according to posts elsewhere they don't have access to sulfur or methane and need the work, and let them come up with solutions to the problem. Asking a bunch of hobbists might get you answers, but also might send you down paths that waste a good deal of time and money. It's one thing to take a chance using a homebrew method for making 50 cc of acetic anhydride using only OTC materials, another to bet a large scale industrial process on such information sources.


[Edited on 22-9-2006 by not_important]


I didn't say that he could hire professional chemist to work on the problem since I'm of opinion that those who do chemistry mostly for the sake of money are more competent than those who have it (also) as a hobby/social activity (if that's what you think). I said it since it's (almost) as inapropriate as if someone selling software protection "solutions" would ask those on cracker/hacker forum/irc channel to come up with solutions (for free) for his corporation to use for financial gain. I hope the reasoning makes some sence.

[Edited on 23-9-2006 by Sandmeyer]

Wittig Reaction

Sriraman - 23-9-2006 at 23:27

Thank you all for the interesting debate posted on the problem of Wittig Reaction by me.

You all would agree with me that when reactions are performed in test tube or multi gallon reactors it is chemistry! only the method of working / technology changes with size of operation.

I have been in the industry for the past four decades and have translated numerous lab processes to industrial scale. many a times we get stuck on trivial mattrers like this where a separation has to be effected and we can share such views on the forum.

Sriraman

Sriraman - 23-9-2006 at 23:29

Can some one suggest who supplies polymer supported Triphenylphosphine oxide.

Dr M C Sriraman

Sandmeyer - 24-9-2006 at 03:46

Quote:
Originally posted by Sriraman
Can some one suggest who supplies polymer supported Triphenylphosphine oxide.

Dr M C Sriraman


I'm surprised that somone who has been in "industry for decades" dosen't own an Aldrich catalogue.

Sriraman - 24-9-2006 at 05:14

whaat I meant as supplier of Polymer supported Triphenylphosphine was for the commercial quantities.


Sriraman

solo - 24-9-2006 at 05:54

Synthesis and reactions of polymer-bound Ph3PCCO: a quick route to tenuazonic acid and other optically pure 5-substituted tetramates
Rainer Schobert*, Carsten Jagusch, Claire Melanophy and Gillian Mullen
Organic & Biomolecular Chemistry, 2004


Abstract
Polystyrene-bound cumulated ylide Ph3PCCO was prepared on a large scale in two steps. It reacts with Grignard compounds, amines and alcohols to give immobilized acyl, amide and ester ylides, respectively. Their Wittig reactions lead to alkenes free of phosphane oxide. Optically pure 5-substituted tetramates were obtained from reactions of resin-bound Ph3PCCO with -ammonium esters in one step. The mycotoxin (–)-tenuazonic acid was accordingly prepared in just three steps.:P

Attachment: Synthesis and reactions of polymer-bound Ph3PCCO.pdf (329kB)
This file has been downloaded 890 times

not_important - 24-9-2006 at 06:18

Most manufacturing companies will not tell a hobbist chemist the time of day, but will send metric tonnes of literature and pricing information to someone who works in the industry and can prove it.