Sciencemadness Discussion Board

Acetylene + 2-propanol

gl92038 - 15-1-2012 at 06:28

Good Day, I have 3 questions
1)Is this scheme correct
2)If yes, what are the conditions of this reaction.
3)And what are the presumable properties of the product.
Thank you:)

Something.PNG - 4kB

ThatchemistKid - 15-1-2012 at 10:57

I Cannot figure out a mechanism or conditions to make that work, I searched through some radical reactions with AIBN and Bu3SnH etc, nothing that gives the radical on the oxygen causing it to then reaction with an acetylene or a double bond, the O-H bond is just too stable that its formation competes with any other reaction and its rate is seemingly much faster.

Usually though such molecules can be accessed through enolates, captured enolates such as silyl enol ethers or even possibly an enolate reacting with with an electrophilic carbon with HMPA as an additive in the reaction mixture.

Silyl enol ethers are generally made by reaction of the ketone with a base such as LDA or KH, other more or less hindered lithium amide bases, depending on whether you want the thermodynamic or kinetic enolate and whether you want the E or Z isomer of your enolate. after the enolate is formed it is reacted with a trialkyl silyl chloride usually such as TMS-Cl,
if you want to read more about silyl enol ethers a quick stop to the wiki page and
might be helpful.

in your case, you would have to react the enolate of acetyl aldehyde ( so there is distinguishing E/Z isomers and thermo/kinetic products, which is always a plus) with a carbon electrophile such as 2-propyl bromide and Hexamethylphosphoramide, in DMSO or DMF (HMPA as well as DMSO and DMF are used to relieve aggregation of the negatively charged oxygen formed and the lewis acidic cation counterion of the base used via chelation to the cation, thereby making the oxygen more open to nucelophilic attack, essentially affecting O-alkylation vs C alkylation). This presents many problems, enolization of acetyl aldehyde tends to give lots of crap polymerization (though you might be able to use acetyl aldehyde generated from paraldehyde). Reaction with LDA may afford reduction products because of a tendency of aldehydes to undergo a reaction akin to the Meerwein-Ponndorf-Verley reduction with LDA ( Also your carbon electrophile is a secondary carbon and you will have elimination by-products.

there are other methods to get to what you are looking for. Do you have a proposed mechanism for your reaction,
(maybe one that is a large oversight on my part)?
Where did you get the idea to do this and what for?

ThatchemistKid - 15-1-2012 at 11:03

Foot in mouth! actually you can form that product from those reactants using chemistry known as Reppe chemistry.
I know nothing about this, though it seems you need a metal catalyst and high pressure to afford the transformation, not commonly had at home.

ScienceSquirrel - 15-1-2012 at 16:53

Reppe chemilstry is still used industrially though less than in previous times as acetylene has fallen out of favour as a starting material.
Organometallic courses tend to focus on newer and sexier catalysts and processes.
But it is still a good way to make some things eg cyclooctatetraene aka COT which is a popular ligand and starting material for other research.

ThatchemistKid - 15-1-2012 at 17:34

both my graduate organometallic courses ( one taught by an inorganic chemist and one taught be an organic chemist so I feel ill get a full picture of the topic :D ) are next quarter would you mind giving me some examples of the catalysts used in the process? or some links or refs to stuff I can read.

ScienceSquirrel - 16-1-2012 at 05:42

Organometallic chemistry is a vast field with lots of industrial examples.
Good industrial examples are;
Ziegler- Natta
Monsanto and Cativa

Thats enough processes - Ed :)

[Edited on 16-1-2012 by ScienceSquirrel]

smuv - 16-1-2012 at 11:02

There are conditions to give ethyl vinyl ether listed in organicum (sp? the old german practical organic text). IIRC the conditions are KOH in alcohol in a bomb, with acetylene under moderate (<100 psi) pressure. I suspect the same conditions would work for isopropanol.