Organic Synthesis Help Required

[chemist101]

Hi there,

I'm a chemistry student in University just now and I've got a synthesis problem that is confusing me slightly. I can't seem to find help in any of my textbooks. The starting molecule for the reaction is a ketone. The reagents for use are H_2, a platinum catalyst and a carboxlic acid molecule. It is my understanding that the ketone will be reduced by the hydrogen and catalyst, to a secondary alcohol. It is also my understanding that the carboxylic acid cannot be reduced under these conditions as stronger reducing agents are required.

 

I am now wondering if the secondary alcohol and carboxylic acid will react together to form an ester? This would be the obvious end to the mechanism, however there aren't any other reagents for use other than the H₂ and platinum catalyst. Can an ester be formed under these conditions?

 

Thanks!

[studiot]

The platinum catalyst is also capable of adding hydrogen to the carbon chain as well as the ketonic oxygen.

 

But I'm sorry I couldn't properly determine you objective perhaps if you clarified it a bit some of the genuine organic chemists who log on later than I do might help.

[Elite Engineer]

You're thinking of an esterification reaction which requires a strong acid or base, not a platinum catalyst.

 

 

~EE

Edited April 21, 2015 by Elite Engineer

[studiot]

You're thinking of an esterification reaction which requires a strong acid or base, not a platinum catalyst.

 

 

~EE

 

Doesn't the ketone have a carbonyl group with a double bond between the carbon and oxygen which is reduced to a single bond to an OH group, leaving one bond free on the carbon that has the other half of the hydrogen molecule attached to it?

[Elite Engineer]

 

Doesn't the ketone have a carbonyl group with a double bond between the carbon and oxygen which is reduced to a single bond to an OH group, leaving one bond free on the carbon that has the other half of the hydrogen molecule attached to it?

Reduction of a ketone yields a secondary alcohol. There aren't any "open/free" bonds. Attached to the central carbon (after reduction) is a jhydrogen, 2 carbon atoms and a hydroxyl group.

[studiot]

Reduction of a ketone yields a secondary alcohol. There aren't any "open/free" bonds. Attached to the central carbon (after reduction) is a jhydrogen, 2 carbon atoms and a hydroxyl group.

 

That's what I said, but I can't draw molecues here.

 

RRC=O + H₂ goes to RRHC-OH

[Elite Engineer]

 

That's what I said, but I can't draw molecues here.

 

RRC=O + H₂ goes to RRHC-OH

Yep. And relative to the OP, there are no reagents present that can react the 2ndary alcohol with the carboxylic acid to form an ester.

[BabcockHall]

I am not as familiar with platinum as I am with palladium as a reduction catalyst. However, in McMurry's textbook, there is a reaction which shows an unsaturated ketone is reduced to a ketone in the presence of Pd and H₂. In other words, you can find conditions that would reduce the carbon-carbon double bond without reducing the ketone. A ketone would be more easily reduced using sodium borohydride.

[John Cuthber]

Acetic acid is used as a solvent for hydrogenations because the reaction is faster than with other solvents.

http://pubs.rsc.org/en/content/articlelanding/1938/jr/jr9380000454#!divAbstract

 

There is not enough information in the question to decide what the outcome is.

In reality, a mixture of the ester and the alcohol will probably be produced.