The other day I converted the carboxylic acid salts in a bar of soap into methyl esters using a Fisher ester synthesis. I then used GCMS to examine the mixture.
I found that the soap contained C12, C14, C16 and C18 carboxylic acids. This made me think.
I know that living things normally only make even carbon carboxylic acids as their fatty acids, but I started to think of some of the alternatives.
1. Could SHOP (Shell Higher Olefins Process) be used to make oligomers of ethylene which could then be converted by a modified hydroformylation into carboxylic acids ?
Answer, no such an industrial synthesis would make odd carbon fatty acids. SHOP will make olefins with even numbers of carbons, the hydroformylation will add a single carbon atom to the chain thus making an odd carbon chain aldehyde.
2. Could SHOP be used to make a mixture of alkenes which could then be converted by Wacker chemistry into aldehydes and then into carboxylic acids.
Answer, no. While the Wacker process makes ethanal (acealdehyde) from ethylene (ethene) the related process published by Jiro Tsuji et. al. forms methyl ketones and not aldehydes. So this method can not be used to make the fatty acids.
3. Maybe is could just be the case that the carboxylic acids were made in a green plant two carbons at a time.
If anyone can think of some alternative method for making the even carbon fatty acids in bulk then please suggest it in the comments.
Filed under: Chemistry |