Apparently hydrogenation of fatty acids creates trans fatty acids. How does this happen? If anything, I would expect hydrogenation to eliminate carbon-carbon double bonds entirely, not cause them to flip from cis to trans form. Does it involve the partial hydrogenation of a alkyne bond? It's been a while since biochem, but I don't recall any fatty acids that contained alkynes.
How does hydrogenation create trans fatty acids?
- Thread starter Nasor
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Hydrogenation reduces the amount of double bonds, but those remaining aren't necessarily the original cis bonds.
Some single bonds get transformed back to double bonds as long as the catalyst is present. The new double bonds can be either cis or tras.
You can find the reaction mechanism here:
http://www.chemsoc.org/exemplarchem/entries/2001/caphane/lipids.html#hydrogenation
"If the catalyst were saturated with hydrogen, most double bonds would be expected to react and you would get the product, d.
By reducing the amount of hydrogen, the possibility of only one hydrogen atom reacting with a double bond increases. This may lead to the half hydrogenation, dehydrogenation sequence and isomerisation giving rise to e, g and f.
It is usually preferred to achieve a balance, minimising isomerisation but avoiding excessive formation of fully saturated materials.
There is an element of selectivity that varies with different catalysts. This may involve some of the double bonds being relocated or transformed from their usual cis configuration to trans. These isomers produced are known as iso acids."
Some single bonds get transformed back to double bonds as long as the catalyst is present. The new double bonds can be either cis or tras.
You can find the reaction mechanism here:
http://www.chemsoc.org/exemplarchem/entries/2001/caphane/lipids.html#hydrogenation
"If the catalyst were saturated with hydrogen, most double bonds would be expected to react and you would get the product, d.
By reducing the amount of hydrogen, the possibility of only one hydrogen atom reacting with a double bond increases. This may lead to the half hydrogenation, dehydrogenation sequence and isomerisation giving rise to e, g and f.
It is usually preferred to achieve a balance, minimising isomerisation but avoiding excessive formation of fully saturated materials.
There is an element of selectivity that varies with different catalysts. This may involve some of the double bonds being relocated or transformed from their usual cis configuration to trans. These isomers produced are known as iso acids."
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