Ochem Question: AAMC 8 #121

[happyfellow]

Which of the following is the most plausible explanation for the fact that the saponification of a triacylglycerol resulted in four different fatty acid salts?

A. the triacylglycerol molecule consisted of four different fatty acid units
B. glycerol was transformed into a fatty acid salt under the reaction conditions
C. one of the fatty acid salts was unsaturated, and it completely isomerized under the reaction conditions
D. one of the fatty acid salts was unsaturated, and a small percentage isomerized under the reaction conditions

I picked B, and nothing else seems correct. There's only 3 fatty acids attached to the glycerol backbone...Any guidance would be much appreciated!

Happy

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[luctoretemergo]

wrong answer

 

[happyfellow]

If I remember correctly, one of the carbons (the one in the middle of the chain) is chiral and thus will create a racemic product (2 diff products/enantiomers) hence 4 products instead of 3.

...but the chains are hydrocarbons and there's no chiral centers. The only chiral center is in the glycerol backbone when the triacylglycerol is intact and the question is asking why we get 4 fatty acids

 

[Rayhaan]

The answer is D. If it's unsaturated the reaction conditions may change that double bond. A and B don't make any sense. And C wouldn't allow for 4 products.

 

[orgohacks]

The answer is D. If it's unsaturated the reaction conditions may change that double bond. A and B don't make any sense. And C wouldn't allow for 4 products.

Good answer.