Chemistry Question!!!!!?

Question

What is an optically pure triglyceride that provides two equivalents of pentanoic acid and one equivalent of butanoic acid after the KOH saponification of trimyristin to isolate myristic acid?? I don't even know how to begin to answer this question and would really appreciate any help!! Thank you!

Answer 1

A triglyceride is a glycerol molecule with all 3 -OH esterified with fatty acids.
Saponification is the hydrolysis of the ester bonds, giving glycerol and the salts of the acids.
So since you get 2 equivalents of pentanoic and 1 of butanoic it means the the 2 out of 3 -OH groups of glycerol are esterified with pentanoic acid and the remaining -OH group with butanoic.
You have 2 possibilities: either the 2 pentanoic acids are esterified with -OH on C1 and C2 or with the -OH on C1 and C3:

.. ..CH2-O-CO-CH2-CH2-CH2-CH3
.. ..l
H-C-O-CO-CH2-CH2-CH2-CH3
.. ..l
.. ..CH2-O-CO-CH2-CH2-CH3

You see that in this case the C-2 of glycerol has 4 different substituents so it is a chiral center and the molecule is optically active. Let's see in the other case what happens

.. ..CH2-O-CO-CH2-CH2-CH2-CH3
.. ..l
H-C-O-CO-CH2-CH2-CH3
.. ..l
.. ..CH2-O-CO-CH2-CH2-CH2-CH3

Now C-2 has 2 identical substituents so it is no longer a chiral center and the molecule is not active (Note that in either case all other C atoms have at least two identical substituents, that's why we don't bother to examine them)

So the first structure corresponds to the molecule you are looking for.