In: Biology
Predict the fatty acid with the highest melting point.
Select one:
a. trans 14:1 (7)
b. cis 14:2 (7,9)
c. trans 14:2 (7,9)
d. cis 14:3 (7,9,11)
Ans) a) trans14:1(7)
Explaination:Greater the number of double bond or higher the unsaturation lower the melting point because presence of double bond make unsaturated chain more rigid so no tight or dense packing so more the no of double bond more will be rigidity and less will be packing resulting in lower melting point.
Fatty acid Trans 14:1(7) has one double bond so have highest melting point as compare to other given options because other option have two and three double bond.
Fatty acid cis14:2(7,9) has two double bond and have less melting point than trans14:2(7,9) because cis bond forces a kink in the hydrocarbon chain. Fatty acid with kinks cannot pack together tightly hence lower melting point.
Fatty acid trans 14:2(7,9) has two double bond but in trans position so more melting point than cis 14:2(7,9) fatty acid.
Fatty acid Cis 14:3(7,9,11) has 3 double bond so has least melting point as compare to other .
So order of decreasing melting point is
Trans14:2(7)> trans14:2(7,9)>cis 14:2(7,9)> cis14:3(7,9,11).