Answer the questions about the following molecules Which of

Answer the questions about the following molecules: Which of these molecules would exhibit free rotation around all of their carbon-carbon bonds? Which would exhibit hindered rotation around one or more carbon-carbon bonds? Identify the location(s) of hindered rotation. Which two of these molecules are structural isomers of one another? Explain your choice. Which of these molecules have asymmetric carbon atoms in them? For those that do, identify the asymmetric carbons.

Solution

a).

(i) Molecules exhibiting free rotation around all the carbon-carbon bonds:

N-hexane; Acetone; Propanal; Serine; Glycine; Alanine

(ii) Molecules exhibiting hindered rotation around one or more carbon-carbon bonds:

1-Hexene

(iii) location of the hindrance is the double bond between first and second carbon of the chain.

b). Acetone and propanal are structural isomers of each other. Both these molecules have same empirical formulae (C₃H₆O) but different structural formulae.

c). Serine and alanine have asymmetric carbon in them.

In Serine, the chiral C is attached to COO^-, NH₃⁺ and H

In Alanine the chiral C is bonded with COO^-, NH₃⁺ and CH₃