Question

Methylethylpropyl amine is optically inactive because
(i) It is not tetrahedral
(ii) Its molecule is superimposable on its mirror image
(iii) The enantiomers are rapidly interconverted
(iv) The nitrogen is ${sp}^2$ hybridized
Which of the above statement(s) is(are) true?

• A. Only (i)
• B. Only (iii)
• C. (i) and (iii)
• D. All the four

Answer 1

Answer: (B)

Only (iii)

Methylethylpropyl amine is optically inactive. It has a tetrahedral ($s{p}^3$) nitrogen atom, and the nitrogen lone pair in a $s{p}^3$ orbital. The tetrahedral amine structures are in equilibrium. Furthermore, these structures are enantiomers. These amine enantiomers have equal but opposite optical activity, so in the $1:1$ equilibrium the mixture is racemic and optically inactive.

Hence, the correct option is $\text{B}$