Question

Which of the following compounds do not exhibit hyperconjugation?
(a)$C{{H}_{3}}CH_{2}^{\bullet }$
(b) ${{(C{{H}_{3}})}_{2}}C{{H}^{\bullet }}$
(c) $C{{H}_{3}}CH=C{{H}_{2}}$
(d) ${{(C{{H}_{3}})}_{2}}C-CH_{2}^{+}$

Answer 1

Hint:The hyperconjugation is the overlapping g between the p-orbital or a pi-orbital and a sigma -orbital and in this the carbon next to $s{{p}^{2}}$ hybridized carbon should have the hydrogen bond attached to it. Now you can easily answer the given statement accordingly.

Complete step-by-step answer:First of let’s discuss what is hyperconjugation. Hyperconjugation is another kind of resonance or delocalization of the electrons which takes place through the overlap between the p-orbital or a pi-orbital and a sigma -orbital of an adjacent C-H bond.
Condition for the compounds to undergo hyperconjugation is that the carbon which is attached to the $s{{p}^{2}}$ hybridized carbon should have hydrogen attached to it.
Now considering the statement as;
In option (a) $C{{H}_{3}}CH_{2}^{\bullet }$ , the carbon attached to the $s{{p}^{2}}$ hybridized carbon consists of the hydrogen atom and thus, it exhibits hyperconjugation.
In option (b) ${{(C{{H}_{3}})}_{2}}C{{H}^{\bullet }}$, the carbon attached to the $s{{p}^{2}}$ hybridized carbon consists of the hydrogen atom and thus, it also exhibits hyperconjugation.
In option (c) $C{{H}_{3}}CH=C{{H}_{2}}$, the carbon attached to the $s{{p}^{2}}$ hybridized carbon consists of the hydrogen atom and thus, it also exhibits hyperconjugation.
In option (d) ${{(C{{H}_{3}})}_{2}}C-CH_{2}^{+}$, the carbon attached to the $s{{p}^{2}}$ hybridized carbon does not consist of the hydrogen atom and thus, it does not exhibit hyperconjugation.

Hence, option (d) is correct.

Note:Hyperconjugation helps to explain the relative stabilities of alkenes( i.e. which consists of the C=C bond), carbocations (i.e. which consists of the positive charge) and the free radicals(i.e. which consists of a single electron).