Question

The least stable free radical is:
A.\[{{C}}{{{H}}_{{3}}}{{C}}{{{H}}^{^{{.}}}}_{{2}}\]
B.${{C}}{{{H}}_{{3}}}{{C}}{{{H}}_{{2}}}{{C}}{{{H}}^{^{{.}}}}_{{2}}$
C.${{{(C}}{{{H}}_{{3}}}{{)}}_{{2}}}{{C}}{{{H}}^{^{{.}}}}$
D.${{{(C}}{{{H}}_{{3}}}{{)}}_{{3}}}{{{C}}^{^{{.}}}}$
E.$^{^{{.}}}{{C}}{{{H}}_{{3}}}$

Answer 1

Hint:In chemistry, a radical is a chemical entity that has an unpaired valence electron. These unpaired electrons make radicals highly chemically reactive, with few exceptions. Most of the organic radicals have short lifetimes. Many radicals often dimerize spontaneously to attain stability.

Complete step by step answer:
The order of stability of organic free radicals is tertiary $ > $ secondary $ > $ primary. This is because as the number of alpha-hydrogens increases the stability of free radicals also increases. The alpha-hydrogens are the hydrogens attached to the carbon atom directly attached to the carbon radical.
\[{{C}}{{{H}}_{{3}}}{{C}}{{{H}}^{^{{.}}}}_{{2}}\] has 3 alpha hydrogens.
${{C}}{{{H}}_{{3}}}{{C}}{{{H}}_{{2}}}{{C}}{{{H}}^{^{{.}}}}_{{2}}$ has two alpha-hydrogens.
${{{(C}}{{{H}}_{{3}}}{{)}}_{{2}}}{{C}}{{{H}}^{^{{.}}}}$ has six alpha-hydrogens
${{{(C}}{{{H}}_{{3}}}{{)}}_{{3}}}{{{C}}^{^{{.}}}}$ has nine alpha alpha-hydrogens.
$^{^{{.}}}{{C}}{{{H}}_{{3}}}$ do not have any alpha hydrogens.
Since the stability of free radicals with the increase in the number of alpha-hydrogens. So the radical having the least number of alpha-hydrogens will be the least stable.
Therefore, $^{^{{.}}}{{C}}{{{H}}_{{3}}}$ will be the least stable free radical.
Radicals can be generated in any number of ways but the most widely used are redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis are also known to give free radicals. Radicals are mostly intermediates in many chemical reactions and can be trapped within a solvent cage.

Hence, the correct answer is option E.

Note:
Radicals are important in atmospheric chemistry, polymerization, plasma chemistry, combustion, biochemistry, and many other chemical processes. A majority of natural products are generated by radical-generating enzymes. In living organisms, a variety of free radicals can be found, for instance, superoxides and nitric oxides free radicals. The products of the reactions involving these radicals regulate many other life-sustaining processes such as control of vascular tone which in turn regulate the blood pressure.