Question
Arrangement of $${\left( {C{H_3}} \right)_3}C - ,{\left( {C{H_3}} \right)_2}CH - ,C{H_3} - C{H_2} - $$ when attached to benzyl or an unsaturated group in increasing order of inductive effect is
A.
$${\left( {C{H_3}} \right)_3}C - < {\left( {C{H_3}} \right)_2}CH - < C{H_3} - C{H_2}$$
B.
$$C{H_3} - C{H_2} - < {\left( {C{H_3}} \right)_2}CH - < {\left( {C{H_3}} \right)_3}C - $$
C.
$${\left( {C{H_3}} \right)_2}CH - < {\left( {C{H_3}} \right)_3}C - < C{H_3}, - C{H_2}$$
D.
$${\left( {C{H_3}} \right)_3}C - < C{H_3} - C{H_2} - {\left( {C{H_3}} \right)_2}CH - $$
Answer :
$$C{H_3} - C{H_2} - < {\left( {C{H_3}} \right)_2}CH - < {\left( {C{H_3}} \right)_3}C - $$
Solution :
$$ - C{H_3}$$ group has $$ + I$$ effect, as number of $$ - C{H_3}$$ group increases, the inductive effect increases.
Therefore the correct order is $$C{H_3} - C{H_2} - < {\left( {C{H_3}} \right)_2}CH - < {\left( {C{H_3}} \right)_3}C - $$