Q which grape of potential energy $v_S{c}_1-c_2$ bond rotation $(0-360)$ is the best represen$-?$ tation of chloroethane?

$($a$)$

$($b$)$

$($c$)$

$($d$)$

$(27)$ In the friedel$-$Crafts reaction, with benzene with $Al{C}_3,$ why is propanoyl choloride preferred to $1-$choluropropane in eventually generating propylbenzene?

$($a$)$ the chlorine atom is easier to move

$($b$)$ it avoids the problem of hydride shift