Question

The correct increasing order of the rate of reaction for alkyl halides undergoing $E_1$ and $E_2$ reaction respectively is:
Here,
$1^{\circ }\text{is primary alkyl halide}$
$2^{\circ }\text{is secondary alkyl halide}$
$3^{\circ }\text{is tertiary alkyl halide}$

• A. $E_1:1^{\circ }<2^{\circ }<3^{\circ }{E}_2:1^{\circ }<2^{\circ }<3^{\circ }$
• B. $E_1:1^{\circ }<2^{\circ }<3^{\circ }{E}_2:3^{\circ }<2^{\circ }<1^{\circ }$
• C. $E_1:3^{\circ }<2^{\circ }<1^{\circ }{E}_2:1^{\circ }<2^{\circ }<3^{\circ }$
• D. $E_1:3^{\circ }<2^{\circ }<1^{\circ }{E}_2:3^{\circ }<2^{\circ }<1^{\circ }$

Answer 1

The correct option is A $E_1:1^{\circ }<2^{\circ }<3^{\circ }{E}_2:1^{\circ }<2^{\circ }<3^{\circ }$

$\text{Rate of}{E}_1\text{reaction}\propto \text{Stability of carbocation formed from alkyl halide}$
For carbocation stability the order is:
$1^{\circ }<2^{\circ }<3^{\circ }$
So, the alkyl halides also follow the same order.
$\text{Primary alkyl halide}<\text{Secondary alkyl halide}<\text{Teritary alkyl halide}$

$\text{Rate of}{E}_2\text{reaction}\propto \text{Stability of alkene formed from alkyl halide}$

For alkene, stability order is:
$1^{\circ }<2^{\circ }<3^{\circ }$
So, the alkyl halides also follow the same order.
$\text{Primary alkyl halide}<\text{Secondary alkyl halide}<\text{Teritary alkyl halide}$