Ncert Exercises & Solutions

Which of the following is correct?

1. ${CH}_{3} - O - {CH}_{2}^{\oplus}$ is more stable than ${CH}_{3} - {CH}_{2}^{\oplus}$

2. ${({CH}_{3})}_{2} {CH}^{\oplus}$ is less stable than ${CH}_{3} - {CH}_{2} - {CH}_{2}^{\oplus}$

3. ${CH}_{2} = CH - {CH}_{2}^{\oplus}$ is more stable than ${CH}_{3} - {CH}_{2} - {CH}_{2}^{\oplus}$

4. ${CH}_{2} = {CH}^{\oplus}$ is more stable than ${CH}_{3} - {CH}_{2}^{\oplus}$

(1, 3)

(i) + I-effect increases the stability of carbocation +I-effect i.e.,

{CH}_{3} - O > - {CH}_{3}

. Thus

{CH}_{3} - O - \overset{+}{C} H_{2}

is more stable than

{CH}_{3} - \overset{+}{C} H_{2}

(ii)

{({CH}_{3})}_{2} {CH}^{+}

is more stable than

{CH}_{3} - {CH}_{2} - \overset{+}{C} H_{2}

because former has stabilised by + I-effect of two

- {CH}_{3}

groups.