Question

Which one of the following statements is correct?

• A. The major product formed when 2-methylpropene reacts with dilute \(H_2SO_4\) is tert-butyl alcohol.
• B. The electrophilic addition to an unsymmetrical alkene always occurs through the formation of a more stable carbanion intermediate.
• C. Between the two alkenes - (i) \((CH_3)_2C=CH-CH_3\) and (ii) \(C_6H_5-CH=CH-CH_2-CH_3\), compound (i) will show geometrical isomerism.
• D. Greater the number of alkyl groups attached to the double bonded carbon atoms, the less stable is the alkene.

Hint:

In electrophilic addition to alkenes, the major product is generally formed through the more stable carbocation intermediate. More substituted alkenes are more stable due to hyperconjugation and inductive effect.

Answer 1

The Correct Option is A

Step 1: Understanding the question.
We need to identify the correct statement related to reactions and stability of alkenes.
Each option must be checked using concepts of electrophilic addition, geometrical isomerism, and alkene stability.

Step 2: Checking option (A).
2-methylpropene is:
\[ (CH_3)_2C=CH_2 \] When it reacts with dilute \(H_2SO_4\), hydration occurs according to Markovnikov's rule.
The \(H^+\) adds to the terminal carbon, forming a more stable tertiary carbocation.
\[ (CH_3)_2C=CH_2 + H^+ \rightarrow (CH_3)_3C^+ \]

Step 3: Formation of tert-butyl alcohol.
The tertiary carbocation then reacts with water, followed by deprotonation, to give tert-butyl alcohol.
\[ (CH_3)_3C^+ + H_2O \rightarrow (CH_3)_3COH_2^+ \] \[ (CH_3)_3COH_2^+ \rightarrow (CH_3)_3COH + H^+ \] Thus, the major product is tert-butyl alcohol.
So, option (A) is correct.

Step 4: Checking option (B).
Electrophilic addition to an unsymmetrical alkene occurs through the formation of a more stable carbocation intermediate, not carbanion.
For example, in Markovnikov addition, the more stable carbocation decides the major product.
Hence, option (B) is incorrect.

Step 5: Checking option (C).
Compound (i) is:
\[ (CH_3)_2C=CH-CH_3 \] For geometrical isomerism, each double-bonded carbon must have two different groups attached to it.
In compound (i), one double-bonded carbon has two identical \(CH_3\) groups.
Therefore, compound (i) cannot show geometrical isomerism.
So, option (C) is incorrect.

Step 6: Checking option (D).
Alkene stability increases with increase in the number of alkyl groups attached to the double-bonded carbon atoms.
This is due to hyperconjugation and \(+I\) effect of alkyl groups.
Therefore, more substituted alkenes are more stable, not less stable.
So, option (D) is incorrect.

Step 7: Final conclusion.
Only option (A) is correct because 2-methylpropene undergoes acid-catalysed hydration to form tert-butyl alcohol as the major product.
\[ \boxed{\text{Option (A)}} \]