The compound which gives the most stable carbonium ion on dehydration is

Options

A. `CH_3 - underset(CH_3)underset(|) CH -CH_2 OH`
B. `CH_3 - underset(CH_3) underset(|) overset(CH_3) overset(|) C-OH`
C. `CH_3 CH_2 CH_2 CH_2 OH`
D. `CH_3 - underset(OH) underset(|) CH - CH_2 -CH_3`

Explanation

To determine which compound gives the most stable carbonium ion (carbocation) upon dehydration, we need to analyze the stability of carbocations formed from different alcohols. Here’s a step-by-step solution:

### Step 1: Understand Carbocation Stability
Carbocations are positively charged carbon species, and their stability is influenced by the number of alkyl groups attached to the positively charged carbon. The general order of stability for carbocations is:
- Tertiary (3°) > Secondary (2°) > Primary (1°) > Methyl (0°)

### Step 2: Identify the Alcohols
We need to consider the alcohols that can undergo dehydration to form carbocations. Common alcohols include:
- Tertiary alcohols (3°)
- Secondary alcohols (2°)
- Primary alcohols (1°)

### Step 3: Analyze the Given Compound
The compound given in the video transcript is:
- CH3-C(OH)(CH3)-CH3 (which is a tertiary alcohol)

### Step 4: Predict the Carbocation Formation
Upon dehydration (loss of water), the tertiary alcohol will lose a water molecule to form a tertiary carbocation:
- CH3-C(OH)(CH3)-CH3 → CH3-C+(CH3)-CH3 + H2O

### Step 5: Determine the Stability of the Carbocation
Since the carbocation formed is tertiary, it is the most stable type of carbocation due to the +I (inductive) effect of the three alkyl groups surrounding the positively charged carbon.

### Conclusion
The compound that gives the most stable carbonium ion upon dehydration is the tertiary alcohol CH3-C(OH)(CH3)-CH3.

### Final Answer:
The correct option is the tertiary alcohol: CH3-C(OH)(CH3)-CH3.

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