Which of the follwing compounds will undergo Friedel Creadfts alylation with faster rate?

Options

A.
B.
C.
D.

Explanation

To determine which compound will undergo Friedel-Crafts alkylation at a faster rate, we need to analyze the effects of substituents on the benzene ring and their influence on the electrophilic substitution reaction. Here’s a step-by-step solution:

### Step 1: Understand Friedel-Crafts Alkylation
Friedel-Crafts alkylation is a reaction where an alkyl group is introduced to a benzene ring in the presence of a Lewis acid catalyst. This process involves the formation of a carbocation, which acts as the electrophile that attacks the benzene ring.

**Hint:** Remember that the presence of a Lewis acid is crucial for generating the electrophile in Friedel-Crafts reactions.

### Step 2: Identify the Compounds
Let’s consider the compounds mentioned in the question. We need to analyze their substituents and how they affect the rate of the reaction.

**Hint:** Look for electron-donating and electron-withdrawing groups attached to the benzene ring.

### Step 3: Analyze the Effects of Substituents
- **Electron-Dongating Groups:** These groups increase the electron density on the benzene ring, making it more reactive towards electrophiles. Examples include alkyl groups (like methyl or isopropyl).
- **Electron-Withdrawing Groups:** These groups decrease the electron density on the benzene ring, making it less reactive. Examples include nitro groups (-NO2).

**Hint:** Identify which groups are present in the compounds and classify them as electron-donating or electron-withdrawing.

### Step 4: Compare the Compounds
1. **Aniline:** This compound has an amino group (-NH2), which is a strong electron-donating group. However, it will react with the Lewis acid to form a salt and will not undergo Friedel-Crafts alkylation.
2. **Toluene (Methylbenzene):** The methyl group is an electron-donating group, which enhances the reactivity of the benzene ring.
3. **Isopropylbenzene (Cumene):** The isopropyl group also donates electrons, and it has more alpha-hydrogens available for hyperconjugation compared to toluene.
4. **Nitrobenzene:** The nitro group is a strong electron-withdrawing group, which will significantly decrease the reactivity of the benzene ring.

**Hint:** Focus on the number of alpha-hydrogens in the alkyl groups, as more alpha-hydrogens lead to greater hyperconjugation and thus higher reactivity.

### Step 5: Determine the Rate of Reaction
- **Toluene:** Has one alpha-hydrogen.
- **Isopropylbenzene:** Has three alpha-hydrogens.

Since isopropylbenzene has more alpha-hydrogens, it will exhibit more hyperconjugation, making it more reactive than toluene.

**Hint:** The compound with the most alpha-hydrogens will typically undergo Friedel-Crafts alkylation at a faster rate.

### Conclusion
Based on the analysis, the compound that will undergo Friedel-Crafts alkylation at a faster rate is **Isopropylbenzene** (option C), not Toluene (option B) as initially concluded in the video.

**Final Answer:** Isopropylbenzene will undergo Friedel-Crafts alkylation at a faster rate.