Which of the following cannot be acylated ?

Options

A. `C_2 H_5 NH_2`
B. `C_6H_5NH_2`
C. `(CH_3)_2 NH`
D. `(CH_3)_(3)N`

Answer

To determine which of the following compounds cannot be acylated, we first need to understand the concept of acylation. Acylation involves adding an acyl group (specifically, a CH3CO group) to a compound, typically through a nucleophilic substitution reaction.

### Step-by-Step Solution:

1. **Understanding Acylation**:
- Acylation is the process of introducing an acyl group (RCO-) into a compound. This is often done using acetic anhydride (CH3CO)2O or similar acylating agents.
- The reaction typically requires the presence of an active hydrogen atom attached to a nitrogen (N), oxygen (O), or sulfur (S) atom in the compound.

2. **Identifying Active Hydrogen**:
- For a compound to undergo acylation, it must have at least one active hydrogen atom. This is crucial because the active hydrogen is replaced by the acyl group during the reaction.
- Compounds like amines (R-NH2), alcohols (R-OH), and thiols (R-SH) can be acylated because they have active hydrogens.

3. **Analyzing the Given Options**:
- We need to analyze each of the options provided to see if they contain an active hydrogen:
- **Option A**: Primary amine (R-NH2) - has active hydrogen.
- **Option B**: Secondary amine (R2NH) - has active hydrogen.
- **Option C**: Alcohol (R-OH) - has active hydrogen.
- **Option D**: Trimethylamine (N(CH3)3) - does not have any active hydrogen attached to nitrogen.

4. **Conclusion**:
- Since trimethylamine (Option D) does not have an active hydrogen atom associated with nitrogen, it cannot undergo acylation.
- Therefore, the correct answer is **D: Trimethylamine**.