Question

Identify compound from following having highest basic strength.

• A. $\text{CH}_3\text{CH}_2\text{NH}_2$
• B. $\text{NH}_3$
• C. $(\text{CH}_3)_2\text{NH}$
• D. $\text{C}_6\text{H}_5\text{NH}_2$

Hint:

For methyl-substituted aliphatic amines in water, remember the numerical shortcut sequence 213 (Secondary $\gt $ Primary $\gt $ Tertiary) to easily recall the absolute basicity order in exams!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The goal is to identify which amine or nitrogenous base among the options has the highest basic strength in aqueous medium.

Step 2: Key Formula or Approach:
Basicity of aliphatic amines in water is governed by the combined effects of +I electron donation, steric hindrance, and solvation of the conjugate acid, giving the order: 2°>1°>3°>NH₃.

Step 3: Detailed Explanation:
Aniline is a very weak base due to lone pair delocalization into the ring. Ammonia lacks +I alkyl groups. Among methylamines, dimethylamine (2°) has the optimal balance of inductive enhancement and minimal steric/solvation penalties, making it the strongest base.

Step 4: Final Answer:
The strongest base is (CH₃)₂NH, corresponding to option (C).