Question

Which of the following amines acts as strongest base?

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

Hint:

Memorize these two specific basicity orders for aqueous solutions:
Methyl series: $2^\circ > 1^\circ > 3^\circ > \text{NH}_3$ (Order: 213)
Ethyl series: $2^\circ > 3^\circ > 1^\circ > \text{NH}_3$ (Order: 231)

Answer 1

The Correct Option is C

Step 1: Three forces decide basicity.
In water, the push of alkyl groups, the help from solvation, and the block from crowding all act together.

Step 2: Find the balance point.
For methyl amines a secondary amine gets a good push from two groups while still being well wrapped by water.

Step 3: Read the order.
The order is secondary above primary above tertiary. So dimethylamine, $(\text{CH}_3)_2\text{NH}$, is the strongest base here.
\[ \boxed{(\text{CH}_3)_2\text{NH}} \]