Write increasing order of basic strength of following:
`(a)NH_(3)" "(b)MeNH_(2)`
`(c)Me_(2)NH" "(d) Me_(3)N (" in" H_(2)O)`

Answer

To determine the increasing order of basic strength of the given amines: (a) NH₃ (ammonia), (b) MeNH₂ (methylamine), (c) Me₂NH (dimethylamine), and (d) Me₃N (trimethylamine), we need to consider the factors affecting their basicity.

### Step-by-Step Solution:

1. **Understanding Basicity**: Basicity refers to the ability of a compound to accept protons (H⁺ ions). In the case of amines, the lone pair of electrons on the nitrogen atom is responsible for its basicity.

2. **Inductive Effect**: The presence of alkyl groups (like methyl groups) increases the electron density on the nitrogen atom due to the +I (inductive) effect. More alkyl groups lead to a stronger basicity because they donate electron density to the nitrogen.

- NH₃ (no alkyl groups) < MeNH₂ (1 alkyl group) < Me₂NH (2 alkyl groups) < Me₃N (3 alkyl groups)

3. **Solvation Effect**: In water, amines can form hydrogen bonds with water molecules. The stability of the ammonium ion formed after protonation is influenced by how many hydrogen bonds can be formed.

- NH₃ can form 3 hydrogen bonds, MeNH₂ can form 2, Me₂NH can form 1, and Me₃N cannot form hydrogen bonds due to steric hindrance.

4. **Steric Hindrance**: The presence of bulky groups around the nitrogen can hinder the approach of protons. Trimethylamine (Me₃N) has the most steric hindrance, making it less basic.

5. **Combining the Effects**:
- From the inductive effect, the order is: Me₃N > Me₂NH > MeNH₂ > NH₃.
- From the solvation effect, the order is: NH₃ > MeNH₂ > Me₂NH > Me₃N.
- From the steric effect, the order is: NH₃ > MeNH₂ > Me₂NH > Me₃N.

6. **Final Order**: Considering all factors, the overall order of basicity is:
- NH₃ < MeNH₂ < Me₂NH < Me₃N.

### Increasing Order of Basic Strength:
Thus, the increasing order of basic strength is:
**NH₃ < MeNH₂ < Me₂NH < Me₃N**