The increasing order of basicity for the following intermediates is (from weak to strong)
`H_(3)C-underset("(i)")underset(CH_(3))underset("| ")overset(CH_(3))overset("| ")(C^(Theta))" "underset("(ii)")(H_(2)C=CH-overset(Theta)CH_(2))" "underset("(iii)")(HC=overset(Theta)C)" "underset("(iv)")(overset(Theta)CH_(3))" "underset("(v)")(overset(Theta)CN)`

Options

A. (v) lt (iii) lt (ii) lt (iv) lt(i)
B. (iii) lt (iv) lt (ii) lt (i) lt (v)
C. (v) lt (i) lt (iv) lt (ii) lt (iii)
D. (iii) lt (i) lt (ii) lt (iv) lt (v)

Answer

To determine the increasing order of basicity for the given intermediates, we need to analyze the structures and their corresponding acidity. Basicity is inversely related to acidity; thus, we will evaluate the acidity of each intermediate based on their pKa values and the stability of their conjugate bases.

### Step-by-Step Solution:

1. **Identify the Intermediates**:
The intermediates given are:
- (i) H₃C-CH(CH₃)-C(Θ) (Alkane)
- (ii) H₂C=CH-C(Θ)H₂ (Alkene)
- (iii) HC≡C (C triple bond C) (Alkyne)
- (iv) (Θ)CH₃ (Methyl anion)
- (v) (Θ)CN (Cyanide anion)

2. **Determine the Acidity of Each Intermediate**:
- **(i)** Alkane: The pKa value is around 50-55. Weak acid, hence strong base.
- **(ii)** Alkene: The pKa value is around 45. Weaker acid than alkynes.
- **(iii)** Alkyne: The pKa value is around 25. Stronger acid than alkenes and alkanes.
- **(iv)** Methyl anion: Extremely basic, as it is the conjugate base of methane (pKa ~ 57).
- **(v)** Cyanide anion: The pKa value is around 9. Strong acid, hence weak base.

3. **Analyze the Conjugate Bases**:
- The conjugate base of (i) is weak, hence it is a strong base.
- The conjugate base of (ii) is stronger than that of (i).
- The conjugate base of (iii) is weaker than that of (ii).
- The conjugate base of (iv) (methyl anion) is the strongest base among all.
- The conjugate base of (v) (cyanide) is weak.

4. **Arrange the Basicity**:
- From the above analysis, the order of basicity (from weak to strong) is:
- (v) CN < (iii) HC≡C < (ii) H₂C=CH < (i) H₃C-CH(CH₃) < (iv) (Θ)CH₃

5. **Final Order**:
Therefore, the increasing order of basicity for the intermediates is:
**CN < HC≡C < H₂C=CH < H₃C-CH(CH₃) < (Θ)CH₃**