In general boiling point of covalent compounds is affect due to increasing molecular weight and hydrogen bonding. Thus it is obversed that the boiling point of octanol is greater that water while that of methanol is lesser than water. The other properties which are considerably affected due to hydrogen bond formation are acidic nature, melting point, anamalous behaviour of water below `4^(@)C`., It is therefore concluded that hydrogen bonding palys a vutal role in explaning many observable facts.
Q. `K_(a_(1))` of maleic acid is lesser than `K_(a_(1))` of fumaric acid due to:

Options

A. Intramolecular hydrogen bonding in the formed after one proton removal in fumaric acid
B. Intermolecular hydrogen bonding in the ion formed after one proton removal in maleic acid
C. Intramolecular hydrogen bonding in the ion formed after one proton removal in maleic acid
D. Intermolecular hydrogen bonding in the ion formed after one proton removal in fumaric acid

Answer

To solve the question regarding why \( K_{a1} \) of maleic acid is lesser than \( K_{a1} \) of fumaric acid, we need to analyze the structures of both acids and the effects of hydrogen bonding.

### Step-by-Step Solution:

1. **Identify the Structures of Maleic and Fumaric Acid**:
- Maleic acid has the structure:
\[ HOOC-CH=CH-COOH \]
- Fumaric acid has the structure:
\[ HOOC-CH=CH-COOH \]
- Both acids have two carboxylic acid groups, but their spatial arrangement differs.

2. **Understanding the Acid Dissociation Constant \( K_a \)**:
- The acid dissociation constant \( K_a \) measures the strength of an acid in solution. A higher \( K_a \) indicates a stronger acid, which dissociates more readily to release protons (H⁺).

3. **Analyze the Proton Removal**:
- For maleic acid, when one proton is removed from the carboxylic group, the resulting structure can form intramolecular hydrogen bonding:
\[ HOOC-CH=CH-COO^- \]
- This intramolecular hydrogen bonding stabilizes the conjugate base, making it less likely to dissociate further, thus lowering \( K_{a1} \).

4. **Compare with Fumaric Acid**:
- In fumaric acid, when one proton is removed, the structure does not allow for intramolecular hydrogen bonding:
\[ HOOC-CH=CH-COO^- \]
- The absence of intramolecular hydrogen bonding means that the conjugate base is less stabilized compared to maleic acid, leading to a higher \( K_{a1} \).

5. **Conclusion**:
- Since maleic acid can form intramolecular hydrogen bonds after the removal of a proton, it is less likely to dissociate further compared to fumaric acid, which cannot form such bonds. Therefore, \( K_{a1} \) of maleic acid is lesser than that of fumaric acid.

### Final Answer:
\( K_{a1} \) of maleic acid is lesser than \( K_{a1} \) of fumaric acid due to the formation of intramolecular hydrogen bonding in maleic acid after the removal of one proton.

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