Conpound `(A) underset(HIO_(4))overset(2 mol of)(rarr) 2` mol of glyoxalic acid.
The compound `(A)` is:

Options

A. a.
B. b.
C. c.
D. d.

Explanation

To determine the compound (A) that reacts with 2 moles of HIO4 to produce 2 moles of glyoxalic acid, we can follow these steps:

### Step 1: Understand the Reaction
HIO4 (periodic acid) is known to react with diols (compounds containing two hydroxyl groups -OH on adjacent carbons) through a mechanism called "syn addition." This means that both hydroxyl groups will be added to the same side of the molecule.

### Step 2: Identify the Product
The product of the reaction is glyoxalic acid, which has the structure:
```
O
||
H-C-C(OH)-C(OH)-H
```
Glyoxalic acid has two carbonyl groups (C=O) and two hydroxyl groups (OH).

### Step 3: Determine the Structure of Compound (A)
Since the reaction consumes 2 moles of HIO4 and produces 2 moles of glyoxalic acid, compound (A) must have a structure that can yield two glyoxalic acid molecules upon oxidation.

The likely candidate for compound (A) is a 1,2-diol that can be oxidized to produce two molecules of glyoxalic acid. The simplest structure that fits this description is 1,2-ethanediol (ethylene glycol), which has the following structure:
```
HO-CH2-CH2-OH
```

### Step 4: Reaction Mechanism
1. The two hydroxyl groups in 1,2-ethanediol are oxidized by HIO4.
2. The syn addition leads to the formation of intermediate structures that eventually rearrange to form glyoxalic acid.
3. The reaction results in the cleavage of the carbon-carbon bond and the formation of two molecules of glyoxalic acid.

### Final Answer
Thus, the compound (A) that reacts with 2 moles of HIO4 to produce 2 moles of glyoxalic acid is **1,2-ethanediol (ethylene glycol)**.

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