`CH_(2)OHCH_(2)OH` on heating with periodic acid gives

Options

A. `2HCOOH`
B. `overset(CHO)underset(CHO)("| ")`
C. `2CH_(2)O`
D. `2CO_(2)`

Explanation

To solve the question of what `CH₂OH-CH₂OH` (ethylene glycol) produces when heated with periodic acid (HIO₄), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Compound**: The compound given is ethylene glycol, which has the structure `CH₂OH-CH₂OH`. This is a 1,2-diol (or glycol).

2. **Understanding the Reaction with Periodic Acid**: Periodic acid (HIO₄) is known to cleave 1,2-diols. When a 1,2-diol reacts with periodic acid, it typically results in the cleavage of the carbon-carbon bond between the two hydroxyl groups.

3. **Cleavage of the Diol**: Upon heating ethylene glycol with periodic acid, the bond between the two carbon atoms is broken. Each carbon atom will form a carbonyl group (C=O), and hydroxyl groups (OH) will be added to the adjacent carbon atoms.

4. **Formation of Intermediate**: The initial reaction will yield an unstable intermediate where both carbon atoms are bonded to hydroxyl groups:
- `CH₂(OH)-C(OH)₂` (this is not stable).

5. **Elimination of Water**: The unstable intermediate will undergo dehydration (loss of water) to stabilize the structure. This results in the formation of two moles of formaldehyde (HCHO):
- `CH₂O` (formaldehyde).

6. **Final Products**: Therefore, the final products of the reaction when ethylene glycol is heated with periodic acid are two moles of formaldehyde.

### Conclusion:
When `CH₂OH-CH₂OH` is heated with periodic acid, it gives formaldehyde (HCHO).