Glyoxal (CHOCHO) on being heated with concentrated NaOH forms

Answer

To determine the product formed when glyoxal (CHOCHO) is heated with concentrated NaOH, we can follow these steps:

### Step 1: Identify the Structure of Glyoxal
Glyoxal has the structure HCHOCHO, which can be represented as:
```
O
||
H-C-C-H
||
O
```
This indicates that glyoxal contains two aldehyde groups.

**Hint:** Recognize the structure of glyoxal and its functional groups.

### Step 2: Reaction with Concentrated NaOH
When glyoxal is heated with concentrated NaOH, it undergoes a reaction that involves the nucleophilic attack of hydroxide ions (OH⁻) on the carbonyl carbon of one of the aldehyde groups.

**Hint:** Understand that hydroxide ions can act as nucleophiles in reactions with carbonyl compounds.

### Step 3: Formation of Alkoxide Intermediate
The hydroxide ion attacks one of the carbonyl carbons, leading to the formation of an alkoxide intermediate. The reaction can be illustrated as follows:
```
O
||
H-C-C-H + OH⁻ → H-C-C-O⁻
|| |
O H
```

**Hint:** Remember that the nucleophilic attack results in the formation of an alkoxide ion.

### Step 4: Intramolecular Cannizzaro Reaction
Glyoxal can undergo an intramolecular Cannizzaro reaction, where one aldehyde group is oxidized to a carboxylic acid while the other is reduced to an alcohol. In this case, one hydrogen atom from the hydroxymethyl group leaves, and the bond shifts, resulting in the formation of a carboxylate ion.

**Hint:** Recognize that the Cannizzaro reaction typically occurs with non-enolizable aldehydes, leading to disproportionation.

### Step 5: Final Product Formation
The final product of the reaction can be represented as:
```
O
||
H-C-C-O⁻
|
OH
```
This can be written as CH₂(OH)COO⁻, which indicates the formation of sodium glycolate (the sodium salt of glycolic acid).

**Hint:** Identify the final product by recognizing the functional groups present after the reaction.

### Conclusion
The product formed when glyoxal is heated with concentrated NaOH is sodium glycolate (CH₂(OH)COO⁻).