Among formaldehyde, acetone and acetaldehyde, the reactivity order is

Options

A. `HCHO gt (CH_(3))_(2)CO gtCH_(3)CHO`
B. `HCHO gt CH_(3)CHO gt(CH_(3))_(2)CO`
C. `(CH_(3))_(2)C=OgtHCHOgtCH_(3)CHO`
D. Unpredictable.

Explanation

To determine the reactivity order among formaldehyde, acetaldehyde, and acetone, we need to analyze the steric hindrance and the structure of these carbonyl compounds. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Identify the Structures
- **Formaldehyde (HCHO)**: It has no alkyl groups attached to the carbonyl carbon, only hydrogen atoms.
- **Acetaldehyde (CH3CHO)**: It has one methyl group (CH3) and one hydrogen attached to the carbonyl carbon.
- **Acetone (CH3COCH3)**: It has two methyl groups attached to the carbonyl carbon.

### Step 2: Analyze Steric Hindrance
- **Formaldehyde**: Since it has only hydrogen atoms, there is minimal steric hindrance. This allows nucleophiles to easily approach the carbonyl carbon, making it highly reactive.
- **Acetaldehyde**: The presence of one methyl group introduces some steric hindrance, but it is still relatively low compared to acetone. Therefore, it is less reactive than formaldehyde but more reactive than acetone.
- **Acetone**: With two bulky methyl groups, acetone experiences significant steric hindrance, making it the least reactive among the three compounds. The bulky groups hinder the approach of nucleophiles to the carbonyl carbon.

### Step 3: Establish the Reactivity Order
Based on the analysis of steric hindrance:
- **Most Reactive**: Formaldehyde (HCHO)
- **Moderately Reactive**: Acetaldehyde (CH3CHO)
- **Least Reactive**: Acetone (CH3COCH3)

Thus, the order of reactivity is:
**Formaldehyde > Acetaldehyde > Acetone**

### Final Answer
The reactivity order among formaldehyde, acetaldehyde, and acetone is:
**Formaldehyde > Acetaldehyde > Acetone**

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