Arrange the following in decreasing order of enol content:
i. Diethyl malonate
ii. Acetoacetic easter (AAE or EAA)
iii. Acetyl acetone
iv. `PhCOH_(2)COH_(3)`

Options

A. `(iv) gt (iii) gt (ii) gt (i)`
B. `(iv) gt (iii) gt (i) gt (ii)`
C. `(iii) gt (iv) gt (ii) gt (i)`
D. `(iii) gt (iv) gt (i) gt (ii)`

Answer

To arrange the given compounds in decreasing order of enol content, we need to analyze each compound and its ability to form enol. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Structures
We start by identifying the structures of the compounds:

1. **Diethyl Malonate**:
- Structure: \( C_2H_5OOC-CH_2-COOC_2H_5 \)
- Enolic form: \( C_2H_5O-C(OH)=C(=O)OC_2H_5 \)

2. **Acetoacetic Ester (AAE)**:
- Structure: \( CH_3C(=O)CH_2C(=O)OC_2H_5 \)
- Enolic form: \( CH_3C(OH)=CHC(=O)OC_2H_5 \)

3. **Acetyl Acetone**:
- Structure: \( CH_3C(=O)CH_2C(=O)CH_3 \)
- Enolic form: \( CH_3C(OH)=CHC(=O)CH_3 \)

4. **Phenylacetone (PhCOH2COH3)**:
- Structure: \( PhC(=O)CH_2C(=O)CH_3 \)
- Enolic form: \( PhC(OH)=CHC(=O)CH_3 \)

### Step 2: Analyze Enol Content
Next, we analyze the enol content based on the stability of the enol forms:

- **Diethyl Malonate**: The enol form is less stable due to the absence of significant stabilization factors (like intramolecular hydrogen bonding). Thus, it has low enol content.

- **Acetoacetic Ester**: This compound has two carbonyl groups separated by a methylene group, which allows for some enol content, but it is less than that of acetyl acetone due to the lack of strong intramolecular hydrogen bonding.

- **Acetyl Acetone**: This compound has a strong tendency to form enol due to intramolecular hydrogen bonding between the hydroxyl group and the carbonyl oxygen. Therefore, it has a high enol content.

- **Phenylacetone**: The extended conjugation due to the phenyl group enhances the stability of the enol form, resulting in the highest enol content among the compounds listed.

### Step 3: Arrange in Decreasing Order
Based on the analysis above, we can arrange the compounds in decreasing order of enol content:

1. **Phenylacetone (PhCOH2COH3)** - Highest enol content due to extended conjugation.
2. **Acetyl Acetone** - High enol content due to intramolecular hydrogen bonding.
3. **Acetoacetic Ester (AAE)** - Moderate enol content due to two carbonyl groups.
4. **Diethyl Malonate** - Lowest enol content due to lack of stabilization.

### Final Order
Thus, the final order of decreasing enol content is:
**Phenylacetone > Acetyl Acetone > Acetoacetic Ester > Diethyl Malonate**