Study of the following names of the organic compounds is not correctly written?

Options

A.
4 -hydroxy -3- methoxy benzaldehyde
B.
5 - methyl cyclohexane carboxaldehyde
C.
2(2-chlorophenyl) ethanal
D. `CH_(2)=CH-overset(O)overset(||)C-CH=CH_(2)`
penta -1, 4 - dien -3- one

Answer

To solve the problem of identifying which organic compound name is not correctly written, we will analyze each option step by step.

### Step 1: Analyze the First Compound
1. **Compound Structure**: The first compound is a benzene derivative with a formyl group (CHO), a methoxy group (OCH3), and a hydroxyl group (OH).
2. **Identify the Functional Groups**: The highest priority functional group is the aldehyde (CHO), which dictates the suffix.
3. **Numbering the Carbon Chain**: The numbering starts from the carbon of the aldehyde (1), followed by the methoxy and hydroxyl groups.
4. **Naming**: The correct name is 4-hydroxy-3-methoxybenzaldehyde. This name is correctly written.

### Step 2: Analyze the Second Compound
1. **Compound Structure**: The second compound is cyclohexane with a carboxaldehyde group (CHO) and a methyl group (CH3).
2. **Identify the Functional Groups**: The main functional group is the aldehyde (CHO).
3. **Numbering the Carbon Chain**: Start numbering from the aldehyde carbon (1). The methyl group is on carbon 3.
4. **Naming**: The correct name should be 3-methylcyclohexanal. However, it is incorrectly written as 5-methyl. This is the incorrect name.

### Step 3: Analyze the Third Compound
1. **Compound Structure**: The third compound has a chloro group (Cl) and an aldehyde group (CHO).
2. **Identify the Functional Groups**: The main functional group is the aldehyde.
3. **Numbering the Carbon Chain**: The numbering starts from the aldehyde carbon (1), with the chloro group on carbon 2.
4. **Naming**: The correct name is 2-chlorophenyl ethanol. This name is correctly written.

### Step 4: Analyze the Fourth Compound
1. **Compound Structure**: The fourth compound has a long carbon chain with double bonds and a ketone group.
2. **Identify the Functional Groups**: The main functional group is the ketone.
3. **Numbering the Carbon Chain**: The longest chain is numbered to give the lowest numbers to the double bonds and the ketone.
4. **Naming**: The correct name is 3-pentene-1,4-dione. This name is correctly written.

### Conclusion
After analyzing all four compounds, the second compound's name is incorrectly written as it should be 3-methylcyclohexanal instead of 5-methyl.

### Final Answer
The compound whose name is not correctly written is the second one.

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