What is the IUPAC nomenclature of vanillin used as a flavouring agent in ice - cream?

Options

A. 3 - Chloro -4- methoxy benzoic acid
B. 4, 6 - Dimethoxy benzaldehyde
C. 3, 4- Dihyroxy benzaldehyde
D. 4 - Hydroxy -3- methoxy benzaldehyde

Answer

To determine the IUPAC nomenclature of vanillin, we need to analyze its structure and identify the functional groups present.

### Step-by-Step Solution:

1. **Identify the Structure of Vanillin**:
Vanillin is an aromatic compound with the following functional groups:
- A methoxy group (-OCH3)
- A hydroxyl group (-OH)
- An aldehyde group (-CHO)

The structure can be represented as:
```
OCH3
|
C6H4 - CHO
|
OH
```

2. **Determine the Parent Chain**:
The longest continuous carbon chain that contains the highest priority functional group (the aldehyde group in this case) is the benzene ring. The aldehyde group is the principal functional group, and it will dictate the suffix of the name.

3. **Number the Carbon Atoms**:
We will number the carbon atoms in the benzene ring starting from the carbon atom that is part of the aldehyde group (which is carbon 1). The numbering will be as follows:
```
1
|
2-C6H4-CHO
|
3
```

4. **Identify and Name the Substituents**:
- The methoxy group (-OCH3) is attached to carbon 3.
- The hydroxyl group (-OH) is attached to carbon 4.

5. **Construct the IUPAC Name**:
According to IUPAC nomenclature rules, we will list the substituents in alphabetical order, followed by the name of the parent compound. The aldehyde group takes precedence and is indicated with the suffix "-al".

Therefore, the name will be:
- Hydroxy (from -OH) is listed first.
- Methoxy (from -OCH3) is listed second.
- The parent compound is benzaldehyde, which is modified to indicate the position of the aldehyde.

The final IUPAC name is:
**4-Hydroxy-3-methoxybenzaldehyde**

### Final Answer:
The IUPAC nomenclature of vanillin is **4-Hydroxy-3-methoxybenzaldehyde**.