`{:(" "OH " "O),(" "|" "||), (CH_(3)-CH-CH-CH-C-O-C_(2)H_(5)),(" "|" "|),(" "CN " "CHO):}`
According to IUPAC, principal functional group of the given compound is :-

Options

A. `-OH`
B. `-CN`
C. `-overset(O)overset(||)-O-`
D. `-overset(O)overset (||) C-H`

Answer

To determine the principal functional group of the given compound according to IUPAC nomenclature, we will follow these steps:

### Step 1: Identify the Functional Groups
First, we need to identify all the functional groups present in the compound. The given structure includes:
- An ester group (C-O-R)
- A cyanide group (CN)
- An aldehyde group (CHO)
- A hydroxyl group (OH)

### Step 2: Assign Priority to Functional Groups
Next, we will assign priority to these functional groups based on the IUPAC priority order:
1. Carboxylic acid
2. Sulfonic acid
3. Ester
4. Acyl halide
5. Amide
6. Nitrile (Cyanide)
7. Aldehyde
8. Alcohol (Hydroxyl)

From the list, we can see that:
- The ester (C-O-R) has a priority of 3.
- The cyanide (CN) has a priority of 6.
- The aldehyde (CHO) has a priority of 7.
- The hydroxyl group (OH) has a priority of 15.

### Step 3: Determine the Principal Functional Group
According to the priority order, the functional group with the highest priority will be considered the principal functional group. In this case, the ester group has the highest priority (3), which is greater than the priorities of the other functional groups.

### Conclusion
Therefore, the principal functional group of the given compound is the **ester** group.

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