In Chlorophyll 'a' `CH_(3)` group is attached at

Options

A. `4^(th)` pyrrole ring
B. `2^(nd)` pyrrole ring
C. `3^(rd)` pyrrole ring
D. `1^(st)` pyrrole ring

Answer

To determine where the CH3 (methyl) group is attached in chlorophyll 'a', we can follow these steps:

### Step-by-Step Solution:

1. **Understand Chlorophyll Structure**: Chlorophyll 'a' is a pigment found in plants that plays a crucial role in photosynthesis. It has a complex structure that includes a porphyrin ring.

2. **Identify the Methyl Group**: The CH3 group refers to a methyl group, which is a functional group derived from methane (CH4). In chlorophyll 'a', this methyl group is significant for its function.

3. **Locate the Carbon in the Porphyrin Ring**: The porphyrin ring in chlorophyll 'a' consists of four nitrogen-containing pyrrole rings. Each of these rings is numbered for identification.

4. **Determine the Attachment Point**: According to the information provided, the methyl group (CH3) is attached to the third carbon of the porphyrin head. This means that we need to identify which pyrrole ring corresponds to this carbon.

5. **Identify the Correct Pyrrole Ring**: The third carbon in the porphyrin structure refers to the third pyrrole ring. Thus, the methyl group is attached to the third pyrrole ring.

6. **Select the Correct Option**: Based on the options provided:
- Option A: Fourth pyrrole ring
- Option B: Second pyrrole ring
- Option C: Third pyrrole ring
- Option D: First pyrrole ring

The correct answer is **Option C: Third pyrrole ring**.

### Final Answer:
In chlorophyll 'a', the CH3 (methyl) group is attached at the **third pyrrole ring**.

---