Which functional group is primarily responsible for the green pigment involved in photosynthesis?

• A. $\mathrm{Carboxylic} \mathrm{acid} \left(\mathrm{–COOH}\right)$
• B. $\mathrm{Ketone} (\mathrm{–C}=O–)$
• C. $\mathrm{Aldehyde} \left(\mathrm{–CHO}\right)$
• D. $\mathrm{Chlorophyll}$

Answer: (D)

Verified step by step guidance

1. Identify the context of the problem: The question is about the green pigment involved in photosynthesis, which is chlorophyll.
2. Understand the structure of chlorophyll: Chlorophyll is a complex molecule that contains a porphyrin ring with a magnesium ion at its center.
3. Recognize the functional groups present in chlorophyll: Chlorophyll contains several functional groups, but the most notable is the porphyrin ring, which is not listed among the options.
4. Evaluate the given options: Carboxylic acid, ketone, and aldehyde are common functional groups in organic chemistry, but they are not the primary functional groups in chlorophyll.
5. Conclude that none of the listed functional groups (carboxylic acid, ketone, aldehyde) are responsible for the green pigment in chlorophyll, as the key structure is the porphyrin ring with magnesium.