Question

On treatment with alkali, chlorophyll changes to

• A. Pheophytin
• B. Chlorophyllin
• C. Xanthophyll
• D. Vitamin A

Hint:

Remember the two main reactions of chlorophyll during processing:

\textbf{Acid + Heat} \(\rightarrow\) Removes Mg$^{2+}$ \(\rightarrow\) \textbf{Pheophytin} (olive brown)
\textbf{Alkali} \(\rightarrow\) Removes phytol tail \(\rightarrow\) \textbf{Chlorophyllin} (bright green, water-soluble) \end{itemize}

Answer 1

The Correct Option is B

Step 1: Briefly describe the structure of chlorophyll. It has a porphyrin ring with a magnesium ion at its center and a long hydrocarbon tail called a phytol group. This tail makes chlorophyll fat-soluble.

Step 2: Describe the effect of alkali treatment. When chlorophyll is treated with a strong alkali (like NaOH or KOH), a process called saponification occurs. The ester linkage holding the phytol tail is cleaved, removing the tail.

Step 3: Identify the resulting product. The product is a salt called chlorophyllin. It still contains the magnesium ion and the porphyrin ring, so it retains a bright green color, but without the phytol tail, it becomes water-soluble.
In contrast, acid treatment removes the central magnesium ion, replacing it with hydrogen, to form the dull olive-brown compound pheophytin.