184. What may be the simplest and most inexpensive way to know that the product is formed in
the reaction given below?
A. Mass spectrometry
B. Reverse Phase HPLC
C. CD spectroscopy
D. Change of color upon addition of alkali

Explanation:

When assessing product formation in a chemical reaction, especially during preliminary or routine screening, cost and simplicity are key factors. Here’s why “change of color upon addition of alkali” is often the best method:

• No need for expensive instruments.

• Visual indicator: If the product or its intermediate has pH-sensitive groups (like phenols, nitrophenols, or azo compounds), a distinct color change can occur upon addition of alkali.

• Immediate feedback without needing complex preparation or analysis.

Why Other Options Are Less Ideal Here:

• A. Mass spectrometry: Highly accurate but expensive and requires specialized training.

• B. Reverse Phase HPLC: Also precise but requires equipment, solvents, standards, and calibration.

• C. CD (Circular Dichroism) spectroscopy: Used for studying chiral molecules, proteins, and conformational changes—not typically used for simple product detection.

Conclusion:

For quick, inexpensive, and effective detection of whether a product has formed, a visible color change upon addition of alkali is the most practical method—especially in a resource-limited setting or during initial experimentation.

Correct Answer: D. Change of color upon addition of alkali