# DBT JRF 2022 — Question 6

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Organic Chemistry Reactions & Detection · Difficulty: Medium

## Question

What may be the simplest and most inexpensive way to know that the product is formed in the reaction given below? ![figure](https://res.cloudinary.com/dxil5euku/image/upload/v1779453123/pyq/6a104cb5920734408bc0c6d8/DBTJRF22-IMGB6.png)

## Options

- **A.** Mass spectrometry
- **B.** Reverse Phase HPLC
- **C.** CD spectroscopy
- **D.** Change of color upon addition of alkali

## Answer

Option D

## Explanation

Simplest detection method for phenol formation ![figure](https://res.cloudinary.com/dxil5euku/image/upload/v1779453123/pyq/6a104cb5920734408bc0c6d8/DBTJRF22-IMGB6.png) : The reaction shown generates a phenol (hydroxybenzene derivative) as the product. Detection methods and their practical applicability: • Color change with alkali (e.g., FeCl₃ test): Phenols give a distinctive purple/violet colour with ferric chloride, or strong red/blue with NaOH and a diazonium salt. This test requires only a drop of reagent and is instantaneous. • Mass spectrometry: Very sensitive but expensive, requires specialised equipment. • Reverse Phase HPLC: Accurate and quantitative but requires expensive instrumentation and expertise. • CD spectroscopy: Measures optical activity; not ideal for simple product detection. The simplest and most inexpensive method is a colorimetric test with alkali/FeCl₃. Answer: Change of color upon addition of alkali (Option 4).

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