Preparation, Chemical Reactions — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Preparation, Chemical Reactions.

Multi-step synthesis involving diazonium salts

high

NEET frequently tests multi-step conversions. A common pattern is starting with an aromatic amine, performing diazotization, and then using the diazonium salt for a subsequent replacement or coupling reaction. For example, converting aniline to p-bromophenol would involve diazotization, followed by Sandmeyer bromination, and then hydrolysis. Students need to be proficient in sequencing these reactions and identifying intermediate products.

Distinguishing between Sandmeyer and Gattermann reactions

medium

While both reactions achieve similar transformations (replacement by Cl or Br), the difference in catalysts (Cu(I) salts vs. Cu powder) is a classic point of confusion and a common test item. Questions might ask to identify the specific catalyst for each or compare their yields. Understanding this subtle distinction is crucial for accuracy.

Conditions for coupling reactions and product prediction

high

The formation of azo dyes via coupling reactions is a visually distinct and industrially important application. Questions often focus on the specific pH conditions required for coupling with phenols (alkaline) versus anilines (acidic), and predicting the structure of the colored azo dye formed. Understanding the electrophilic nature of the diazonium ion and the activation of the coupling component is key.

Stability and decomposition of diazonium salts

medium

The inherent instability of diazonium salts, especially aliphatic ones, and the critical role of low temperature in their preparation are fundamental concepts. Questions might probe why aliphatic diazonium salts are not useful intermediates or what happens if aromatic diazonium salts are warmed above $5^circ ext{C}$. This tests the foundational understanding of their chemical nature.