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Strategy: Convert carboxylic acid to amide. Then use the Hoffmann Bromamide Degradation to remove the carbonyl carbon and obtain an amine with one less carbon.
NCERT Ex 12.15 Solved: Aldehydes & Ketones Conversions | ChemCa
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NCERT Exercise 12.15 Solved
Detailed "2-step" conversion strategies for Aldehydes, Ketones, and Carboxylic Acids. Master reagents like Grignard, Rosenmund Catalyst, and Aldol Condensation.
Strategy: Cross-Aldol condensation with acetaldehyde gives Cinnamaldehyde. Catalytic hydrogenation reduces both the double bond and the aldehyde to alcohol.
(viii) Benzaldehyde to $\alpha$-Hydroxyphenylacetic acid
Strategy: Nitration first (-COOH is meta directing). Then reduce the carboxylic acid to alcohol (Diborane is preferred as it doesn't reduce the nitro group easily).
Concept: Add HBr (Markovnikov) to move the leaving group to the secondary carbon. Elimination yields the more substituted, stable alkene (But-2-ene) as the major product.
Strategy: Direct hydration follows Markovnikov's rule (giving propan-2-ol). To get primary alcohol (Anti-Markovnikov product), use Hydroboration-Oxidation.
Step-by-step strategies to calculate pH and ion concentrations for Diprotic and Triprotic acids like $H_2S$, $H_3PO_4$, and $H_2SO_4$.
Ionic EquilibriumpH Calculation
The Dominant Step Principle
Polyprotic acids dissociate in steps. For most weak polyprotic acids (like $H_2CO_3, H_2S, H_3PO_4$), the first dissociation constant ($K_{a1}$) is significantly larger than the second ($K_{a2}$).
Typically: $K_{a1} \gg K_{a2} \gg K_{a3}$ (often by factors of $10^4$ to $10^6$).
Key Approximation: Since the first step produces the vast majority of $H^+$, we can calculate the pH by treating the acid as monoprotic using only $K_{a1}$. The subsequent steps contribute negligible $H^+$.
*Step 2 is suppressed by the Common Ion Effect ($H^+$ from Step 1).
Case 1: Weak Diprotic Acid ($K_{a1} \gg K_{a2}$)
Solved Example: Carbonic Acid
Calculate the pH and $[CO_3^{2-}]$ concentration in a $0.05 M$ solution of $H_2CO_3$. Given: $K_{a1} = 4 \times 10^{-7}$, $K_{a2} = 5 \times 10^{-11}$.
Step 1: Determine pH (First Dissociation)
Since $K_{a1} \gg K_{a2}$, we treat it as a monoprotic acid. Check if we can neglect $\alpha$ ($C/K_{a1} > 100$).
