Question 1

Complete the following reaction sequence and give the name of major product 'P'. CH_3-CH_2-C N [ (ii) H_3O^+] (i) OH^-/H_2O/ [ (iv) H_2O] (iii) Cl_2/ Red P P (Major product)

Accepted Answer

Step 1: Hydrolysis of the nitrile. Propanenitrile on basic hydrolysis followed by acidic workup gives propanoic acid: CH_3-CH_2-C N [(ii)\ H_3O^+] (i)\ OH^-/H_2O/ CH_3-CH_2-COOH Step 2: Hell-Volhard-Zelinsky (HVZ) reaction. Propanoic acid has an sp^3 -carbon bearing two -hydrogens. In the HVZ reaction, Cl_2 in the presence of red phosphorus selectively replaces one -hydrogen by chlorine, giving the -chloro acid after aqueous workup: CH_3-CH_2-COOH [(iv)\ H_2O] (iii)\ Cl_2/ Red P CH_3-CH(Cl)-COOH

Question 2

The descending order of acidity among the following compounds is: A. Phenol B. 4-nitrophenol C. 4-methoxyphenol D. 4-nitrobenzoic acid E. Benzoic acid Choose the correct answer from the options given

Accepted Answer

Carboxylic acids are stronger acids than phenols because the carboxylate anion is stabilized by equivalent resonance structures. Thus, D and E are more acidic than A, B, and C. For the carboxylic acids, the -NO_2 group in D is an electron-withdrawing group (-I, -R), which stabilizes the conjugate base, making D more acidic than E. For the phenols, electron-withdrawing groups increase acidity while electron-donating groups decrease it. The -NO_2 group in B is electron-withdrawing, making it more

Question 3

The correct order of acidic strength of the major products formed in the given reactions, is : A. B. CH _ 3 CH _ 2 CHO [ ] [ Ag ( NH _ 3 )_ 2 ]^ + , OH ^ - [ B ] C. CH _ 4 + O _ 2 [ (ii) Na _ 2 Cr _ 2

Accepted Answer

Product [A]: From PhNH₂, steps (1) NaNO₂ + HCl forms diazonium salt, (2) CuCN gives benzonitrile, (3) H₃O⁺/Δ hydrolyzes to benzoic acid (PhCOOH), pKa ≈ 4.2. Product [B]: From CH₃CH₂CHO, Tollens' oxidation with [Ag(NH_3)_2]^+ produces acetic acid (CH₃COOH), pKa ≈ 4.8. Product [C]: From CH₄ + O₂ with heat and Na₂Cr₂O₇/H⁺ produces formic acid (HCOOH), pKa ≈ 3.8 (strongest acid). Product [D]: From PhCH₂MgBr + CO₂, the Grignard reaction produces phenylacetic acid (PhCH₂COOH), pKa ≈ 4.3. Acidic streng

Carboxylic Acid Derivatives — Previous Year Questions & Solutions