Chemistry MCQs for NEET — Practice Questions with Answers

 ${}_{\mathrm{H}}{}^{{\mathrm{CH}}_3}>\mathrm{C}=\mathrm{O} \stackrel{\mathrm{HCN}}{\to }{}_{\mathrm{H}}{}^{{\mathrm{CH}}_3}>\mathrm{C}{<}_{\mathrm{CN}}^{\mathrm{OH}}\stackrel{\mathrm{HOH}}{\to }{\mathrm{CH}}_3\mathrm{CH}\left(\mathrm{OH}\right)\mathrm{COOH}$

                                                           (Lactic acid)

(a) Higher is K_a or lower is pK_a, stronger is acid.

(b) In (a) t-alcohol, in (c) initially s-alcohol converting to ether. In (d) p-alcohol

(d) pK_a for (a) , (b), (c) and (d) are 4.17, 4.09, 3.49 and 3.43 respectively.

Ethanal (acetaldehyde) reacts with HCN to form an addition product, which upon hydrolysis forms lactic acid (2-hydroxypropanoic acid). Lactic acid exhibits optical isomerism due to the presence of a chiral carbon atom.

C₆H₅CHO+HCHO$\stackrel{\mathrm{NaOH}(\mathrm{conc}.) }{\to }$C₆H₅CH₂OH+HCOONa

                                              Benzyl alcohol      Sod. Formate

Phenolphthalein is produced by the condensation reaction between phthalic anhydride and phenol in the presence of conc. H2SO4. Phenol acts as a nucleophile and attacks the carbonyl carbon of the anhydride.

Aldehyde is more reactive than ketone towards nucleophilic addition