Question

Distinguish between following :

(i) CH₃ – CH = CH – CO – CH₃ and CH₃ – CH₂ – CO – CH = CH₂

(ii) Benzaldehyde and Benzoic acid.

Answer 1

(i)

 \(CH_3-CH {\displaystyle =\,} CH - \underset{O}{\underset{||}C} -CH_3\) 

give Iodoform test but \(CH_3 - CH_2COCH {\displaystyle =\,}CH_2 \) does not give Iodoform test

\(CH_3 - CH {\displaystyle =\,}CH - \underset{O}{\underset{||}C} - CH_3 \xrightarrow {I_2+NaOH} \underset{\text{(yellow crystals)}}{CHI_3} + CH_3 - CH {\displaystyle =\,}CH - COO^{\ominus}\overset{+}{Na}\)

\(CH_3 - CH_2CO - CH {\displaystyle =\,}CH_2 \xrightarrow {I_2+NaOH} \text{NO}\) 

Iodoform formed

(ii)   \(\Rightarrow \)  Benzoic acid gives effervescence of CO₂ with NaHCO₃ but benzaldehyde does not give effervescence of CO₂

_{\(\Rightarrow \)}  Benzaldehyde gives silver mirror in presence of Tollen's reagent whereas benzoic acid does not give this test.