CBSE 2025, Set 3

Question

Write the products formed in the following reactions:

(a) CH$_3$CHO + NH$_2$CONHNH$_2$ →

(b) CH$_3$CHO $\xrightarrow{	ext{dil. NaOH}}$

(c) CH$_3$COOH $\xrightarrow{	ext{Cl}_2/	ext{red P, then H}_2	ext{O}}$

Edvaya · Accepted Answer

The correct answer is Subjective. **(a) CH$_3$CHO + NH$_2$CONHNH$_2$ (semicarbazide):** The carbonyl group (C=O) undergoes nucleophilic addition–elimination with semicarbazide: $$	ext{CH}_3	ext{CHO} + 	ext{NH}_2	ext{CONHNH}_2 ightarrow \underbrace{	ext{CH}_3	ext{CH=NNHCONH}_2}_{	ext{acetaldehyde semicarbazone}} + 	ext{H}_2	ext{O}$$ **Product: CH$_3$CH=NNHCONH$_2$ (acetaldehyde semicarbazone)** **(b) CH$_3$CHO + dil. NaOH (Aldol addition):** $$2	ext{CH}_3	ext{CHO} \xrightarrow{	ext{dil. NaOH}} \underbrace{	ext{CH}_3	ext{CH(OH)CH}_2	ext{CHO}}_{	ext{3-hydroxybutanal (aldol)}}$$ **Product: CH$_3$CH(OH)CH$_2$CHO (3-hydroxybutanal / aldol)** **(c) CH$_3$COOH + Cl$_2$/red P, then H$_2$O (Hell–Volhard–Zelinsky reaction):** $$	ext{CH}_3	ext{COOH} \xrightarrow{	ext{Cl}_2/	ext{red P}} 	ext{CH}_2	ext{ClCOCl} \xrightarrow{	ext{H}_2	ext{O}} \underbrace{	ext{ClCH}_2	ext{COOH}}_{	ext{chloroacetic acid}}$$ **Product: ClCH$_2$COOH (chloroacetic acid / 2-chloroethanoic acid)**

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Chemistry > Organic Chemistry > Aldehydes Ketones And Carboxylic Acids

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