CBSE 2025, Set 2

Question

Complete each synthesis by giving missing starting material, reagent or products:

![Q32B five synthesis completions](https://www.edvaya.com/images/chemistry/cbse/2025/set2/q32b-five-synthesis-completions.webp)

(a) Cyclopentanone + HO–NH₂ → ?

(b) ? + (i) O₃, (ii) Zn–H₂O → 2 × cyclopentanone

(c) Cyclohexane-1,2-dicarboxylic acid + SOCl₂ → ?

(d) A compound with both CHO and COOH groups on cyclohexane + NaCN/HCl → ?

(e) Benzene → acetophenone (phenyl methyl ketone) using what reagent?

Edvaya · Accepted Answer

The correct answer is Subjective. **(a) Cyclopentanone + H₂N–OH $\xrightarrow{	ext{H}^+}$ ?** Nucleophilic addition-elimination of hydroxylamine with the ketone group: **Product = Cyclopentanone oxime** (the C=O becomes C=N–OH) **(b) ? + (i) O₃, (ii) Zn–H₂O → 2 cyclopentanone** Ozonolysis cleaves a C=C double bond. Two identical cyclopentanone fragments means the alkene was symmetrical with two cyclopentanone rings connected at a C=C: **Starting material = Cyclopentylidene cyclopentane** (bicyclopentylidene / 1,1'-bi(cyclopentylidene)) **(c) Cyclohexane-1,2-dicarboxylic acid + SOCl₂ $\xrightarrow{\Delta}$ ?** SOCl₂ converts –COOH to –COCl. With two adjacent –COOH groups and heat, intramolecular cyclisation occurs: **Product = Cyclohexane-1,2-dicarboxylic acid anhydride** (cyclic anhydride) **(d) Compound with CHO and COOH on cyclohexane + NaCN/HCl → ?** NaCN adds HCN to the aldehyde group (cyanohydrin formation). The –COOH group is unaffected: **Product = Cyanohydrin** (–CHO becomes –CH(OH)CN) **(e) Benzene → Acetophenone (C₆H₅COCH₃):** **Reagent: CH₃COCl / Anhydrous AlCl₃ (Friedel-Crafts acylation)** OR: **(CH₃CO)₂O / Anhydrous AlCl₃** $$	ext{C}_6	ext{H}_6 + 	ext{CH}_3	ext{COCl} \xrightarrow{	ext{Anhy. AlCl}_3} 	ext{C}_6	ext{H}_5	ext{COCH}_3 + 	ext{HCl}$$

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Chemistry > Organic Chemistry > Aldehydes Ketones And Carboxylic Acids

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