Match the LIST-I with LIST-II.
| LIST-I Conversion | LIST-II Reagents | ||
| A. | Hexan-1-ol to Hexanal | I. | Anhydrous CrO3 |
| B. | Cyclohexanol to cyclohexanone | II. | O3/H2O-Zn dust |
| C. | But-2-ene to ethanal | III. | (Diisobutyl)aluminiumhydride(DIBAL-H) |
| D. | Ethanenitrile to ethanal | IV. | C5H5NH+CrO3Cl− (PCC) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-IV, B-I, C-II, D-III
Aldehydes and ketones can be prepared by controlled oxidation of alcohols, by ozonolysis of alkenes and by partial reduction of nitriles. The reagent must stop the reaction at the carbonyl stage:
(A) Hexan-1-ol to Hexanal — This matches (IV) C5H5NH+CrO3Cl− (PCC). Pyridinium chlorochromate is a mild oxidising agent that converts a primary alcohol to an aldehyde without further oxidation to the acid.
\( \displaystyle \ce{CH3(CH2)4CH2OH} \xrightarrow{\text{PCC}} \ce{CH3(CH2)4CHO} \)
(B) Cyclohexanol to cyclohexanone — This matches (I) Anhydrous CrO3. Chromic anhydride oxidises a secondary alcohol to a ketone; a ketone is not oxidised further under these conditions.
\( \displaystyle \text{cyclohexanol} \xrightarrow{\text{anhydrous }\ce{CrO3}} \text{cyclohexanone} \)
(C) But-2-ene to ethanal — This matches (II) O3/H2O-Zn dust. Ozonolysis breaks the C=C bond and puts a C=O group on each carbon; zinc dust prevents further oxidation of the aldehyde.
\( \displaystyle \ce{CH3CH=CHCH3} \xrightarrow[\text{(ii) }\ce{Zn}/\ce{H2O}]{\text{(i) }\ce{O3}} \ce{2CH3CHO} \)
(D) Ethanenitrile to ethanal — This matches (III) (Diisobutyl)aluminiumhydride(DIBAL-H). DIBAL-H reduces a nitrile to an imine, which is hydrolysed to an aldehyde.
\( \displaystyle \ce{CH3CN} \xrightarrow[\text{(ii) }\ce{H2O}]{\text{(i) DIBAL-H}} \ce{CH3CHO} \)
Shortcut: The pair A–IV appears only in Option (4).