Aldehydes and ketones: HCN, NH3 derivatives, Grignard, oxidation, reduction (Wolff-Kishner, Clemmensen)
- Identify the suitable reagent for the following conversion.Methyl benzoate (Ph-COOCH3) → benzaldehyde (Ph-CHO) Answer: 2. (i) AlH(iBu)₂ (ii) H₂O Key idea: partial reduction of an ester to an aldehyde needs DIBAL-H at low temperature. AlH(i-Bu)₂ follow... 1
- The major product of the following reaction is :Reactant: Ph-CO-CH2CH2-CN; (i) CH_3MgBr (excess); (ii) H_3O^+ Answer: 2. structure (2) Key idea: Grignard reagent adds to both the ketone and the nitrile, but the nitrile adduct is hydrolysed to a keton... 1
- Match List I with List II.List I (Reactions): A. [structure: bicyclohexylidene → 2 cyclohexanone] B. [structure: benzene → benzophenone] C. [structure: cyclohexanol → cyclohexanone] D. [structure: ethylbenzene → potassium benzoate]List II (Reagents/C… Answer: 4. A-IV, B-I, C-II, D-III Key idea: identify the reagent for each conversion. A: alkene to two ketones is ozonolysis, O₃ , then Zn-H... 1
- Identify the correct reagents that would bring about the following transformation.[structure transformation shown in figure: ring-CH_2-CH=CH_2 → ring-CH_2-CH_2-CHO] Answer: 3. (i) BH₃ (ii) H₂O₂/oversetominusOH (iii) PCC Key idea: the -CH=CH₂ group must become -CH₂CH₂CHO , a terminal aldehyde, which needs... 1
- Identify product (A) in the following reaction :3-(3-acetylphenyl)-substituted cyclohexyl methyl ketone: a cyclohexane ring bearing an acetyl group, joined to a benzene ring bearing an acetyl group (meta), [conc. HCl]Zn-Hg (A) + 2H_2O Answer: 2. both acetyl groups reduced to ethyl groups (structure) Key idea: Zn-Hg/conc. HCl is the Clemmensen reduction, which converts >C=O... 1
- Complete the following reaction :cyclohexanone [A] HCN cyclohexanone cyanohydrin (1-hydroxycyclohexanecarbonitrile) [B] [Δ]conc.\ H_2SO_4 [C][C] is ________. Answer: 1. cyclohex-1-ene-1-carboxylic acid (structure) Key idea: Conc. H₂SO₄ with heat does two things to a cyanohydrin: it hydrolyses -CN... 1
- Match List - I with List - II.List - I (Products formed): (a) Cyanohydrin (b) Acetal (c) Schiff's base (d) OximeList - II (Reaction of carbonyl compound with): (i) NH_2OH (ii) RNH_2 (iii) alcohol (iv) HCNChoose the correct answer from the options giv… Answer: 1. (a) - (iv), (b) - (iii), (c) - (ii), (d) - (i) Key idea: link each product to the reagent used with a carbonyl compound. Cyanohyd... 1
- RMgX + CO_2 dry ether Y H_3O^+ RCOOHWhat is Y in the above reaction ? Answer: 2. RCOO^(-M)g^+X Key idea: a Grignard reagent adds to CO₂ to give a magnesium carboxylate salt, which acid hydrolysis converts to th... 1
- The product formed in the following chemical reaction is :2-(methyl-substituted) cyclohexanone bearing CH_2-C(=O)-OCH_3 and CH_3 groups [C_2H_5OH]NaBH_4 ? Answer: 4. Cyclohexane ring with OH, CH₃ and CH₂-C(=O)-OCH₃ substituents Key idea: NaBH₄ is a mild reducing agent. It reduces aldehydes and... 1
- Match List - I with List - II.List - I : (a) benzene [Anhyd. AlCl_3/CuCl]CO,\ HCl (b) R-CO-CH_3 + NaOX → (c) R-CH_2-OH + R'COOH Conc. H_2SO_4 (d) R-CH_2COOH [(ii) H_2O](i) X_2/Red PList - II : (i) Hell-Volhard-Zelinsky reaction (ii) Gattermann-Koch r… Answer: 4. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i) Key idea: match each reaction with its name. (a) benzene + CO, HCl, anhydrous AlCl₃ /CuCl:... 1
- The intermediate compound 'X' in the following chemical reaction is :toluene + CrO_2Cl_2 CS_2 X H_3O^+ benzaldehyde Answer: 1. C₆H₅-CH(OCrOHCl₂)₂ Key idea: this is the Etard reaction: toluene is partially oxidised to benzaldehyde by chromyl chloride. Tolue... 1
- What is the IUPAC name of the organic compound formed in the following chemical reaction ?Acetone [(ii) H_2O, H^+](i) C_2H_5MgBr,\ dry Ether Product Answer: 4. 2-methyl butan-2-ol Key idea: a Grignard reagent adds to a ketone to give a tertiary alcohol. mathrm(CH₃)₂C=O+C₂H₅MgBr→(CH₃)₂C(C₂... 1
- Reaction between acetone and methylmagnesium chloride followed by hydrolysis will give : Answer: 3. Tert. butyl alcohol Grignard reagents add to the carbonyl group. A ketone gives a tertiary alcohol after hydrolysis. mathrm(CH₃)₂... 1
- The correct structure of the product A formed in the reaction [cyclohex-2-enone, H_2 (gas, 1 atmosphere), Pd/carbon, ethanol → A] is Answer: 1. [structure shown in figure] Key idea: H₂ with Pd/C at 1 atm reduces the C=C bond selectively; the C=O is not reduced under these... 1
- The product formed by the reaction of an aldehyde with a primary amine is : Answer: 1. Schiff base Key idea: an aldehyde (or ketone) condenses with a primary amine with loss of water to give an imine, R-CH=N-R' , als... 1