Question 1

Consider the following reaction. The major product (P) formed is:

Accepted Answer

The reaction sequence proceeds as follows: The reagent NaBH _4 is a mild reducing agent that selectively reduces the aldehyde group (- CHO ) to a primary alcohol (- CH _2 OH ). The lactam (cyclic amide) ring remains unaffected. Heating with aqueous NaOH causes the base-catalyzed hydrolysis of the lactam ring. The amide bond breaks, forming a carboxylate salt (- COO ^-) and a secondary amine (- NH -). Acidification with H _3 O ^+ protonates the carboxylate ion to form a carboxylic acid (- COOH ).

Question 2

'x' is the product which is obtained from benzene by reacting it with carbon monoxide and hydrogen chloride in the presence of cuprous chloride. 'y' is the major product obtained from the benzene by r

Accepted Answer

Benzene reacts with CO and HCl in the presence of CuCl to give benzaldehyde (x) via the Gattermann-Koch reaction. Benzene reacts with ethanoyl chloride (CH_3COCl) in the presence of anhydrous AlCl_3 to give acetophenone (y) via Friedel-Crafts acylation. Heating benzaldehyde (x) and acetophenone (y) in the presence of alkali results in a crossed aldol condensation to form benzalacetophenone (z). C_6H_5CHO + CH_3COC_6H_5 OH^-, C_6H_5-CH=CH-CO-C_6H_5 + H_2O The structure of z (C_6H_5-CH=CH-CO-C_6H_

Question 3

'x' is the product which is obtained by the hydrolysis of prop-1-yne in the presence of mercuric sulphate under dilute acidic medium at 333 K. 'y' is the product which is obtained by the reaction of e

Accepted Answer

Hydrolysis of prop-1-yne in the presence of HgSO_4 and dilute H_2SO_4 yields acetone. CH_3-C CH + H_2O Hg^ 2+ , H^+ CH_3-CO-CH_3 Thus, x is acetone. Reaction of ethane nitrile (CH_3CN) with methyl magnesium bromide (CH_3MgBr) followed by hydrolysis also yields acetone. CH_3-C N + CH_3MgBr CH_3-C(CH_3)=NMgBr H_3O^+ CH_3-CO-CH_3 Thus, y is acetone. Reaction of x and y (both acetone) in the presence of Ba(OH)_2 followed by heating results in an aldol condensation. 2 CH_3-CO-CH_3 Ba(OH)_2 CH_3-C(OH)

Question 4

Given below are two statements: Statement-I: The condensation reaction between CH_3-CH=O and under optimum pH will produce . Statement-II: The molecule will generate Ph-CH=O in the presence of dilute

Accepted Answer

In Statement-I, evaluating the structure of semicarbazide ( H _2 N - NH - C (= O )- NH _2), the lone pair of electrons on the - NH _2 group directly attached to the carbonyl carbon is delocalized due to resonance. The terminal - NH _2 group of the hydrazine part is not involved in resonance with the carbonyl group, making it significantly more nucleophilic. Therefore, the condensation reaction of acetaldehyde with semicarbazide under optimum pH occurs at the terminal - NH _2 group to yield aceta

Question 5

An organic compound "x" where molar ratio of C, O and H are equal, on treatment with 50\% KOH under reflux followed by acidification produced "y". The most likely structure of "y" is: [Molar mass of '

Accepted Answer

Given the molar ratio of C, O, and H in compound x is equal, the empirical formula is CHO. Empirical mass = 12 + 1 + 16 = 29 g mol^ -1 . Since the molar mass of x is 58 g mol^ -1 , the molecular formula is (CHO)_2 or C_2H_2O_2. The structure of x is glyoxal, OHC-CHO. Treatment of glyoxal with 50\% KOH under reflux results in an intramolecular Cannizzaro reaction. One aldehyde group is oxidized to a carboxylate ion, and the other is reduced to a primary alcohol. OHC-CHO 50\% KOH HOCH_2-COO^ - K^

Question 6

Given below are the four isomeric compounds ( P , Q , R , S ) Identify correct statements from below. A. Q , R and S will give precipitate with 2,4- DNP . B. P and Q will give positive Bayer's test. C

Accepted Answer

(A) Q, R, S all three give 2, 4 DNP test as they have Aldehyde/ketone group (C) Q & R gives sooty flame (E) Q gives Tollens reagent test

Question 7

Given below are two statements: Statement I : Cross aldol condensation between two different aldehydes will always produce four different products. Statement II : When semicarbazide reacts with a mixt

Accepted Answer

Statement I: Cross aldol condensation between two different aldehydes produces four products only if both aldehydes have -hydrogen atoms. If one aldehyde lacks -hydrogen (e.g., benzaldehyde and acetaldehyde), only two products are typically formed (one self and one cross). If neither has -hydrogen, no aldol condensation occurs. Thus, it does not 'always' produce four products. Statement I is false. Statement II: Benzaldehyde is an aldehyde and acetophenone is a ketone. Aldehydes are generally mo

Question 8

Which of the following statements are TRUE about Haloform reaction?: A. Sodium hypochlorite reacts with KI to give KOI. B. KOI is a reducing agent. C. , -unsaturated methylketone ( CH _ 3 - CH = CH -

Accepted Answer

In the haloform reaction: (A) Sodium hypochlorite reacts with KI in acidic medium to generate the active halogenating species, forming KOI (potassium iodite/hypoidite). TRUE. (B) KOI serves as an oxidizing agent (not reducing) in the reaction, converting methyl ketones to carboxylic acids. FALSE. (C) α,β-unsaturated methylketones possess the essential methyl ketone group (CH_3CO-) required for haloform reaction, allowing iodination and subsequent cleavage. TRUE. (D) Isopropyl alcohol (CH_3)_2CHO

Question 9

Iodoform test can differentiate between A. Methanol and Ethanol B. CH _ 3 COOH and CH _ 3 CH _ 2 COOH C. Cyclohexene and cyclohexanone D. Diethyl ether and Pentan-3-one E. Anisole and acetone Choose t

Accepted Answer

The iodoform test is given by compounds containing the methyl ketone group (CH_3CO-) or alcohols that can be oxidized to methyl ketones (CH_3CH(OH)-). A. Methanol (CH_3OH) does not give the test, while Ethanol (CH_3CH_2OH) gives a positive iodoform test because it contains the CH_3CH(OH)- group. Thus, they can be differentiated. B. Acetic acid (CH_3COOH) and Propanoic acid (CH_3CH_2COOH) both do not give the iodoform test. Carboxylic acids generally do not respond to this test. Thus, they cannot

Question 10

' x ' is the product which is obtained from propanenitrile and stannous chloride in the presence of hydrochloric acid followed by hydrolysis. ' y ' is the product which is obtained from the but-2-ene

Accepted Answer

Product x is obtained by the Stephen reduction of propanenitrile (CH_3CH_2CN). CH_3CH_2CN SnCl_2/HCl CH_3CH_2CH=NH H_2O CH_3CH_2CHO (Propanal). Product y is obtained by the reductive ozonolysis of but-2-ene (CH_3CH=CHCH_3). CH_3CH=CHCH_3 O_3, H_2O/Zn 2CH_3CHO (Ethanal). When propanal (x) and ethanal (y) react in the presence of alkali followed by heating, they undergo cross-aldol condensation. Possible products are: 1. Self-aldol of propanal: CH_3CH_2CHO + CH_3CH_2CHO CH_3CH_2CH=C(CH_3)CHO (2-Me

Question 11

The compound A, C _ 8 H _ 8 O _ 2 reacts with acetophenone to form a single product via cross-Aldol condensation. The compound A on reaction with conc. NaOH forms a substituted benzyl alcohol as one o

Accepted Answer

(On cross aldol reaction, a single structure is obtained but it can show geometrical isomerism).

Question 12

Match the LIST-I with LIST-II \( array |c|l|c|l| & List-I (Reagents) & & List-II (Name of reaction \ & & & involving carbonyl compounds) \ A. & NH_2 - NH_2,\ KOH & I. & Tollen's Test \ B. & Ag(NH_3

Accepted Answer

The matching of reagents with their respective named reactions is as follows: A. NH_2-NH_2, KOH (Hydrazine in basic medium) is the reagent for Wolff-Kishner Reduction, which reduces carbonyl groups to alkanes. So, A matches with III. B. [Ag(NH_3)_2]OH (Ammoniacal silver nitrate) is Tollen's reagent used for Tollen's Test to identify aldehydes. So, B matches with I. C. Aqueous CuSO_4 (Fehling's A) and Sodium potassium tartarate in KOH (Fehling's B) are the components of Fehling's solution used fo

Question 13

Match List - I with List - II. array l List - I & List - II \ Reagents & Reaction Name (Involving aldehydes) \ A. H _ 2 , Pd - BaSO _ 4 & I. Etard Reaction \ B. SnCl _ 2 , HCl & II. Rosenmund Reduc

Accepted Answer

Matching reagents with aldehyde reaction types: A (H2, Pd-BaSO4) is the Lindlar/Rosenmund catalyst used in Rosenmund Reduction to convert acyl chlorides to aldehydes, matching with II. B (SnCl2, HCl) is used in Stephen Reaction where nitriles are converted to aldehydes via imine intermediate, matching with IV. C (CrO2Cl2, CS2) is Jones-like reagent used in Etard Reaction for oxidizing methyl groups on aromatic rings to aldehydes, matching with I. D (CO, HCl, Anhyd. AlCl3) is the Gatterman-Koch R

Question 14

An organic compound " P " of molecular formula C _ 6 H _ 12 O _ 3 gives positive Iodoform test but negative Tollen's test. When " P " is treated with dilute acid, it produces " Q ". " Q " gives positi

Accepted Answer

P gives positive iodoform (has CH_3CO-) but negative Tollen's (no -CHO). Q (after acid hydrolysis) gives both tests, meaning Q has both CH_3CO- and -CHO. This indicates P has an acetal protecting an aldehyde group. Option (1): CH_3-CO-CH_2-CH(OCH_3)_2 Has CH_3CO- → positive iodoform Has acetal -CH(OCH_3)_2, no free aldehyde → negative Tollen's Hydrolysis: -CH(OCH_3)_2 H^+/H_2O -CHO Q = CH_3-CO-CH_2-CHO gives both iodoform and Tollen's test Molecular formula: C_6H_ 12 O_3

Aldehydes and Ketones — Previous Year Questions & Solutions