Aldehydes, Ketones, and Carboxylic Acids (Class 12 NCERT) Revision Notes

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 short question-and-answer pairs covering the essential concepts, preparation, properties, and reactions from the NCERT Class 12 Chemistry Chapter:

Short Q&A for Aldehydes, Ketones, and Carboxylic Acids (Class 12 NCERT)

Part 1: Structure and Nomenclature

Q. No.	Question	Answer
1	What is the common functional group present in aldehydes and ketones?	The Carbonyl Group (C=O).
2	What is the hybridization of the carbonyl carbon?	sp2 hybridization.
3	What is the geometry around the carbonyl carbon?	Trigonal Planar (bond angle ≈120∘).
4	Why is the carbonyl group polar?	Oxygen is more electronegative than carbon, resulting in a partial positive charge on C.
5	Define an Aldehyde.	A carbonyl group bonded to at least one hydrogen atom (RCHO).
6	Define a Ketone.	A carbonyl group bonded to two alkyl or aryl groups (RCOR′).
7	What is the functional group in Carboxylic Acids?	The Carboxyl Group (-COOH).
8	Write the IUPAC name for CH3​CHO.	Ethanal (Acetaldehyde).
9	Write the IUPAC name for CH3​COCH3​.	Propanone (Acetone).
10	Write the IUPAC name for C6​H5​CHO.	Benzaldehyde.
11	What is the common name for Methanoic Acid?	Formic Acid.
12	What is the common name for Ethanoic Acid?	Acetic Acid.

Part 2: Preparation of Aldehydes and Ketones

Q. No.	Question	Answer
13	What is the product of the oxidation of a Primary (1∘) alcohol using PCC?	Aldehyde (RCHO).
14	What is the product of the oxidation of a Secondary (2∘) alcohol?	Ketone (RCOR′).
15	What is the use of the reagent PCC (Pyridinium Chlorochromate)?	Selective oxidation of 1∘ alcohols to aldehydes (prevents over-oxidation).
16	What is the main product of the ozonolysis of But-2-ene followed by workup with Zn/H2​O?	Ethanal (CH3​CHO).
17	What is the process of converting an alkyne to a carbonyl compound using H2​SO4​ and HgSO4​?	Hydration of Alkynes.
18	What is the specific reagent used in Stephen Reaction?	SnCl2​ and HCl followed by hydrolysis, used to convert nitriles to aldehydes.
19	What is the major product when Toluene is oxidized with CrO2​Cl2​ (Chromyl Chloride)?	Benzaldehyde (Etard Reaction).
20	What is the process of converting an alkyl benzene to an aldehyde using CrO3​ in Acetic Anhydride?	Etard Reaction (alternative method).
21	Name the reaction used to prepare aromatic aldehydes by treating benzene with CO/HCl in the presence of AlCl3​.	Gattermann-Koch Reaction.
22	How are ketones prepared from Acyl Chlorides?	Reaction with Dialkylcadmium (R2​Cd).
23	How is Benzaldehyde prepared by the reduction of Benzoyl Chloride over a poisoned catalyst?	Rosenmund Reduction (H2​/Pd−BaSO4​).
24	What is the function of the BaSO4​ in Rosenmund Reduction?	It acts as a catalytic poison to prevent the over-reduction of the aldehyde to an alcohol.

Part 3: Chemical Reactions of Aldehydes and Ketones

Q. No.	Question	Answer
25	What is the characteristic reaction type of the carbonyl group?	Nucleophilic Addition Reactions.
26	Rank the reactivity of aldehydes and ketones toward nucleophilic addition.	Aldehydes > Ketones (Aldehydes are less sterically hindered and more electrophilic).
27	What is the product when Acetone reacts with HCN?	Acetone Cyanohydrin (a hydroxynitrile).
28	What is the product when an aldehyde reacts with a Grignard Reagent followed by hydrolysis?	Alcohol (1∘,2∘, or 3∘ depending on the starting material).
29	What is the product when an aldehyde reacts with R-OH in the presence of H+?	Acetal (followed by hemiacetal).
30	What is the product when a ketone reacts with Ethylene Glycol?	Ethylene Glycol Ketal (used as a protecting group).
31	Name the reaction where the carbonyl group is reduced to a CH2​ group using Zn-Hg/conc. HCl.	Clemmensen Reduction.
32	Name the reaction where the carbonyl group is reduced to a CH2​ group using Hydrazine(NH2​NH2​) and KOH/Ethylene Glycol.	Wolff-Kishner Reduction.
33	What is the functional group formed when a carbonyl compound reacts with Ammonia derivatives (Z-NH2​)?	Imine (C=N−Z).
34	Name the reagent used to test for the presence of an aldehyde functional group.	Tollen's Reagent or Fehling's Solution.
35	What is the observation when an aldehyde reacts with Tollen's Reagent?	Formation of a Silver Mirror (Ag).
36	What is the observation when an aldehyde reacts with Fehling's Solution?	Formation of a Red-brown precipitate (Cu2​O).
37	Why do ketones generally not give Tollen's and Fehling's tests?	Ketones are not easily oxidized; the tests require oxidation to a carboxylic acid.
38	What is the product when an aldehyde/ketone containing the CH3​CO− group is treated with I2​/NaOH?	Iodoform (CHI3​, yellow precipitate) (Iodoform Test).

Part 4: Acidity and Reactions of Carboxylic Acids

Q. No.	Question	Answer
39	Why are Carboxylic Acids more acidic than Phenols and Alcohols?	The Carboxylate Anion (RCOO−) is stabilized by two equivalent resonance structures.
40	How does the stability of the Carboxylate Anion affect acidity?	Greater stability means stronger acid.
41	How does an Electron-Withdrawing Group (EWG) affect the acidity of a carboxylic acid?	Increases acidity (stabilizes the RCOO− anion).
42	How does an Electron-Donating Group (EDG) affect the acidity of a carboxylic acid?	Decreases acidity (destabilizes the RCOO− anion).
43	Rank the acidity: F3​CCOOH,Cl3​CCOOH,CH3​COOH.	F3​CCOOH>Cl3​CCOOH>CH3​COOH (Stronger −I effect is more acidic).
44	How does the acidity of a substituted benzoic acid change with increasing distance of the EWG?	Decreases (Inductive effect diminishes with distance).
45	What is the product when a carboxylic acid reacts with an alcohol in the presence of an acid catalyst?	Ester (RCOOR′) (Esterification).
46	Is Esterification a reversible or irreversible reaction?	Reversible (water must be removed to drive the equilibrium forward).
47	What is the product when a carboxylic acid is reduced with LiAlH4​?	Primary (1∘) alcohol.
48	What is the final product when Ethanoic Acid is treated with Cl2​/Red P?	Chloroacetic Acid (ClCH2​COOH) (Hell-Volhard-Zelinsky reaction).
49	What is the term for the reaction of a carboxylic acid with Br2​/Red P?	Hell-Volhard-Zelinsky (HVZ) Reaction.
50	What part of the carboxylic acid is substituted in the HVZ reaction?	The α-hydrogen atom.
51	What is the general term for the reaction used to prepare amines by converting the COOH group to an NH2​ group?	Decarboxylation (loss of CO2​).
52	What is the purpose of heating a carboxylate salt with Soda Lime (NaOH+CaO)?	Decarboxylation (to form an alkane with one less carbon).

Part 5: Aldol and Cannizzaro Reactions

Q. No.	Question	Answer
53	What is the essential structural requirement for a compound to undergo Aldol Condensation?	Presence of at least one α-hydrogen atom.
54	What reagent is used to catalyze Aldol Condensation?	Dilute base (NaOH,Ba(OH)2​, etc.).
55	What is the final stable product of the Aldol Condensation?	An α,β-unsaturated carbonyl compound (formed by dehydration of the aldol).
56	What is the name of the reaction between two different carbonyl compounds, both containing α-hydrogens?	Cross-Aldol Condensation.
57	What is the structural requirement for a compound to undergo Cannizzaro Reaction?	Absence of α-hydrogen atoms.
58	What reagent is used to catalyze the Cannizzaro Reaction?	Concentrated base (NaOH,KOH).
59	What type of reaction is the Cannizzaro reaction?	A Disproportionation (self-oxidation and reduction).
60	What are the two products formed when Formaldehyde undergoes the Cannizzaro reaction?	Methanol (Reduction) and Sodium Formate (Oxidation).
61	What is the name of the reaction between two different aldehydes, both lacking α-hydrogens?	Cross-Cannizzaro Reaction.
62	What is the reaction where a carbonyl compound reacts with an aromatic aldehyde?	Claisen-Schmidt Condensation (a type of cross-aldol).
63	Name the reaction where an aldehyde with no α−H reacts with an enolizable ketone.	Claisen-Schmidt Condensation.

Part 6: Physical Properties and Miscellaneous Concepts

Q. No.	Question	Answer
64	Why do carboxylic acids have higher boiling points than corresponding aldehydes, ketones, and even alcohols?	Extensive formation of Intermolecular Hydrogen Bonded Dimers.
65	What state (monomer or dimer) does Ethanoic Acid exist in the vapour phase?	Dimer (held by two H-bonds).
66	Why are lower aldehydes and ketones soluble in water?	They can form H-bonds with water molecules.
67	How does the solubility of aldehydes/ketones change with increasing size?	Decreases (due to increased non-polar hydrocarbon part).
68	What is the product when an aldehyde reacts with Hydrazine(NH2​NH2​)?	Hydrazone.
69	What is the product when an aldehyde reacts with Phenylhydrazine?	Phenylhydrazone.
70	What is Schiff's Reagent used for?	Distinguishing between aldehydes and ketones (Aldehydes restore the pink/magenta color).
71	What is the product of the reaction of an aldehyde with a Grignard Reagent followed by oxidation?	A secondary alcohol (from RCHO).
72	What is the term for the reaction of Benzaldehyde with Acyl Anhydride and Sodium Salt of the acid?	Perkin Reaction.
73	What is the product of the Perkin reaction?	α,β-unsaturated carboxylic acid (e.g., Cinnamic Acid).
74	What is the product when Ethanoic Acid is heated with P2​O5​?	Acetic Anhydride (CH3​CO2​O).
75	What is the product when Ethanoic Acid reacts with PCl5​?	Acetyl Chloride (CH3​COCl).
76	What is the name of the reaction where Benzaldehyde reacts with KCN to form benzoin?	Benzoin Condensation.
77	What is the role of the Cyanide ion (CN−) in the Benzoin Condensation?	It acts as a nucleophilic catalyst.
78	What compound is used commercially as a food preservative?	Sodium Benzoate (C6​H5​COONa).
79	What is the product when Ethanal reacts with Tollen’s Reagent?	Ammonium Acetate (CH3​COONH4​) and Ag mirror.
80	Why is Formalin solution used to preserve biological specimens?	It is an aqueous solution of Formaldehyde (≈40%).
81	Why is the Carbonyl Carbon considered an Electrophilic Center?	Due to the partial positive charge caused by the C=O polarity.
82	How many α-hydrogens are in Propanal (CH3​CH2​CHO)?	Two (on the C−2 carbon).
83	How many α-hydrogens are in Acetophenone (C6​H5​COCH3​)?	Three (on the CH3​ group).
84	Which is the only aldehyde that undergoes Cannizzaro Reaction exclusively?	Formaldehyde (HCHO).
85	Why is the Benzoyl group m-directing and deactivating in electrophilic substitution?	The C=O group is EWG, showing a strong −M effect.
86	What is the common name for Benzene-1,4-dicarboxylic acid?	Terephthalic Acid.
87	What is the product of the reaction of Formaldehyde with Ammonia?	Urotropine (Hexamethylenetetramine).
88	What is the major product when Butanal undergoes Aldol Condensation?	2-Ethylhex-2-enal.
89	What is the pKa​ value used to express?	The strength of an acid (lower pKa​ is stronger acid).
90	What are Lactones?	Cyclic Esters formed from hydroxy acids.
91	What are Lactams?	Cyclic Amides.
92	What is the name of the reaction that converts a ketone to an ester using Peroxyacid?	Baeyer-Villiger Oxidation.
93	What is the role of the Tollens Reagent in the test for aldehydes?	It acts as a mild oxidising agent.
94	What is the product when Ethanal is oxidized by strong oxidizing agents like KMnO4​?	Ethanoic Acid (CH3​COOH).
95	What is the final product when Propanoic Acid undergoes HVZ reaction and subsequent hydrolysis?	α-Hydroxypropanoic Acid.
96	What is the key difference between Acyl Chlorides and Carboxylic Acids in terms of reactivity?	Acyl Chlorides are much more reactive toward nucleophilic attack (better leaving group, Cl−).
97	What is the product when Benzaldehyde is heated with conc.NaOH?	Benzyl Alcohol and Sodium Benzoate (Cannizzaro Reaction).
98	Why are Ketones used in the body for energy production during starvation?	They can be converted into Acetoacetate (ketone bodies) in the liver.
99	Name the reaction that is a combination of two Cannizzaro reactions occurring within the same molecule.	Intramolecular Cannizzaro Reaction.
100	What is the product when Acetone is treated with Ammonia followed by reduction?	Isopropylamine.
101	What is the product of Acetaldehyde reacting with a strong oxidizing agent like KMnO4​?	Acetic Acid.
102	What is the common name for the reaction of Benzaldehyde with Aniline?	Formation of a Schiff's Base (Imine formation).
103	What is the most stable form of the Carboxylic Acid dimer in the solid state?	A ring structure held by two H-bonds.
104	Give the name of the product when Benzoyl Chloride reacts with water.	Benzoic Acid (Hydrolysis).
105	What is the final product of the reaction of an Aldehyde with Ammoniacal Silver Nitrate (Tollen’s)?	The salt of the carboxylic acid and elemental Silver.
106	Why does Benzoic Acid not undergo Friedel-Crafts reaction?	The -COOH group is a strong deactivating group (and complexes with the AlCl3​ catalyst).
107	What is the intermediate formed during the Clemmensen reduction mechanism?	Generally involves a zinc amalgam intermediate.
108	What is the common use of Adipic Acid (Hexane-1,6-dioic acid)?	Manufacturing Nylon-6,6.
109	What is the order of reactivity in nucleophilic addition: Formaldehyde,Acetaldehyde,Acetone?	Formaldehyde>Acetaldehyde>Acetone.
110	Why is the Cannizzaro reaction preferred over Aldol at high base concentration?	The high base concentration favors the hydride ion transfer (disproportionation).
111	Name the reaction that converts a primary amide to a primary amine with one less carbon atom.	Hofmann Bromamide Degradation.

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