Reagents in Organic Chemistry ( Class 11 & 12)

 

Over 110 Q&A on Reagents in Organic Chemistry (NCERT Class 11 & 12)

Part 1: Oxidizing Agents and Reducing Agents

Q. No.	Reagent	Reactant	Role/Major Product
1	PCC (Pyridinium Chlorochromate)	1∘ Alcohol (RCH2​OH)	Oxidizes to Aldehyde (RCHO), prevents over-oxidation.
2	Acidified KMnO4​ (Hot)	Alkene (C=C)	Cleavage of C=C to form Carboxylic Acids or Ketones.
3	Acidified KMnO4​ (Hot)	Alkyl Benzene (Ar-R)	Oxidizes the side chain to Benzoic Acid (Ar-COOH).
4	CrO3​ in Acetic Anhydride	Toluene (C6​H5​CH3​)	Oxidizes to Benzaldehyde (C6​H5​CHO) (Etard Reaction).
5	Tollen's Reagent (Ag(NH3​)2+​)	Aldehyde (RCHO)	Oxidizes to Carboxylate salt, depositing a silver mirror.
6	Fehling's Solution (Cu2+ complex)	Aldehyde (RCHO)	Oxidizes to Carboxylate salt, forming red-brown Cu2​O ppt.
7	Ozone (O3​), then Zn/H2​O	Alkene (C=C)	Cleaves C=C to form Aldehydes and/or Ketones (Ozonolysis).
8	LiAlH4​ (Lithium Aluminium Hydride)	Carboxylic Acid (RCOOH)	Strongly reduces to 1∘ Alcohol (RCH2​OH).
9	LiAlH4​	Aldehyde (RCHO) or Ketone (R2​CO)	Reduces to corresponding 1∘ or 2∘ Alcohol.
10	NaBH4​ (Sodium Borohydride)	Aldehyde (RCHO) or Ketone (R2​CO)	Selectively reduces to 1∘ or 2∘ Alcohol (does not reduce COOH or NO2​).
11	Zn-Hg/conc. HCl	Carbonyl Group (C=O)	Reduces C=O to CH2​ (Clemmensen Reduction).
12	NH2​NH2​,KOH/heat	Carbonyl Group (C=O)	Reduces C=O to CH2​ (Wolff-Kishner Reduction).
13	H2​/Pd−BaSO4​	Acyl Chloride (RCOCl)	Reduces to Aldehyde (RCHO) (Rosenmund Reduction).
14	DIBAL-H (Diisobutylaluminium Hydride)	Nitrile (RCN)	Selectively reduces to Aldehyde (RCHO) after hydrolysis.

Part 2: Nucleophiles, Bases, and Acid Catalysts

Q. No.	Reagent	Reactant	Role/Major Product
15	Grignard Reagent (RMgX)	Formaldehyde (HCHO)	Forms 1∘ Alcohol after hydrolysis.
16	Grignard Reagent (RMgX)	Ketone (R2​CO)	Forms 3∘ Alcohol after hydrolysis.
17	Aqueous KOH	Haloalkane (R−X)	Nucleophilic Substitution (SN​) to form Alcohol (R−OH).
18	Alcoholic KOH	Haloalkane (R−X)	Elimination (E) to form Alkene (Dehydrohalogenation).
19	KCN (Potassium Cyanide)	Haloalkane (R−X)	Nucleophilic Substitution (R−CN), major product.
20	AgCN (Silver Cyanide)	Haloalkane (R−X)	Nucleophilic Substitution (R−NC), major product (Isocyanide).
21	Na metal (or K metal)	Alcohol (R−OH)	Acts as a base, forming Alkoxide (R−O−Na+) and H2​ gas.
22	Dilute NaOH	Aldehyde with α−H	Catalyzes Aldol Condensation (forms β-hydroxy carbonyl).
23	Conc. NaOH	Aldehyde without α−H	Catalyzes Cannizzaro Reaction (Disproportionation).
24	Conc. H2​SO4​/heat (443 K)	Alcohol (R−OH)	Dehydration to form Alkene (E1 elimination).
25	Conc. H2​SO4​/heat (413 K)	Alcohol (R−OH)	Condensation to form Ether (SN​2 substitution).
26	H3​O+ (H+ catalyst)	Alkene (C=C)	Hydration to form Alcohol (R−OH) (Markownikoff's Rule).
27	NH3​	Haloalkane (R−X)	Nucleophilic Substitution to form Primary Amine (R−NH2​).

Part 3: Halogenating and C-C Bond Forming Reagents

Q. No.	Reagent	Reactant	Role/Major Product
28	PCl5​ (Phosphorus Pentachloride)	Alcohol (R−OH)	Halogenates to form Alkyl Chloride (R−Cl) and POCl3​.
29	SOCl2​ (Thionyl Chloride)	Alcohol (R−OH)	Halogenates to form Alkyl Chloride (R−Cl) (Best method).
30	Br2​/FeBr3​	Benzene (C6​H6​)	Electrophilic Substitution to form Bromobenzene (C6​H5​Br).
31	CH3​Cl/Anhydrous AlCl3​	Benzene (C6​H6​)	Friedel-Crafts Alkylation to form Toluene (C6​H5​CH3​).
32	CH3​COCl/Anhydrous AlCl3​	Benzene (C6​H6​)	Friedel-Crafts Acylation to form Acetophenone (C6​H5​COCH3​).
33	NaI in Acetone	Alkyl Chloride/Bromide (R−X)	Halogen Exchange to form Alkyl Iodide (R−I) (Finkelstein Reaction).
34	AgF or Hg2​F2​	Alkyl Bromide/Chloride (R−X)	Halogen Exchange to form Alkyl Fluoride (R−F) (Swarts Reaction).
35	Br2​ in CCl4​	Alkene (C=C)	Addition of Halogen to form Vicinal Dibromide (Decolorizes Br2​ water).
36	HBr in presence of Peroxide	Unsymmetrical Alkene	Anti-Markownikoff Addition to form R−CH2​CH2​Br.
37	Na/Dry Ether	Alkyl Halide (R−X)	Coupling to form Alkanes (R−R) (Wurtz Reaction).
38	Na/Dry Ether	Haloarene + Alkyl Halide	Coupling to form Alkyl Arenes (Wurtz-Fittig Reaction).
39	Na/Dry Ether	Haloarene (Ar−X)	Coupling to form Biphenyl (Ar−Ar) (Fittig Reaction).

Part 4: Specific and Named Reaction Reagents

Q. No.	Reagent	Reactant	Role/Major Product
40	SnCl2​/HCl then H3​O+	Nitrile (R−CN)	Reduction to form Aldehyde (RCHO) (Stephen Reaction).
41	Zn dust	Phenol (Ar−OH)	Reduces Phenol to Benzene (C6​H6​).
42	CHCl3​/NaOH then H+	Phenol (Ar−OH)	Formylation to yield Salicylaldehyde (Reimer-Tiemann Reaction).
43	CO2​/NaOH then H+	Phenoxide Ion (Ar−O−)	Carboxylation to yield Salicylic Acid (Kolbe's Reaction).
44	Br2​ water (Aqueous)	Phenol (Ar−OH)	Polybromination to yield 2,4,6-Tribromophenol.
45	Cu2​Cl2​/HCl	Benzene Diazonium Salt (Ar-N2+​Cl−)	Substitution of -N2​Cl by -Cl (Sandmeyer Reaction).
46	Cu powder/HCl	Benzene Diazonium Salt (Ar-N2+​Cl−)	Substitution of -N2​Cl by -Cl (Gattermann Reaction).
47	H2​/Ni (Sabatier-Senderens)	Alkyne (C≡C)	Complete Hydrogenation to Alkane (C−C).
48	H2​/Pd−CaCO3​ (Lindlar’s)	Alkyne (C≡C)	Partial Hydrogenation to Cis-Alkene.
49	Na/liquid NH3​	Alkyne (C≡C)	Partial Hydrogenation to Trans-Alkene (Birch Reduction).
50	Red P/X2​	Carboxylic Acid (RCH2​COOH)	α-Halogenation to form α-Halo Acid (HVZ Reaction).
51	I2​/NaOH	CH3​CH(OH)R or CH3​COR	Iodoform Test, forming CHI3​ (yellow ppt).
52	NH2​OH (Hydroxylamine)	Carbonyl Group (C=O)	Forms Oxime (C=N−OH).
53	NH2​NH2​ (Hydrazine)	Carbonyl Group (C=O)	Forms Hydrazone (C=N−NH2​).

Part 5: Identifying Reaction Types by Reagents

Q. No.	Reagent	Reactant	Type of Reaction
54	FeSO4​ (in Ring Test)	Nitrate Ion (NO3−​)	Redox Reaction (Fe2+→Fe3+).
55	BaCl2​	Sulphate Ion (SO42−​)	Precipitation (Ionic Analysis).
56	HCl (gas) + Alkene	Propene (CH3​CH=CH2​)	Electrophilic Addition (Markownikoff's).
57	Br2​/FeBr3​	Phenol (Ar−OH)	Electrophilic Substitution.
58	AgCN	Alkyl Halide (R−X)	Nucleophilic Substitution (SN​2).
59	Conc. H2​SO4​	Alcohol (R−OH) at 443 K	Elimination (E1).
60	H2​SO4​ (catalyst)	Carboxylic Acid + Alcohol	Condensation (Esterification).
61	Zn dust	Chloroform (CHCl3​)	Reduction (to Methane).
62	Na2​Cr2​O7​/H2​SO4​	Toluene (C6​H5​CH3​)	Oxidation (Side-chain oxidation).
63	NaOH/CaO (Soda Lime)	Carboxylate Salt (RCOONa)	Decarboxylation.
64	LiAlH4​	Nitrile (RCN)	Reduction (to Primary Amine).
65	ZnCl2​/HCl (Lucas Reagent)	Alcohol (R−OH)	Substitution (SN​) to form R−Cl.
66	HI (hot, excess)	Ether (R−O−R′)	Cleavage (SN​) to form Alkyl Iodides.

Part 6: Intermediate and Mechanistic Reagents

Q. No.	Reagent	Reactants to Distinguish	Observation
76	Lucas Reagent (ZnCl2​/HCl)	1∘,2∘,3∘ Alcohols	3∘ shows immediate turbidity; 1∘ shows none.
77	Tollen’s Reagent	Aldehyde vs Ketone	Aldehyde gives a Silver Mirror; Ketone gives none.
78	I2​/NaOH (Iodoform Test)	Ethanol vs Methanol	Ethanol gives Yellow Precipitate (CHI3​); Methanol gives none.
79	Fehling’s Solution	Glucose vs Sucrose	Glucose (reducing sugar) gives Red-brown ppt; Sucrose gives none.
80	Br2​ water (CCl4​)	Alkane vs Alkene	Alkene immediately decolorizes the brown color (Addition).
81	AgNO3​ (aqueous/ethanolic)	R−Cl vs Ar−Cl	R−Cl gives white AgCl ppt (ionic Cl); Ar−Cl gives none (strong C−Cl bond).
82	Neutral FeCl3​ solution	Phenol vs Alcohol	Phenol gives a Violet/Green color (complex formation); Alcohol gives none.
83	Tollen’s Reagent	Terminal Alkyne vs Non-terminal Alkyne	Terminal Alkyne gives a White ppt (Ag acetylide); Non-terminal gives none.

Part 7: Distinguishing and Analytical Reagents

Q. No.	Reagent	Reactant	Mechanistic Role/Intermediate
67	Anhydrous AlCl3​	Alkyl Halide (R−X)	Lewis Acid, facilitates formation of Electrophile/Carbocation.
68	UV Light or Δ	Alkane + Cl2​	Initiates Homolysis, forming Free Radicals.
69	Peroxide (R−O−O−R)	Alkene + HBr	Initiates Homolysis, forming Free Radicals.
70	NaOH (dilute)	CH3​CH2​Br	Nucleophile (OH−) for SN​2 reaction.
71	AgNO3​ (with R−X)	Tertiary Halide (3∘R−X)	Aids SN​1 ionization, Ag+ removes X−.
72	Diazomethane (CH2​N2​)	Carboxylic Acid (RCOOH)	Methylates to form Methyl Ester (RCOOCH3​).
73	H+ (Acid)	Carbonyl Compound	Activates the carbonyl group towards Nucleophilic Attack.
74	HNO3​/H2​SO4​	Benzene (C6​H6​)	Generates NO2+​ (Nitronium Ion) Electrophile.
75	I2​/Red Phosphorus	Carboxylic Acid (RCOOH)	Forms Acyl Iodide intermediate for HVZ reaction.

Part 8: Further Reagents and Reactants (Quickfire)

Q. No.	Reagent	Reactant	Role/Type of Product
84	H2​/Pd on BaSO4​	Alkyne (C≡C)	Partial Cis-Hydrogenation to Alkene.
85	Dilute KMnO4​ (Cold)	Alkene (C=C)	Hydroxylation to form Glycol (Bayer's Test).
86	Zn/H+	Haloalkane (R−X)	Reduces to Alkane (R−H).
87	CuCl/HCl	Benzene Diazonium Salt (Ar-N2+​Cl−)	Substitutes -Cl (Sandmeyer).
88	KI	Benzene Diazonium Salt (Ar-N2+​)	Substitutes -I (no catalyst needed).
89	HCN	Carbonyl Compound (C=O)	Nucleophilic Addition to form Cyanohydrin.
90	R′OH/H+	Aldehyde (RCHO)	Forms Acetal (RCH(OR′)2​).
91	P2​O5​/heat	Carboxylic Acid (RCOOH)	Dehydration to form Acid Anhydride.
92	PCl5​	Carboxylic Acid (RCOOH)	Forms Acyl Chloride (RCOCl).
93	Br2​/UV Light	Alkane (R−H)	Free Radical Substitution (Halogenation).
94	Sodamide (NaNH2​)	Terminal Alkyne (R−C≡CH)	Forms Acetelyde salt (R−C≡C−Na+).
95	H2​O/H+	Nitrile (RCN)	Hydrolyzes to Carboxylic Acid (RCOOH).
96	NaOH (molten)	Haloarene (Ar−Cl)	Substitution to Phenol (Dow’s Process).
97	CrO3​/H+	2∘ Alcohol (R2​CHOH)	Oxidizes to Ketone (R2​CO).
98	CH3​CH2​OH/Na+	CH3​CH2​Br	Forms Diethyl Ether (Williamson's Synthesis).
99	HI (cold, equimolar)	Ether (R−O−R′)	Cleavage to form R−I and R′−OH.
100	KNO2​	Haloalkane (R−X)	Forms Alkyl Nitrite (R−ONO).
101	AgNO2​	Haloalkane (R−X)	Forms Nitroalkane (R−NO2​).
102	I2​/Red P	Carboxylic Acid (RCOOH)	Reduces to Alkane (RCH3​) (Harsh reduction).
103	H2​O/Base	Ester (RCOOR′)	Saponification (Base hydrolysis) to RCOOH salt and R′OH.
104	HOCl (Hypochlorous Acid)	Alkene (C=C)	Addition to form Halohydrin (RCH(OH)CH2​Cl).
105	HBr (without peroxide)	Cyclohexene	Electrophilic Addition to form Bromocyclohexane.
106	CH3​OH (Methanol) H+	Benzoic Acid (ArCOOH)	Esterification to form Methyl Benzoate.
107	NH3​/heat	Carboxylic Acid (RCOOH)	Forms Amide (RCONH2​).
108	Cu at 573 K	2∘ Alcohol (R2​CHOH)	Dehydrogenation (Oxidizes) to Ketone.
109	Cu at 573 K	3∘ Alcohol (R3​COH)	Dehydration (Elimination) to Alkene.
110	KOH/heat (in Baeyer-Villiger Oxidation)	Ketone (R2​CO)	Oxidizes to Ester (RCOOR).
111	Soda Lime (NaOH+CaO)	Carboxylate Salt (RCOONa)	Decarboxylation to Alkane (R−H).
112	NH4​OH (Ammoniacal)	Terminal Alkyne (R−C≡CH)	Forms Copper Acetylide (Red ppt with Cu2​Cl2​).

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