JEE Main Previous year questions (2021-23): Organic Chemistry - Some Basic Principles & Technique | 35 Years Chapter wise Previous Year Solved Papers for JEE PDF Download

Q.1.  Given below are two statements:
Statements I:  under Clemmensen reduction conditions will give
Statements II:     under Wolff-Kishner reduction conditions will give
In the light of the above statements, choose the correct answer from the options given below:       (JEE Main 2023)
(a) Statement I is false but Statement II is true
(b) Statement I is true but Statement II is false
(c) Both Statement I and Statement II are true
(d) Both Statement I and Statement II are false

Ans. b

Q.2. Choose the correct representation of conductometric titration of benzoic acid vs sodium hydroxide.        (JEE Main 2023)
(a)
(b)
(c)
(d)

Ans. a
C₆H₅COOH + NaOH → C₆H₅COONa + H₂O
when weak acid C₆H₅COOH titrated against strong base NaOH in the beginning the conductance Inc. slowly and after equivalent point it increase rapidly.

Q.3. Find out the major products from the following reaction        (JEE Main 2023)
(a)
(b)
(c)
(d)

Ans. b

Q.4. Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Benzene is more stable than hypothetical cyclohexatriene
Reason R: The delocalized π electron cloud is attracted more strongly by nuclei of carbon atoms.

In the light of the above statements, choose the correct answer from the options given below:        (JEE Main 2023)
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are correct but R is NOT the correct explanation ofA
(c) A is false but R is true
(d) A is true but R is false

Ans. a

Q.5. Optical activity of an enantiomeric mixture is +12.6^∘ and the specific rotation of (+) isomer is +30^∘. The optical purity is __________%.      (JEE Main 2022)

Ans. 42


= 42%

Q.6. Total number of isomers (including stereoisomers) obtained on monochlorination of methylcyclohexane is ___________.       (JEE Main 2022)

Ans. 12

Q.7. The total number of monobromo derivatives formed by he alkanes with molecular formula C₅H₁₂ is (excluding stereo isomers) __________.        (JEE Main 2022)

Ans. 8

Q.8. The number of sp³ hybridised carbons in an acyclic neutral compound with molecular formula C₄H₅N is ___________.        (JEE Main 2022)

Ans. 1

Q.9. Observe structures of the following compounds         (JEE Main 2022)
The total number of structures/compounds which possess asymmetric carbon atoms is ______________.         (JEE Main 2022)

Ans. 3 

Q.10. Total number of possible stereoisomers of dimethyl cyclopentane is ____________.          (JEE Main 2022)

Ans. 5

Q.11. Number of electrophilic centres in the given compound is _______________.           (JEE Main 2022)

Ans. 3
Given compounds:

Number of electrophilic centres = 3 

Q.12. Given below are two statements.

Statement I: The compound  is optically active.

Statement II:  is mirror image of above compound A.

In the light of the above statement, choose the most appropriate answer from the options given below.        (JEE Main 2022)
(a) Both Statement I and Statement II are correct.
(b) Both Statement I and Statement II are incorrect.
(c) Statement I is correct but Statement II is incorrect.
(d) Statement I is incorrect but Statement II is correct.

Ans. c

Compound (A) in Statement-I and compound in Statement-II is not the mirror image of (I). 

Q.13. Which among the following is the strongest Bronsted base?         (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. d
 is the strongest base among the given compounds due to the maximum +I effect and the lone pair of N is not in dynamic state so it can be donated easily.

Q.14. Among the following marked proton of which compound shows lowest pK_a value?         (JEE Main 2022) 
(a)
(b)
(c)
(d)

Ans. c



The conjugate base of compound (C) is stabilized by extended conjugation. Hence the indicated proton of compound C is most acidic i.e. will have lowest pK_a. 

Q.15. Match List - I with List - II:
Choose the correct answer from the options given below:         (JEE Main 2022) 
(a) (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
(b) (A) - (IV), (B) - (III), (C) - (I), (D) - (II)
(c) (A) - (III), (B) - (IV), (C) - (I), (D) - (II)
(d) (A) - (IV), (B) - (III), (C) - (II), (D) - (I)

Ans. c

Q.16. Given below are two statements: one is labelled as Assertion A and, the other is labelled as Reason R.
Assertion A: [6] Annulene, [8] Annulene and cis-[10] Annulene, are respectively aromatic, not-aromatic and aromatic.

Reason R: Planarity is one of the requirements of aromatic systems.
In the light of the above statements, choose the most appropriate answer from the options given below.         (JEE Main 2022)
(a) Both A and R are correct and R is the correct explanation of A. 
(b) Both A and R are correct but R is NOT the correct explanation of A. 
(c) A is correct but R is not correct. 
(d) A is not correct but R is correct. 

Ans. d
[6] Annulene is aromatic because it is planar.
[8] Annulene and [10] Annulene are both not aromatic because they are not planar. So, Assertion (A) is not correct.
Reason (R) is correct because planarity is one of the requirements of aromatic system. 

Q.17. Which of the following is not an example of benzenoid compound?         (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. b

Q.18. The correct decreasing order of priority of functional groups in naming an organic Question: compound as per IUPAC system of nomenclature is         (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. b

Q.19. Which of the following compounds is not aromatic?          (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. c

Q.20. Arrange the following in decreasing acidic strength.          (JEE Main 2022)
(a) A > B > C > D
(b) B > A > C > D
(c) D > C > A > B
(d) D > C > B > A

Ans. a

Q.21. Which of the following is an example of conjugated diketone?          (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. c
is a conjugated diketone.
In the rest of the diketones given in the question, the two (C = O) groups are not in conjugation with each other. 

Q.22. Arrange the following carbocations in decreasing order of stability.          (JEE Main 2022)
(a) B > A > C
(b) A > B > C
(c) C > B > A
(d) C > A > B

Ans. a
The given carbocations are

Carbocation (A) is stabilised by hyperconjugation due to 4α hydrogen atoms. Carbocation (C) is also stabilised by hyperconjugation due to 4 a hydrogen atoms but destabilised by −1 effect of O-atom. Carbocation (B) is most stable as it is stabilised by resonance. 

∴ Correct decreasing order of stability is B > A > C

Q.23. The IUPAC name of ethylidene chloride is:          (JEE Main 2022)
(a) 1-Chloroethene
(b) 1-Chloroethyne
(c) 1, 2-Dichloroethane
(d) 1, 1-Dichloroethane

Ans. d
Ethylidene chloride is CH₃– CHCl₂, its IUPAC name is 1,1-Dichloromethane. 

Q.24. In the following structures, which on is having staggered conformation with maximum dihedral angle?          (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. c
 
It is the staggered conformation with maximum dihedral angle. 

Q.25. The correct order of nucleophilicity is          (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. d

Conjugate base of acid is always a stronger nucleophile. 

Q.26. Which of the following is most stable?          (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. a

Q.27. Which of the following structure are aromatic in nature?          (JEE Main 2022)
(a) A, B, C, and D 
(b) Only A and B 
(c) Only A and C 
(d) Only B, C and D

Ans. b

Q.28. The correct IUPAC name of the following compound is:           (JEE Main 2022)

(a) 4-methyl-2-nitro-5-oxohept-3-enal
(b) 4-methyl-5-oxo-2-nitrohept-3-enal
(c) 4-methyl-6-nitro-3-oxohept-4-enal
(d) 6-formyl-4-methyl-2-nitrohex-3-enal

Ans. c

Q.29. Which of the following carbocations is most stable?           (JEE Main 2022)
(a)
(b)
(c)
(d)

Ans. d

Q.30. The maximum number of possible isomers (including stereoisomers) which may be formed on mono-bromination of 1-methylcyclohex-1-ene using Br₂ and UV light is ___________.        (JEE Advanced 2021)

Ans. 13
Monobromination of 1-methyl cyclohex-1-ene in presence of UV-light gives following products (1 achiral and 6 optically active (*) compounds). So, total 13 products are formed (1 + 6 + 6 enantiomers) 

Radicals formed are

Q.31. The amount of energy required to break a bond is same as the amount of energy released when the same bond is formed. In gaseous state, the energy required for homolytic cleavage of a bond is called Bond Dissociation Energy (BDE) or Bond Strength. BDE is affected by s-character of the bond and the stability of the radicals formed. Shorter bonds are typically stronger bonds. BDEs for some bonds are given below:




For the following reaction 

the correct statement is         (JEE Advanced 2021)
(a) A Initiation step is exothermic with ΔH^∘ = −58 kcal mol⁻¹. 
(b) Propagation step involving ^∙CH₃ formation is exothermic with ΔH^∘ = −2 kcal mol⁻¹. 
(c) Propagation step involving CH₃Cl formation is endothermic with ΔH^∘ = +27 kcal mol⁻¹. 
(d) The reaction is exothermic with ΔH^∘ = −25 kcal mol⁻¹.

Ans. d
The reaction is exothermic with ΔH∘ = −25 kcal mol⁻¹ 

(a) Initiation step is breaking of Cl−Cl bond which requires energy and hence, this step is endothermic.

(b) Propagation step involving formation of CH₃ is also endothermic as bond between C−H is breaking. 

(c) Propagation step involving formation of CH₃Cl is exothermic as bond is formed between C−Cl 



= 58 + 105 − 85 − 103
= −25 kcal mol⁻¹
Hence, the reaction is exothermic with ΔH^o = −25 kcal/mol

Q.32. The amount of energy required to break a bond is same as the amount of energy released when the same bond is formed. In gaseous state, the energy required for homolytic cleavage of a bond is called Bond Dissociation Energy (BDE) or Bond Strength. BDE is affected by s-character of the bond and the stability of the radicals formed. Shorter bonds are typically stronger bonds. BDEs for some bonds are given below:          (JEE Advanced 2021)

Correct match of the C-H bonds (shown in bold) in Column J with their BDE in Column K is 

(a) P - iii, Q - iv, R - ii, S - i
(b) P - i, Q - ii, R - iii, S - iv
(c) P - iii, Q - ii, R - i, S - iv
(d) P - ii, Q - i, R - iv, S - ii

Ans. a
A more stable radical means lesser the bond dissociation energy.
Radicals formed are

Radical formed from Q (PhCH₂−H) is most stable due to resonance.

Stability of free radical decreases with increase in % s-character.

P radical → sp³ → % s-character 25%

R radical → sp² → % s-character 33%

S radical → sp → % s-character 50%

Thus, order of stability of free radical is

Q > P > R > S

Order of bond dissociation energy is

S > R > P > Q

Q.33. The dihedral angle in staggered form of Newman projection of 1, 1, 1-Trichloro ethane is ___________ degree. (Round off to the nearest integer)          (JEE Main 2021)

Ans. 60
1, 1, 1-Trichloro ethane [CCl₃-CH₃] 

Q.34. The number of sigma bonds in

is _______________.          (JEE Main 2021)

Ans. 10

Numbers of σ bonds = 10 

Q.35. The number of acyclic structural isomers (including geometrical isomers) for pentene are ___________.          (JEE Main 2021)

Ans. 6

Q.36. Which one of the following compounds is aromatic in nature?         (JEE Main 2021)
(a)
(b)
(c)
(d)

Ans. d
(a) (Acenaphthene) 

Note: For multiple cyclic ring compound, in aromatic compound (4n +2) πe^- should present in largest conjugated periphery. Here those cyclic rings are not counted which have sp³ carbon atoms as because of sp³ carbon atoms even if those rings have π bonds it can't take part in the resonance with π bonds of other cyclic ring.
(b)
→ 4 πe⁻ in ring conjugation ⇒ Anti Aromatic 
(c) 
⇒ 4 πe⁻ in ring conjugation ⇒ Antiaromatic
(d) 
6πe⁻ in ring conjugation ⇒ Aromatic 

Q.37. Arrange the following conformational isomers of n-butane in order of their increasing potential energy:          (JEE Main 2021)

(a) II < III < IV < I
(b) I < IV < III < II
(c) II < IV < III < I
(d) I < III < IV < II

Ans. d
More stable less potential energy.
Stability order: I > III > IV > II
So
Potential energy: II > IV > III > I 

Q.38. Choose the correct name for compound given below:         (JEE Main 2021)
(a) (4E)-5-Bromo-hex-4-en-2-yne
(b) (2E)-2-Bromo-hex-4-yn-2-ene
(c) (2E)-2-Bromo-hex-2-en-4-yne
(d) (4E)-5-Bromo-hex-2-en-4-yne

Ans. c

First prioritise the groups according to CIP rule
It is (2E)-2-Bromo-hex-2-en-4-yne 

Q.39. The compound/s which will show significant intermolecular H-bonding is/are:          (JEE Main 2021)
(a) (b) only
(b) (c) only
(c) (a) and (b) only
(d) (a), (b) and (c)

Ans. a
(a) Shows intra molecular H-bonding
(b) Shows significant intermolecular H-bonding
(c) It do not show intermolecular H-bonding due to steric hindrance. 

Q.40. The number of stereoisomers possible for 1, 2-dimethyl cyclopropane is:          (JEE Main 2021)
(a) One
(b) Four
(c) Two
(d) Three

Ans. d

Q.41. Which one of the following compounds is not aromatic?          (JEE Main 2021)
(a)
(b)
(c)
(d)

Ans. c

Q.42. Given below are two statements:
Statement I: Hyperconjugation is a permanent effect.
Statement II: Hyperconjugation in ethyl cationinvolves the overlapping ofbond with empty 2p orbital of other carbon.
Choose the correct option:          (JEE Main 2021)
(a) Both statement I and statement II are false 
(b) Statement I is incorrect but statement II is true 
(c) Statement I is correct but statement II is false 
(d) Both statement I and statement II are true

Ans. c
Statement I: It is correct statement
Statement II:bond with empty 2p orbital hence given statement is false.

Q.43.
The correct order of stability of given carbocation is:          (JEE Main 2021)
(a) A > C > B > D
(b) D > B > C > A
(c) D > B > A > C
(d) C > A > D > B

Ans. a

Q.44. Which among the following is the strongest acid?          (JEE Main 2021)
(a) CH₃CH₂CH₂CH₃
(b)
(c)
(d)

Ans. d
Strongest acid because its conjugate base is aromatic 

Q.45. The correct decreasing order of densities of the following compounds is:          (JEE Main 2021)

(a) (D) > (C) > (B) > (A)
(b) (C) > (D) > (A) > (B)
(c) (C) > (B) > (A) > (D)
(d) (A) > (B) > (C) > (D)

Ans. a
The density order 

Q.46. Which one among the following resonating structures is not correct?          (JEE Main 2021)
(a)
(b)
(c)
(d)

Ans. a

It is unstable Resonating Structure (due to similar charge on adjacent atom). 

Q.47. Which of the following molecules does not show stereo isomerism?          (JEE Main 2021)
(a) 3, 4-Dimethylhex-3-ene
(b) 3-Methylhex-1-ene
(c) 3-Ethylhex-3-ene
(d) 4-Methylhex-1-ene

Ans. c

Q.48. hich of the following compounds does not exhibit resonance?          (JEE Main 2021)
(a) CH₃CH₂OCH = CH₂
(b)
(c) CH₃CH₂CH₂CONH₂
(d) CH₃CH₂CH = CHCH₂NH₂

Ans. d

(D) CH₃−CH₂−CH = CH−CH₂−NH₂
For (D) no conjugation thus resonance is not possible. 

Q.49.
The correct order of their reactivity towards hydrolysis at room temperature is:          (JEE Main 2021)
(a) (A) > (B) > (C) > (D)
(b) (D) > (A) > (B) > (C)
(c) (D) > (B) > (A) > (C)
(d) (A) > (C) > (B) > (D)

Ans. a

Q.50. Which one of the following pairs of isomers is an example of metamerism?         (JEE Main 2021)
(a)
(b)
(c)
(d)

Ans. d
Metamers are compounds which have different alkyl groups present along both side of polyvalent functional group.

No polyvalent functional group in option (a).

The two functional groups are different in option (b).

Alcohol is not a polyvalent functional group.

Alkyl groups are different along both sides of polyvalent functional group.

Q.51.
Among the given species the Resonance stabilised carbocations are:         (JEE Main 2021)
(a) (C) and (D) only
(b) (A), (B) and (D) only
(c) (A) and (B) only
(d) (A), (B) and (C) only

Ans. c

For resonance positive charged carbon atom ( Name it carbon 1) should be connected with the carbon atom( Name it carbon 2) using only sigma bond. Then carbon 2 should attach with another carbon with double bond. Here you can see (A) and (B) satisfies this situation but (C) and (D) don’t satisfy the situation. 

Q.52. Given below are two statements:
Statement I: C₂H₅OH and AgCN both can generate nucleophile.
Statement II: KCN and AgCN both will generate nitrile nucleophile with all reaction conditions.
Choose the most appropriate option:          (JEE Main 2021)
(a) Statement I is false but statement II is true. 
(b) Both statement I and statement II are true. 
(c) Both statement I and statement II are false. 
(d) Statement I is true but statement II is false.

Ans. d
Both C₂H₅OH and AgCN can generate nucleophile.
KCN generates nitriles on substitution reactions with haloalkanes where AgCN generates isonitriles on substitution reactions with haloalkanes. Because KCN is ionic and has ‘C’ nucleophilic centre whereas AgCN is covalent and has ‘N’ nucleophilic centre. 

Q.53. In the following molecule, 
Hybridisation of Carbon a, b, and c respectively are:          (JEE Main 2021)
(a) sp³, sp², sp² 
(b) sp³, sp, sp² 
(c) sp³, sp², sp 
(d) sp³, sp, sp

Ans. a

Q.54. Compound with molecular formula C₃H₆O can show:          (JEE Main 2021)
(a) Positional isomerism 
(b) Both positional isomerism and metamerism 
(c) Metamerism 
(d) Functional group isomerism 

Ans. d
C₃H₆O (degree of unsaturation = 1) 

Functional group isomerism. 

Q.55. Which of the following is an aromatic compound?          (JEE Main 2021)
(a)
(b)
(c)
(d)

Ans. a
A compound which has (4n + 2)π electrons completely delocalised over the cyclic ring is aromatic. 
 
Here 6 π electrons are present which follow the rule. 

Q.56. Which of the following is least basic?           (JEE Main 2021)
(a)
(b)
(c)
(d)

Ans. a
Basic strength ∝ availability of lone pair. 

In this case lone pair ofis highly participating in resonance.

Q.57. Match List - I with List - II:           (JEE Main 2021)

The correct match is:
(a) (a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)
(b) (a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)
(c) (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
(d) (a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)

Ans. c
(i) Lassaigne test is used to detect N, S, P, X element
(ii) Carbon and hydrogen are detected by heating the compound with copper (ii) oxide.
(iii) Halides are detected by silver nitrate
(iv) Sodium fusion extract gives black ppt. with acetic acid and lead acetate to confirm the presence of sulphur. 

Q.58. Among the following, the aromatic compounds are:           (JEE Main 2021) 
Choose the correct answer from the following options:
(a) (B), (C) and (D) only
(b) (B) and (C) only
(c) (A), (B) and (C) only
(d) (A) and (B) only

Ans. b

Q.59. Which of the following is 'a' FALSE statement?           (JEE Main 2021) 
(a) Carius method is used for the estimation of nitrogen in an organic compound.
(b) Kjeldahl's method is used for the estimation of nitrogen in an organic compound.
(c) Carius tube is used in the estimation of sulphur in an organic compound.
(d) Phosphoric acid produced on oxidation of phosphorus present in an organic compound is precipitated as Mg₂P₂O₇ by adding magnesia mixture.

Ans. a
Carius method is used in the estimation of halogen and sulphur in organic compounds. 

Q.60. Inmolecule, the hybridization of carbon 1, 2, 3 and 4 respectively, are:           (JEE Main 2021)  
(a) sp², sp, sp², sp³
(b) sp², sp², sp², sp³
(c) sp³, sp, sp³, sp³
(d) sp², sp³, sp², sp³

Ans. a

Q.61. The correct order of acid character of the following compounds is:           (JEE Main 2021)  

(a) IV > III > II > I
(b) III > II > I > IV
(c) II > III > IV > I
(d) I > II > III > IV

Ans. c
Acidic strength

Since carboxylic acids are more acidic than phenols.
–I and – R effect increase the acidic strength where as +I and +R effect decrease the acidic strength of carboxylic acids. 

Q.62. Which one of the following compounds is non-aromatic?           (JEE Main 2021) 
(a) 
(b)
(c)
(d)

Ans. d
Molecules are aromatic if they are

(1) Cyclic

(2) Planar

(3) Conjugated

(4) Molecules who have (4n + 2) π electrons [This is called Huckel's Rule]

Aromatic compounds are highly stable.

(a)

(1) Molecule is cyclic.

(2) All atoms which are completing the cyclic ring have sp² hybridisation. So it is shape is planar. If any one atom is sp³ hybridised then molecule shape will be non planar.

(3) It is conjugated means all π bonds are showing resonance with each other.

So all atoms which are forming cyclic ring are perticipating in resonance. That is called conjugated.

(b)

(1) This compounds is cyclic

(2) All atoms are sp² hybridised. So molecule shape is planar.

(3) It is conjugated as all π bonds are showing resonance.

(4) It has 6πe⁻. So obey Huckel Rule.

∴ Compound is aromatic.

(c)

(1) This compound is cyclic

(2) All atoms are sp² hybridised. So molecule shape is planar.

(3) It is conjugated as π bond is showing resonance.

(4) It has 2πe⁻. So obey Huckel Rule.

∴ Compound is aromatic.

Anti-Aromatic :-

It is highly unstable.

Anti-aromatic compounds are -

(1) Cyclic

(2) All atoms which is forming cyclic ring are planar.

(3) it is conjugated.

(4) It has 4nπe⁻.

Here no anti-aromatic compounds presents.

Non-Aromatic :-

Those compounds which are not either aromatic or anti-aromatic.

Definition : All cyclic compounds which are comparatively stable with its open chain analogous system, compound is known as non aromatic compound.

(a)

Here one carbon is sp³ hybridised that is why it's structure is non planar. So this cyclic compound will be neither aromatic nor anti-aromatic. It will be non aromatic.

Multiple cyclic rings :-

To find nature of this ring, make maximum possible π bonds in the outer ring. This is a hypothetical structure. Here outer ring should be largest conjugated ring means outer ring should have these π bonds which are in resonance with each other.

And the nature of the outer ring will be same as the original molecule.

(d)

From this structure we can't decide the nature as all π bonds are not present in the outer ring that is why we make right resonating structure where all π bonds present in the outer ring.

Outer ring :

As outer ring is aromatic so original compound will also be aromatic.

Note: Even though from left resonating structure we can't decide the nature of the molecule, it does not mean it's nature is not aromatic. As different resonating structures don't have different nature. All resonating structure have same nature.

Q.63. The correct order of the following compounds showing increasing tendency towards nucleophilic substitution reaction is:           (JEE Main 2021) 
(a) (iv) < (i) < (ii) < (iii)
(b) (iv) < (iii) < (ii) < (i)
(c) (iv) < (i) < (iii) < (ii)
(d) (i) < (ii) < (iii) < (iv)

Ans. d

Greater the number of nitro (−NO₂) group in chlorobenzene, greater the rate of nucleophilic substitution reaction in aromatic halides.

When a nitro group is present at ortho and para position, it can withdraw electrons from the benzene ring.