Organic Chemistry

01

PYQ 1980

medium

chemistry ID: neet-ug-

Which of the following undergoes nucleophilic substitution exclusively by 1 mechanism?

1

Benzyl chloride

2

Ethyl chloride

3

Chlorobenzene

4

Isopropyl chloride

02

PYQ 1988

medium

chemistry ID: neet-ug-

Which one of the following can exhibit cis-trans-isomerism?

1

CH - CHCI - COOH

2

H - C C - Cl

3

Cl - CH =CHCI

4

CICH CI

03

PYQ 1988

medium

chemistry ID: neet-ug-

The Cl-C-Cl angle in 1,1,2,2-tetrachloroethene and tetrachloromethane will be about

1

120 and 109 28'

2

90 and 109.5

3

109.5 and 90

4

109.5 and 120

04

PYQ 1988

medium

chemistry ID: neet-ug-

How many chain isomers could be obtained from the alkane, C ?

1

Four

2

Five

3

Six

4

Seven

05

PYQ 1989

medium

chemistry ID: neet-ug-

Lassaigne?s test is used in qualitative analysis to detect

1

nitrogen

2

sulphur

3

chlorine

4

all of these

06

PYQ 1990

medium

chemistry ID: neet-ug-

An organic compound X(molecular formula C6H7O2N) has six carbon atoms in a ring system, two double bonds and a nitro group as substituent, X is

1

homocyclic but not aromatic

2

aromatic but not homocydic

3

homocyclic and aromatic

4

heterocyclic and aromatic

07

PYQ 1991

medium

chemistry ID: neet-ug-

An hybrid orbital contains

1

- s-character

2

- s-character

3

- s-character

4

- s-character

08

PYQ 1991

medium

chemistry ID: neet-ug-

In sodium fusion test of organic compounds, the nitrogen of the organic compound is converted into

1

sodamide

2

sodium cyanide

3

sodium nitrite

4

sodium nitrate

09

PYQ 1992

easy

chemistry ID: neet-ug-

Among the following compound one that is most reactive towards electrophilic nitration is

1

Benzoic acid

2

Nitrobenzene

3

Toluene

4

Benzene

10

PYQ 1993

medium

chemistry ID: neet-ug-

The most suitable method of separation of mixture of ortho and para-nitrophenols is :

1

Chromatography

2

Crystallisation

3

Steam distillation

4

Sublimation

11

PYQ 1994

medium

chemistry ID: neet-ug-

Correct the increasing order of acidity is as

1

, phenol

2

phenol

3

Phenol,

4

C

12

PYQ 1994

easy

chemistry ID: neet-ug-

Lassaigne's test for the detection of nitrogen fails in

1

NH CONHNH . HCI

2

NH . HCI

3

4

13

PYQ 1996

medium

chemistry ID: neet-ug-

Liquid benzene bums in oxygen according to the equation, How many litres of at STP are needed to complete the combustion of 39 g of liquid benzene?

1

74 L

2

11.2 L

3

22.4 L

4

84 L

14

PYQ 1997

medium

chemistry ID: neet-ug-

Which of the following techniques is most suitable for purification of cyclohexanone from a mixture containing benzoic acid, isoamyl alcohol, cyclohexane and cyclohexanone?

1

Crystallisation

2

IR spectroscopy

3

Sublimation

4

Evaporation

15

PYQ 1999

medium

chemistry ID: neet-ug-

The most suitable method of the separation of a mixture of ortho and para nitrophenol mixed in the ratio of 1 : 1 is

1

distillation

2

crystallisation

3

vaporisation

4

colour spectrum

16

PYQ 2000

easy

chemistry ID: neet-ug-

2-butene shows geometrical isomerism due to :

1

Free rotation about single bond

2

Free rotation about double bond

3

Chiral carbon

4

Restricted rotation about double bond

17

PYQ 2001

medium

chemistry ID: neet-ug-

In HS -,I -,R-NH 2, NH 3 order of proton excepting tendency will be :-

1

I - > NH 3 > R-NH 2 > HS -

2

NH 3 > R-NH 2 > HS - > I -

3

RNH 2 > NH 3 > HS - > I -

4

HS - > RNH 2 > NH 3 > I -

18

PYQ 2001

medium

chemistry ID: neet-ug-

The incorrect IUPAC name is

1

CH3-C-CH-CH3 O CH3-methyl-3-butanone

2

CH3-CH-CHCH3 CH2-CH3-CH3 2, 3-dimethyl pentane

3

CH3-C\equivCCH(CH3)2 4-methyl-2-pentyne

4

)CH3-CH-CH-CH3 Cl Br 2-bromo-3-chloro butane

19

PYQ 2001

medium

chemistry ID: neet-ug-

In steam distillation of toluene, the pressure of toluene in vapour is

1

Equal pressure of barometer

2

Less than pressure of barometer

3

Equal to vapour pressure to toluene in simple distillation

4

More than vapour pressure of toluene in simple distillation

20

PYQ 2002

medium

chemistry ID: neet-ug-

CH 2 -C-CH 3 O and CH 2 -C-CH 3 O are

1

Resonating structures

2

Tautomers

3

Geometrical isomers

4

Optical isomers

21

PYQ 2002

medium

chemistry ID: neet-ug-

IUPAC name of the following CH2 = CH - CH2 - CH2 - C \equiv CH is

1

1, 5-hexenyne

2

1-hexene-5-yne

3

1-hexyne-5-ene

4

1, 5-hexynene

22

PYQ 2003

medium

chemistry ID: neet-ug-

Acrolein is a hard,horny and a high melting point material. Which of the following represent its structure:

1

2

3

4

23

PYQ 2003

medium

chemistry ID: neet-ug-

For the reaction: at constant temperature, ∆H-∆E is:

1

RT

2

-3RT

3

3RT

4

-RT

24

PYQ 2003

medium

chemistry ID: neet-ug-

Which of the following statements is not correct for sigma and pi-bonds formed between two carbon atoms:

1

Sigma-bond is stronger than a pi-bond

2

Bond energies of sigma- and pi-bonds are of the order of 264 KJ/mol and 347 KJ/mol, respectively

3

Free rotation of atoms about a sigma bond is allowed but not in case of a pi-bond

4

Sigma-bond determines the direction between carbon atoms but a pi-bond has no primary effect in this regard

25

PYQ 2003

easy

chemistry ID: neet-ug-

Which one of the following orders of acidic strength is correct ?

1

RCOOH > HOH > HC CH > ROH

2

RCOOH > HC CH > HOH >ROH

3

RCOOH >ROH > HOH > HC CH

4

RCOOH > HOH > ROH >HC CH

26

PYQ 2004

medium

chemistry ID: neet-ug-

Among the following, the pair in which the two species are not isostructural is

1

IO 3 - and XeO 3

2

BH 4 - and NH 4 +

3

PF 6 - and SF

4

SiF 4 and SF 4

27

PYQ 2004

medium

chemistry ID: neet-ug-

Using anhydrous AlCl 3 as catalyst, which one of the following reactions produces ethylbenzene (PhEt)

1

CH 3 -CH = CH 2 + C 6 H 6

2

H 2 C = CH 2 + C 6 H 6

3

H 3 C - CH 3 + C 6 H 6

4

H 3 C - CH 2 OH + C 6 H 6

28

PYQ 2004

medium

chemistry ID: neet-ug-

The molecular formula of diphenylmethane How many structural isomers are possible when one of the hydrogens is replaced by a chlorine atom

1

4

2

8

3

7

4

6

29

PYQ 2004

medium

chemistry ID: neet-ug-

A solid compound 'X' on heating gives CO 2 gas and a residue. The residue mixed with water forms 'Y'. On passing an excess of CO 2 through 'Y' in water, a clear solution, 'Z' is obtained. On boiling 'Z', compound 'X' is reformed. The compound 'X' is

1

CaCO 3

2

Na 2 CO 3

3

K 2 CO 3

4

Ca(HCO 3) 2

30

PYQ 2004

medium

chemistry ID: neet-ug-

Which of the following will not form a yellow precipitate on heating with an alkaline solution of iodine

1

CH 3 CH 2 CH(OH)CH 3

2

CH 3 OH

3

CH 3 CH 2 OH

4

CH 3 CH(OH)CH 3

31

PYQ 2004

medium

chemistry ID: neet-ug-

Among K, Ca Fe and Zn, the element which can form more than one binary compound with chlorine is

1

Zn

2

K

3

Ca

4

Fe

32

PYQ 2004

medium

chemistry ID: neet-ug-

Which one of the following can be oxidised to the corresponding carbonyl compound

1

o-Nitrophenol

2

Phenol

3

2-methyl-2-hydroxy propane

4

2-hydroxy propane

33

PYQ 2004

medium

chemistry ID: neet-ug-

Ionic radii are

1

Inversely proportional to square of effective nuclear charge

2

Directly proportional to effective nuclear charge

3

Directly proportional to square of effective nuclear charge

4

Inversely proportional to effective nuclear charge

34

PYQ 2004

medium

chemistry ID: neet-ug-

The -OH group of an alcohol or the carboxylic acid can be replaced by - Cl, using

1

Hypochlorous acid

2

Chlorine

3

Hydrochloric acid

4

Phosphorous pentachloride

35

PYQ 2004

medium

chemistry ID: neet-ug-

Aniline, when diazotized in cold and then treated with dimethyl aniline, gives a colored product. Its structure would be

1

2

3

4

36

PYQ 2004

medium

chemistry ID: neet-ug-

The maximum number of molecules is present in

1

5L of N 2 gas at STP

2

0.5 g of H 2 gas

3

10g of O 2 gas

4

15 L of H 2 gas at STP

37

PYQ 2004

medium

chemistry ID: neet-ug-

Number of chiral carbons in β-D-(+)- glucose is

1

Six

2

Three

3

Four

4

Five

38

PYQ 2004

medium

chemistry ID: neet-ug-

Which is the best description of the behavior of bromine in the reaction given below:- H 2 O + Br 2 HOBr + HBr

1

Both oxidized and reduced

2

Oxidized only

3

Reduced only

4

Proton acceptor only

39

PYQ 2004

easy

chemistry ID: neet-ug-

Which of the following does not have a metal-carbon bond

1

C 2 H 5 MgBr

2

K[Pt(C 2 H 4)Cl 3]

3

Ni(CO) 4

4

Al(OC 2 H 5) 3

40

PYQ 2005

medium

chemistry ID: neet-ug-

The best method for the separation of naphthalene and benzoic acid from their mixture is

1

chromatography

2

crystallisation

3

distillation

4

sublimation

41

PYQ 2005

easy

chemistry ID: neet-ug-

Which amongst the following is the most stable carbocation?

1

2

3

4

42

PYQ 2005

medium

chemistry ID: neet-ug-

Names of some compounds are given. Which one is not correct in IUPAC system ?

1

2

3

4

43

PYQ 2005

medium

chemistry ID: neet-ug-

The major organic product formed from the following reaction:

1

2

3

4

44

PYQ 2005

medium

chemistry ID: neet-ug-

Which one of the following pairs represents stereoisomerism ?

1

Chain isomerism and rotational isomerism

2

Structural isomerism and geometric isomerism

3

Linkage isomerism and geometric isomerism

4

Optical isomerism and geometric isomerism

45

PYQ 2005

medium

chemistry ID: neet-ug-

Electrolytic reduction of nitrobenzene weakly acidic medium gives:

1

Aniline

2

Nitrosobenzene

3

N-phenylhydroxylamine

4

p-hydroxyaniline

46

PYQ 2006

medium

chemistry ID: neet-ug-

The IUPAC name of is :

1

3, 4-dimethylpentanoyl chloride

2

1-chloro-1-oxo-2, 3-dimethylpentane

3

2-ethyl-3-methylbutanoyl chloride

4

2, 3-dimethylpentanoyl chloride

47

PYQ 2007

medium

chemistry ID: neet-ug-

For the following: (a) (b) (c) The increasing order of nucleophilicity would be:

1

2

3

4

48

PYQ 2008

medium

chemistry ID: neet-ug-

Base strength of (i) (ii) (iii) is in the order of

1

(ii) > (i) > (iii)

2

(iii) > (ii) > (i)

3

(i) > (iii) > (ii)

4

(i) > (ii) > (iii)

49

PYQ 2008

medium

chemistry ID: neet-ug-

-The stability of carbanions in the following (i) (iii) (iv), is in the order of

1

(i) > (ii) > (iii) > (iv)

2

(ii) > (iii) > (iv) > (i)

3

(iv) > (ii)>(iii)>(i)

4

(i) > (iii) > (ii) > (i)

50

PYQ 2010

medium

chemistry ID: neet-ug-

Which of the following species is not electrophilic in nature ?

1

2

3

4

51

PYQ 2013

medium

chemistry ID: neet-ug-

Reaction by which Benzaldehyde cannot be prepared

1

2

3

4

52

PYQ 2013

medium

chemistry ID: neet-ug-

The structure of isobutyl group in an organic compound is

1

2

3

4

53

PYQ 2013

medium

chemistry ID: neet-ug-

The radical is aromatic because it has

1

6 p-orbitals and 6 unpaired electrons

2

7 p-orbitals and 6 unpaired electrons

3

7 p-orbitals and 7 unpaired electrons

4

6 p-orbitals and 7 unpaired electrons

54

PYQ 2013

easy

chemistry ID: neet-ug-

Which of the following compounds will not undergo Friedal-Craft's reaction easily?

1

Cumene

2

Xylene

3

Nitrobenzene

4

Toluene

55

PYQ 2013

medium

chemistry ID: neet-ug-

Arrange the following in increasing order of stability:-

1

e < d < c < a < b

2

d < e < c < a < b

3

a < e < d < c < b

4

e < d < c < b < a

56

PYQ 2013

medium

chemistry ID: neet-ug-

The structure of isobutyl group in an organic compound is :-

1

2

3

4

57

PYQ 2013

medium

chemistry ID: neet-ug-

What is the hybridisation state of benzyl carbonium ? :-

1

2

3

4

58

PYQ 2013

medium

chemistry ID: neet-ug-

Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour formed corresponds to which of the following formulae ?

1

2

3

4

59

PYQ 2014

medium

chemistry ID: neet-ug-

In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from of sample neutralized of . The percentage of nitrogen in the soil is :

1

37.33

2

45.33

3

35.33

4

43.33

60

PYQ 2015

medium

chemistry ID: neet-ug-

Consider the following compounds:

1

III only

2

I and III

3

I only

4

II only

61

PYQ 2016

medium

chemistry ID: neet-ug-

Which among the given molecules can exhibit tautomerism?

1

III only

2

Both I and III

3

Both I and II

4

Both II and III

62

PYQ 2017

medium

chemistry ID: neet-ug-

Which of the following reactions is appropriate for converting acetamide to methanamine?

1

Carbylamine reaction

2

Hoffmann hypobromamide reaction

3

Stephens reaction

4

Gabriels phthalimide synthesis

63

PYQ 2018

medium

chemistry ID: neet-ug-

Which of the following molecules represents the order of hybridisation from left to right atoms ?

1

2

3

4

64

PYQ 2018

medium

chemistry ID: neet-ug-

Which of the following is correct with respect to effect of the substituents ? alkyl

1

2

3

4

65

PYQ 2018

easy

chemistry ID: neet-ug-

The difference between amylose and amylopectin is

66

PYQ 2018

easy

chemistry ID: neet-ug-

In the reaction the electrophile involved is

67

PYQ 2018

medium

chemistry ID: neet-ug-

Which of the following is correct with respect to - I effect of the substituents ? (R = alkyl)

1

- NH 2 < - OR < - F

2

- NH 2 > - OR > - F

3

- NR 2 < - OR < - F

4

- NR 2 > - OR > - F

68

PYQ 2018

medium

chemistry ID: neet-ug-

Identify the major products P, Q and R in the following sequence of reactions :

1

2

3

4

69

PYQ 2018

medium

chemistry ID: neet-ug-

Which of the following carbocations is expected to be most stable ?

1

2

3

4

70

PYQ 2019

medium

chemistry ID: neet-ug-

Among the following, the reaction that proceeds through an electrophilic substitution, is:

1

2

3

4

71

PYQ 2019

medium

chemistry ID: neet-ug-

Conjugate base for Brönsted acids and are

1

and, respectively

2

and, respectively

3

and, respectively

4

and, respectively

72

PYQ 2019

medium

chemistry ID: neet-ug-

The number of and bonds in pent-2-en-4-yne is:

1

bonds and bonds

2

bonds and bonds

3

bonds and bonds

4

bonds and no bonds

73

PYQ 2020

medium

chemistry ID: neet-ug-

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following ?

1

effect of groups

2

effect of groups

3

effect of groups

4

Hyperconjugation

74

PYQ 2020

medium

chemistry ID: neet-ug-

Identify compound in the following sequence of reactions :

1

2

3

4

75

PYQ 2021

medium

chemistry ID: neet-ug-

The dihedral angle of the least stable conformer of ethane is

1

0°

2

120°

3

180°

4

60°

Official Solution

Correct Option: (4)

76

PYQ 2021

medium

chemistry ID: neet-ug-

Given below are two statements : Statement I: Aspirin and Paracetamol belong to the class of narcotic analgesics. Statement II: Morphine and Heroin are non-narcotic analgesics. In the light of the above statements, choose the correct answer from the options given below

1

Statement I is incorrect but Statement II is true

2

Both Statement I and Statement II are true

3

Both Statement I and Statement II are false

4

Statement I is correct but Statement II is false

77

PYQ 2021

easy

chemistry ID: neet-ug-

Which one of the following polymers is prepared by addition polymerization

1

Dacron

2

Teflon

3

Nylon-66

4

Novolac

78

PYQ 2021

medium

chemistry ID: neet-ug-

An organic compound contains 78% (by wt.) carbon and the remaining percentage of hydrogen. The right option for the empirical formula of this compound is : [Atomic wt. of C is 12, H is 1]

1

CH 4

2

CH

3

CH 2

4

CH 3

79

PYQ 2021

medium

chemistry ID: neet-ug-

Ethylene diaminetetraacetate (EDTA) ion is

1

Tridentate ligand with three “N” donor atoms

2

Hexadentate ligand with four “O” and two “N” donor atoms

3

Unidentate ligand

4

Bidentate ligand with two “N” donor atoms

80

PYQ 2021

easy

chemistry ID: neet-ug-

Match List - I with List - II. List - I List - II (a) (i) Hell-VolhardZelinsky reaction (b) (ii) Gattermann-Koch reaction (c) (iii) Haloform reaction (d) (iv) Esterification Choose the correct answer from the options given below.

81

PYQ 2021

easy

chemistry ID: neet-ug-

The product formed in the following chemical reaction is:

82

PYQ 2022

medium

chemistry ID: neet-ug-

The correct IUPAC name of the following compound is

1

1 - bromo - 5 - chloro - 4 - methyl hexan - 3- ol

2

6 - bromo - 2 - chloro - 4 - methyl hexan - 4- ol

3

1 - bromo - 4 - chloro - 5 - chloro hexan - 3- ol

4

6 - bromo - 4 - chloro - 4 - chloro hexan - 4- ol

83

PYQ 2024

medium

chemistry ID: neet-ug-

Match List I with List II List-I (Complex) List-II (Type of isomerism) (A) [Co(NH3)5(NO2)]Cl2 (I) Solvate isomerism (B) [Co(NH3)5(SO4)]Br (II) Linkage isomerism (C) [Co(NH3)6] [Cr(CN)6] (III) Ionization isomerism (D) [Co(H2O)6]Cl3 (IV) Coordination isomerism Choose the correct answer from the options given below:

1

A-II, B-III, C-IV, D-I

2

A-I, B-III, C-IV, D-II

3

A-I, B-IV, C-III, D-II

4

A-II, B-IV, C-III, D-I

84

PYQ 2024

medium

chemistry ID: neet-ug-

The most stable carbocation among the following is:

1

2

3

4

85

PYQ 2024

easy

chemistry ID: neet-ug-

$The compound that will undergo S N 1 reaction with the fastest rate is$

1

2

3

4

Official Solution

Correct Option: (4)

$Reactivity towards S N 1 depends upon the stability of the carbocation.$

86

PYQ 2024

medium

chemistry ID: neet-ug-

$Given below are two statements : Statement I : The boiling point of three isomeric pentanes follows the order n-pentane > isopentane > neopentane Statement II : When branching increases, the molecule attains a shape of sphere. This results in smaller surface area for contact, due to which the intermolecular forces between the spherical molecules are weak, thereby lowering the boiling point. In the light of the above statements, choose the most appropriate answer from the options given below :$

1

$Both Statement I and Statement II are correct.$

2

$Both Statement I and Statement II are incorrect.$

3

$Statement I is correct but Statement II is incorrect.$

4

$Statement I is incorrect but Statement II is correct.$

Official Solution

Correct Option: (1)

$Statement I discusses the boiling points of three isomeric pentanes: n-pentane, isopentane, and neopentane. The order mentioned is: n-pentane > isopentane > neopentane. This statement is correct because boiling point is influenced by the surface area available for intermolecular forces. n-Pentane, being a linear molecule, has the largest surface area, resulting in greater van der Waals forces, and thus a higher boiling point compared to its branched isomers. Statement II explains the effect of branching on the molecule's shape and boiling point. As branching increases, molecules assume a more spherical shape, which minimizes the surface area available for intermolecular interactions like van der Waals forces. This decrease in surface area weakens these forces, thereby reducing the boiling point. This statement correctly explains the molecular behavior and its impact on boiling point. Since both statements accurately describe the relationship between molecular structure and boiling point, the correct answer is: B oth Statement I and Statement II are correct.$

87

PYQ 2024

medium

chemistry ID: neet-ug-

$Methyl group attached to a positively charged carbon atom stabilizes the carbocation due to$

1

$-I inductive effect$

2

$electromeric effect$

3

$hyperconjugation$

4

$mesomeric effect$

Official Solution

Correct Option: (3)

$A methyl group attached to a carbocation stabilizes it through hyperconjugation. Hyper-conjugation involves the interaction of the electrons in the C-H sigma bonds of the methyl group with the empty p-orbital of the positively charged carbon. This delocalization of electron density stabilizes the carbocation.$

88

PYQ 2024

hard

chemistry ID: neet-ug-

$Match List I with List II List-I (Conversion) List-II (Shape/geometry) (A) 1 mol of H 2 O to O 2 (I) 3F (B) 1 mol of MnO - 4 to Mn 2+ (II) 2F (C) 1.5 mol of Ca from molten CaCl 2 (III) 1F (D) 1 mol of FeO to Fe 2 O 3 (IV) 5F Choose the correct answer from the options given below:$

1

$A-II, B-IV, C-I, D-III$

2

$A-III, B-IV, C-I, D-II$

3

$A-II, B-III, C-I, D-IV$

4

$A-III, B-IV, C-II, D-I$

Official Solution

Correct Option: (1)

$We are tasked with matching chemical transformations to the corresponding number of Faradays (F) required for each process. Let us analyze each case step by step: (A) 1 mol of to : The oxidation of water involves the following half-reaction: . For 1 mole of, 2 moles of electrons are involved. Therefore, the number of Faradays required is . So, (A) matches with (II) . (B) 1 mol of to : The oxidation state of Mn in is calculated as: . The oxidation state of Mn in is . The change in oxidation state is . The balanced half-reaction in acidic medium is: . For 1 mole of reduced to, 5 moles of electrons are involved. Therefore, the number of Faradays required is . So, (B) matches with (IV) . (C) 1.5 mol of Ca from molten : The reduction half-reaction for to Ca is: . For 1 mole of Ca, 2 moles of electrons are required (). For 1.5 moles of Ca, moles of electrons are required. Therefore, the number of Faradays required is . So, (C) matches with (I) . (D) 1 mol of to : The oxidation state of Fe in is . The oxidation state of Fe in is calculated as: . The change in oxidation state of Fe is . The conversion involves 2 moles of Fe in for every "unit" of conversion. The reaction can be written as: . For 2 moles of, the total change in oxidation state of Fe is, meaning 2 moles of electrons are involved. However, the question asks for 1 mole of . For 1 mole of, the oxidation state change of Fe is, meaning 1 mole of electrons () is required. So, (D) matches with (III) . Final Matches: (A) - (II) (B) - (IV) (C) - (I) (D) - (III) Final Answer: The final answer is:$

89

PYQ 2024

medium

chemistry ID: neet-ug-

$On complete combustion, 0.3 g of an organic compound gave 0.2 g of CO 2 and 0.1 g of H 2 O. The percentage composition of carbon and hydrogen in the compound, respectively, is:$

1

$4.07% and 15.02%$

2

$18.18% and 3.70%$

3

$15.02% and 4.07%$

4

$3.70% and 18.18%$

Official Solution

Correct Option: (2)

$Percentage of Carbon: The mass of carbon in 0.2 g of CO can be calculated using the molar masses: Molar mass of CO = 44 g/mol Molar mass of C = 12 g/mol Mass of C in 0.2 g CO Percentage of C Percentage of Hydrogen: The mass of hydrogen in 0.1 g of H O can be calculated using the molar masses: Molar mass of H O = 18 g/mol Molar mass of H = 1 g/mol (but there are 2 H atoms, thus, 2 g/mol) Mass of H in 0.1 g H O Percentage of H Therefore, the percentage composition of carbon and hydrogen is 18.18% and 3.70%, respectively.$

90

PYQ 2025

easy

chemistry ID: neet-ug-

$The correct order of decreasing acidity of the following aliphatic acids is:$

1

$(CH_{3})_{2}CHCOOH HCOOH$

2

3

4

Official Solution

Correct Option: (2)

$The acidity of carboxylic acids depends on the stability of the conjugate base formed after losing a proton (i.e., the carboxylate anion). This stability is influenced by the inductive effect of alkyl groups: - Electron-donating groups (like alkyl groups) destabilize the carboxylate ion by increasing electron density, thus decreasing acidity . - Electron-withdrawing groups stabilize the anion, increasing acidity . Now, analyze each acid: - HCOOH (Formic acid): No alkyl group \to Highest acidity. - CH 3 COOH (Acetic acid): One methyl group \to lower than formic acid. - (CH 3) 2 CHCOOH: Isopropyl group \to stronger +I effect \to lower acidity. - (CH 3) 3 CCOOH: Tertiary butyl group \to even more +I effect \to least acidic. Hence, the correct order of decreasing acidity is: $ $$

91

PYQ 2025

hard

chemistry ID: neet-ug-

$The major product of the following reaction is: (i)$

1

2

3

4

Official Solution

Correct Option: (1)

$The given compound is a substituted aryl ketone with a cyano group at the terminal position. Reagent: excess CH 3 MgBr (a Grignard reagent) + acidic hydrolysis. Step 1: Grignard Reaction with Ketone - CH 3 MgBr adds a methyl group to the carbonyl carbon of the ketone (nucleophilic attack), forming a tertiary alcohol after hydrolysis. Step 2: Reaction with -CN group - Since excess Grignard reagent is used, it also reacts with the nitrile group (-CN) to give an imine intermediate, which on hydrolysis gives a ketone. Net Result: - The carbonyl group (initial ketone) gives a tertiary alcohol: Ph-C(OH)(CH 3)-CH 2 -CH 2 -CN - The -CN gets converted into a ketone group: -CH 2 -COCH 3 After tautomerization or rearrangement, we obtain the product: Ph-CH(CH 3)-CH 2 -COCH 3 — this matches option (1).$

92

PYQ 2025

hard

chemistry ID: neet-ug-

$Predict the major product in the following sequence of reactions: (i) HBr, benzoyl peroxide (ii) KCN (iii) Na(Hg),$

1

2

3

4

Official Solution

Correct Option: (3)

$The sequence of reactions involves the following steps: Step (i) HBr, benzoyl peroxide: This is a free radical halogenation reaction, where the alkyl group on the benzene ring undergoes bromination at the benzylic position due to the formation of free radicals, resulting in the product (benzyl bromide). Step (ii) KCN: The next step is the nucleophilic substitution of the bromine atom by the cyanide ion (CN -), leading to the formation of (benzyl cyanide). Step (iii) Na(Hg), C 2 H 5 OH: This is a reduction reaction (Clemmensen reduction), which typically reduces a carbonyl group (in this case, the nitrile group) to a methylene group (-CH 2 -). However, since there is no carbonyl group here, this reaction doesn't affect the cyanide group. Hence, the major product remains as . Thus, the major product is, and the correct answer is (3).$

93

PYQ 2025

medium

chemistry ID: neet-ug-

$How many products (including stereoisomers) are expected from monochlorination of the following compound?$

1

$3$

2

$6$

3

$5$

4

$2$

Official Solution

Correct Option: (1)

$Monochlorination involves replacing one hydrogen atom with a chlorine atom. We need to consider all possible positions where chlorine can substitute a hydrogen and whether any of these substitutions create a stereocenter. 1. Chlorination at C1: CH 2 Cl-CH 2 -CH 2 -CH 3 . This is 1-chlorobutane. 2. Chlorination at C2: CH 3 -CHCl-CH 2 -CH 3 . This is 2-chlorobutane. Since C2 becomes a chiral center, there are two stereoisomers (enantiomers): (R)-2-chlorobutane and (S)-2-chlorobutane. 3. Chlorination at C3: CH 3 -CH 2 -CHCl-CH 3 . This is also 2-chlorobutane (same as chlorination at C2 when considering connectivity). The molecule now has a chiral center, again producing two stereoisomers: (R)-2-chlorobutane and (S)-2-chlorobutane. 4. Chlorination at C4: CH 3 -CH 2 -CH 2 -CH 2 Cl. This is 1-chlorobutane, identical to the product from C1 chlorination. Therefore, there are three distinct monochlorinated products: 1-chlorobutane, (R)-2-chlorobutane, and (S)-2-chlorobutane. The number of products including stereoisomers is 3.$

94

PYQ 2025

medium

chemistry ID: neet-ug-

$The correct order of decreasing basic strength of the given amines is:$

1

$N-ethylmethanamine ethanamine benzenamine N-methylaniline$

2

$N-ethylmethanamine ethanamine N-methylaniline benzenamine$

3

$N-methylaniline ethanamine benzenamine N-ethylmethanamine$

4

$N-methylaniline N-ethylmethanamine benzenamine ethanamine$

Official Solution

Correct Option: (2)

$Basic strength of amines depends on the availability of the nitrogen lone pair for protonation. The basicity of amines can be influenced by electron-donating and electron-withdrawing groups attached to the nitrogen. The general trend is: - Alkyl groups (like ethyl and methyl) donate electrons to the nitrogen, increasing its basicity. - A benzene ring (as in benzenamine) is electron-withdrawing due to resonance, which decreases the basicity of the nitrogen. Let’s analyze the amines in the options: - N-ethylmethanamine (ethylamine): The ethyl group is electron-donating, making the nitrogen more basic than ethanamine. - Ethanamine (ethylamine): The amine group is attached to an ethyl group, giving it good electron-donating effects, but the effect is weaker than in N-ethylmethanamine. - N-methylaniline: The methyl group is electron-donating, but the aromatic ring in benzenamine withdraws electron density through resonance, making N-methylaniline less basic than ethanamine. - Benzenamine (aniline): The aromatic ring has a strong electron-withdrawing effect on the nitrogen, making this the least basic of all the options. Thus, the correct order of basicity is N-ethylmethanamine ethanamine N-methylaniline benzenamine.$

95

PYQ 2025

medium

chemistry ID: neet-ug-

$Given below are two statements: Statement I: Benzendiazonium salt is prepared by the reaction of aniline with nitrous acid at 273-278 K. It decomposes easily in the dry state. Statement II: Insertion of iodine into the benzene ring is difficult and hence iodobenzene is prepared through the reaction of benzendiazonium salt with KI. In the light of the above statements, choose the most appropriate answer from the options given below:$

1

$Both Statement I and Statement II are incorrect.$

2

$Statement I is correct but Statement II is incorrect.$

3

$Statement I is incorrect but Statement II is correct.$

4

$Both Statement I and Statement II are correct.$

Official Solution

Correct Option: (3)

$- Statement I: The preparation of benzene diazonium salt involves the reaction of aniline with nitrous acid (generated in situ from sodium nitrite and hydrochloric acid). This reaction occurs at temperatures between 0-5°C, not 273-278 K (which corresponds to much higher temperatures, typically above room temperature). Hence, Statement I is incorrect. - Statement II: The insertion of iodine into the benzene ring is indeed difficult as iodine does not react readily under normal conditions with the benzene ring. However, iodobenzene can be prepared effectively by reacting benzene diazonium salt with KI (Potassium iodide), which leads to the formation of iodobenzene. This is a typical reaction, known as the Sandmeyer reaction. Therefore, Statement II is correct. Thus, the correct answer is (3) Statement I is incorrect but Statement II is correct.$

96

PYQ 2025

medium

chemistry ID: neet-ug-

$Identify the suitable reagent for the following conversion:$

1

$(i) (ii)$

2

$(i), (ii)$

3

4

$(i), (ii)$

Official Solution

Correct Option: (1)

$The transformation is from an ester () to an aldehyde (). This selective reduction requires a mild and bulky reducing agent that reduces esters only to aldehydes without further reducing to alcohols. - Option (1): Diisobutylaluminium hydride (DIBAL-H or) at low temperatures (-78°C), followed by hydrolysis, reduces esters to aldehydes. This is the correct reagent. - Option (2): is too mild to reduce esters. - Option (3): is used for Rosenmund reduction (acid chlorides to aldehydes), not esters. - Option (4): is strong and will reduce esters all the way to primary alcohols. Thus, only DIBAL-H allows selective conversion of ester to aldehyde.$

97

PYQ 2025

easy

chemistry ID: neet-ug-

$Which one of the following compounds does not decolorize bromine water?$

1

$Phenol$

2

$CH CH$

3

$NH$

4

$Cyclohexane$

Official Solution

Correct Option: (4)

$Let's analyze each compound: Phenol: Phenol contains an electron donating group (OH) attached to a benzene ring, activates the ring toward electrophilic substitution. Phenol readily undergoes electrophilic substitution reactions with bromine, leading to decolourisation. Styrene: Styrene contains a vinyl group (CH=CH 2) attached to a benzene ring. The alkene part of styrene will readily react with bromine water by addition reaction. Aniline: Aniline also contains an activating amine group (NH 2) attached to a benzene ring. It readily undergoes electrophilic substitution reactions with bromine, leading to decolourisation. Cyclohexane: Cyclohexane is a saturated cyclic alkane. It lacks double or triple bonds and isn't readily susceptible to electrophilic attack (it would require much higher temperatures and/or UV light to react). So Cyclohexane does not decolourise bromine water under normal conditions. Therefore, cyclohexane does not decolourise bromine water. The compound that does not decolourise bromine water is (4) Cyclohexane.$

98

PYQ 2025

hard

chemistry ID: neet-ug-

$Which one of the following compounds can exist as cis-trans isomers?$

1

$2-Methylhex-2-ene$

2

$1,1-Dimethylcyclopropane$

3

$1,2-Dimethylcyclohexane$

4

$Pent-1-ene$

Official Solution

Correct Option: (1)

$Cis-trans isomerism occurs when there are two different groups attached to each carbon of a double bond, resulting in non-superimposable mirror images. Let's analyze each compound: - Option (1) 2-Methylhex-2-ene: The structure has a double bond between C2 and C3, with different groups (methyl and hydrogen) on C2 and C3. This allows for cis-trans isomerism. - Option (2) 1,1-Dimethylcyclopropane: In this case, both methyl groups are attached to the same carbon (C1) in the cyclopropane ring, and Thus, cis-trans isomerism is not possible due to the symmetry of the molecule. - Option (3) 1,2-Dimethylcyclohexane: This compound does not have a double bond and is a saturated hydrocarbon, so cis-trans isomerism does not apply here. - Option (4) Pent-1-ene: While this compound has a double bond, there are no two different substituents attached to the same carbon in the double bond, so cis-trans isomerism does not exist. Thus, the correct compound that can exhibit cis-trans isomerism is 2-Methylhex-2-ene.$

99

PYQ 2025

easy

chemistry ID: neet-ug-

$Among the given compounds I-III, the correct order of bond dissociation energy of the C-H bond marked with is:$

1

$I II III$

2

$III II I$

3

$II I III$

4

$I III II$

Official Solution

Correct Option: (3)

$Bond dissociation energy is the energy required to break a bond, and it depends on the stability of the bond. In the case of C-H bonds, the following factors affect their bond dissociation energy: Aromatic C-H bond (I): The C-H bond in an aromatic compound is stabilized by resonance and the delocalization of electrons in the aromatic ring. This results in a relatively high bond dissociation energy. Aliphatic C-H bond (II): The C-H bond in a typical aliphatic compound (like an alkane) is weaker compared to the C-H bond in an aromatic system because there is no such resonance stabilization. Thus, the bond dissociation energy will be moderate. C-H bond in a cyclopropane-like structure (III): The C-H bond in a strained structure like cyclopropane is weaker due to the angle strain, making it easier to break. Hence, this bond has the lowest bond dissociation energy. Thus, the correct order of bond dissociation energy is II>I>III.$

100

PYQ 2025

medium

chemistry ID: neet-ug-

$Sugar ‘X’: A. is found in honey. B. is a keto sugar. C. exists in and anomeric forms. D. is laevorotatory. ‘X’ is:$

1

$D-Fructose$

2

$Sucrose$

3

$Maltose$

4

$D-Glucose$

Official Solution

Correct Option: (1)

$Let’s analyze each statement: - A. Fructose is commonly found in honey, making it a suitable candidate. - B. Fructose is a keto sugar because it contains a ketone functional group (unlike glucose, which is an aldose). - C. Fructose exists in and anomeric forms when it cyclizes to form a furanose ring. - D. Fructose is laevorotatory, meaning it rotates plane-polarized light to the left. Therefore, X is D-Fructose.$

101

PYQ 2025

medium

chemistry ID: neet-ug-

$Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): I undergoes SN reaction faster than Cl . Reason (R): Iodine is a better leaving group because of its large size. In the light of the above statements, choose the correct answer from the options given below:$

1

$Both A and R are true but R is not the correct explanation of A.$

2

$A is true but R is false.$

3

$A is false but R is true.$

4

$Both A and R are true and R is the correct explanation of A.$

Official Solution

Correct Option: (4)

$- Assertion (A): It is true that I undergoes SN reactions faster than Cl . This is because I is a larger ion with a more diffuse electron cloud compared to Cl, making it a better nucleophile and more willing to leave in an SN mechanism. - Reason (R): Iodine is indeed a better leaving group than chlorine due to its larger size and better ability to stabilize the negative charge once it departs from the carbon atom. The larger atomic size allows iodine to better accommodate the electron density, which is why it is a better leaving group. Thus, both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is (4) Both A and R are true and R is the correct explanation of A.$

102

PYQ 2025

medium

chemistry ID: neet-ug-

$Which one of the following reactions does NOT give benzene as the product?$

1

$n-hexane$

2

$H\textsubscript{2}C=CH\textsubscript{2}$

3

4

Official Solution

Correct Option: (3)

$Let's analyze each reaction: n-Hexane with Mo 2 O 3 at 773K and 10-20 atm: This is catalytic reforming or aromatization. n-Hexane can be converted to benzene under these conditions. Acetylene (Ethyne) with Red Hot Iron Tube at 873 K: This is a classic method for synthesizing benzene. Three molecules of acetylene undergo cyclic polymerization to form benzene. Benzenediazonium Ion with Warm Water: Benzenediazonium ion (C 6 H 5 N 2 +) reacts with warm water to form phenol (C 6 H 5 OH), not benzene. The diazonium group is replaced by a hydroxyl group. Benzoate with Sodalime and Heat: This is decarboxylation. The benzoate loses CO 2 to form benzene. Therefore, the reaction that does not produce benzene as a major product is the reaction of benzenediazonium ion with warm water.$

103

PYQ 2025

easy

chemistry ID: neet-ug-

$Which one of the following reactions does NOT belong to “Lassaigne's test”?$

1

2

3

4

Official Solution

Correct Option: (3)

$Lassaigne's test is used to detect the presence of extra elements (like nitrogen, sulfur, halogens) in organic compounds. In this test, organic compounds are fused with sodium to convert these elements into their ionic detectable forms: - Nitrogen \to NaCN - Sulfur \to Na 2 S - Halogens \to NaX (NaCl, NaBr, NaI) Now evaluate the reactions: - Option (1) : Formation of Na 2 S \to Used to test sulfur — part of Lassaigne's test. - Option (2) : Formation of NaX (halide salts) \to Used to test halogens — part of Lassaigne's test. - Option (3) : This is a reduction reaction of CuO by carbon — NOT related to detection of any element in organic analysis. Not part of Lassaigne's test. - Option (4) : Formation of NaCN — used for nitrogen detection — is part of Lassaigne's test. Therefore, only option (3) is unrelated to Lassaigne's test.$

List - I	List - II
(a)	(i)	Hell-VolhardZelinsky reaction
(b)	(ii)	Gattermann-Koch reaction
(c)	(iii)	Haloform reaction
(d)	(iv)	Esterification

List-I (Complex)		List-II (Type of isomerism)
(A)	[Co(NH3)5(NO2)]Cl2	(I)	Solvate isomerism
(B)	[Co(NH3)5(SO4)]Br	(II)	Linkage isomerism
(C)	[Co(NH3)6] [Cr(CN)6]	(III)	Ionization isomerism
(D)	[Co(H2O)6]Cl3	(IV)	Coordination isomerism

List-I (Conversion)		List-II (Shape/geometry)
(A)	1 mol of H₂O to O₂	(I)	3F
(B)	1 mol of MnO^-₄ to Mn²⁺	(II)	2F
(C)	1.5 mol of Ca from molten CaCl₂	(III)	1F
(D)	1 mol of FeO to Fe₂O₃	(IV)	5F

High-Yield Trend

Chapter Questions 103 MCQs

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Chapter Questions
103 MCQs