Isomerism - AtoZ CHEMISTRY

AtoZ CHEMISTRY ISOMERISM

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63

Isomerism

1. Structural Isomers – Chain, Positional Isomers

Q 1. The compound which is not isomeric with

diethyl ether is [IIT JEE 1981]

(A) n-propyl methyl ether (B) butan-1-ol

(C) 2-methylpropan-2-ol (D) butanone

Q 2. An isomer of ethanol is [IIT JEE 1986]

(A) methanol (B) diethyl ether

(C) acetone (D) dimethyl ether

Q 3. Which of the following statements is (are) true

about these compounds:

(A) I and II are chain isomerss

(B) I and II are positional isomers

(C) III is the functional isomer of both I and II

(D) I and III are not isomers.

Q 4. Which of the given is the chain isomer of

(A) (B)

(C) (D) All of these

Q 5. Which of the given is not the chain isomer of

(A) (B)

(C) (D)

Q 6. How many chain isomer of the compound n-

heptanes. (including the given compound)

(A) 6 (B) 7 (C) 8 (D) 9

Q 7. How many chain isomers of the compound 2,2-

Dimethyl pentane. (Including the given compound)

(A) 6 (B) 7 (C) 8 (D) 9

Q 8. Which of the given is incorrect

(A)

(B)

(C)

(D)

Q 9. How many chain isomers are possible for the

pentanal (Including the given

compound)

(A) 2 (B) 3 (C) 4 (D) 5

Q 10. For the given compounds

The correct chain isomers to each other is

CH – OH

CH3

CH3

ICH – CH – CH – OH3 2 2

IICH – CH – OCH3 2 3

III

O

HO

(I)

HO

O

(II)

O

HO

(III)

OH O

(IV)

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64

(A) I, II, III and IV (B) II, III and IV

(C) I, II and III (D) Only II and III

Q 11. Which of the given is the position isomers of

(A) (B)

(C) (D)

Q 12. Which of the given is the position isomers of

(A) (B)

(C) (D) All of these

Q 13. For the given compounds

The incorrect statement is

(A) I and II are position isomers

(B) III and IV are position isomers

(C) II and III are not the position isomers

(D) I, III and IV are Position isomers

Q 14. How many position isomers of methyl bicyclo

[4,4,0] decane

(A) 2 (B) 3 (C) 4 (D) 5

Q 15. How many position isomer of bromo spiro [3,4]

octane

(A) 2 (B) 3 (C) 4 (D) 5

2. Metamers, Functional & Ring Chain Isomers

Q 1. The incorrect metameric pair is

(A)

(B)

(C)

(D)

Q 2. Functional isomers of

is

(A)

(B)

(C)

(D) All of these

Q 3. Which of the following pairs of compounds are

functional isomers ?

(A)

(B)

(C)

(D)

Q 4. Isomers of propionic acid are

(A) 2 5 3 3HCOOC H &CH COOCH




65

(B) 2 5 3 7HCOOC H &C H COOH

(C) 3 2 5 3 7CH COOC H &C H OH

(D) 3 7 3 3C H OH &CH COOCH

Q 5. Which of the following is not the correct

relationship?

(A) II & III are functional isomer

(B) I & II are functional isomer

(C) I & III are chain isomer

(D) I and IV are positional isomer

Q 6.

Which among these are structural isomers?

(A) I and II (B) I and III

(C) II and III (D) All of these

Q 7.

Among these, positional isomers are


(C) II and III (D) All of these

Q 8.

Among these, ring – chain isomers are


(C) I and IV (D) All of these

Q 9.

II is the functional isomer of

(A) I only (B) III only

(C) Both I and III (D) None of these

Q 10. O

is the metamers of

(A) O

(B)

O

(C)

O

(D) A and C

Q 11. CH – CH – CH – CH and CH – CH – CH – CH3 2 2 2 3 2 3

CHO CHO

are

(A) Positional isomers (B) Functional isomers

(C) metamers (D) Chain isomers

Q 12. The functional isomers of 1-butyne are

(1) 3 3CH C C CH− −

(2)

CH – C = CH3 2

CH3

(3) 2 3CH C CH CH= = −

(4) 2 2CH CH CH CH− − =

(A) 1, 3 and 4 only (B) 2 and 3 only

(C) 2 and 4 only (D) 3 and 4 only

Q 13. Which of the following compound will show

metamerism ?

(A) 3 3 7CH O COC H− − (B) 3 2 5CH S C H− −

(C) 3 3CH O CH− − (D) 3 2 5CH O C H− −

Q 14. What type of isomerism is shown by the following

compounds ?

(A) Metamerism (B) Positional

(C) Functional (D) Tautomerism

Q 15. The compound which is not isomeric with diethyl

ether is

(A) n propyl methyl dther (B) 1 butanol

(C) 2 methyl 2 popanol (D) butanone

Q 16. Molecular formula 5 12C H O will show

(A) Position isomerism (B) Chain isomerism

(C) Functional isomerism (D) All of these

Me

MeMeOH

I

MeMe

O – Me

IIMe

OH

III

Me

O – Me

IV




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3. Tautomerism

Q 1. Which statement is correct for Keto-enol

tautomerism?

(A) Tautomersim is catalysed by acid and base

(B) Tautomers are present in dynamic eqb. state

(C) Generally keto form is more stable than enol

form

(D) All

Q 2. Which compound show tautomerism

(A) (B)

(C) (D) None of these

Q 3. Tautomer of following compound is

(A)

(B)

(C)

(D)

Q 4. Which of the following compounds can exhibit

tautomerism?

(A) (B)

(C) (D)

(E) (F)

(G) (H)

(I) (J)

(K) (L)

(M) (N)

(O)

(P)

Q 5. In each of the following pairs which is more

stable?

O

C

H N3NH2 NO2CH3

CH3

CH3

O

O

O

OCH3

NO2

CCl

O

CH = C2

OH

Cl

CH2

CH3

NH

NH

OH

O

O

OH NH – CH NH

CH N – NH

CH – NO3

O N H

N HO II I

C O

NH 2 H H C

NH

OH

C O

NH 2 C

NH

OH

CH 3 = CH 2

2

II I

I II

C O

CH 3 O C O

CH 3 C O

CH 3 O C

CH 3

OH

C O

CH 3 C O

CH 3 C O

CH 3 C

CH 3 CH 2

H O

CH

I II

I II

O O O O H

I II

(A)

(B)

(C)

(D)

(E)

(F)




67

H

C

OC

IICH3

C

O

CH3

CH3

O

C

CH2

O

I II

C

O

C

II

CH3 CH3

O

CH2

CH2C

CH3

O

H

CH

CH3

O=C

CH3

I

I

OHO

O OHII

(G)

(H)

(I)

Ph

CH

Ph

N

O

Ph Ph

N

C

OH

(J)

Q 6. Among the following compounds having the

highest enol content?

(A) CH3CHO (B) CH3COCH3

(C) CH3COCH2CHO (D) CH3COCH2COOCH3

Q 7. In each of the following pairs which will have

higher enol content:

C

CH3

O

CH2

COO Et

COO Et CH

And

2

C

O

OCH3

C

CH3

O

CH2

C

O

CH3

C

CH3

O

CH

And

2

C

O

OCH3

C

CH3

O

CH2

C

O

CH3

C

O

CH

And

2

C

O

Ph Ph

OAnd C

CH3

O

CH3

OAnd

O

OAnd

O

O

OH

C

O

CH3And

OH

C

O

CH3

NO2 Cl

CH2-CHO and CH -CHO2

(A)

(B)

(C)

(D)(E)

(F)(G)

(H)

C

CH3

O

CH2

C

O

CH3

C

O

CH

And C

O

CH3C2H5

CH3

CO OCH3

And

CO O CH3

O

+ And

O

+

(I)

(J)

(K) O And O

+

(L)

Q 8. In each of the following sets of compounds

write the order of % enol content?

O O

OO

I II III I

>(A)

O O NO2

ONO2O2N

O O

NO2

O

NO2H

O O O O

Cl

O ClO O

NO2

III

III

I II III

I II IIINO2

I

>

I II III

(B)

(C)

(D)

(E)

I II III I

>OO

O O

O OO

O

N

O

I II III I

>

N

OO

Cl

O

N

H

O

I I

>IIIII

OO

O

I II III

(F)

(G)

(H)

(I)

H




68

Q 9. In which of the following solvent, % enol content

is maximum?

(A) 2H O (B) Ethanol

(C) Liq. State (D) hexane

Q 10. In which of the following case, % enol contant is

independent from solution ?

(A)

O OH

(B) CH – C – NH3 2

O

CH – C – NH3

OH

(C)

CH – N3

O

OCH – N2

OH

O

(D) All of these

Q 11. Which of the following statements is (are) true

about these compounds:

OH

I

O O

II III

I

(A) I is the functional isomer of both II and III

(B) I is tautomer of III but not of II

(C) All three are tautomers of each other

(D) Only II and III are tautomers of each other.

Q 12. The given compound II is respectively isomeric

with I, III and IV as

(I)

(II) (III)

(IV)

(A) Tautomer, functional, geometrical

(B) Metamers, tautomer, identical

(C) Functional, tautomer, identical

(D) Functional, tautomers and geometrical

Q 13. The most stable keto isomer of the following

compound is

(A) (B)

(C) (D)

Q 14. Which of the following has highest % enol content

in the liquid ?

(A) (B)

(C)

(D)

Q 15. Which of the following pairs of structures do not

represent tautomers?

(A)

(B)

(C) (D)




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Q 16. In the ketone,

O

CH3

O the acid catalysed enol

form is

(A)

O

CH3

OH (B)

OH

CH3

O

(C)

O

CH3

OH (D)

OH

CH3

O

Q 17. In which case, acid & base catalysed enol are

identical?

(A) CH – C – CH – C – CH3 2 3

O O

(B)

O

CH3

O

(C) CH – C – CH – CH3 2 3

O

(D) None of these

Q 18. The acid catalysed enol in the compound

is

(A)

(B)

(C)

(D) None of these

4. Stereo Isomers - Geometrical Isomerism

Q 1. Which of the following can show geometrical

isomerism?

(A) (B)

(C) (D)

Q 2. Geometrical isomerism is possible in

(A) (B)

(C) (D)

Q 3. Compound ‘X’ can exhibit ....... isomerism

(A) Tautomerism (B) Geometrical isomerism

(C) Optical isomerism (D) metamerism

Q 4. Which of the following compounds will show

geometrical isomerism

(A) Ph C C Me− − (B) ( )6 5 22C H N

(C)

(D)

Q 5. Which of the following compounds will have a

geometrical isomer ?

(A) (B)

(C)

Cl – CH – C – CH – CH2 2 3

O

Cl – CH = C – CH – CH2 3

OH

Cl – CH – C = CH – CH2 3

OH

Cl – CH = C – CH = CH3

OH




70

(D)

Q 5. Which of the following compounds will exhibit

cis-trans (geometrical) isomerism?

(A) 2-Butene (B) 2-Butyne

(C) 2-Butanol (D) Butanal

Q 6. The ‘E’ – isomer is/are

(A) (B)

(C) (D)

Q 7. Identify (Z) -2- pentene

(A) (B)

(C) (D)

Q 8. Dipole moment is shown by

(A) 1,4-Dichlorobenzene

(B) Trans -1-chloroprop-1-ene

(C) E-1,2-dibromoethene

(D) 2 2CH C CH= =

Q 9. Out of the following compounds, which will have a

zero dipole moment? [IIT JEE 1987]

(A) 1,1-dichloroethylene

(B) cis-1,2-dichloroethylene

(C) trans-1, 2-dichloroethylene

(D) None of these

Q 10. Which of the following hydrocarbons has the

lowest dipole moment?

C

H3C

=CCH3

H H(A) CH3C=

_CCH3

CH3CH2C CH=_ CH2=CH-C CH=

_

(B)

(C)(D)

Q 11. Identify the compound which can show

geometrical isomerism.

(A) (B)

(C) (D)

(E) (F)

(G) (H)

5. Properties of Geometrical Isomerism

Q 1. Which of the following is (are) capable of

exhibiting geometrical isomerism & how many

geometrical isomers are possible in each case

(i)

(A) (B)

(C) (D)

(F) (G)

(H) (I)

(J) (K)

(L) (M)

Br

Cl

Br

Cl

CH3

Br Cl Br Cl

Br Cl




71

(N)

(ii):

Br Cl

O

O

Br

Cl

Br

Br

=NOH

BrCl =C=C=

A) B)

C) D)

E) F) G)

H) I) J)

(iii)

A) B) C)

D)E)

Br

Q 2. Propose a suitable mechanism for each of the

following reactions.

CH3

C

H

=CCH3

H

H+

CH3

C

H

=C

CH3

H

CH3

C

H

=C

H

H+

CH3

C

H

=C

HCHO

CHO

CH3

C

H

=C

H

CH3

C

H

=C

HCHO

CHO

(C H3)3N

CH3

C

H

=C

H

CH3

C

H

=C

HI2

Light

CH3

CH3

OH

H H H+

OH H

BrHBr

A)

B)

C)

D)

E)

Q 3. In which of the following cases, cis-isomer is more

stable than trans-isomer:

(A)

(B)

(C)

(D) Both B and C

Q 4. Which of the following compounds has maximum

difference in heat of hydrogenation of their cis and

trans isomers.

(A)

(B)

(C)

(D)

Q 5. The correct order/s for the given pair of isomers is

(A)

(B)

(C)

(D)

Q 6. Consider the following graph which shows Heat of

combustions of isomeric Pentenes and answer the

given.

(i) Which of the following can show Geometrical

isomerism ?

(A) V (B) S (C) R (D) T

(ii) Which of the following pair shows chain

isomerism ?

(A) V,P (B) S,R (C) T,Q (D) R,Q

(iii) Which of the following pair shows positional

isomerism ?

(A) Q, T (B) S, T (C) V, S (D) P, R

Q 7. Which of the following compound does not show

geometrical isomerims?

C = C = C Br

Cl

Br

Cl

CH – CH = CH – CH3 3

Cl – CH = CH – Cl

CH – C = CH – CH3

CH3

CH3CH3

CH – CH = CH – CH3 3

D – CH = CH – D

CH – C – CH = CH – C – CH3 3

CH3

CH3

CH3

CH3

Et – CH = CH – Et




72

(A)

(B)

(C) MeCH CH CH CHEt= − =

(D)

Q 8. Which of the following will not have any

geometrical isomer ?

(A)

(B)

(C)

(D) Not applicable to single isomer

Q 10. Total number of geometrical isomers of the

compound 3 2 5CH CH CH CH CH C H− = − = −

is

(A) 2 (B) 3 (C) 4 (D) 5

Q 11. In general, which has higher solubility in 2H O

(A) cis form (B) trans form

(C) eqnal (D) None of these

6. Optical Isomerism

Q 1. Write the structures of two different compounds-

each having following structural Features.

Molecular formula = C8H14O

A six- member ring

One carbonyl group

Two similar asymmetric centres.

Q 2. Write the structure of a compound having

following structural features:

molecular formula = C7H12

a six – member ring

One asymmetric centre.



Molecular formula = C5H9N

A five member ring

one asymmetric centre.



Molecular formula = C5H9N

A five member ring

N is 10

One asymmetric centre.



Molecular formula = C8H10

Aromatic

Can produce only 3 monobromo derivatives.

Q 6. Write the structure of two compound having


Molecular formula = C6H9Br2C1

6 membered ring & Both Br atoms are germinal

Optically inactive



Molecular formula = C4H5NO

Only two SP3 hybridised carbon atoms, Only

one SP2 hybridised carbon atoms

Only one SP hybridised carbon atoms &

Optically active

Q 8. Which of the following is (are) optically active?




73

Q 9. Which of the following have asymmetric carbon

atoms?

H C C HCl

H

Br

HH C C

ClH

Br

HH

Cl

H C C HCl

H H

HH C C

HCH3

H

OH

(A) (B)

(C) (D)

Q 10. Indicate whether each of the following structure

has the R configuration of the S-configuration

(A)

(B)

(C) (D)

(E) (F)

(G) (H)

(I) (J)

(K) (L)

(M) (N)

(O) (P)

(Q) (R)

(S)

C

CH3

CH (CH )3 2

CH CH2 3

CH Br2

C

OH

CH Br2

CH CH Cl2 2

CH CH2 2

C

F

Br

HCl

C

CH3

CH – Br2

OHH

C

H

D

CH3

CH CH3 2

C

CH3

Br

H

CH CH3 2

Cl

CH3CH CH2 3

H

H

CH CH2 3

Cl

F

CH = CH2

F

CH3

OH

SH

H

Me

NH2

CH3

H

CH – CH2 3

Cl

CH – Br2

H NH2

CH2

CH CH2 3

CH I2

H

CH3

CHO

OH

CH OH2

H

CH3

COOH

CH –2 CH3

H

CH – OH2

HO CH3

CH CH CH OH2 2 2

CH3

HO

Cl

CH CH2 3

H

H

CH3

Br

BrCH CH2 3

H

H

CH3

H

Br

CH CH2 3

H

Br

O

Br

N N +

Cl -

N + H

Br Cl Br

Br Cl NO 2

NO 2

NO 2 NO 2

NO 2

O H

H CH 3

H

CH 3 H

H

OH

H

H H

CH 3

H H

OH CH

OH OH

N

Br Cl

3

OH COOH

A) B) C)

D) E) F)

G) H) I)

J) K) L)

M) N) O)

P)




74

Q 11. Which of the following does not have an

asymmetric ‘C’ atom?

(A) (B)

(C) (D)

Q 12. Which of the following have same optical rotation

?

(I) (II)

(III) (IV)

(A) I,IV (B) I, II

(C) III, IV (D) I, III

Q 13. The non identical species are

(A)

(B)

(C)

(D)

Q 14. Which of the following statements regarding the

projections shown below is true?

(A) ‘a’ and ‘b’ both represent the same

configuration

(B) Both ‘a’ and ‘b’ are optically active

(C) ‘b’ alone is optically active

(D) ‘a’ alone is optically active

Q 15. Which of the following is an achiral molecules ?

(A) (B)

(C) (D)

Q 16. Which statement is correct about the following

structures

(A) I & III are structural isomers

(B) I & II & I & III are enantiomers

(C) I, III, are enantiomers and I, II are structural

isomers

(D) I, II & III are stereoisomers




75

7. Mirror Image, Element of Symmetry

Q 1. Which of the following structures are

superimposable?

(I) (II)

(III) (IV)

(A) I and II (B) II and III

(C) I and IV (D) I and III

Q 2. How are the compound I and II are related ?

(A) Enantiomers (B) Diastereomers

(C) Constituional (D) Identical

Q 3. are

(A) Diastereomrs (B) Enantiomers

(C) Tautomers (D) Conformers

Q 4. which one is diastereomers of

(A) (B)

(C) (D)

Q 5. The correct statements(s) about the compound

given below is (are) [IIT JEE 2008]

(A) The compound is optically active

(B) The compound has centre of symmetry

(C) The compound has plane of symmetry

(D) The compound has axis of symmetry

Q 6. Examine each of the following pairs and state

whether they are identical or enantiomers or

diastereomers.

H

COOH

OH

CH3

H

COOH

OH

CH3

H OH

CH3

C2H5

CH3

C2H5

COH H

H

CH3CH3

C

C

Cl

CH3H

Br H

CH3

H

ClBr

HD

Br

Cl

DHCl Br

CH3

BrH

Cl

CH3

H CH3

BrH

Cl

CH3

H

A)

B)

C)

D)

E)

HCH3

Cl Br

CH3H

CH3

Br

H

HCH3

Cl

CH3ClH

CH3

Br H

CH3H CH3

H

H O

HO

O

H

CH3

O

H

CH3

OO

O

O

H

HHH

F)

G)

H)

I)J)

K)

HCH3

Cl Br

CH3H




76

H H Br

COOHCOOH3

H H COOHCOOH3

H H

HBrBr

H

O

Br

O

Br

H

H

H H

H

CH3CH3

H H

CH3CH3

Br

Br

H

OH

CH3

H

CH3

O CH3

H

CH3

H

L)

M)

N)

O) P)

Br

Q 7. In each of the following cases find out the

following numbers:

Number of geometrical isomers =?;

Number of optical isomers =?;

Number of stereoisomers=?

Number of optically active isomers=?;

Number of mesomers = ?;

Number of racemic mixtures=?

Br+

O

O OH

C=C=C C=C=C=C

OH

OH

OH

OH OH

CH3

OH

Br

Br

NO2

Br

O

O

A) B) C)

D) E) F)

G) H) I)

J) K)

L) M) N)

O)

Q 8. Which statement is wrong about symmetry?

(A) Plane of symmetry is an imaginary plane

which bisects the molecule in two equal halves in

such a way that each half of the molecule is the

mirror image of the other half

(B) Centre of symmetry is the point in a

molecule through which if the straight line is drawn

from any part of the molecule and if then this line

encounters identical groups at equal distances in

opposite direction

(C) A molecule which does not possess any

element of symmetry is called asymmetric

molecule

(D) A molecule which does not possess any

element of symmetry is called symmetric molecule

Q 9. Which of the following compound possess plane of

symmetry?

(A) (B)

(C) (D)

Q 10. Which of the given compound do not have axis of

symmetry

(A) (B)

(C) 4CH (D) All

Q 11. In which 2C axis of symmetry is present along the

given axis ?

(A) (B)

(C) (D)




77

8. Enantiomers, Diasteromers, Mesomers

Q 1. Which of the following is/are chiral?

(1) (2)

(3) (4)

(A) 1,2,3 (B) 1,2,4

(C) 2,3,4 (D) 1,3,4

Q 2. Which of the following statements is not correct

(A) Enantiomers are essentially chiral and

optically active

(B) Diasteromers are not neccesarily chiral and

optically active

(C) All geometrical isomers are diastereomers

(D) All diastereomers are chiral and optically

active

Q 3. Which of the following pairs of compounds are

enatiomers

(A)

(B)

(C)

(D)

Q 4. Which one among the following is not

diastereomeric pair

(A) I and III (B) I and II

(C) II and III (D) I and IV

Q 5. How are compounds I and II related?

(A) Enantiomer (B) Diasteeomers

(C) Constitutional isomer

(D) Identical molecules

Q 6. Total number of stereoisomers of compound is

(A) 2 (B) 4 (C) 6 (D) 8

Q 7. Which of the following molecules have

pseudoasymmetric centre?

CH3-CH-CH-CH3

OH OH

CH2-CH-CH2OH OH OH

CH3-CH-CH-CH-CH3

OHOH Br

CH3-CH=CH-CH-CH=CH-CH3

OH

CH3CH3CH3

CH3

CH3CH3

CH3

O

CH3CH3

CH3

CH3

Br CH3

Br

A) B)

C) D)

E)F)

G) H) I)

Q 8. Which of the following compounds is (are)

prochiral?




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O

A) CH3-CH2-CH2-CH3 CH3-CH-CH2-Br

CH3

CH3-C-CH2-CH3CH3

CH3

CH3-C-CH-CH3CH3CH3

CH3

CH3-CH=CH-CH2-CH2-CH=CH2

CH3

O

CH2COOH

COOH

O

CH2=C=CH-CH3

CH3-CH=C=CH-CH3CH2

B)

C) D)

O

E)F)

G) H)

I) J)

K)

L)

Q 9. Which of the following is (are) erythro isomer and

which is (are) threo isomer and which is (are)

none?

CH3OH

C2H5

H

OHHOHH

H

COOH

Cl

COOCH3

C2H5

CH3

Ph

HHPh

H CH3H C2H5

A) B)

C)D)

Q 10. Which of the following compound is L-amino

acid?

CH3

PhNH2

COOHH

NH2

COOH

H

COOH

H

CH3

OHH2N

H

COOH

CH3

H

NH2HO

H

A) B)

C) D)

Q 11. Examine each of the following reactions and state

whether they are leading to retention of

configuration or walden inversion or both retention

and walden inversion

CH3

H

CH3

OHH

A)

C2H5

Br NaOH

CH3

OHH

C2H5

HBr

CH3

NaOH CH3

OH

H

H

CH3OH

C2H5

Ph

CH2

H

MgBrH2O

C2H5

Ph

H

CH3

H Br

CH3

D

H2O H

CH3

OH

DHBr

H

CH3 D

Br

OHHNi/H2

CH3

OHH

B)

C)

D)

E)

CH3




79

9. Properties of Optical Isomers

Q 1. Number of fractions on fractional distillation of

mixture of

(A) 2 (B) 3 (C) 4 (D) 1

Q 2. Which of the following pairs in solid state have

same melting points and solubility?

(A) (+)- Lactic acid and ( )-Lactic acid.

(B) (+)- Lactic acid and (-) – Lactic acid.

(C) (-)- Tartaric acid and ( )- tartaric acid.

(D) (+)- Tartaric aicd and ( )- tartaric aicd.

(E) All

Q 3. Which of the following pair of isomers can not be

seperated by fractional crystallisation of fractional

distillation

(A) Maleic acid and Fumaric acid

(B) (+) – Tartaric acid and meso – tartaric acid

(C)

(D) (+) – lactic acid and (–) –lactic acid

Q 4. Which of the following compounds will show

optical activity ?

(A) (B)

(C) (D)

Q 5. The following molecules are

(A) Enantiomers (B) Diastereomers

(C) Identical (D) Conformers

Q 6. Total number of optically active stereoisomers of

(A) 2 (B) 4 (C) 6 (D) 8

Q 7. Total number of optical active stereoisomers of the

following compound is

3 3CH CH CH CHCl CH C CH CH CH CH− = − − = = − = −

(A) 8 (B) 6 (C) 16 (D) 10

Q 8. The structure of the enantiomer of an optical

isomer is obtained if its Fisher projection formula

is rotated by:

(A)900 (B)1800 (C)2700 (D)none.

Q 9. An optical isomer can be converted into its

diastercomer if it is roatated by :

(A)900 (B)1800 (C)2700 (D)none.

Q 10. Magnitude of optical rotation is affected by which

of the following factors:

a) Temperature b) Pressure

c) Concentration of the optical isomer

d) Configuration of the asymmetric centre.

e) Nature of groups attached with asymmetric

centre.

f) Length of polarimeter tube.

g) The solvent used.

h) Wavelength of the monochromatic light used.

i) Melting point of the compound.

Q 11. Magnitude of specific rotation of a compound is

independent of

(A) Temperature. (B) Concentration.

(C) Length of tube (D) Solvent.

(E)Wave length of the light.

Q 12. Is it possible to assign the direction and magnitude

of specific rotation of a molecule by simply

analysing its structure.

(A)Yes (B)No

(C) Sometimes possible & sometimes not

(D)Yes, if melting point is known.

Q 13. 0.5 gm of a compound was dissolved in 10ml of a

solvent. Optical rotation of this Solution was

measured to be 1.50at 250C using a polarimeter

tube of 1 dm length. Calculate its specific rotation.

What will be the specific rotation if its enantiomer.

Q 14. Given that

[α]23/D=30o

Concentration= 0.3gm/ml

Length of tube = 4.5 cm;

calculate the observed rotation.




80

Q 15. [α]25/D = 300

αobs = 4.050

Which of the following statements will be true?

(A) Doubling the concentration of the compound

will give [α]25/D= 600 and αobs= 8.10 (B) Doubling the concentration of the compound

will give [α]25/D=300 and αobs= 8.10

(C) Doubling the length of polarimeter tube will

give [α]25/D=600 and α obs=8.10

(D) Doubling the length of polarimeter tube will

give [α]25/D=300 and α obs=8.10

(E) Doubling the both length of polarimeter tube

and the concentration both will give

[α]25/D=300 and αobs=16.20

(F) Doubling the both length of polarimeter tube

and the concentration will give [α]25/D= 7.50

and αobs =16.20

Q 16. The observed optical rotation of a sample

containing two enantiomers is found to be +120 and

the specific rotation of one of the enantiomers is

+240. Both observed and specific rotations are

measured under indentical conditions.

Now,calculate

(A) optical purity of the sample

(B) % Composition of the sample.

Q 17. The enantiomeric excess and observed rotation of

mixture containing 6 gm of (+) – 2butanol and 4

(gm) of (–)–2–butanol are respectively (if the

specific rotation of enantiomerically pure (+) –2–

butanol is +13.5 unit)

(A) 80%, +2.7 unit (B) 20%, –27 unit

(C) 20%, +2.7 unit (D) 80%, –27 unit

Q 18. (+) tartaric acid has a specific rotation of +12 unit

when measured in 12 cm polarimeter tube and 2

g/ml concentration at given temperature and light.

When it is diluted to half the concentration, length

of the tube and other parameters being the same,

the specific rotation will be

(A) + 6 units (B) + 12 units

(C) – 6 units (D) + 24 units

10. Conformational Isomers

Q 1. Which of the following compounds will exhibit

conformational isomerism?

A) B)H2O CH3OH

CH3-C

CH3

CH3

-CH3

CH3

CH3-NH2

E) F)

G) H)

I)

C) CH3-CH=CH2 CH3-CH3D)

Q 2. The most stable conformation of

3-fluorobutan-2-ol is

(A) Fully elipsed from

(B) Partially eclipsed form

(C) Gauche form

(D) Anti form

Q 3. Eclipsed from of ethane is unstable due to

(A) High degree of torsional strain

(B) High degree of angle strain

(C) High degree of steric strain

(D) All of these

Q 4. The two structures I and II represents

(A) Conformational isomers (B) Homologs

(C) Structural isomers (D) Stereoisomers

Q 5.

(A) Conformational isomers

(B) Configurational isomer

(C) Constitutional isomers

(D) Identical




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Q 6.

(A) Conformational isomers (B) Stereoisomers

(C) Constitutional isomers (D) Identical

Q 7. The eclipsed and staggered conformation of ethane

is due to

(A) Free rotation about C-C single bond

(B) Restricted rotation about C-C single bond

(C) Absence of rotation about C-C bond

(D) None of the above

Q 8. Which is most stable conformation

(A) (B)

(C) (D)

Q 9. Select the correct statement/s

(A) Eclipsed and staggered ethanes give diferent

product on reaction with chlorin in presence of

light

(B) The conformational isomers can be isolated

at room temperature

(C) Torsional strain is ethane is minimum at

dihedral angles 60°, 180° and 300°

(D) Steric strain is minimum in staggered gauche

form of n-butane

Q 10. Which of the following is associated with

Torsional strain?

(A) Repulsion between bond pair of electrons

(B) Size of the groups present at adjacent atoms

(C) Bond angle strain

(D) Attraction of opposite charges

Q 11. The correct stability of conformer of 1,2-

dibromoethane

(A) Fully eclipsed > Partially eclipsed

(B) Partially eclipsed > Gauche

(C) Gauche > Anti

(D) Anti > Gauche

Q 12. The minimum torsional strain developed in butane

is at dihedral angles (S)

(A) 0°, 108° (B) 120°, 240°

(C) 60º, 180°, 300° (D) 60°, 120°, 180°

Q 13. In the following the most stable conformation of n-

butane is

(A) (B)

(C) (D)

Q 14. Which of the following is most stable conformer?

(A) (B)

(C) (D)

Q 15. Which of the given is not the conformer of 2-

methylbutane

(A) (B)

(C) (D)




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11. Torsional Strain,

Conformers of Cyclic Compounds

Q 1. Which of the two has more torsional strain:

(A) I (B) II

Q 2. Which of the following plots represent correctly

the graph of relation between potential energy and

rotation angle in case of ethane.

(A) 1 (B) 2 (C) both (D) none

Q 3. Isomers which can be interconverted through

rotation around a single bond are

(A) conformers (B) diastereomers

(C) enantiomers (D) positional isomrs

Q 4. In the molecule,

2C is rotated anticlockwise 120° about 2 3C C−

bond. The resulting conformer is

(A) partially eclipsed (B) eclipsed

(C) gauche (D) staggered

Q 5. In the Fischer projection formula, the

representation of meso-butene 2, 3 diol is

(A) in its stagered conformation

(B) in its eclipsed conformation

(C) in the gauche conformation

(D) unrelated to the conformational naming

Q 6. Consider the following statements about

conformational isomers.

1. They are interconverted by rotation about single

bond

2. The energy barrier separating them is less

than 15 kcal/mole

3. They are best represented by means of Fischer

projection formulae

Of these statements

(A) 1, 2 and 3 are correct

(B) 2 and 3 are correct

(C) 1 and 3 are correct

(D) 1 and 2 are correct

Q 7. Which one of the following is the MOST stable

conformation ?

Q 8. Which one of the following Newmann projection

formulae correctly represents a meso structure ?

Q 9. The correct order of stability for the conformer of

cyclohexane

(I) Boat conformer (II) Twisted Boat conformer

(III) Chair conformer (IV) Half chair conformer

(A) I II III IV (B) III I II IV

(C) III IV II I (D) III II I IV

Q 10. The correct statement is

(A) Chair conformer is free from torisional strain

while other conformers are not




83

(B) cyclohexane undergoes a rapid

conformational change referred to as ring inversion

or ring flipping

(C) Due to ring inversion all the axial bonds to

become equatorial and vice versa

(D) All of these

Q 11. Which of the given is not the conformer of

(A) (B)


Q 12. Which of the given is not the conformer of

(A) (B)


Q 13. The most stable conformer of

(A) (B)

(C) (D)

Q 14. The most stable conformer of

(A) (B)

(C) (D)




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Answer Key

1. Structural Isomers – Chain, Positional

Isomers

(1). D (2). D (3). B, C

(4). D (5). D (6). D

(7). A (8). C (9). C

(10). C (11). C (12). A

(13). D (14). B (15). C

2. Metamers, Functional & Ring Chain Isomers

(1). B (2). D (3). B

(4). A (5). D (6). D

(7). A (8). D (9). B

(10). D (11). D (12). D

(13). A (14). C (15). D

(16). D

3. Tautomerism

(1). D (2). A, C (3). A

(4). A, C, D, H, J, K, L, M, N, O, P

(5). A – II , B – I , C – I , D – I, E – II, F – II,

G – II , H – I, I – II, J – I

(6). C

(7). A – II, B – I, C – I, D – I, E – II, F – II,

G –I, H – I, I – II, J – I, K – I , B – II

(8).

(A) II > I > III > IV (B) III > II > I

(C) II > III > I (D) III > IV > I > II

(E) III > II > I (F) IV > II > I > III

(G) IV > II > I > III (H) I > III > IV > II

(I) III > II > I

(9). D

(10). A (11). A (12). C

(13). C (14). B (15). D

(16). C (17). A (18). A

4. Stereo Isomers - Geometrical Isomerism

(1). A (2). D (3). B

(4). B (5). D (6). A

(7). D (8). A (9). B

(10). C (11). B

(12). A, C, D, G

5. Properties of Geometrical Isomerism

(1). (i) C, F, H, K, L – all Have 2 G.I.

(ii) A – 4, B – 6, C – 4, D – 3, E – 2,

F – 2, G – 2, H – 4, I – 2, J – 2

(iii) A – 2, B – 2, C – 3, D – 4, E – 6

(2). SEE THE NOTES

(3). C (4). B (5). D

(6). (i) – D , (ii) – B, (iii) – C

(7). D (8). A, C (9). C

(10). A

6. Optical Isomerism

1.

2.

3.

4.

5. 6.

7.

O

H C3CH3

O

H C3 CH3

CH3

NH2

CH3

CH3

Br Br

Cl

H – C – CH – C N

CH3

O

NH 2 or N – CH 3




85

(8). C, F, G, I, J, L, O

(9). D

(10).

A – R B – R C – S D – S

E – R F – S G – R H – S

I – S J – S K – S L – R

M – S N – R O – S P – S

Q–2R, 3R R–2R, 3R S–2S, 3R

(11). C (12). D (13). B

(14). C (15). A (16). C

7. Mirror Image, Element of Symmetry

(1). D (2). C (3). A

(4). D (5). A, D

(6).

A – Enantiomers B – Entantiomers

C – Enantiomers D – Enantiomers

E – Diasteromers F – Identical

G – Identical H – Enantiomers

I – Enantiomers J – Enantiomers

K – Diasteromers L – Enantiomers

M – Enantiomers N – Diasteromers

O – Identical P – Enantiomers

(7).

G.I. O.I. S.I. Active Meso R.M.

A 2 4 4 4 0 2

B 2 8 8 8 0 4

C 2 4 4 4 0 2

D 2 3 3 2 1 1

E 2 3 3 2 1 1

F 2 3 3 2 1 1

G 0 3 3 2 1 1

H 0 4 4 4 0 2

I 4 8 8 8 0 4

J 2 4 4 4 0 2

K 2 4 4 4 0 2

L 2 0 2 0 0 0

M 3 0 3 0 0 0

N 4 8 8 8 0 4

O 2 4 4 4 0 2

(8). D (9). C (10). D

(11). B

8. Enantiomers, Diasteromers, Mesomers

(1). A (2). D (3). A

(4). A (5). B (6). B

(7). B, C, D, E, F, I

(8). A, B, C, D, E, H, I, J, K

(9). A – Erythrose, B – None

C – Erythrose, D – Erythrose

(10). A, B, C

(11). A – Inversion , B – Retention

C – Retention , D – Inversion, Inversion

E – Retention

9. Properties of Optical Isomers

(1). C (2). E (3). D

(4). C, D (5). A (6). A

(7). C (8). B (9). D

(10). A, C, D, E, F, G, H

(11). A, D, E (12). C

(13). + 30o & - 30o

(14). 4.05o

(15). B, D, E

(16). (i) – 50 % optical purity

(ii) – 75 % retention & 25 % inversion

(17). C (18). B

10. Conformational Isomers

(1). B, C, D, E, F, G, H, I

(2). C (3). A (4). B

(5). A (6). C (7). A

(8). B (9). C (10). A

(11). D (12). C (13). A

(14). B (15). D

11. Torsional Strain,

Conformers of Cyclic Compounds

(1). B (2). A (3). A

(4). C (5). A (6). D

(7). A (8). C (9). D

(10). D (11). B (12). B

(13). B (14). A


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