LEADER

IIT CHEMISTRY
ORGANIC CHEMISTRY
ISOMERISM

Methyl butyrate and propyl acetate are

organic flavor and fragrance molecules
found in apples and pears, respectively.

O O
CH3CH2CH2COCH3 CH3 COCH2 CH2 CH 3 We both looks same but
Methyl butyrate Propyl acetate Are we actually same ?

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 RESULTS OF BEST MENTORSHIP BY THE NUCLEUS TEAM

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CHITRAANG MURDIA GOVIND LAHOTI NISHIT AGARWAL AMEY GUPTA
Gen. Category - 2014 Gen. Category - 2014 Gen. Category - 2012 Gen. Category - 2014

JEE MAIN RESULTS 2020 (January Attempt) OF NUCLEUS EDUCATION

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SHASHANK AGRAWAL RAAGHAV RAAJ SHREYA PATHAK SIDDHANT CHOUDAHRY ANISWAR S KRISHNAN AAYUSH KADAM SARTHAK BEHERA ANDREWS G. VARGHESE
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HIMANSHU GAURAV SINGH VIBHAV AGGARWAL S. PRAJEETH SOHAM MISTRI SAYANTAN DHAR GAURAV KRISHAN GUPTA SATVIK JAIN
Gen. Category - 2019 Gen. Category - 2019 Gen. Category - 2019 Gen. Category - 2019 Gen. Category - 2019 Gen. Category - 2019 Gen. Category - 2019
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 EXERCISE-I
Q.1 The compounds C2H5OC2H5 and CH3OCH2CH2CH3 are
(A) Chain isomers (B) Geometrical isomers
(C) Metamers (D) Conformational isomers

Q.2 The number of primary, secondary and tertiary amines possible with the molecular formula C3H9N
respectively.
(A) 1, 2, 2 (B) 1, 2, 1 (C) 2, 1, 1 (D) 3, 0, 1

Q.3 How many benzenoid aromatic isomers shown by C7H7Cl ?

(A) 4 (B) 3 (C) 5 (D) 6

Q.4 Molecular formula C3H6Br2 can have:

(A) Two gem dibromide (B) Three vic dibromide
(C) Two tert.- dibromo alkane (D) Two sec.-dibromo alkane

Q.5 Following compounds are :

Br COOH COOH Br

HOOC Br Br COOH

(A) Position isomer (B) Chain isomer (C) Geometrical isomer (D) Functional isomer

Q.6 Which of the following is incorrect relation :

Me
Pr Pr
(A) & identical
Me

Me Et
(B) & positional isomers
Pr Pr

Et Et
(C) & positional isomers
Pr
Pr

Me
Me
Et
(D) & homologues
Pr

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Q.7 Select whether given realationship is true or false?
COOH
OCOH
& functional isomer

OMe OEt
Et
& metamers
Me

CH2 – CH2 – OH CH2 – O – CH3

& metamers

Me – N – Me CH2 – NH – CH3

& functional isomers

(A) TFTF (B) FTTF (C) TTFT (D) TFFT

Q.8 Following compounds are :

O O
Cl C—O C—O Cl
H CH3
C=C C=C
H CH3 H H
(A) Functional isomer (B) Geometrical isomer
(C) Metamer (D) Position isomer

Q.9 The type of isomerism observed in urea molecule is

(A) Chain (B) Position (C) Geometrical (D) Functional

Q.10 How many minimum no. of C-atoms are required for position & geometrical isomerism in alkene?
(A) 4, 3 (B) 4, 4 (C) 3, 4 (D) 3, 3

Q.11 Which of the following cannot be written in an isomeric form?

(A) CH3–CH(OH)–CH2–CH3 (B) CH3–CHO
(C) CH2=CH–Cl (D) Cl–CH2CH2–Cl
Q.12 Given compound shows which type of isomerism
O O
S—O and S—O
O O
(A) Chain isomerism (B) Positional isomerism
(C) Metamerism (D) Functional group isomerism
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Q.13 Which of the following involves Diad system for prototropy :
O

(A) CH3COCH3 (B) CH3CH2NO2 (C) (D) HCN

Q.14 Which of the following does not show geometrical isomerism?

(A) 1, 2-dichloro-1-pentene (B) 1, 3-dichloro-2-pentene
(C) 1, 1-dichloro-1-pentene (D) 1, 4-dichloro-2-pentene

Q.15 What characteristic is the best common to both cis-2-butene and trans-2-butene?
(A) Boiling point (B) Dipole moment
(C) Heat of hydrogenation (D) Product of hydrogenation

Q.16 The number of cis-trans isomer possible for the following compound

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

Q.17 Which of the following have zero dipole moment?

(A) benzene 1,4- diol (B) trans-1,2-dichloro ethene
(C) cis-1,2-dichloro ethene (D) 1,1-dichloro ethene

Q.18 Which of the following will not show geometrical isomerism.

Me Me
(A) (B) (C) Cl (D)
Me

Q.19 Geometrical isomerism is possible in:

(A) isobutene (B) acetone oxime
(C) acetophenone oxime (D) benzophenone oxime

Q.20 How many structural isomers of C5H10 are possible.

(A) 10 (B) 11 (C) 12 (D) 13
Q.21 The number of isomers of dibromoderivative of an alkene (molar mass 186 g mol–1) is
(A) 2 (B) 3 (C) 4 (D) 6
Q.22 How many structural isomeric primary amines are possible for the formula C4H11N?
(A) 2 (B) 3 (C) 4 (D) 5
Q.23 For the given compound, choose the incorrect option ?
O
CH3–CH=CH–C–CH3
(A) It can show both geometrical isomerism & tautomerism.
(B) It has all types of permanent electronic displacement effect present.
(C) It has IUPAC name "Pent-2-en-4-one."
(D) On treatment with NaOD/D2O for long time, it has 7 deuterium in its enol form

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Q.24 Among the following the compounds having the highest enol content :
(A) CH3CHO (B) CH3COCH3
(C) CH 3  C  CH 2 CHO (D) CH3–CO–CH2–CO2CH3
||
O
Q.25 Given interconversion takes place in
O O

(A) Acidic medium (B) Basic medium (C) Both (D) None
Q.26 (I) isomerizes to (II) on addition on small amount of base then structure of (II) is
O OH
|| |

OH –
CH 3  C  CH  Ph  
 (II)
( I)

OH OH O OH
| | || |
(A) CH3  CH — CH  Ph (B) H  C  CH 2  CH  Ph

(C) CH 3  CH  C  Ph (D) CH 3  C — C  Ph
| || || ||
OH O O O
Q.27 Major product (P) obtained is :
O

 
–
OD / D 2 O
Ph 
(Prolonged)
 (P)
O D O D
C
(A) Ph CD3 (B) Ph CH3
D D
O H O
(C) Ph CD3 (D)
D Ph CH3

Q.28 Which of the following will show geometrical isomerism.

(A) (B) (C) (D)

Q.29 Decreasing order of enol content of the following compounds in liquid phase is :
O O
O O
O
||
CH 3  C  OEt
(1) (2) (3) ( 4)
(A) 2 > 1 > 3 > 4 (B) 1 > 2 > 3 > 4 (C) 4 > 3 > 2 > 1 (D) 3 > 1 > 2 > 4
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Q.30 Decreasing order of enol content of the following compound in liquid phase
O O O O
|| || || ||
(a) CH 3  C  CH 2  C  O  Et (b) CH 3  C  CH 2  C  CH 3

O
O O
|| ||
(c) Ph  C  CH 2  C  Ph (d)
(A) a > b > c > d (B) c > b > a > d (C) c > b > d > a (D) b > c > a > d
Q.31 What is the correct IUPAC name of the following compound

(A) 2E, 4E, 6Z 4-methyl octa-2, 4, 6 triene (B) 2E, 4Z, 6Z 5-methyl octa-2, 4, 6 triene
(C) 2Z, 4Z, 6Z 5-methyl octa-2, 4, 6 triene (D) 2E, 4Z, 6E 4-methyl octa-2, 4, 6 triene
Q.32 The IUPAC name of the given compound is
H CH3

H3C H
(A) 2, 4-di[(E)-ethylidene] cyclobutane (B) 1, 3-di-[(E)-ethylidene] cyclobutane
(C) 1, 4-di-E-ethyldenecyclobutane (D) (E)-1, 4-diethylidenecyclobutane
Q.33 Which of the following will show geometrical isomerism.
Me Br
Me
(A) (B) (C) (D)
Br
Br Me

Q.34 Total number of geometrical isomer of following compound is:

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

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 EXERCISE-II
Q.1 The IUPAC name of the compound is :

(A) (2E, 4E, 6Z)-octa-2,4,6-triene (B) (2E, 4E, 6E)-octa-2,4,6-triene

(C) (2Z, 4E, 6Z)-octa-2,4,6-triene (D) (2Z, 4Z, 6Z)-octa-2,4,6-triene
Q.2 Which of the following have zero dipole moment?
(A) 1, 4-Benzo nitrile (B) Benzene-1, 4-dithiol
(C) Fumaric acid (D) Maleic acid
Q.3 Which of the following statements is (are) not correct?
(A) Metamerism belongs to the category of structural isomerism
(B) Tautomeric structures are the resonating structures of a molecule
(C) Keto form is always more stable than the enol form
(D) Geometrical isomerism is shown only by alkenes
Q.4 Which compound can show tautomerism:
O
OH N OH

(A) (B) (C) (D) Acetyl acetone

CH3
Q.5 Tautomerism form of this compound is(are) : N=O
OH
HO OH

HO OH
OH
O O
HO O HO OH
(A) (B)
HO OH O O
O OH
O O
O O HO OH
(C) (D)
HO OH HO O
OH OH
Q.6 Which of the following is not the correct relationship
Me Me Me
Me Me

Me Me
O – Me O–Me
OH OH
I II III IV
(A) II & IV are metamer (B) I & II are functional isomer
(C) I & III are chain isomer (D) I and IV are positional isomer

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Q.7 Which of the following compounds have higher enolic content than Keto content:
O O O O O
|| || O
(A) CH 3  C  C  CH 3 (B) O (C) (D)

Q.8 In which of the following pairs first will have higher enol content than second :

(A) and

(B) and

(C) and

(D) and

Q.9 Among these tautomers, correct stability order is :

OH O OH

I II III
(A) I > II > III (B) III > II > I (C) II > I > III (D) II > III > I
Q.10 Most stable tautomer of following compound is :
O O

C – CH2 – C

(A) C – CH = C (B) C – CH2 – C

O OH OH O
(C) CH – CH = CH (D) C – CH2 – C

OH OH O OH
Q.11 Which of the following can tautomerise.

O O O

(A) CD3  C  Ph (B) (C) (D)

|| N
O H

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Q.12 Tautomer of which of the following can show geometrical isomerism
O
O
(A) CH3–CHO (B) CH3CH2–CHO (C) (D)

Q.13 Enol form of which compound is more stable than it's keto form and also shows geometrical isomerism ?
(A) Acetyl acetone (B) 1, 2, 3-cyclobutantrione
(C) Propanal (D) Cycohexanone
Q.14 What is relation between (I), (II) and (III) ?
O OH O–
+ +
HN NH N N HN NH
(I) (II) (III)
– +
O N O HO OH O N O–
H N
H
(A) I and II are tautomers (B) III is conjugate base of II
(C) III is resonance structure of I (D) no relation exists
Q.15 Which will form geometrical isomers ?
Cl

(A) (B) CH3CH NOH (C) (D) Annulene [10]

Cl
Q.16 Which will show geometrical isomerism ?
Me Me Me Me

(A) N2H2 (B)

Et Me Me Et
(C) Lactic acid (D) HO—N N—OH
Q.17 The isomerism observed in cyclo alkanes is(are) :
(A) metamerism (B) chain isomerism
(C) position isomerism (D) geometrical isomerism
Q.18 Only two isomeric monochloro derivatives structure are possible for :
(A) n-butane (B) 2, 4-dimethyl pentane
(C) benzene (D) 2-methyl propane

Q.19 An organic compound with molecular formula C2H5NO contains doubly linked atoms. It can shows:
(A) chain isomerism (B) geometrical isomerism
(C) tautomerism (D) positional isomerism

Q.20 Which of the following can exist in 'syn' and 'anti' form ?
(A) C6H5—N N—OH (B) C6H5—N N—C6H5
(C) C6 H5 —CH N—OH (D) (C6H5)2C N—OH

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Q.21 The Z-isomer among the following are :
(A) CH3—C—H (B) CH3—C—H (C) Cl—C—Br (D) Cl—C—Br
C3H7—C—C2H5 C2H5—C—C3H7 H—C—F F—C—H

Q.22 Which of the following is/are correct matchings ?

O O
(A) CH3—C—OH and H—C—OCH3 – Metamers

(B) CH3—CH2—C CH and CH3—C C—CH3 – Position isomers

(C) CH3CH2CH2NH2 and CH3—CH—CH3 – Tautomers

NH2
(D) CH3CH2OH and (CH3)2O – Functional isomer

Q.23 Which of the following is correctly mathed ?

Compound Number of geometrical
isomers
(A) CH3—CH CH—CH CH—C2H5  4

(B) CH3—(CH CH)4—CH3  10

(C) CH2 CH—CH CH2  2

(D) CH3 (—CH CH)3 —CH3  6

Q.24 Which of the following compounds can show tautomerism ?

O S
(A) NH2—C—NH2 (B) NH2—C—NH2
O
(C) HO N O (D) CH3—C—CH3

Q.25 Total number of geometrical isomer of following compound.

(A) 2 (B) 4 (C) 8 (D) 16

Q.26 Which of the following has (have) more number of stable conformations than ethyl chloride?
(A) Butane (B) Isopropanol (C) n-pentane (D) Neohexane

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Q.27 Statement-1 : E-cycl odecene i s hav i ng m or e H C (Heat of combustion) than
Z isomer.
Statement-2 : E-cyclodecene is more stable than Z isomer.
(A) Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1.
(B) Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1.
(C) Statement-1 is true, statement-2 is false.
(D) Statement-1 is false, statement-2 is true.

Q.28 Match the Column I with Column II :

Column I (Pair) Column II (Relation)
O O
|| ||
(A) CH 3  C  O  C3H 7 & Et  C  O  Et (P) Chain isomer

(B) & (Q) Positional isomers

(C) & (R) Metamers

(D) CH 3  CH  O  CH 3 & CH3–CH2–CH2–O–CH3 (S) Tautomers

|
CH 3

Q.29 Column-I Column-II

(A) (P) Geometrical isomers

Br Br
(B) (Q) Structural isomers
Br

Br
F I

Br F
(C) Cl Br (R) First compound has Z nomenclature

I Cl

(S) Second compound has trans nomenclature

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Q.30 Match the column :
Column I Column II
O OH

(A) (P) Tautomers

O OH

(B) (Q) Structural isomers

OH OH

(C) (R) Position isomers

O CH2

(D) (S) Atleast one of the two structures is enol

OH

Q.31 Column I Column II

(A) (P) Position isomers

(B) (Q) Geometrical isomers

Me OH Me
C=N C=N
(C) OH (R) First is E and second is Z form

OH OH
(D) (S) Structural isomer
OH
OH

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Q.32 Column I Column II
Compound Number of geometrical isomers

(A) (P) 2

(B) (Q) 4

(C) (R) 6

(D) (S) 8

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 EXERCISE-III
Q.1 How many benzenoid isomer are possible for molecular formula of cresol :
Q.2 Find out the total number of cyclic structural isomers of C6H12.
Q.3 How many pair(s) of geometrical isomers are possible with C6H12 (only in open chain structures)
Q.4 Calculate the number of Benzenoid isomers possible for C6H3ClBrI.
Q.5 Calculate the total number of structural isomers of 3°-amines for the molecular formula C6H15N are?
Q.6 How many cyclopentane structures (excluding stereo isomer) are possible for C7H14.
Q.7 Mention the specific type of isomerism exhibited by each of the following pairs:
(a) 1,2-dichloro ethane and 1,1-dichloro ethane (b) Propanoic acid and methyl acetate
(c) Methyl acetate and ethyl formate (d) o-Nitrophenol and P-nitrophenol
(e) Anisole and o-cresol (f) Phenol and Cyclohexa-2,4-dien-1-one
Q.8 In each of the following pairs which is more stable :

(a) 
 (b) 
 (c) 


(d) 
 (e) 


Q.9 In each of the following pairs which is more stable :

(a) (b)

(c) l (d) l

(e) l

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Q.10 In each of the following pairs which will have less enol content :

(a) and (b) and

(c) and (d) and

(e) CH 2  CHO and CH 3  CHO

|
Cl

Q.11 In each of the following pairs which will have less enol content :

(a) and (b) and

Q.12 In each of the following sets of compounds write the decreasing order of % enol content.

(a)

(b)

Q.13 In each of the following sets of compounds write the decreasing order of % enol content.

(i)

(ii)

Q.14 In each of the following sets of compounds write the decreasing order of % enol content.

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Q.15

Among these give ease of enolization.

Q.16 % enol content of acetylacetone in following solvents is found as :

Solvent % enol content
H2O 15
Liquid state 76
hexane 92
gas phase 92
Explain the observation.

Q.17

Explain the observation.

Q.18 Decreasing order of enol content of the following. (along with proper explanation).

(a) , (b) , (c) , (d) , (e)

Q.19 Ph  CH  CHO
|
OH
(A )
(A), (B) and (C) are structural isomers and isomerization is effectively carried out by trace of base. Give
structure of (B) and (C) and also write base catalysed mechanism for this interconversion.

Q.20 Calculate the total number of open chain isomeric carbonyl compounds of molecular formula C5H8O
which can't show geometrical isomerism.

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 ANSWER KEY
EXERCISE-I
Q.1 C Q.2 C Q.3 A Q.4 A Q.5 A Q.6 B Q.7 C
Q.8 C Q.9 D Q.10 B Q.11 C Q.12 C Q.13 D Q.14 C
Q.15 D Q.16 A Q.17 B Q.18 A Q.19 C Q.20 A Q.21 B
Q.22 C Q.23 C Q.24 C Q.25 C Q.26 C Q.27 C Q.28 D
Q.29 B Q.30 B Q.31 D Q.32 B Q.33 A Q.34 A

EXERCISE-II
Q.1 C Q.2 A Q.3 B;C;D Q.4 A; C; D Q.5 ABD
Q.6 AD Q.7 B; D Q.8 A; C Q.9 C Q.10 A
Q.11 A; B; C Q.12 B; C Q.13 A Q.14 A
Q.15 A;B;C;D Q.16 A; B; D Q.17 B; C; D Q.18 A; D Q.19 B; C
Q.20 C Q.21 A; C Q.22 B; D Q.23 ABD
Q.24 A; B; C; D Q.25 B Q.26 A; B; C Q.27 C
Q.28 (A) R, (B) Q, (C) S, (D) Q Q.29 (A) Q,R,S (B) Q (C) P,R
Q.30 (A) P,Q,S; (B) Q,S; (C) Q,R,S; (D) Q,S Q.31 (A) P,R,S ;(B) Q; (C) Q,R; (D) P,R,S
Q.32 (A) P (B) P (C) S (D) P

EXERCISE-III
Q.1 5 Q.2 12 Q.3 4 Q.4 10 Q.5 7 Q.6 4

Q.7 (a) Positional (b) Functional (c) Metamerism (d) Positional (e) Functional (f) Tautomerim

Q.8 (a) 2; (b) 2; (c) 1; (d) 1; (e) 1 Q.9 (a) 2; (b) 2; (c) 1; (d) 2; (e) 1

Q.10 (a) 2; (b) 1; (c) 2; (d) 1; (e) 2 Q.11 (a) 2; (b) 2

Q.12 (a) 3>1>2; (b) 4>2>1>3; Q.13 (i) 4 > 1 > 3 > 2 ; (ii) 3 > 1 > 4 > 2

Q.14 3 > 4 > 2 > 1 Q.15 3>1>2

Q.15 > > > >

(a) (b) (c) (d) (e)

(a) Tightly on stable keto due to repulsion between – CO groups has 100 % enol.
(b) Active 'H' atom / Acidic 'H' atom so has more enolic content (enol stabilise by resonance & Intra
molecular H–bonding)

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 (c) Enolic contents decreases with introduction of e– donator group which causes repulsion in enolic
form .
(d) Due to ester group acidic structure of active H decreases & C=C of enol undergoese cross
resonance.
(e) Lowest enolic content because is more stable than Bond

Q.19 Ph  C  CH Ph  C  CH 2
| | || |
OH OH O OH
(B) (C )
(Mechanism)

Ph  CH  CH 
 P h  C  C H Ph  C  CH
| || | |
OH O – | |
OH O OH OH
(B)

Ph  C  CH 2 Ph  C  CH
|| | || |
O OH O OH
( C)

Q.20 8

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