Organic Reaction Mechanisms-IV Apsp PDF
Organic Reaction Mechanisms-IV Apsp PDF
Organic Reaction Mechanisms-IV Apsp PDF
This Section is not meant for classroom discussion. It is being given to promote self-
study and self testing amongst the Resonance students.
H O
+ PhMgBr A
H3PO4
1. 3
B C
C is :
2. The correct increasing order of reactivity for following alkyl halides towards elimination reaction with
alcoholic KOH is :
(1) II > I > III (2) I > II > III (3) II > III > I (4) III > II > I
conc. H2SO4
3. In the given reaction: [X] as major product
[X] will be :
O OH
4.
NaOH,
(Product)
The major product of the above reaction is obtained by mechanism
(1) SN2 (2) E2 (3) E1cB (4) SN1
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Organic Reaction Mechanisms-IV
Conc. H SO
6.
2 4
Major product is :
7. Which of the following conformations of meso 2,3-dibromobutane will give bromoalkene with alcoholic
KOH ?
(1) Gauche form (2) Anti form
(3) Partial eclipsed form (4) Fully eclipsed form
8. 2-Bromopentane is heated with potassium ethoxide in ethanol. The major product obtained is
(1) 2-Ethoxypentane (2) pent-1-ene
(3) cis-pent-2-ene (4) trans-pent-2-ene
CrO / H 1) CH MgBr
9.
3
P
3
Q
H
R
2) H3O
OH (major)
R is :
(1) But-1-ene (2) 2-methylbut-1-ene
(3) 2-methylbut-2-ene (4) 2-methyl propene
NaNH / NH ( )
10. Ph
Conc. HBr
2 3
Major product is :
OH
CH2
(1) Ph (2) Ph (3) Ph (4) Ph
NH 2
NH 2
C H O– K
2 5
Trans
12. P, Product P is :
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14. Which of the following statement is correct regarding following reaction ?
t BuOH
+ t-BuO–K+ ?
16. Which of the following compound will give three alkenes after dehydrohalogenation.
(1) CH3–CH2–CH2–CH2–Br (2)
(3) (4)
The product is :
(1) PhSO2CH=CH2 (2) CH2=CH–OMe
(3) PhSO2CH2–CD2OMe (4) CD2=CH2
CH2 – OH
H SO / H
18.
2 4
A. The product A is :
OH
19. Typical features of E2 involve :
(1) Two step reaction
(2) Second step is the rate determining step
(3) Anti-periplanar transition state
(4) Formation of a carbanion intermediate, stabilized by conjugation with a strong –M group
20. An alkyl chloride produces a single alkene on reaction with sodium ethoxide and ethanol. The alkene
further undergoes hydrogenation to yield-2-methylbutane. Identify the alkyl chloride from amongst the
following :
(1) ClCH2C(CH3)2CH3 (2) ClCH2CH2CH2CH3
(3) ClCH2CH(CH3)CH2CH3 (4) CH3C(Cl)(CH3)CH2CH3
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22. Which of the following is the correct major product for given reaction ?
H SO
2 4
Product
(1) (2)
(3) (4)
(2) CHCl3 + KOH CCl2
HO /
(3)
NaNH
(4) CH2=CH–Cl
2
HCCH
24. Correct order of E2/SN2 ratio is :
P= Q= R = CH3–Br S = CH3–CH2–Br
(1) P > Q > S > R (2) P > Q > R > S (3) R > S > Q > P (4) P > S > Q > R
25. The product C of the following reaction sequence is :
HBr
A
alc. KOH
B
HBr
C
R2O2
–
EtO (1eq)
27. What is the correct sequence of reagent/s for the following conversion:
CH3 CH CH3 CH3–CH2–CH2–I
|
Br
alc. KOH
HI aq. KOH H2SO4 HI
(1) (2)
alc. KOH HBr / R2O2 KI alc. KOH KI
HCl
(3)
(4)
acetone acetone
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28. In which of the following reaction the single product formed is not the saytzeff’s product
H SO H SO
(1)
2 4
(2)
2 4
(3)
alc. KOH
(4)
alc. KOH
29. In the following reaction the correct order of percentage of products X, Y and Z is
CH3 CH3 CH3 CH3 CH2CH3 CH3 CH3
| | | | || | | |
CH3 CH2 C CH CH3 CH3 CH C CH CH3 + C2H5 C – CH CH3 + C2H5 C C CH3
alc. KOH
2. Which of the following most readily undergoes E2 elimination with a strong base ? [NSEC-2000]
(A) 2-bromopentane (B) 2-bromo-2-methylbutane
(C) 1-bromo-2, 2-dimethylpropane (D) 2-bromo-3-methylbutane
3. An alkyl chloride produces a single alkene on reaction with sodium ethoxide and ethanol. The alkene
further undergoes hydrogenation to yield 2-methylbutane. Identify the alkyl chloride from amongst the
following : [NSEC-2001]
(A) CICH2CH(CH3)CH2CH3 (B) CICH2CH2CH2CH3
(C) CICHC(CH3)2CH3 (D) CH3C(CI)(CH3)CH2CH3
4. On heating glycerol with conc. H2SO4, a compound obtained which has an unpleasant odour. This
compound is : [NSEC-2001, 2004]
(A) ethylene glycol (B) allyl alcohol (C) acrolein (D) glycerol sulphate
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5. n-Propylbromide and ethanolic potassium hydroxide react to give : [NSEC-2001]
(A) propyne (B) propene (C) propane (D) propanol
H SO
2 4
Major product
Heat
9. Arrange the following compounds in order of decreasing reactivity in the elimination (bimolecular)
reaction with C2H5ONa [NSEC-2007]
(A) II > I > III > IV (B) IV > III > I > II (C) III > I > II > IV (D) I > III > IV > II
10. Compound X on treatment with HI gives Y. Y on treatment with ethanolic KOH gives Z (an isomer of X).
Ozonolysis of Z (with H2O2 workup) gives a two-carbon carboxylic acid and four carbon ketone. Hence,
X is :
(A) 2-methyl-2-pentene (B) 4-methyl-1-pentene [NSEC-2009]
(C) 2, 3-dimethyl-2-butene (D) 3-methyl-1-pentene
(i) H PO , 150ºC
3 4
(ii) C6H5COOOH
13. The compound that is most reactive with alcoholic KOH is [NSEC-2014]
(A) CH2=CH–Br (B) CH3CH2Br (C) (CH3)2CH–Br (D) CH3COCH2CH2Br
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14. Four processes are indicated below : [NSEC-2015]
(i)HBr / no peroxide (ii) alcoholic KOH,
(I)
Br
(i) Mg, ether (ii) CH O (iii) H , H O
(III)
2 2
Br
(i) aq. KOH (ii) CH MgBr, ether (iii) H O
(IV) Br
3 3
16. An alkyl halide (X) on reaction with ethanolic sodium hydroxide forms an alkene (Y) which on further
reaction with HBr gives the same alkyl halide. The alkene (Y) on reaction with HBr/peroxide followed by
reaction with Mg metal followed by reaction with HCN produces an aldehyde (Z). Z is : [NSEC-2016]
CHO
(A) (B) CHO
CHO
CHO
(C) (D)
17. Spodoptol, a sex attractant, produced by a female fall armyworm moth, can be prepared as follows. The
structure of Spodoptol is (pKa : terminal alkynes ~ 25, alcohols ~ 17) [NSEC-2016]
i. NaNH2 (excess)
ii. n-C4H9Br (1eq)
iii. H2/Lindlar cat
HO—CH2 (CH2 )7 C CH Spodoptol
H H
(A) n-C4H9–O–CH2–(CH2)7—HC=CH2 (B)
HO–CH2 –(CH2 )7 n-C 4H9
H n-C4 H9
(C) (D) HO–CH2–(CH2)12–CH3
HO–CH2 –(CH2 )7 H
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Organic Reaction Mechanisms-IV
Important Instructions
A. General %
1. The test is of 1 hour duration.
2. The Test Booklet consists of 22 questions. The maximum marks are 66.
B. Question Paper Format :
3. Each part consists of five sections.
4. Section 1 contains 8 multiple choice questions. Each question has four choices (A), (B), (C) and (D) out
of which ONE is correct.
5. Section 2 contains 6 multiple choice questions. Each question has four choices (A), (B), (C) and (D) out
of which ONE OR MORE THAN ONE are correct.
6. Section 3 contains 4 questions. The answer to each of the questions is a single-digit integer, ranging from
0 to 9 (both inclusive).
7. Section 4 contains 1 paragraphs each describing theory, experiment and data etc. 3 questions relate to
paragraph. Each question pertaining to a partcular passage should have only one correct answer among
the four given choices (A), (B), (C) and (D).
8. Section 5 contains 1 multiple choice questions. Question has two lists (list-1 : P, Q, R and S; List-2 : 1, 2,
3 and 4). The options for the correct match are provided as (A), (B), (C) and (D) out of which ONLY ONE
is correct.
C. Marking Scheme
9. For each question in Section 1, 4 and 5 you will be awarded 3 marks if you darken the bubble
corresponding to the correct answer and zero mark if no bubble is darkened. In all other cases, minus one
(–1) mark will be awarded.
10. For each question in Section 2, you will be awarded 3 marks. If you darken all the bubble(s)
corresponding to the correct answer(s) and zero mark. If no bubbles are darkened. No negative marks will
be answered for incorrect answer in this section.
11. For each question in Section 3, you will be awarded 3 marks if you darken only the bubble corresponding
to the correct answer and zero mark if no bubble is darkened. No negative marks will be awarded for
incorrect answer in this section.
(i) Cl
Base
(ii) H
Base
E2 E2
Cl
(A) Same for both conformers (B) i > ii
(C) ii > i (D) Can’t say anything about rate of E-2 reaction
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Organic Reaction Mechanisms-IV
3. The compound 'X' is
O
||
H2SO4 HIO4
[X]
O
OH
(A) (B)
OH
(C) (D)
OH OH OH OH
4. When the all-cis isomer of C6H6Cl6 (1, 2, 3, 4, 5, 6-Hexachlorocyclohexane) is heated with alc. KOH,
the most probable product is :
CHD2MgI Conc.H2SO4
5. CH2O X Y
H3 O
In the above reaction compound X & Y respectively will be
OH
|
(A) CHD CH2 OH , CHO–CHO (B) CHD2–CH2–OH , CHO–CHO
Conc. H SO / 60ºC
7.
2 4
The product is –
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Organic Reaction Mechanisms-IV
8. Which one of the following hexachlorocyclohexane is least reactive and which one is most reactive for
E2 reactions with a strong base for dehydrohalogenation.
(A) I least & II most (B) II least & I most (C) III least & I most (D) III least & II most
9. In which of the following reactions the correct major products are mentioned
CH3
(A)
EtO
Br
H3C CD3 H3C CD3
(B)
EtO
NaOEt
(C) EtOH
H SO ,
(D)
2 4
10. When ethyl bromide is added to potassium t-butoxide, the product is ethyl t-butyl ether.
(CH3 )3 C – O – CH2CH3
CH3CH2 – Br + (CH3 )3 C – OK
ethyl bromide potassium t butoxide ethyl t butyl ether
CH CH O– CH CH O–
(A)
3 2
(B)
3 2
DMSO DMF
HO
(C)
2
(D)
13. Which of the following statements is/are correct for alkyl halide ?
(A) In most unimolecular reactions of alkyl halide SN1 reaction is favoured over E1 reaction.
(B) E1 mechanism is favoured as compared to SN1 mechanism by branching at carbon
(C) In unimolecular reaction, increasing the temperature favours E1 mechanism
(D) E1 reactions are favoured by the use of weak bases and by the use of polar solvents.
(D) The compound gives product (P) on treatment with conc. H2SO4 as well as with Al2O3/
H SO /
2 4
17. CH3–C—CH–CH3
H3C Br
Report your answer as XY
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Organic Reaction Mechanisms-IV
18. The number of products (stereoisomers) formed in the following reaction is (consider only major
product)
C H O– (excess) /
19.
2 5
P (major)
Product P is
20.
21. Which of the following substrate will undergo fastest reaction through E1cB route
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Organic Reaction Mechanisms-IV
SECTION-5 : Matching List Type (Only One options correct)
This section contains 1 questions, each having two matching lists. Choices for the correct
combination of elements from List-I and List-II are given as options (A), (B), (C) and (D) out of
which one is correct
22. Match List I (Reaction) with List II (Type of reaction) and select the correct answer using the code given
below the lists :
List I List II
(P) CH CH O– (1) E1
3 2
CH CH O–
(Q)
3 2
(2) E2
CH3CH2OD
Ag O, moist
2
Codes :
P Q R S P Q R S
(A) 1 3 4 2 (B) 3 4 2 1
(C) 1 3 2 4 (D) 2 3 4 1
Ans.
Que. 11 12 13 14 15 16 17 18 19 20
Ans.
Que. 21 22
Ans.
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Organic Reaction Mechanisms-IV
PART - I
11. (3) 12. (2) 13. (4) 14. (3) 15. (3)
16. (2) 17. (1) 18. (3) 19. (3) 20. (3)
21. (1) 22. (2) 23. (4) 24. (1) 25. (3)
26. (1) 27. (3) 28. (2) 29. (3) 30. (2)
PART - II
11. (A) 12. (A) 13. (D) 14. (D) 15. (B)
PART - III
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Organic Reaction Mechanisms-IV
PART - I
CH3 CH3 CH3 CH3
OH
H2SO4
3.
–H2O
O OH O
4.
NaOH,
(E1cB mechanism)
Conc. H SO –H
6.
2 4
Alc. KOH
7.
C H O– K
8.
2 5
OH
CrO3 / H 1) CH3MgBr H
9.
OH O 2) H3O E1 R
CH3
Br
NaNH / NH ( )
10. Ph
Conc. HBr
2 3
OH Ph Ph
C H O– K
11.
2 5
12.
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Organic Reaction Mechanisms-IV
t BuOH
14. + t-BuO–K+
17. The reaction follows E1cb mechanism in which reactant undergoes D exchange alongwith an
elimination product.
+ CH3 CH3
CH2OH CH2 CH3
H Carbocation elimination
18. + +
H2O rearrangement
H
19. It is a basic fact.
C H O–Na H / Ni
20.
2 5
2
E2
H SO
22.
2 4
(Pinacol–Pinacolone rearrangement).
23. -elimination is that elimination reaction in which substrate looses two atoms from 1 & 2 position.
CH CH + HCl
25.
HBr
alc. KOH
HBr
R2O2
–HBr
26. The T.S. involves
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PART - III
1. The more stable conformation of chlorocyclohexane does not undergo an E-2 elimination easily while
the less stable conformer, with the chloro group in the axial position, readily undergoes an E-2 reaction.
2. [C] is incorrect because more than one isomer gives a single alkene on E2 elimination.
HIO4
2 0
3. [X] =
OH OH H2SO4
Pinacol-pinacolone
Rearrangement
O
4.
5.
7.
H
H2O* H
8.
No E2 reaction because -hydrogen and leaving group not present in anti
position.
HO
2
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Conc. H SO O
14.
2 4
3
(Q)
Zn / H2O
O
3
Zn / H2O
15. E1
(cis + Trans)
OH
conc. H2SO4
* + +
16.
(d + ) (E + Z)
CH3 CH3
SN1
CH3–C—CH–CH3 + CH3–C—CH–CH3
CH3
H3C OC2H5 H5C2O CH3
C2H2OH
17. CH3–C—CH–CH3 (d+)
CH3 CH3 CH3
H3C Br
E1
CH3–C=C–CH3 + CH3–C—CH=CH2 + CH2=C–CH–CH3
(Trans-Trans)
C H O– (excess) /
19.
2 5
20. CH2=CH2
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