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Test: Reaction Mechanism Level - 5

30 Questions MCQ Test Organic Chemistry | Test: Reaction Mechanism Level - 5

Description

Attempt Test: Reaction Mechanism Level - 5 | 30 questions in 60 minutes | Mock test for Chemistry preparation | Free important questions MCQ to study Organic Chemistry for Chemistry Exam | Download free PDF with solutions

QUESTION: 1

The major product formed in the following reaction is:

Solution:

QUESTION: 2

The major product formed in the following reaction is:

Solution:

QUESTION: 3

In the cyclisation reaction given below, the most probable product formed is:

Solution:

QUESTION: 4

The major product formed in the reaction given below is

Solution:

QUESTION: 5

The major product formed in the following reaction is:

Solution:

QUESTION: 6

The correct order of the solvolysis for the following chlorides in acetic acid is:

A.
II > I > III
B.
III > II > I
C.
III > I > II
D.
I > III > II

Solution:

QUESTION: 7

The correct order of reactivity of p-halonitrobenzens in the following reaction is

A.
p-Chloronitrobenzene > p-iodonitrobenezene > p-fluoronitrobenzene > p-bromonitrobenzene
B.
p-floronitrobenzene > p-chloronitrobenzene > p-bromonitrobenzene > p-iodonitrobenzene
C.
p-iodonitrobenzene > p-bromonitrobenzene > p-chloronitrobenzene > p-fluronitrobenzene
D.
p-bromonitrobenzene > p-fluronitrobenzene > p-iodonitrobenzene > p-chloronitrobenzene

Solution:

QUESTION: 8

Solvolysis of the optically active compound X gives, mainly:

Solution:

QUESTION: 9

The major product obtained in the following reaction, is

Solution:

Explanation:
DIBAL-H (Di-isobutyl aluminium hydride) is a reducing agent with the preparation of aldehydes. Using DIBAL - H, Lactones are reduced directly to aldehydes.

QUESTION: 10

The major product formed in the following reaction is:

Solution:

QUESTION: 11

Increasing order of stability of following carbocations (give least stable first)?

A.
III < I <II <IV
B.
IV < II <III <I
C.
I < III <II <IV
D.
IV < III <II <I

Solution:

QUESTION: 12

What is the nucleophilicity order for S_N2 reaction:

A.
V > II > IV > I > III
B.
III > IV > V > II > I
C.
I > IV > V > II > III
D.
II > IV > V > III > I

Solution:

QUESTION: 13

Select order of effectiveness of Lewis acid catalyst in Friedel-Crafts reaction:

A.
AlCl₃ > FeCl₃ > ZnCl₂ > BF₃
B.
AlCl₃ > BF₃ > ZnCl₂ > FCl₃
C.
AlCl₃ > ZnCl₂ > BF₃ > FeCl₃
D.
AlCl₃> FeCl₃ > BF₃ > ZnCl₂

Solution:

QUESTION: 14

For the reaction between alkyl halide and OH- increase in solvent polarity generally

A.
Decreases the rate of S_N1 reaction
B.
Increases the rate of S_N1 reaction
C.
Increases the rate of S_N2 reaction
D.
Does not alter the rate of S_N1 and S_N2 reaction

Solution:

QUESTION: 15

In an S_N2 reaction there is:

A.
Complete racemisation
B.
Mostly inversion and little racemisation
C.
Partial racemisation
D.
A little inversion and mostly racemisation

Solution:

QUESTION: 16

Reactive intermediate formed in the following reaction is:

A.
Carbene
B.
Isocyanate
C.
Nitrene
D.
Carbanion

Solution:

QUESTION: 17

Cannizzaro reaction is not given by:

A.
Formaldehyde
B.
Acetaldehyde
C.
Benzaldehyde
D.
Trimethylacetaldehyde

Solution:

QUESTION: 18

An S_N2 reaction at an asymmetric carbon atom of a dextro alkyl halide always gives a:

A.
Laevo product
B.
Racemic mixture
C.
Single optically active isomer
D.
Dextro product

Solution:

QUESTION: 19

Reaction of ethyne with HCN in presence of Ba (CN)₂ is an example of:

A.
Electrophilic addition
B.
Nucleophilic addition
C.
Free radical addition
D.
Electrophilic substation

Solution:

QUESTION: 20

Consider the following carbocations is most stable:

A.
C₆H₅CH₂⁺
B.
C₆H₅CH₂CH₂⁺
C.
C₆H₅CH⁺CH₃
D.
C₆H₅C⁺ (CH₃)₂

Solution:

QUESTION: 21

When 2-chloro-2-methylbutane is refluxed with alcoholic KOH, the main product obtained is:

Solution:

QUESTION: 22

Using given codes, arrange the following compounds in decreasing order of the rate of solvolysis by S_N1 mechanism:

A.
I > III > II
B.
III > II > I
C.
I > II > III
D.
II > I > III

Solution:

QUESTION: 23

1, 3-Dichloropropane one reaction with Zn and NaI gives:

A.
Propane
B.
1-chloropropane
C.
Cyclohexene
D.
Cyclopropane

Solution:

QUESTION: 24

Which is the final main product of the following reaction of trans-1,2-dibromocyclohexane?

Solution:

Correct answer:

Elimination reactions by the E2 mechanism are facilitated when the nucleofuge and H on adjacent C atoms can achieve an antiperiplanar relationship. This is only possible in chair trans-1,2-dibromocyclohexane when both Br atoms are axial. The Br at C1 can then be eliminated with a trans axial H on C6 from this (unfavourable) conformation, and the Br at C2 can be eliminated with a trans axial H on C3. Either way, the product is 3-bromocyclohexene which can then undergo a further E2 elimination to give cyclohexa-1,3-diene.