Test: Ambident Nucleophiles & NGP In SN2 Reactions


19 Questions MCQ Test Chemistry Class 12 | Test: Ambident Nucleophiles & NGP In SN2 Reactions


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This mock test of Test: Ambident Nucleophiles & NGP In SN2 Reactions for Class 12 helps you for every Class 12 entrance exam. This contains 19 Multiple Choice Questions for Class 12 Test: Ambident Nucleophiles & NGP In SN2 Reactions (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Ambident Nucleophiles & NGP In SN2 Reactions quiz give you a good mix of easy questions and tough questions. Class 12 students definitely take this Test: Ambident Nucleophiles & NGP In SN2 Reactions exercise for a better result in the exam. You can find other Test: Ambident Nucleophiles & NGP In SN2 Reactions extra questions, long questions & short questions for Class 12 on EduRev as well by searching above.
QUESTION: 1

Only One Option Correct Type

Direction (Q. Nos. 1-8) This section contains 8 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONLY ONE is correct.

Q. 

Cyanide anion has two atoms th at have lone pair of electrons. Either could act as nucleophile in the reaction. Yet in the vast majority of the cases, carbon acts as nucleophile and forms a bond to the substrate, why?

Solution:

Both carbon and nitrogen are capable of donating electron pair but carbon is better electron donor than nitrogen, carbon donates electron pair in most of the cases.

QUESTION: 2

In the following two phase reaction, catalyst works by

C6H5CH2Br + KCN  C6H5CH2CN + KBr

Solution:

By the following equilibrium

Cyanide ion is transferred to organic phase otherwise KCN is insoluble in organic solvents.

QUESTION: 3

Which of the following would react most rapidly with sodium ethoxide to produce an ether?

Solution:


In all other cases leaving group is on phenyl ring, not substituted, usually by nucleophiles under ordinary condition.

QUESTION: 4

In the given reaction,

X will be

Solution:

QUESTION: 5

In the given reaction,

X will be

Solution:


QUESTION: 6

Consider the following reaction,

Q. 

What can be correctly predicted regarding this reaction?

Solution:

QUESTION: 7

Pick out the alkyl bromide which proceeds with retention of configuration in an SN2 reaction with CH3ONa (aq).

Solution:



Due to inversion of configuration twice at α-carbon, there will be overall retention of configuration.

QUESTION: 8

For the following reaction, pick out the best term which describe its mechanism

Solution:


*Multiple options can be correct
QUESTION: 9

One or More than One Options Correct Type

Direction (Q. Nos. 9-13) This section contains 5 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONE or MORE THAN ONE are correct.

Q. 

Pick out the alkyl bromides which proceeds with retention of configuration in an SN2 reaction with CH3ONa(aq)

Solution:

All will react via cyclic sulphonium ion intermediate involving SN2 reaction twice giving over all retention of configuration.

*Multiple options can be correct
QUESTION: 10

Which of the following is/are ambident nucleophile?

Solution:

All have more than one donor atoms within the same donor group, hence ambident nucleophiles.

*Multiple options can be correct
QUESTION: 11

Which of the following gives the same substitution (SN2) product with C2H5Br no matter whether sodium or silver salt is used? 

Solution:

Both donate lone pair from better donor nitrogen atom.

*Multiple options can be correct
QUESTION: 12

Which of the following gives the different substitution product with CH3CH2Br when their sodium and silver salts are used?

Solution:


Silver salts have covalent character, hence lone pair of free atom i.e. nitrogen in both cases donate lone pair. With sodium salts, nucleophiles are free ions in solution, better donor donate lone pair.

*Multiple options can be correct
QUESTION: 13

Consider the following substitution reaction,

Q. 

The correct statement(s) is/are

Solution:

Due to neighbouring group participation, reaction occurs at much faster rate than 2-bromo-3, 3-dimethylpentane. Also it involves SN2 reaction twice, overall retention of configuration is observed.

QUESTION: 14

Comprehension Type

Direction (Q. Nos. 14-16) This section contains a paragraph, describing theory, experiments, data, etc.
Three questions related to the paragraph have been given. Each question has only one correct answer among the four given options (a), (b), (c) and (d).

Passage

Nucleophiles which have more than one type of donor atoms within the same donor group are known as ambident nucleophile e.g.
CN- : Both carbon and nitrogen are donor.
OCN- : Both oxygen and nitrogen are donor etc.
In case of free anionic and ambident nucleophiles, the better donor atom donate its lone pair of electron and forms bond with a-carbon after substitution reaction, in a given period, donor ability decreases from left to right. In a group, donor ability increases from top to bottom.

Q. 

When CH3CH2Br is treated with aqueous NaCN, CH3CH2CN is formed while CH3CH2NCis formed when AgCN is used in the similar reaction. It is due to

Solution:

With NaCN free cyanide (CN-) is obtained in solution, hence better donor atom carbon donate lone pair. In AgCN, due to covalent character of Ag — C bond CN- is not free in solution hence, lone pair of ‘N’ is donated

QUESTION: 15

Nucleophiles which have more than one type of donor atoms within the same donor group are known as ambident nucleophile e.g.
CN- : Both carbon and nitrogen are donor.
OCN- : Both oxygen and nitrogen are donor etc.
In case of free anionic and ambident nucleophiles, the better donor atom donate its lone pair of electron and forms bond with a-carbon after substitution reaction, in a given period, donor ability decreases from left to right. In a group, donor ability increases from top to bottom.

Q. 

Treatment of CH3CH2Br with either NaNO2 or AgNO2 gives the same nitroethane as major product because

Solution:

In both salts, lone pair on nitrogen (better donor atom than oxygen) is free for donation to alkyl halide.

QUESTION: 16

Nucleophiles which have more than one type of donor atoms within the same donor group are known as ambident nucleophile e.g.
CN- : Both carbon and nitrogen are donor.
OCN- : Both oxygen and nitrogen are donor etc.
In case of free anionic and ambident nucleophiles, the better donor atom donate its lone pair of electron and forms bond with a-carbon after substitution reaction, in a given period, donor ability decreases from left to right. In a group, donor ability increases from top to bottom.

Q. 

When iodomethane is treated with sodium isocyanate (NaNCO), CH3NCO is the major product while AgNCO gives CH3CH2OCN as major product because

Solution:

With free NCO-, better donor atom (nitrogen) donate its lone pair. If AgNCO is used, due to covalent character of Ag—N bond lone pair of oxygen is donated giving CH3CH2— OCN as major product.

*Answer can only contain numeric values
QUESTION: 17

One Integer Value Correct Type

Direction (Q. Nos. 17 and 18) This section contains 2 questions. When worked out will result in an integer from 0 to 9 (both inclusive).

Q. 

If meso form of the 2,4-dibromopentane is treated with excess of KCN(aq), how many SN2 products with both bromide substituted, wouid result?


Solution:


*Answer can only contain numeric values
QUESTION: 18

Consider the foiiowing SN2 reactions.

Q. 

Only neighbouring effect increases reactivity of (II) by a factor of 5 x 104. If reaction (I) is carried out with initial concentration of C4H9Br = 0.05 M and NaOH 0.01 M and reaction (II) is carried out with initial concentration of both CH3SCH2CH2Br and NaOH = 0.1 M each, rate of reaction (II) would be 10x times greater than the rate of reaction (I) under identical experimental condition. What is the value of x?


Solution:


kII/kI= 5 x 104 

Dividing the above two rates gives

QUESTION: 19

Matching List Type

Direction (Q. No. 19) Choices for the correct combination of elements from Column I and Column II are given as options (a), (b), (c) and (d), out of which one is correct.

Q. 

Match the Column I with Column II and mark the correct option from the codes given below.

Solution:

(i) Due to ‘S' at β-position, neighbouring group participation occur giving net retention (twice inversion).
(ii) SN2 at α-carbon gives inversion and product is meso diol,
(iii) Only SN2 hence inversion
(iv) Show neighbouring group effect

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