Haloalkanes and Haloarenes Test

Result

Haloalkanes and Haloarenes Test - 8

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
4 / -1

Which of the S_N2 reaction is fastest?

A

B

C

D

Solution

CH₃ Br is more reactive termed and is stronger nucleophile.
Question 2
4 / -1

Which statement is true about S_N2 mechanism?

A
The rate of reaction increases on increasing strength of the nucleophile

B
The reaction is faster in polar aprotic solvents

C
The rate of reaction increases as the leaving group ability increases

D
All of the above

Solution

Stronger the nucleophile, faster the S_N2 reaction. Polar aprotic solvent solvate cations, makes anionic nucleophile more available for reaction, hence faster reaction. A better leaving group lowers the activation energy increasing rate of S_N2 reaction.
Question 3
4 / -1

A correct statement about transition state of S_N2 reaction is

A
the transition state proceeds and follow an unstable reaction intermediate

B
the transition state will always have net negative charge

C
existence of this state implies an exothermic reaction

D
the single transition state represents the point of maximum free energy of the reaction

Solution

S_N2 reaction is a one step (concerted) reaction that involes a single transition state.
Question 4
4 / -1

What is the correct increasing order of reactivity of the followings in S_N2 reaction ?
I. CH₂ = CHCH₂ — Br
II. CH₂ = CH— I
III. CH₃CH₂CH₂ — I
IV. CH₃OCH₂CH₂ — I

A
I < II < III < IV

B
III < II < I < IV

C
II < III < IV < I

D
II < I < III < IV

Solution

Allyl bromide (I) is most reactive among the given halides as pi bonds from allylic position stabilises the transition state. Vinyl iodide (II) is least reactive due to partial double bond character. Electron withdrawing inductive effect of CH₃O^- increases reactivity of (IV) over (III)
Question 5
4 / -1

What is the correct increasing order of reactivity of the following in the S_N2 reaction?

A
I < II < III < IV

B
III < II < I < IV

C
II < III < IV < I

D
Ill < I < II < I V

Solution

(IV) is most reactive as it is benzylic as well as electron withdrawing effect of — NO₂ further increases the reactivity. (Ill) is least reactive due to resonance effect resulting in partial double bond character between carbon and chlorine. (I) is less reactive in S_N2 reaction than II, due to greater steric hindrance in (I).
Question 6
4 / -1

Consider the two lines shown in the diagram given below.
Q.
In a S_N2 reaction, these two lines compare the effect of the

A
substrate

B
nucleophile

C
leaving group

D
substrate or nucleophile

Solution

Substrates are same as they are at same potential energies. Nucleophiles are different as magnifested by different activation energies and different products with different potential energies,
Question 7
4 / -1

Consider the two lines shown in the diagram given below.
Q.
Which of the following apply appropriately to a S_N2 reaction?

A
Graph I could represent Cl^- and Graph II represents I^- leaving group

B
Graph I could represent HO^- and Graph II represents CH₃COO^- nucleophile

C
Graph I could represent H₂O and Graph II H₂S as nucleophile

D
Graph I could represent (CH₃)₂NH and Graph II to (CH₃)₂N^- nucleophiles

Solution

HO^-is stronger nucleophile than CH₃COO^- . Hence, lower activation energy of (I) than (II).
Question 8
4 / -1

The correct statement concerning a S_N2 reaction is

A
the reaction mechanism involve atleast one reactive intermediate

B
transition state is pentavalent

C
product is formed after passing through several transition states

D
nucleophile attacks from front side on which leaving group is present

Solution

The transition state in S_N2 reaction is pentavalent as indicated here.
Question 9
4 / -1

The chloro compound which can be used as fire extinguisher is:

A
CH₃Cl

B
COCl₂

C
CCl₄

D
CHCl₃

Solution

The correct answer is Option C.

Its use in the home as a spot remover should be avoided because of its poisonous nature.
Because it's vapours (incombustible vapours) are denser than air which leads to a smoother flame.
Question 10
4 / -1

Exposure to lower levels of a compound in air can lead to slightly impaired hearing and vision. Identify the compound.

A
Chloroform

B
Chloromethane

C
Carbon tetrachloride

D
Methylene chloride

Solution

The correct answer is Option D.

Methylene chloride (Dichloromethane) Dichloromethane, also known as methylene chloride, is one of the polyhalogen compounds present in the form of solvent. Low levels of methylene chloride exposure in the air can cause slight hearing and vision impairment.
Question 11
4 / -1

The antiseptic properties of iodoform is due to which of the following:

A
Liberation of iodine

B
Smell of iodoform

C
Colour of iodoform

D
None of the above

Solution

Iodoform liberates I₂, when it comes in contact with skin Antiseptic property of iodine is due to the liberation of I2, not because of iodoform itself.
Question 12
4 / -1

Central nervous system can be depressed by the use of which of the following:

A
Chloroform

B
Freon

C
Iodoform

D
DDT

Solution

The correct answer is option A

Chloroform, or trichloromethane, is an organic compound with formula CHCl3. It is a colorless, sweet-smelling, dense liquid that is produced on a large scale as a precursor to PTFE. It is also a precursor to various refrigerants. It is one of the four chloromethanes and a trihalomethane. It is a powerful anesthetic, euphoriant, anxiolytic and sedative when inhaled or ingested.
Question 13
4 / -1

Depletion of Ozone is believed to increase:

A
Population

B
Ultraviolet rays

C
Pollution

D
Greenery

Solution

The correct answer is Option B

Ozone layer depletion increases the amount of UVB that reaches the Earth's surface. Because all sunlight contains some UVB, even with normal stratospheric ozone levels, it is always important to protect your skin and eyes from the sun.
Question 14
4 / -1

Which is the correct formula of Freon-12?

A
CCl₂F₂

B
CClF₃

C
CHCl₂F

D
CCl₃F

Solution

The correct answer is option A
Question 15
4 / -1

Comprehension Type
Direction (Q. Nos. 15-17) 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
The general mechanism of a S_N2 reaction is as follows.
Factors that limit the rate of reaction are steric hindrance at α-cabron of substrate and strength of C—X bond. Any factor which stabilises transition state increases the rate of reaction.
Q.
Consider the following S_N2 reaction,
Which of the following energy diagram is correctly labelled?

A

B

C

D

Solution

Products are same in both reactions, hence same potential energies of products are shown. Also I^- is better leaving group, has lower activation energy in S_N2 reaction as indicated by curve-l in diagram.
Question 16
4 / -1

Passage
The general mechanism of a S_N2 reaction is as follows.
Factors that limit the rate of reaction are steric hindrance at α-cabron of substrate and strength of C—X bond. Any factor which stabilises transition state increases the rate of reaction.
Q.
In the previous question, under identical reaction condition, i.e. tem perature, concentration of substrate and nucleophile, the correct relationship between rate constant is

A
k_I < k_II

B
k_I + k_II

C
k_I > k_II

D
k_I = k_II

Solution

Since I^- is better leaving group, k_I > k_II
Question 17
4 / -1

Passage
The general mechanism of a S_N2 reaction is as follows.
Factors that limit the rate of reaction are steric hindrance at α-cabron of substrate and strength of C—X bond. Any factor which stabilises transition state increases the rate of reaction.
Q.
Which of the following is not a correct representation of S_N2 reaction ?

A

B

C
CH₃CH₂OH + NaNH₂ → CH₃CH₂NH₂

D

Solution

Following neutralisation reaction is preferred over S_N2 reaction :
Question 18
4 / -1

Direction (Q. Nos. 18-20) This section contains 3 questions. When worked out will result in an integer from 0 to 9 (both inclusive).

Consider the following reaction,

Q.

The above reaction was started taking equal concentrations of ethyl iodide and NaOH. After 1.0 h, concentration of iodoethane is dropped to (1/3)rd of initial value. By what factor, the rate of reaction would have been decreased by the same time?

A
9

B
8

C
7

D
6

Solution

Rate = A [C₂H₅I] [OH^-] Rate is linear function of both alkyl halide and nucleophile concentration both will decrease by same factor. Hence, if after 1.0 h concentration of iodoethane decreases to concentration of hydroxide will also decrease by the same factor and rate by , i.e. by 9 times.
Question 19
4 / -1

Under identical experimental condition, how many of the following substrate react at faster rate with aqueous NaOH than 2-bromobutane as substrate?

A
4

B
5

C
6

D
7

Solution

Compounds (II), (III), (IV), (V), (VIII) and (X) react at faster rate than 2-bromobutane in S_N2 reaction.
Question 20
4 / -1

Consider the following compound,

Q.

If the above compound is treated with excess of NaCN(aq), how many CN^- group would be incorporated by S_N2 reaction?

A
0

B
1

C
2

D
3

Solution

Only the circled groups are substituted in S_N2,