Haloalkanes and Haloarenes Test

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Haloalkanes and Haloarenes Test - 36

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Weekly Quiz Competition

Question 1
1 / -0

$$CH_3-\underset{CH_3}{\underset{|}{\overset{CH_3\!\!\!\!\!\!}{\overset{|}{C}}}-}CH_2-\overset{CH_3}{\overset{|}{C}H}-CH_3$$ $$\xrightarrow{Br_2/hu}$$

For the given reaction how many products are optically active (all isomers) :

A
1

B
2

C
3

D
4

Solution

Optimally active isomers are-
$$1-Chloro-2,2,4-trimethyl \ pentane$$
$$2-Chloro-2,2,4-trimethyl \ pentane$$
$$3-Chloro-2,2,4-trimethyl \ pentane$$
$$4-Chloro-2,2,4-trimethyl \ pentane$$
Question 2
1 / -0

The false statement regarding alkane is :

A
this does not perform polymerization reaction.

B
this does not gives elimination reaction.

C
it does not disappear the colour of dilute $$KMnO_{4}$$ solution..

D
it does not decolourise bromine water.

Solution

Alkanes show elimination reactions. Higher alkanes eliminate hydrogen and give lower alkanes and alkenes on heating in the absence of air at high temperatures.

$$R-CH_2-CH_3\xrightarrow{catalyst} R-CH=CH_2$$
Question 3
1 / -0

Under identical conditions, the $$S_{N}1$$ reaction will occur most efficiently with:

A
tert-butyl chloride

B
1-chlorobutane

C
2-methyl-1-chloropropane

D
2-chlorobutane

Solution

$$S_{N}1$$ reaction is most effective in $$3^{\circ}$$ carbon.
The order goes as $$Tert>secondary>primary>methyl$$

$$\underset {tert-butyl\ chloride (3^{\circ})}{(CH_{3})_{3} - C - Cl}$$

$$ \underset {1 - chlorobutane (1^{\circ})}{CH_{3}CH_{2}CH_{2}CH_{2}Cl} $$

$$\underset {2 - methyl-1-chloropropane (1^{\circ})}{Cl - CH_{2} - CH(CH_{3})-CH_{3}}$$

$$ \underset {2-chlorobutane (2^{\circ})}{CH_{3}CH_{2}CH(Cl)CH_{3}}$$
Question 4
1 / -0

Following reaction,
$${({CH}_{3})}_{3}CBr+{H}_{2}O\longrightarrow {({CH}_{3})}_{3}COH+HBr$$ is an example of:

A
elimination rection

B
free radical substitution

C
nucleophilic substitution

D
electrophilic substitution

Solution

$${({CH}_{3})}_{3}Br+{H}_{2}O\longrightarrow {({CH}_{3})}_{3}C-OH+HBr$$
$$Br$$ is substituted by $$-{OH}^{-}$$ (nucleophile)
$${S}_{N}1$$ (unimolecular substitution reaction)
Question 5
1 / -0

Which of the following compounds have highest melting point?

A
Only I

B
Only II

C
I and II

D
II and III
Question 6
1 / -0

t-Butyl chloride preferably undergo hydrolysis by:

A
$$S_N 1$$ mechanism

B
$$S_N 2$$ mechanism

C
any of (A) and (B)

D
none of these

Solution

The SN1 reaction proceeds stepwise. The leaving group first leaves, whereupon a carbocation forms that is attacked by the nucleophile.

The SN2 occurs in one step, and both the nucleophile and substrate are involved in the rate determining step. Therefore the rate is dependent on both the concentration of substrate and that of the nucleophile.

For tertiary butyl chloride, it form tertiary carbocation which is highly stable. So tertiary butyl chloride undergo hydrolysis by SN1 mechanism.
Question 7
1 / -0

Which of the following is more readily hydrolysed by $$\displaystyle { S _ N }^1$$ mechanism?

A
$$\displaystyle { \left( { C }_{ 6 }{ H }_{ 5 } \right) }_{ 2 }C\left( { CH }_{ 3 } \right) Br$$

B
$$\displaystyle { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }Br$$

C
$$\displaystyle { C }_{ 6 }{ H }_{ 5 }CH\left( { CH }_{ 3 } \right) Br$$

D
$$\displaystyle { \left( { C }_{ 6 }{ H }_{ 5 } \right) }_{ 2 }CHBr$$

Solution

$$\displaystyle { \left( { C }_{ 6 }{ H }_{ 5 } \right) }_{ 2 }C\left( { CH }_{ 3 } \right) Br$$ is more readily hydrolyzed by $${S_N} ^1$$ mechanism.

The carbocation intermediate $$\displaystyle { \left( { C }_{ 6 }{ H }_{ 5 } \right) }_{ 2 }C^{+}\left( { CH }_{ 3 } \right) $$ is a tertiary carbocation and is stabilized by resonance with two benzene ring.
Question 8
1 / -0

Which of the following statements is incorrect regarding benzyl chloride ?

A
It gives white precipitate with alcoholic $$AgNO_3$$.

B
It is an aromatic compound with substitution in the side chain.

C
It undergoes nucleophilic substitution reaction.

D
It is less reactive than vinyl chloride.

Solution

Benzyl chloride is more reactive than vinyl chloride. The halogen atom in vinyl chloride is not reactive as in other alkyl halides. The non-reactivity of chlorine atom is due to resonance stabilization. The lone pair on chlorine can participate in delocalization (Resonance) to give two canonical structures. Carbon-chlorine bond in vinyl chloride has some double bond character and is, therefore, stronger than a pure single bond.
Question 9
1 / -0

Alkanes having odd carbons cannot be prepared as a major product in:
(A) Wurtz reaction
(B) Frankland reaction
(C) Kolbe's electrolysis
(D) Sabatier - sendersen reaction

A
B, C and D

B
A, C and D

C
A, B and D

D
A, B and C

Solution

Alkanes having odd carbons can be prepared in Sabatier - sendersen reaction.
In this reaction, alkenes add hydrogen in the presence of platinum or nickel catalyst, to form alkanes. The reaction termed as hydrogenation, is an exothermic reaction.
$$\displaystyle CH_3-CH=CH_2 +H_2 \xrightarrow [473 K]{Ni} CH_3-CH_2-CH_3 $$
Alkanes having odd carbons cannot be prepared in
(A) Wurtz reaction
(B) Frankland reaction
(C) Kolbe's electrolysis
Wurtz reaction and Kolbe's electrolysis can be used for the preparation of alkanes having even carbon atoms.

When Zn is used in Wurtz reaction in place of Na, the reaction is named as Frankland method. In wourtz reaction a solution of alkyl halide in ether on heating with sodium gives alkane.
Question 10
1 / -0

Which of the following statements about benzyl chloride is incorrect?

A
It is less reactive than alkyl halides

B
It can be oxidised to benzaldehyde by boiling with copper nitrate solution

C
It is a lachrymatory liquid and answers Beilstein's test

D
It gives a white precipitate with alcoholic silver nitrate

Solution

Benzyl chloride is more reactive than alkyl halides. Benzyl carbocation is stabilised by resonance hence, benzyl chloride easily gives nucleophilic substitution reaction.

Hence, option A is correct.

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Haloalkanes and Haloarenes Test - 36

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Haloalkanes and Haloarenes Test - 36

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Question 1

1

2

3

4

Solution

Question 2

this does not perform polymerization reaction.

this does not gives elimination reaction.

it does not disappear the colour of dilute $$KMnO_{4}$$ solution..

it does not decolourise bromine water.

Solution

Question 3

tert-butyl chloride

1-chlorobutane

2-methyl-1-chloropropane

2-chlorobutane

Solution

Question 4

elimination rection

free radical substitution

nucleophilic substitution

electrophilic substitution

Solution

Question 5

Only I

Only II

I and II

II and III

Question 6

$$S_N 1$$ mechanism

$$S_N 2$$ mechanism

any of (A) and (B)

none of these

Solution

Question 7

$$\displaystyle { \left( { C }_{ 6 }{ H }_{ 5 } \right) }_{ 2 }C\left( { CH }_{ 3 } \right) Br$$

$$\displaystyle { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }Br$$

$$\displaystyle { C }_{ 6 }{ H }_{ 5 }CH\left( { CH }_{ 3 } \right) Br$$

$$\displaystyle { \left( { C }_{ 6 }{ H }_{ 5 } \right) }_{ 2 }CHBr$$

Solution

Question 8

It gives white precipitate with alcoholic $$AgNO_3$$.

It is an aromatic compound with substitution in the side chain.

It undergoes nucleophilic substitution reaction.

It is less reactive than vinyl chloride.

Solution

Question 9

B, C and D

A, C and D

A, B and D

A, B and C

Solution

Question 10

It is less reactive than alkyl halides

It can be oxidised to benzaldehyde by boiling with copper nitrate solution

It is a lachrymatory liquid and answers Beilstein's test

It gives a white precipitate with alcoholic silver nitrate

Solution

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