Haloalkanes and Haloarenes Test

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Haloalkanes and Haloarenes Test - 68

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Weekly Quiz Competition

Question 1
1 / -0

Out of the following, the alkene that exhibits optical isomerism is:

A
3-methyl-2-pentene

B
4-methyl-1-pentene

C
3-methyl-1-pentene

D
2-methyl-2-pentene

Solution

$$ \begin{array}{l} \text { As, } C^{*} \text { has } 4 \text { different groups } \text { attached to it, so it is a chiral } \text { carbon. } \\ \text { so, above compound is optically } \text { active. } \end{array} $$
Question 2
1 / -0

Which of the following reactions is not correctly matched?

A
$$2C_2H_5Br +2Na\xrightarrow{dry\ ether}C_4H_{10}+2NaBr$$

Wurtz reaction

B
$$CH_3Br+AgF\rightarrow CH_3F +AgBr$$

Etards reaction

C
$$C_6H_5Br +2Na+BrC_2H_5\xrightarrow{dry\ ether}C_6H_5C_2H_5+2NaBr$$

Wurtz-fittig reaction

D
$$2C_6H_5Br +2Na\xrightarrow{dry\ ether}C_6H_5C_6H_5+2NaBr$$

Fittig reaction

Solution

Reaction in option $$B$$ is not correctly matched. Etards reaction is an organic transformation in which alkyl group $$(-CH_3)$$ bonded to an aromatic (benzene) ring undergoes oxidization and becomes an aldehyde functional group.

Also, the reaction given in option $$B$$ is Swarts reaction. Here when methyl bromide reacts with silver fluoride, it decomposes and gives rise to methyl fluoride and silver bromide.
Question 3
1 / -0

Arrange the following alkyl halides in decreasing order of the rate of $$\beta$$-elimination reaction with alcoholic $$KOH$$.
(I) $$ CH_{ 3 }-\overset { \overset { H }{ | } }{ \underset { \underset { CH_{ 3 } }{ | } }{ C } } -CH_{ 2 }Br$$
(II) $$CH_3-CH_2-Br$$
(III) $$CH_3-CH_2-CH_2-Br$$

A
$$I > II > III$$

B
$$III > II > I$$

C
$$II > III > I$$

D
$$I > III > II$$

Solution

More the number of $$\beta$$- substituents (alkyl groups), more stable alkene it will form on $$\beta$$- elimination and more will be the reactivity.

Hence, the decreasing order of the rate of $$\beta$$-elimination reaction with alcoholic $$KOH$$ is $$\rightarrow$$
$$\underset{2 \; \beta-substituents}{I} > \underset{1 \; \beta-substituents}{III} > \underset{0 \; \beta-substituents}{II}$$.
Question 4
1 / -0

Ethyl iodide and n-propyl iodide are allowed to undergo Wurtz reaction. The alkane which will not be obtained in this reaction is:

A
butane

B
propane

C
pentane

D
hexane

Solution

$$CH_3CH_2I+CH_3CH_2CH_2I$$
(Wurtz reaction) $$\downarrow Na$$
$$\underset {butane}{CH_3CH_2CH_2CH_3}+\underset {hexane}{CH_3CH_2CH_2CH_2CH_2CH_3}+\underset {pentane}{CH_3CH_2CH_2CH_2CH_3}$$

Ethyl iodide and n-propyl iodide are allowed to undergo Wurtz reaction and they form butane and hexane as self-addition products and pentane as cross addition product.

$$\therefore$$ So, propane will not be formed.
Question 5
1 / -0

Which of alkyl halides exhibits complete racemisation in $$S_N1$$ reaction?

A
$$(CH)_3CCl$$

B
$$CH_3CH_2CH_2Cl$$

C
$$CH_3CH_2Cl$$

D
$$C_6H_5CH_2Cl$$

Solution

All the molecules undergoing $$S_N1$$ reaction shows racemisation as there is formation of 2 types of product in equal amount. Out of all these 4 alkyl halides , $$C_6H_5CH_2Cl $$ i.e benzylic chloride has the strongest tendency to undergo $$S_N1$$ here thus leading to formation of racemic mixture as it contains benzylic carbocation which is most stable.
Question 6
1 / -0

Match the reaction given in column I and II :

A
A=i, B=iv, C=ii , D=iii

B
A=i, B=ii, C=iv, D=iii

C
A=ii, B=iii, C=iv, D=i

D
A=iii, B=i, C=ii, D=iii

Solution

(A) Secondary alkyl halide$$\rightarrow SN^1$$ nucleophilic substitution.
(B)Primary alkyl halide $$\rightarrow SN^2$$ nucleophilic substitution
(C)$$CH_3CH=CH_2+HBr\rightarrow CH_3CH_2CH_2Br$$ Kharasch Effect
(D)$$CH_3-CH_2Br\rightarrow CH_2=CH_2+HBr$$ $$E_2$$ elimination
Question 7
1 / -0

Which of the following alkane cannot be prepared by Wurtz's reaction in good yield?

A

B

C

D

Solution

Wurtz reaction is a reaction in which alkyl halide is converted to alkane by Na/ether. It is limited to the synthesis of symmetrical alkanes.
(Image ) As this molecule involves ring strain the reaction will be of poor yield.
Question 8
1 / -0

Which of the following alkyl halides will undergo $$S_N1$$ reaction most readily?

A
$$(CH_3)_3C-F$$

B
$$(CH_3)_3C-Cl$$

C
$$(CH_3)_3C-Br$$

D
$$(CH_3)_3C-I$$

Solution

All options given are alkyl halide (tertiary) so all will form tertiary carbocation.

But order of leaving group ability Is $$I^-$$ > $$Br^-$$ > $$Cl^-$$ > $$F^-$$

$$S_{N}{1}$$ mechanism goes through formation of carbocation.

More easily leaving group leaves more easily the carbocation will form.

Option D is correct.
Question 9
1 / -0

Match the column I with column II.
Columns I Columns II
A Carbon tetrachloride i Paint remover
B Methylene chloride ii Refrigerators and air conditioners
C DDT iii Fire extinguisher
D Freons iv Non biodegradable insectiside

A
A-(ii), (B)-(iii), (C)-(i), (D)-(iv)

B
A-(i), (B)-(ii), (C)-(iii), (D)-(iv)

C
A-(iv), (B)-(iii), (C)-(ii), (D)-(i)

D
A-(iii), (B)-(i), (C)-(iv), (D)-(ii)

Solution

A) Carbon tetrachloride is colorless, non-inflammable, and is used as a fire extinguisher.

B) Methylene chloride is used as a paint remover.

C) DDT is a chlorinated organic and non-biodegradable insecticide.

D) Freons are produced for aerosol propellants, refrigerators, and air conditioners.

Hence, option D is correct.
Question 10
1 / -0

In which of the following reactions, it proceeds via free radical mechanism?

A
Halogenation of benzene

B
Nitration of benzene

C
Sulphonation of benzene

D
Chlorination of toluene at high temperature

Solution

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	Columns I		Columns II
A	Carbon tetrachloride	i	Paint remover
B	Methylene chloride	ii	Refrigerators and air conditioners
C	DDT	iii	Fire extinguisher
D	Freons	iv	Non biodegradable insectiside

Haloalkanes and Haloarenes Test - 68

Result

Haloalkanes and Haloarenes Test - 68

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Question 1

3-methyl-2-pentene

4-methyl-1-pentene

3-methyl-1-pentene

2-methyl-2-pentene

Solution

Question 2

$$2C_2H_5Br +2Na\xrightarrow{dry\ ether}C_4H_{10}+2NaBr$$ Wurtz reaction

$$CH_3Br+AgF\rightarrow CH_3F +AgBr$$ Etards reaction

$$C_6H_5Br +2Na+BrC_2H_5\xrightarrow{dry\ ether}C_6H_5C_2H_5+2NaBr$$ Wurtz-fittig reaction

$$2C_6H_5Br +2Na\xrightarrow{dry\ ether}C_6H_5C_6H_5+2NaBr$$ Fittig reaction

Solution

Question 3

$$I > II > III$$

$$III > II > I$$

$$II > III > I$$

$$I > III > II$$

Solution

Question 4

butane

propane

pentane

hexane

Solution

Question 5

$$(CH)_3CCl$$

$$CH_3CH_2CH_2Cl$$

$$CH_3CH_2Cl$$

$$C_6H_5CH_2Cl$$

Solution

Question 6

A=i, B=iv, C=ii , D=iii

A=i, B=ii, C=iv, D=iii

A=ii, B=iii, C=iv, D=i

A=iii, B=i, C=ii, D=iii

Solution

Question 7

Solution

Question 8

$$(CH_3)_3C-F$$

$$(CH_3)_3C-Cl$$

$$(CH_3)_3C-Br$$

$$(CH_3)_3C-I$$

Solution

Question 9

A-(ii), (B)-(iii), (C)-(i), (D)-(iv)

A-(i), (B)-(ii), (C)-(iii), (D)-(iv)

A-(iv), (B)-(iii), (C)-(ii), (D)-(i)

A-(iii), (B)-(i), (C)-(iv), (D)-(ii)

Solution

Question 10

Halogenation of benzene

Nitration of benzene

Sulphonation of benzene

Chlorination of toluene at high temperature

Solution

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$$2C_2H_5Br +2Na\xrightarrow{dry\ ether}C_4H_{10}+2NaBr$$

Wurtz reaction

$$CH_3Br+AgF\rightarrow CH_3F +AgBr$$

Etards reaction

$$C_6H_5Br +2Na+BrC_2H_5\xrightarrow{dry\ ether}C_6H_5C_2H_5+2NaBr$$

Wurtz-fittig reaction

$$2C_6H_5Br +2Na\xrightarrow{dry\ ether}C_6H_5C_6H_5+2NaBr$$

Fittig reaction