Haloalkanes and Haloarenes Test

Result

Haloalkanes and Haloarenes Test - 45

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following is a primary halide?

A
iso-propyl iodide

B
sec-butyl iodide

C
tert-butyl bromide

D
neo-hexyl chloride

Solution

Neo-hexyl chloride is the primary halide. Because in it Cl atom is attached to a primary carbon atom. It is can be seen in its structure.

While others are not primary halides. They are secondary or tertiary halides.

The correct option is D.
Question 2
1 / -0

$$S_N1$$ reaction is fastest in?

A
$$CH_3CH_2Br$$

B
$$CH_3-{\underset{CH}{\underset{|}{CH}}}-Cl$$

C

D
$$CH_3-{\underset{Ch_3}{\underset{|}{\underset{CH_2}{\underset{|}{CH}}}}}-Cl$$

Solution

The $$S_N1 $$, reaction proceeds in two steps. First step involves slow separation of halogen to form carbonium ion. Second step involves attack of nucleophile on carbonium ion from both sides to form alcohol.
So any species which is capable of forming stable carbonium ion would undergo nuleophilic substitution by $$S_N1 $$. Benzyl is very stablilised. Hence benzyl chloride follow $$S_N1 $$ most readily. So C is the correct option.
Question 3
1 / -0

Which of the following compounds can yield only one monochlorinated product upon free radical chlorination?

A
2, 2-Dimethyipropane

B
2-Methylpropane

C
2-Methylbutane

D
n-Butane

Solution

Free radical chlorination of alkanes gives a complex mixture of isomeric mono- polyhaloalkanes which is difficult to separate as pure compounds. So the yield of any one compound is low. Therefore 2, 2 Dimethyipropane is the compound that can yeild only one monochlorinated product upon free radical chlorination.
Question 4
1 / -0

Which of the following statement regarding the $$S_N1$$ reaction shown by alkyl halide is correct?

A
The added nucleophile plays no kinetic role in $$S_N1$$ reaction.

B
The $$S_N1$$ reaction involves the inversion of the configuration of the optically active substrate

C
The $$S_N1$$ reaction on the chiral starting material ends up with racemisation o f the product.

D
The more stable the carbocation intermediate the faster the $$S_N1$$ reaction.

Solution

In $$S_N1$$ reaction, rate of substitution depends on the concentration of substrate. In case of $$S_N1$$ reaction there is racemisation. $$S_n1$$ reaction will be faster, if carbocation formed is more stable .
Question 5
1 / -0

Which of the following alkyl halides is hydrolysed by $$S_N1$$ mechanism?

A
$$CH_3Cl$$

B
$$CH_3CH_2Cl$$

C
$$CH_3CH_2CH_2Cl$$

D
$$(CH)_3CCl$$

Solution

More stable carbocation formed from alkyl halide than reactivity of that alkyl halide will increase to hydrolysis via $$SN^1$$ mechanism.
$$3^o$$ carbocation $$>2^o$$ carbocation $$>1^o$$ carbocation(order of stability.).
Question 6
1 / -0

The reaction proceeds with 98% racemisation. The reaction may follow:

A
$$S_N1$$ mechanism

B
$$S_N2$$ mechanism

C
E1 mechanism

D
E2 mechanism

Solution

The mixture containing two enantiomers in equal proportions will have zero optical rotation, as the rotation due to one isomer will be cancelled by the rotation due to the other isomer. Such mixture is racemic modification. The process of conversion of enantiomer into a racemic mixture is called as racemisation. In case of optically active alkyl halides $$S_N1 $$ reactions are accompanied by racemisation. This is because the carbocation formed in slow step is planar.
Question 7
1 / -0

Choose the correct answer among the alternatives given :Bromination of methane in presence of sunlight is a:

A
nucleophilic substitution

B
free radical substitution

C
electrophilic substitution

D
nucleophilic addition

Solution

The reaction between bromine and methane happens in the presence of sunlight. $$ CH_4 + Br_2 \to CH_3 + H Br $$. The product obtained is bromomethane. One of the hydrogen atom in the methane is replaced by a bromine atom. So this is substitution reaction. During the chain reaction, a new species is generated at the end. The overall process is called as free radical substitution.
Question 8
1 / -0

A compound X with molecular formula $$C_7H_8$$ is treated with $$Cl_2$$ in presence of $$FeCl_3$$. Which of the following compounds are formed during the reaction?

A

B

C

D

Solution

In case of substituted aromatic compounds, the functional group already present directs the next incoming group to a particular position in the aromatic ring. It is called directive influence of the group already attached to the benzene ring. So option A is correct option.
Question 9
1 / -0

Which of the following is the most reactive towards nucleophilic substitution reaction?

A
$$ClCH_2-CH=CH_2$$

B
$$CH_2=CH-Cl$$

C
$$CH_3CH=CH-Cl$$

D
$$C_6H_5Cl$$

Solution

Order of reactivity of different halo compounds towards nucleophilic substitution reaction are:

Allyl chloride > Vinyl chloride > Chlorobenzene
Question 10
1 / -0

Which of the following is not correctly matched with its IUPAC name?

A
$$CHF_2CBrClF$$ : 1-Bromo-1-chloro-1, 2, 2 -trifluoroethane

B
$$(CCl_3)_3CCl$$ : 2-(Trichloromethyl)-1,1,1,2,3,3, 3 -heptachioropropane

C
$$CH_3C(p-ClC_6H_4)_2CH(Br)CH_3$$ : 2-Bromo-3,3-bis(4-chlorophenyl) butane

D
$$o-BrC_6H_4CH(CH_3)CH_2CH_3$$ : 2-Bromo-1-methylpropylbenzene

Solution

IUPAC system is one of the systematic method of naming organic compound. The numerals 1,2; 1,3 and 1,4 are used in IUPAC system. The option D is not correctly matched with its IUPAC name because the correct IUPAC name for the structure $$ o - BrC_6H_4CH(CH_3)CH_2CH_3$$ is 1 Bromo-2-1-methlypropylbenzene.