Haloalkanes And Haloarenes(12th Grade > Chemistry ) Questions and answers for exam Preparation

Question 1. Biphenyl is obtained by treating chlorobenzene with Na metal in presence of ether, the reaction is called as :

Wurtz reaction
Fittig reaction
Wurtz-Fittig reaction
None

Explanation:-

Answer: Option B. -> Fittig reaction
:
B
When 2 molecules of same aryl halides reacts in presence of Na metal the reaction is called as Fittig reaction

Question 2. The reaction

is known as

Wurtz reaction
Fitting reaction
Wurtz-Fitting reaction
Freund reaction

Explanation:-

Answer: Option D. -> Freund reaction
:
D
Conversion of α,ω-dihalogen derivatives to cycloalkanes using Na and ether is Freund’s reaction.

Question 3. Which of the following are arranged in the decreasing order of dipole moment?

CH3Cl,CH3Br,CH3F
CH3Cl,CH3F,CH3Br
CH3Br,CH3Cl,CH3F
CH3Br,CH3F,CH3Cl

Explanation:-

Answer: Option B. -> CH3Cl,CH3F,CH3Br
:
B
Due to much smaller size of F than Cl, the dipole moment of

C H_{3} F

is lower than that of

C H_{3} C l

.

Question 4. Chloropicrin is

Picric acid
Nitrochloroform
Nitromethane
Nitroethyl chloride

Explanation:-

Answer: Option B. -> Nitrochloroform
:
B
Chloroform on nitration with nitrating mixture gives chloropicrin

Question 5. Arrange the following compounds in increasing order of their boiling points.
I.

C H_{3} C H_{2} C H_{2} B r

II.

C H_{3} C H_{2} C H_{2} C H_{2} B r

III.

(C H_{3})_{2} C H C H_{2} B r

IV.

(C H_{3})_{3} C B r

II
III
IV
I

Explanation:-

Answer: Option D. -> I
:
D
Boiling points increases as the number of carbon atoms increases in the alkyl halides. Therefore the B.P of II, III and IV with four carbon atoms is higher than that of I with three carbon atoms. Further, the B.P decreases with the number of branches. Thus the B.P of the four alkyl halides increases in the order I

<

IV

<

III

<

II.

Question 6.

The reagent for the above conversion is

Alcoholic KOH
Alcoholic KOH followed by NaNH2
Aqueous KOH followed by NaNH2
Zn/ CH3COOH

Explanation:-

Answer: Option B. -> Alcoholic KOH followed by NaNH2
:
B

Question 7. Arrange the following:

C H_{3} C H_{2} C H_{2} C H_{2} C l

(I),

C H_{3} C H_{2} C H C l - C H_{3}

(II),

(C H_{3})_{2} C H C H_{2} C l

(III) and

(C H_{3})_{3} C - C l

(IV) in order of decreasing tendency towards

S_{N} 2

reaction

I>III>II>IV
III>IV>II>I
II>I>III>IV
IV>III>II>I

Explanation:-

Answer: Option A. -> I>III>II>IV
:
A
Reactivity decreases as the steric hinderance increases for

S_{N} 2

reaction

Question 8.

C_{6} H_{5} - C H_{3} | C | H - B r + H_{2} O ⟶ H O - C H_{3} | C | H - C_{6} H_{5} + H B r

The above reaction results in 98% racemization. The reaction mainly follows

SN1 mechanism
SN2 mechanism
E1 mechanism
E2 mechanism

Explanation:-

Answer: Option A. -> SN1 mechanism
:
A
The outgoing nucleophile does not leave the reactant and therefore, attack is mainly from backside .

Question 9. Which is used in the manufacture of plastic

Explanation:-

Answer: Option A. -> SN1 mechanism
:
A

Question 10. In the solvolysis of 3-methyl-3-bromohexane, which of the following statements is not correct?

The intermediate involves sp2−carbon
Polar solvents accelerate the reaction
The rate of the reaction depends upon 3-methyl-3-bromohexane concentration
It involves inversion of configuration

Explanation:-

Answer: Option D. -> It involves inversion of configuration
:
D
3-methyl-3-bromohexane is a

3^{0}

alkyl halide and undergoes solvolysis by

S_{N} 1

mechanism followed byracemization.