Chemistry

Haloalkanes and Haloarenes

Question:

Which of the following structure is enantiomeric with the molecule (A) given below:
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-14

Answer:

(a) Compound (a) is enantiomer of compound (A) because the configuration of two groups, i.e., CH3 and C2H5 in them is reversed at the chiral carbon.

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Haloalkanes and Haloarenes

Q 1.

Write the isomers of the compound having formula C4H9Br.

Q 2.

Match the structures of compounds given in Column I with the classes of compounds given in Column II.
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-84

Q 3.

Chloromethane on treatment with excess of ammonia yields mainly
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-26

Q 4.

Draw the structures of major monohalo products in each of the following reactions:
ncert-class-12-solutions-chemistry-chapter-10-haloalkanes-haloarenes-5

Q 5.

Chlorobenzene is formed by reaction of chlorine with benzene in the presence of AlCl3. Which of the following species attacks the benzene ring in this reaction?
(a) CP     (b) Cl+   (c) AlCl3     (d) [AlCl4]

Q 6.

In which of the following molecules carbon atom marked with asterisk (*) is
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-13

Q 7.

Alkyl halides are prepared from alcohol by treating with
(a) HCl + ZnCl2     (b) RedP + Br2
(c) H2SO4 + KI    (d) all the above

Q 8.

Diphenyls are potential threat to the environment. How are these produced from arylhalides?

Q 9.

Which of the following compounds will give racemic mixture on nucleophilic substitution by OH ion?
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-31

Q 10.

Which of the products will be major product in the reaction given
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-53

Q 11.

Molecules whose mirror image is non superimposable over them are known as chiral. Which of the following molecule is chiral in nature?
(a) 2-Bromobutane (b) 1-Bromobutane
(c) 2-Bromopropane (d) 2-Bromopropan-2-ol

Q 12.

How do polar solvents help in the first step in SN1 mechanism?

Q 13.

ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-36

Q 14.

Elimination reactions (especially Beta-elimination) are as common as the nucleophilic substitution reaction in case of alkyl halides. Specify the reagents used in both cases.

Q 15.

Benzene < Chlorobenzene < Dichlorobenzene < Bromochlorobenzene Arrange the following compounds in increasing order of their boiling points
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-11
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-12

Q 16.

ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-33

Q 17.

Questions on the basis of the following reaction:
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-38

 Which of the following statements are correct about the mechanism of this reaction?
(a) Acarbocation will be formed as an intermediate in the reaction.
(b) OH will attach the substrate (iii) from one side and Cl will leave it simultaneously from other side.
(c) An unstable intermediate will be formed in which OH  and Cl will be attached by weak bonds.
(d) Reaction proceeds through SN1 mechanism.

Q 18.

Assertion (A): Nitration of chlorobenzene leads to the formation of m-nitrochlorobenzene.
Reason (R): N02 group is a w-directing group.

Q 19.

How will you bring about the following conversions?
(i)Ethanol to but-l-yne . (ii)Ethane to bromoethene
(iii)Propene to 1-nitropropane (iv)Toluene to benzyl alcohol
(v)Propene to propyne (vi)Ethanol to ethyl fluoride
(vii)Bromomethane to propanone (viii)But-l-ene to but-2-ene
(ix)1-Chlorobutane to n-octane (x)Benzene to biphenyl

Q 20.

Identify the compound Y in the following reaction:
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-4

Q 21.

Which of the following is halogen exchange reaction?
(a)
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-7

Q 22.

Which of the carbon atoms present in the molecule given below are asymmetric?
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-30

Q 23.

Ethylene chloride and ethylidene chloride are isomers. Identify the correct statements.  
(a) Both the compounds form same product on treatment with alcoholic KOH
(b) Both the compounds from same product on treatment with aqueous NaOH
(c) Both the compounds form same product on reduction
(d) Both the compounds are optically active

Q 24.

Which of the following are secondary bromides?
(a) (CH3),CHBr     (b) (CH3)3C CH2Br
(c) CH3CH(Br)CH2CH3     (d) (CH3)2CBrCH2CH3

Q 25.

Out of o- and p-dibromobenzene, which one has higher melting point and why?

Q 26.

Compound (A) with molecular formula C4H9Br is treated with aq. KOH solution. The rate of this reaction depends upon the concentration of the compound A' only. When another optically active isomer B' of this compound was treated with aq. KOH solution, the rate of reaction was found to be dependent on concentration of compound and KOH both.
(i) Write down the structural formula of both compounds A' and B'.
(ii) Out of these two compounds, which one will be converted to the product with inverted configuration.

Q 27.

How can you obtain iodoethane from ethanol when no other iodine containing reagent except Nal is available in the laboratory?

Q 28.

Write structures of the following compounds:
(i) 2-Chloro-3-methylpentane
(ii) 1-Chloro-4-ethylcydohexane
(iii) 4-tert. Butyl-3-iodoheptane
(iv) 1,4-Dibromobut-2-ene
(v) 1-Bromo-4-sec. butyl-2-methylbenzene.

Q 29.

Arrange the following compounds in the increasing order of their densities Cl
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-10

Q 30.

What is A in the following reaction?
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-18
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-19

Q 31.

How will you obtain monobromobenzene from aniline?

Q 32.

Predict the major product formed when HCl is added to isobutylene. Explain the mechanism involved.

Q 33.

Discuss the nature of C – X bond in the haloarenes.
C – X bond in haloarenes is extremely less reactive towards nucleophilic

Q 34.

Identify A, B, C, D, E, R and  R1 in the following:
ncert-class-12-solutions-chemistry-chapter-10-haloalkanes-haloarenes-13

Q 35.

A hydrocarbon C5H10 does not react with chlorine in dark but gives a single monochloro compound C5H9CI in bright sunlight. Identify the hydrocarbon.

Q 36.

Write the isomers of the compound having formula C4H9Br.

Q 37.

Write the equations for the preparation of 1-iodoobutanefrom (i)1-butanol (ii)1-chlorobutane (iii) but-l-ene.

Q 38.

Which compound in each of the following-pairs . will react faster in SN2 reaction with -OH? (i)CH3Br or CH3I
(ii)(CH3)3CCl or CH3Cl

Q 39.

ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-35

Q 40.

Haloalkanes contain halogen atom(s) attached to sp3 hybridised carbon atom of an alkyl group. Identify haloalkane from the following compounds.
(a) 2-Bromopentane (b) Vinyl chloride (chloroethene)
(c) 2-Chloroacetophenone (d) Trichloromethane

Q 41.

Aryl chlorides and bromides can be easily prepared by electrophilic substitution of arenas with chlorine and bromine respectively in the presence of Lewis acid catalysts. But why does preparation of aryl iodides require presence of an oxidizing agent?

Q 42.

Which of the compounds will react faster in SN1 reaction with the OH ion?
CH3 – CH2 – Cl or C6H5 – CH2 – Cl

Q 43.

Which of the following compounds (a) and (b) will not react with a mixture of NaBr and H2S04. Explain why?
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-51

Q 44.

Why is the solubility of haloalkanes in water very low?

Q 45.

Identify the products A and B formed in the following reaction:
CH3-CH2-CH=CH-CH3 + HCl–>A+B

Q 46.

What are the IUPAC name of the insecticide DDT and benzenehexachloride?
Why is their use banned in India and other countries?

Q 47.

Match the reactions given in column I with the types of reactions given in column II.
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-85

Q 48.

Assertion (A): tert-Butyl bromide undergoes Wurtz reaction to give 2, 2, 3, 3-tetramethylbutane.
Reason (R): In Wurtz reaction, alkyl halides react with sodium in dry ether to give hydrocarbon containing double the number of carbon atoms present in the halide.

Q 49.

Assertion (A): Aryl iodides can be prepared by reaction of arenas with iodine in the presence of an oxidizing agent.
Reason (R): Oxidising agent oxidises I2 into HI.

Q 50.

Out of C6H5CH2Cl and C6H5CHCIC6H5which is more easily hydrolysed by aqueous KOH.