Chemistry

Haloalkanes and Haloarenes

Question:

The order of reactivity of following alcohols with halogen acids is
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-1

Answer:

(b) The reactivity order of alcohols towards halogen acids is 3 ° > 2 ° > 1 °, since the stability of carbocations is of the order 3 ° > 2 ° > 1 °.
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-`2

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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.

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

Q 4.

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 5.

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

Q 6.

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 7.

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 8.

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

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.

Match the items of Column I and Column II.
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-83

Q 11.

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 12.

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

Q 13.

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

Q 14.

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

Q 15.

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

Q 16.

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

Q 17.

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

Q 18.

Which of the following statements are correct about the reaction intermediate?
(a) Intermediate (iii) is unstable because in this carbon is attached to 5 atoms.
(b) Intermediate (iii) is unstable because carbon atom is sp2 hybridised.
(c) Intermediate (iii) is stable because carbon atom is sp2 hybridised.
(d) Intermediate (iii) is less stable than the reactant (ii).

Q 19.

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 20.

Write the structures and names of the compounds formed when compound ‘A' with molecular formula, C7H8 is treated with Cl2 in the presence of FeCl3.

Q 21.

Some alkylhalides undergo substitution whereas some undergo elimination reaction on treatment with bases. Discuss the structural features of alkyl halides with the help of examples which are responsible for this difference.

Q 22.

Assertion (A): KCN reacts with methyl chloride to give methyl isocyanide Reason (R): CN–  is an ambident nucleophile.

Q 23.

Which reagent will you use for the following reaction?
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-8

Q 24.

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 25.

How will you obtain monobromobenzene from aniline?

Q 26.

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

Q 27.

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

Q 28.

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

Q 29.

Which of the following compounds can be classified  as aryl  halides ? (a) p-ClC6H4CH2CH(CH3)2 (b) p-CH3CHCl(C6H4)CH2CH3  (c) o-BrH2CC6H4CH(CH3)CH2CH3 (d) C6H5Cl

Q 30.

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

Q 31.

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 32.

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 33.

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 34.

Why is sulphuric acid not used during the reaction of alcohols with KI?

Q 35.

Write structures of different dihalogen derivatives of propane.

Q 36.

In the following pairs of halogen compounds, which compound undergoes faster SN1  reaction?
ncert-class-12-solutions-chemistry-chapter-10-haloalkanes-haloarenes-10

Q 37.

In the following pairs of halogen compounds, which compound undergoes faster SN1  reaction?
ncert-class-12-solutions-chemistry-chapter-10-haloalkanes-haloarenes-10

Q 38.

Name the following halides according to IUPAC system and classify them as alkyl, allyl, benzyl (primary, secondary, tertiary), vinyl or aryl halides:
(i)(CH3)2CHCH(Cl)CH3
(ii) CH3CH2CH(CH3)CH(C2H5)CI
(iii) CH3CH2C(CH3)2CH2I
(iv)(CH3)3CCH2CH(Br)C6H5
(v)CH3CH(CH3)CH(Br)CH3
(vi)CH3C(C2H5)2CH2Br
(vii)CH3C(Cl)(C2H5)CH2CH3
(viii)CH3CH=C(CI)CH2CH(CH3)2
(ix)CH3CH=CHC(Br)(CH3)2
(x)P-CIC6H4CH2CH(CH3)2
(xi)m-ClCH2C6H4CH2C(CH3)3
(xii)o-Br -C6H4CH (CH3)CH2CH3

Q 39.

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

Q 40.

Give the uses of freon 12, DDT, carbon tetrachloride and iodoform.

Q 41.

Write the mechanism of the following reaction:

ncert-class-12-solutions-chemistry-chapter-10-haloalkanes-haloarenes-27

Q 42.

Primary alkyl halide C4H9Br (a) reacted with alcoholic KOH to give compound (b) Compound (b) is reacted, with HBr to give (c) which is an isomer of (a). When (a) is reacted with sodium metal it give compound (d), C8H18 which is different from the compound formed when n-butyl bromide is reacted with sodium. Give the structural formula of (a) and write the equations for all the reactions.

Q 43.

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

Q 44.

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

Q 45.

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

Q 46.

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 47.

ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-21

Q 48.

The reaction of toluene with chloride in the presence of iron and in the absence of light yields
>ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-24

Q 49.

ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-34

Q 50.

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