Chemistry

Haloalkanes and Haloarenes

Question:

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

Answer:

ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-48

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Haloalkanes and Haloarenes

Q 1.

p-Dichlorobenzene has higher m.p. and lower solubility than those of o-and m-isomers. Discuss.

Q 2.

Write down the structure and IUPAC name for neo-pentylbromide.

Q 3.

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 4.

Write the mechanism of the following reaction:

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

Q 5.

Assertion (A): The boiling points of alkyl halides decrease in the order: RI > RBr > RCl > RF
Reason (R): The boiling points of alkyl chlorides, bromides and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.

Q 7.

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

Q 8.

Classify the following compounds as primary, secondary and tertiary halides.
(i) l-Bromobut-2-ene
(iii) 2-Bromo-2-methylpropane

Q 9.

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

Q 10.

Which of the following alcohol will yield the corresponding alkyl chloride on reaction with concentrated HCl at room temperature?
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-3

Q 11.

Arrange the following compounds in the increasing order of their densities Cl
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Q 12.

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 13.

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

Q 14.

Assertion (A): It is difficult to replace chlorine by -OH in chlorobenzene in comparison to that in chloroethane.
Reason (R): Chlorine-carbon (C – Cl) bond in chlorobenzene has a partial double bond character due to resonance.

Q 15.

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

Q 16.

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

Q 17.

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

Q 18.

Which of the following statements are correct about this reaction?
(a) The given reaction follows SN2 mechanism.
(b) (ii) and (iv) have opposite configuration.
(c) (ii) and (iv) have same configuration.
(d) The given reaction follows SN1 mechanism.

Q 19.

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 20.

Why is the solubility of haloalkanes in water very low?

Q 21.

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 22.

Assertion (A): Hydrolysis of (-)-2-bromooctane proceeds with inversion of configuration.
Reason (R): This reaction proceeds through the formation of a carbocation.

Q 23.

The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but in the presence of alcoholic KOH, alkenes are major products. Explain.

Q 24.

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

Q 25.

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

Q 26.

Which of the following haloalkanes reacts with aqueous KOH most easily? Explain giving reason.
(i) 1-Bromobutane (ii) 2-Bromobutane
(iii) 2-Bromo-2-methylpropane (iv) 2-Chlorobutane

Q 27.

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

Q 28.

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

Q 29.

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 30.

Assertion (A): In monohaloarenes, further electrophilic substitution occurs at ortho and para positions.
Reason (R): Halogen atom is a ring deactivator.

Q 31.

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 32.

Which one of the following has the highest dipole moment?
(i)CH3CI2 (ii) CHCl3 (iii) CCI4

Q 33.

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

Q 34.

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 35.

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 36.

Which of the following is an example of vie-dihalide?
(a) Dichloromethane (b) 1, 2-dichloroethane
(c) Ethylidene chloride (d) Allyl chloride

Q 37.

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

Q 38.

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

Q 39.

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

Q 40.

Why is it necessary to avoid even traces of moisture during the use of a Grignard reagent?

Q 41.

How will you obtain monobromobenzene from aniline?

Q 42.

Cyanide ion acts as an ambident nucleophile. From which end it acts as a stronger nucleophile in aqueous medium? Give reason for your answer.

Q 43.

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

Q 44.

Arrange each set of compounds in order of increasing boiling points.
(i)Bromomethane, Bromoform, Chloromethane, Dibromomethane.
(ii)1-Chloropropane, Isopropyl chloride, 1-Chlorobutane.

Q 45.

Write the isomers of the compound having formula C4H9Br.

Q 46.

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

Q 47.

What are ambident nucleophiles ? Explain with an example.

Q 48.

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 49.

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 50.

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