Chemistry

Haloalkanes and Haloarenes

Question:

Write the isomers of the compound having formula C4H9Br.

Answer:

ncert-class-12-solutions-chemistry-chapter-10-haloalkanes-haloarenes-4

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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.

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

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.

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 7.

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 8.

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

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.

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

Q 11.

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

Q 12.

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

Q 13.

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 14.

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 15.

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 16.

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

Q 17.

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

Q 18.

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

Q 19.

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 20.

Which of the following statements are correct about the kinetics of this reaction?
(a) The rate of reaction depends on the concentration of only (ii).
(b) The rate of reaction depends on concentration of both (i) and (ii).
(c) Molecularity of reaction is one.
(d) Molecularity of reaction is two.

Q 21.

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 22.

Which of the following compounds would undergo SN1 reaction faster and why?
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-67

Q 23.

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

Q 24.

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 25.

Explain why
(i)the dipole moment of chlorobenzene is lower than that of cyclohexyl chloride?
(ii)alkyl halides, though polar, are immiscible with water?
(iii)Grignard reagents should be prepared under anhydrous conditions?

Q 26.

Toluene reacts with a halogen in the presence of iron (III) chloride giving ortho and para halo compounds. The reaction is
(a) electrophilic elimination reaction
(b) electrophilic substitution reaction
(c) free radical addition reaction
(d) nucleophilic substitution reaction

Q 27.

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

Q 28.

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

Q 29.

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 30.

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 31.

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 32.

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 33.

What happens when .
(i)n-butyi chloride is treated with alcoholic KOH.
(ii)bromobenzene is treated with Mg in the presence of dry ether.
(iii)chlorobenzene is subjected to hydrolysis.
(iv)ethyl chloride is treated with aqueous. KOH.
(v)methyl bromide is treated with sodium in the presence of dry ether,
(vi) methyl chloride is treated with KCN.

Q 34.

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

Q 35.

Consider the following reaction and answer the questions
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-37

Which of the statements are correct about above reaction?
(a) Both (i) and (v) are nucleophiles
(b) In (iii), carbon atom is sp3 hybridised
(c) In (iii), carbon atom is sp2  hybridised
(d) Both (i) and (v) are electrophiles

Q 36.

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

Q 37.

Draw other resonance structures related to the following structure and find out whether the functional group present in the molecule is ortho, para directing or meta directing.
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-54

Q 38.

Why can aryl halides not be prepared by reaction of phenol with HCl in the presence of ZnCl2?

Q 39.

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

Q 40.

Aryl halides are extremely less reactive towards nucleophilic substitution. Predict and explain the order of reactivity of the following compounds towards nucleophilic substitution:
ncert-exemplar-problems-class-12-chemistry-haloalkanes-and-haloarenes-75

Q 41.

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 42.

In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(a)Assertion and Reason both are correct and Reason is the correct explanation of Assertion.
(b)Assertion and Reason both are wrong.
(c)Assertion is correct but Reason is wrong.
(d)Assertion is wrong but Reason is correct.
(e)Assertion and Reason both are correct statements but Reason is not the correct explanation of Assertion.

Assertion (A): Phosphorus chlorides (tri and penta) are preferred over thionyl chloride for the preparation of alkyl chlorides from alcohols.
Reason (R): Phosphorus chlorides give pure alkyl halides.

Q 43.

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 44.

Some halogen containing compounds are useful in daily life. Some compounds of this class are responsible for exposure of flora and fauna to more and more of UV light which causes destruction to a great extent. Name the class of these halo compounds. In your opinion, what should be done to minimize harmful effects of these compounds.

Q 45.

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 46.

Write structures of different dihalogen derivatives of propane.

Q 47.

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

Q 48.

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

Q 49.

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

Q 50.

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