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NCERT Class 12 Chemistry Chapter 10 Notes Haloalkanes and Haloarenes - Download PDF

NCERT Class 12 Chemistry Chapter 10 Notes Haloalkanes and Haloarenes - Download PDF

Edited By Shivani Poonia | Updated on Jun 18, 2025 02:47 PM IST

Haloalkanes and Haloarenes are an important part of our daily lives; they are everywhere, from refrigerants in air conditioners to medicines. These are organic compounds containing Halogens (Fluorine, Chlorine, Bromine, Iodine). These compounds play a crucial role in pharmaceuticals and industries. These words are made up of two words: the first is ‘Halo’, which means Halogens, and the second word is ‘alkanes’ or ‘arenes’, which means aliphatic or aromatic hydrocarbons. So, basically, in these compounds, one or more Hydrogen atoms of Hydrocarbons are replaced by Halogens. Many organic compounds containing halogens occur naturally and have clinical significance.

This Story also Contains
  1. Detailed notes for chapter 6: Haloalkanes and Haloarenes
  2. Polyhalogen Compounds
  3. Important Questions for class 12 Chemistry chapter 6: Haloalkanes and Haloarenes
  4. Approach to Solve Questions of Class 12 Chemistry Chapter 6: Haloalkanes and Haloarenes
  5. Topics and Subtopics Covered in the NCERT Textbook
  6. NCERT Class 12 Notes Chapter-Wise
  7. Subject-Wise NCERT Solutions
  8. Subject-Wise NCERT Exemplar Solutions
NCERT Class 12 Chemistry Chapter 10 Notes Haloalkanes and Haloarenes - Download PDF
NCERT Class 12 Chemistry Chapter 10 Notes Haloalkanes and Haloarenes - Download PDF

Some of the widely used Haloalkanes are Chloroform (CHCl3 ) and Carbon tetrachloride (CCl4 ), and Haloarenes are DDT, Bromobenzene, etc. Haloalkanes And Haloarenes play a vital role in the Class 12 Chemistry curriculum. Chapter 6 starts with the basics and gradually moves to complex topics. NCERT notes have been created according to the latest CBSE curriculum.

Background wave

Haloalkanes and haloarenes Class 12 notes cover a brief outline of topics such as preparation methods, Chemical and Physical properties of haloalkanes, and haloarenes. On this page, we provide a structured overview of the syllabus, guiding students through the essential topics and highlighting crucial points for effective revision.

Also, students can refer,

Detailed notes for chapter 6: Haloalkanes and Haloarenes

Nomenclature

a)For haloalkanes-

Common name- alkyl halides

Example- methyl chloride, ethyl bromide, n-propyl iodide

IUPAC Name- haloalkane

Example- bromoethane, chloromethane, iodopropane.

b)For haloarenes-

Halo+ name of aromatic hydrocarbon

Example- chlorobenzene, Iodobenzene, 3-chlorotoluene.

Methods of Preparation of Haloalkanes

a)From phosphorus halides-

R−OH+PCl5⟶RCl+POCl3+HCl

b)From alkanes-

1663574805317

c)From alkenes- Haloalkenes are prepared by the addition of halogens to alkenes

  • Addition of halogens-

1663574832642

Methods of Preparation for Haloarenes

a)By direct halogenation of the aromatic ring-

It is an electrophilic substitution reaction.

1663575029867

b)By the use of silver salt of aromatic acids-

This reaction is known as the Hunsdiecker reaction

1663575054039

Physical Properties of Haloalkanes

  • Haloalkanes are colourless and their a sweet-smelling taste.

  • Since haloalkanes cannot break the hydrogen bonds of water, they are slightly soluble in water.

  • As the size of the alkyl group increases, density increases.

  • The boiling as well as melting points of haloalkanes are higher than their parent hydrocarbon.

  • These are not as flammable as hydrocarbons.

  • Dipole moment decreases on going from methyl chloride, methyl bromide, and methyl iodide. However, the dipole moment of methyl fluoride is lower than compared of methyl chloride.

Physical Properties of Haloarenes

  • Haloarenes are colourless in nature and heavier than water.

  • Mostly soluble in organic solvents and insoluble in inorganic solvents.

  • As the size of the halogen attached to benzene increases, the boiling point also increases.

  • Out of the three isomers, the boiling point of the ortho isomer is the highest.

  • The dipole moment of the ortho isomer is larger than the meta isomer. Para isomer has zero dipole moment.

Chemical Reactions of Haloalkanes

The reactions of haloalkanes may be divided into the following categories:

1. Nucleophilic substitution

2. Elimination reactions

3. Reaction with metals

  1. Nucleophilic substitution reaction

a)Substitution by hydroxyl group-

CH3CH2Br+K+OH⟶CH3CH2OH+KBr

b)Substitution by cyano group-

CH3−I+K+−CN⟶CH3−C≡N+KI

1663575198646

c)Substitution by isocyanide group-

1663575257269

d)Substitution by ammonia group-

The following reaction is known as the Hofmann ammonolysis reaction.

1663575291840

Nucleophilic substitution reactions are of two types

1) SN1

2) SN2

Substitution nucleophilic reaction (SN1 reaction)

  • The rate is given as –

Rate=k[(CH3Br]

  • This reaction occurs in two steps. The first step leads to the formation of a carbonation, and the second step leads to the nucleophilic attack on the carbocation.

  • In SN1 reaction alkyl halide reacts in the following manner-

  • Tertiary alkyl halide> secondary alkyl halide> primary alkyl halide> primary alkyl halide> methyl halide

Substitution nucleophilic reaction (SN2 reaction)

  • The rate is given as -

Rate=k[CH3Br][OH-]

  • This reaction occurs in a single concerted step.

  • In SN2 reaction alkyl halide reacts in the following manner-

Methyl halide > primary halide> secondary halide> tertiary halide

  1. Elimination reaction

  • Formation of an alkene takes place.

  • Also known as the dehydrohalogenation reaction.

  • The general reaction is given as –

1663575335564

  • The reaction proceeds by the removal of hydrogen from a carbon atom situated next to a carbon atom carrying a halogen atom.

Example-

1663575374666

Saytzeff’s rule- This rule decides which alkene will be formed if there are chances of elimination of more than one hydrogen atom. That alkene will be formed in which the more substituted alkene is formed.

  1. Reaction with active metals- Haloalkanes react with metals such as Magnesium and sodium.

a)Reaction with magnesium-

RX+MgdryetherRMgX

b)Reaction with sodium-

2RX+2NadryetherRR+2NaX

  • Reaction with active metals

CH3CH2Br+2Li dryether CH3CH2Li+LiBr

CH3CH2Br+Zn inert atmosphere  CH3CH2ZnBr

  1. Reduction

  • The reaction of an alkyl halide with nickel, platinum, or palladium in the presence of a metal catalyst.

CH3CH2Br+H2 525 K Ni or Pd CH3CH3+HBr

  • The reaction of ethyl alcohol with the zinc-copper couple

CH3CH2OH+2[H]ZnCu/HClCH3CH3+H2O

  • The reaction of hydroiodic acid in the presence of red phosphorus.

1663575594939

Chemical Properties of Haloarenes

  • Resonance effect- Due to resonance, haloarenes are not reactive towards nucleophilic substitution reactions.

  • Hybridization of carbon atoms in haloarenes and haloalkanes- In haloalkanes, carbon is sp3 hybridized, whereas in haloarenes, carbon is sp2 hybridized.

  • The polarity of the carbon and hydrogen bond-

Sp2 hybridized carbon of haloarene attached to a halogen has a lesser tendency to release its electrons to a halogen atom. Hence, the bond is less polar compared to the carbon-halogen bond of haloalkanes.

  • Instability of phenyl cation- Phenyl cation is not stable since there is no resonance. Therefore, SN1 mechanism cannot occur.

  • Nucleophilic substitution reactions

Replacement by the hydroxy group-

1663575665365

Reaction for the replacement by the amino group-

1663575684380

Reaction for substitution with the cyano group-

1663575707363

  • Reactions with metal

Reaction with magnesium-

1663575731372

Reaction with lithium-

1663575754962

Reaction with sodium-

1663575774199

Reaction with copper powder-

1663581399980

  • Reduction reaction-

1663581447588

  • Electrophilic substitution reactions

Halogenation-

1663581473394

Nitration-

1663581499365

Sulphonation-

1663581529908

Alkylation-

1663581862975

Acylation-

1663581895903

Polyhalogen Compounds

Carbon compounds containing more than one halogen atom are usually referred to as polyhalogen compounds. Many of these compounds are useful in industry and agriculture.

  1. Dichloromethane (Methylene chloride)
  2. Triiodomethane (Iodoform)
  3. Tetrachloromethane (Carbon tetrachloride)
  4. Trichloromethane (Chloroform)
  5. Freons
  6. p,p’-Dichlorodiphenyltrichloroethane(DDT)

p,p’-Dichlorodiphenyltrichloroethane(DDT)

DDT, the first chlorinated organic insecticide. The use of DDT increased enormously on a worldwide basis after World War II, primarily because of its effectiveness against the mosquito that spreads malaria and the lice that carry typhus. However, problems related to the extensive use of DDT began to appear in the late 1940s. Many species of insects developed resistance to DDT, and it was also discovered to have a high toxicity towards fish. The chemical stability of DDT and its fat solubility compounded the problem. DDT is not metabolised very rapidly by animals; instead, it is deposited and stored in the fatty tissues.


Important Questions for class 12 Chemistry chapter 6: Haloalkanes and Haloarenes

Question1. The products A and B obtained in the following reactions, respectively, are

3ROH+PCl33RCl+AROH+PCl5RCl+HCl+B

(A) POCl3 and H3PO3

(B) POCl3 and H3PO4

(C) H3PO4 and POCl3

(D) H3PO3 and POCl3

Answer:

These reactions are the preparation of haloalkanes from alcohols.

3ROH+PCl33RCl+H3PO3
(A)

ROH+PCl5RCl+HCl+POCl3
(B)

A and B are H3PO3 and POCl3 respectively.

Hence, the correct answer is option (D).

Question 2. The incorrect statement regarding chirality is :

(A) The product obtained by SN2 reaction of a haloalkane having chirality at the reactive site shows inversion of configuration.

(B) Enantiomers are superimposable mirror images on each other.

(C) A racemic mixture shows zero optical rotation.

(D) SN1reaction yields 1:1 mixture of both enantiomers.

Answer: Chirality refers to the property of asymmetry in a molecule, where the molecule and its mirror image cannot be superimposed onto each other. In simpler terms, a chiral molecule cannot be rotated or flipped in a way that matches its mirror image. This property is essential in fields such as chemistry and biochemistry, particularly in understanding how molecules interact with each other and with biological systems.

Therefore, Enantiomers are non-superimposable mirror images of each other.

Hence, the correct answer is option (B).

Approach to Solve Questions of Class 12 Chemistry Chapter 6: Haloalkanes and Haloarenes

To effectively solve questions of the chapter on haloalkanes and haloarenes, follow a systematic and structured approach that helps understand the concepts and the mechanism of reactions:

  • Understand the structure of the chapter and break the chapter into manageable sections.
  • After that, try to learn and memorize key concepts of the chapter, such as SN1 reaction, SN2 reaction, and Elimination reaction, reactivity of aryl and alkyl halides, and the effect of group on reactivity.
  • To solve questions properly, use proper chemical terminology.
  • Always identify the reaction type, substrate type, nucleophilic strength, and solvent.
  • Also, use some common tricks, such as identifying major products, the stability of carbocation, the stereochemical outcomes of reactions,
  • Use flowcharts for mechanisms.
  • Timely revise your notes.
  • Practice as many questions as asked in previous exams, like JEE Main, NEET, Board exam, etc.

Topics and Subtopics Covered in the NCERT Textbook

6.1 Classification

6.2 Nomenclature

6.3 Nature of C-X bond

6.4 Methods of Preparation of Haloalkanes

6.5 Preparation of Haloarenes

6.5 Physical properties

6.7 Chemical reaction

6.8 Polyhalogen compounds

NCERT Class 12 Notes Chapter-Wise

The hyperlinks of ncert notes chapter-wise are given below:

Subject-Wise NCERT Solutions

The hyperlinks of ncert solutions subject-wise are given below:

Subject-Wise NCERT Exemplar Solutions

The hyperlinks of the NCERT exemplar solutions, subject-wise, are given below:

Frequently Asked Questions (FAQs)

1. What are haloalkanes and haloarenes in Class 12 Chemistry?

Haloalkanes and Haloarenes are organic compounds containing halogens (Fluorine, Chlorine, Bromine, Iodine). One or more hydrogen is replaced by halogens in Hydrocarbons to form Haloalkanes and Haloarenes.

2. What are the types of haloalkanes and haloarenes?

 Haloalkanes are classified based on several Halogen atoms bonded to the Carbon atom. They are classified into primary, secondary and tertiary haloalkanes, depending on how many carbon atoms are attached to the carbon bearing the halogen. 

 Haloarenes derived from aromatic compounds, follow a similar classification as monohaloarenes. Di haloarenes can exist in ortho (o-), meta (m), or para (p) positions based on the placement of halogens on the benzene ring.

3. What is the IUPAC nomenclature of haloalkanes?

The IUPAC nomenclature of haloalkanes 

  • The longest carbon chain containing the halogen is identified and numbered from the end closest to the halogen to assign it the lowest possible position. 
  • The halogen is named as a prefix (Fluoro-, chloro-, bromo-, iodo-) followed by the parent alkane name.
  • If multiple halogens exist, they are listed alphabetically with numerical positions and prefixes like di, tri-, or tetra.
4. How are haloalkanes prepared in Class 12 Chemistry?

 Haloalkanes can be prepared using various methods, primarily involving substitution or addition reactions.

  • From Alcohols: Haloalkanes are obtained by reacting alcohols with halogen acids (HX), phosphorus halides, or thionyl chloride 
  • From Alkanes: Free radical halogenation of alkanes with Cl₂ or Br₂ in the presence of UV light produces haloalkanes, though it gives a mixture of products.
5. What are the applications of haloalkanes and haloarenes in daily life?

 Haloalkanes and haloarenes have numerous applications in daily life due to their chemical properties. 

  • Compounds like chloroform and carbon tetrachloride are used as industrial solvents for fats, oils, and waxes. 
  • Many medicines, such as chloroquine and halothane, contain halogenated compounds. 
  • Haloalkanes like CFCs are used in refrigeration and air conditioning.

Articles

A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg

 

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)

K/2\,

Option 2)

\; K\;

Option 3)

zero\;

Option 4)

K/4

In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)

0.02

Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)

Molality

Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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