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Haloalkanes & Chloroform: Class 12 Organic Chemistry Notes

Haloalkanes and Chloroform Notes unit 8 Class 12 Organic Chemistry, including detailed NEB notes, MCQs, exercises, important questions, and solutions.
Unit 8 Haloalkanes class 12
8.1 Nomenclature
8.2Classification
8.3Isomerism
8.4 Preparation (alkanes, alkenes, and alcohols)
8.5 Physical properties
8.6 Chemical properties (SN1 and SN2)
8.7 Formation (alcohol, nitrile, amine, ether, thioether, carbylamine, nitrite, and nitroalkane)
8.8 Elimination Reaction ( Saytzeff ’s rule)
8.9 Reaction with Sodium metal (Wurtz's Reaction)
8.10 Reduction Reaction of Haloalkane
8.11 Preparation of Chloroform
8.12 Physical properties of Chloroform
8.13 Chemical properties of Chloroform

Class 12 Haloalkanes and Chloroform Notes NEB
Class 12 notes: Haloalkanes with important Questions

Unit 8: Haloalkane class 12

Introduction

Haloalkanes are the derivatives of hydrocarbon because they are derived by replacing hydrogen with halogen atoms, therefore the halogen derivatives of alkane are called haloalkanes. Or

The organic compound containing halogen atom (X = -F,-Cl, -Br, -I) as a functional group is called Haloalkanes.

R-H + X⟶R-X+ HX
alkane  haloalkane
CH₃-H + Cl₂⟶CH₃-Cl+ HCl
methane chloromethane

They are also called Alkyl halides.

Uses: Solvent, Medicine, Insecticide, etc.

Haloalkanes are formed by the replacement of one or more hydrogen atoms of alkane by the same number of halogen atoms and are bonded with the carbon atom of alkane through a strong covalent bond. They are presented by the general molecular formula

CnH2n+1X.

Nomenclature of haloalkanes

Prefix + Word root + Primary suffix
Prefix: side chain branches substituents
Word root: number of C-atoms
Primary suffix: nature of C-atoms (-ane or -one or -one)
(-X=halo,-F=fluoro, -Cl=chloro, -Br=bromo, -I=iodo)

Formula Common name (Alkyl+halide) IUPAC name (Halo +word)
R-X alkyl halide halo alkane
CH₃F methyl fluoride fluoro methane
CH₃CH₂-Cl ethyl chloride chloro 
ethane
CH₃CH₂CH₂Br propyl bromide 1-Bromo propane
CH₃CH₂-I ethyl iodide iodo ethane
CHCl₃ chloroform tri chloro
methane
CHI₃ iodoform tri iodo
methane
CCl₄ carbon tetrachloride tetra chloro methane 
CH₃-CH-Cl₂ ethylidene chloride
(geminal dichloride)
1,1-dichloro
ethane
Cl-CH₂-CH₂-Cl ethylene dichloride
(Vicinal dichloride)
1,2-dichloro
ethane
CH₃CH₂CH₂Cl n-propyl chloride 1-Chloro propane

tertiary butyl bromide
(Neo-butyl bromide)
2-Bromo,
2-methyl propane
CH₃CH₂CH₂CH₂Br n-butyl bromide 1-Bromo butane
1-Bromo-2-methyl propane
iso-butyl bromide 1-Bromo-2-methyl propane
isopropyl chloride
isopropyl chloride 2-chloro propane
2-Bromo butane
secondary butyl bromide 2-Bromo butane

Classification of haloalkanes

[A] Based on the nature of the carbon atom

1. Primary haloalkane (1 ̊)

The haloalkane in which the halogen-containing carbon is further bonded to one carbon atom (one alkyl group) or primary carbon is called primary haloalkane.

1-chloro propane
Primary haloalkane

2. Secondary haloalkane (2 ̊)

The haloalkane in which the halogen-containing carbon is further bonded to two carbon atoms (two alkyl groups) or secondary carbon is called secondary haloalkane.

secondary haloalkane,2-chloropropane
Secondary Haloalkane

3. Tertiary haloalkane (3 ̊)

The haloalkane in which the halogen-containing carbon is further bonded to three carbon atoms (three alkyl groups) or tertiary carbon is called tertiary haloalkane.

Tertiary Haloalkane, 2 chloro 2 methyl propane
Tertiary Haloalkane

[B] based on the number of halogen atoms

1. Mono-halo alkane

Haloalkane contains only one halogen atom.

Mono-halo alkane, chloro methane
Mono-haloalkane

2. Di-haloalkane

Haloalkane contains two halogen atoms.

Di-haloalkane
Di-haloalkane

3. Poly-haloalkane

Haloalkane contains three or more halogen atoms.

Poly-haloalkane
Poly-haloalkane

Isomerism in haloalakanes

1. Chain isomerism

Haloalkanes have the same number of carbon atoms but the different number in carbon chain length is called chain isomers.

chain isomers of bromo pentane
chain isomerism: Bromo pentane 

2. Position isomerism

Haloalkanes have the same molecular formula but the different positions of halogen atoms on the carbon chain are called position isomers.

Position isomerism 1-Chloro propane 2-Chloro propane
position isomerism: chloropropane

Self-test:

Q.Write all possible isomers with the molecular formula C4H9I and give their IUPAC name.

General methods of preparation of haloalkane

1. From alkanes (Halogenation of alkanes)

The haloalkanes are prepared by treating alkane with a limited amount of halogen in presence of halogen carriers and sunlight or heat.

methane to chloro methane
Formation of haloalkane from an alkane

On excess supply of chlorine poly-substituted product is formed.

methane to tetrachloromethane reaction
methane to tetra chloromethane in excess of chlorine

In the case of higher alkanes two or more possible products are formed.

propane gives 2-chloro propane and 1-chloro propane
higher alkanes give more than one products

The bromination is carried out in presence of FeBr₃ under sunlight or heat.

CH₃CH₃+Br₂ Δ, FeBr3 CH₃CH₂Br + HBr
ethane   Bromo ethane

The iodination of an alkane is a reversible reaction. So to obtain iodoalkane strong oxidizing agent like conc.HNO₃ or HIO₃ is used to increase the rate of the forward reaction.

alkane to iodoalkane mechanism
A reaction mechanism for iodoalkane from an alkane

Thus, formed iodine increases the rate of forwarding reaction. Hence the iodination of alkane must be carried out in presence of a strong oxidizing agent.

methane to iodomethane in presence of strong reducing agent
The reaction of formation of iodomethane from methane in presence of conc.HNO3
Reactivity of alkane = 3 ̊  > 2 ̊  > 1 ̊
Reactivity of halogen = F > Cl > Br > I

2. From alkenes(Hydrohalogenation of alkenes)

The haloalkanes are prepared by the reaction of an alkene with halogen acid (HF, HCl, HBr, HI). The reaction is called the Hydrohalogenation reaction.

CH₂=CH₂+HCl ⟶ CH₃CH₂Cl
ethene                chloroethane

If an unsymmetrical alkene is taken then two possible products are formed.

           Cl
CH₃CH=CH₂+HCl ⟶ CH₃CHCH₃+ CH₃CH₂CH₂Cl
Propene         2-chloropropane 1-chloropropane

The Formation and stability of these two products can be explained by following two rules:

[A] Markovnikov’s rule:

According to this rule “when an unsymmetrical alkene reacts with an unsymmetrical reagent than the positive part of reagent goes to that double bonded carbon containing greater number of the hydrogen atoms”. For example

                                        Cl
CH₃-CH=CH₂ + HCl ⟶ CH₃-CH-CH₃
Propene           2-chloropropane

[B] Peroxide effect (Anti- Markovnikov’s rule)

According to this rule “when an unsymmetrical alkene reacts with the unsymmetrical reagent in presence of organic peroxide (R-O-O-R)then the positive part of the reagent goes to that double bonded carbon containing less number of
the hydrogen atom”. For example,

Anti-Markovnikov's reaction
Anti-Markovnikov's reaction

It is also called the Kharasch effect.

HCl and HI do not give Markovnikov’s addition, why?

Ans: H-Cl is highly polar and hence does not undergo hemolysis easily. HI undergoes homolysis to give iodine free radicals which instantly combine to give I2.

3. From Alcohol

Generally, haloalkanes are prepared by the reaction of alcohols with haloacids or phosphorous halide, or thionyl chloride.

(a) Reaction with halogen acid(HX)

The chloroalkane is prepared by the reaction of alcohol with HCl in presence of anhydrous  zinc chloride (ZnCl₂).

The mixture of conc. HCl and anhydrous ZnCl₂ is called Lucas reagent.

alcohol to chloroalkane with 1,2,3 degree alcohol.
A reaction from 1,2,3 degree alcohol to respective Chloro substituted product.
Reactivity of Alcohol: 3° > 2° > 1°
Reactivity of Halo acid: HI> HBr > HCl

(b) Reaction with a phosphorous halide (PX₅ or PX₃)

The haloalkanes are prepared by the action of alcohol with PX₅ or PX₃.

R-OH+ PX₅ Δ⟶ R-X+POX₃+HX
3R-OH+ PX Δ⟶ 3R-X +H₃PO₃
alcohol       haloalkane
CH₃CH₂OH+PCl₅  -Δ⟶ CH₃CH₂Cl+ POCl₃+HCl
ethanol           Chloroethne+phosphoryl chloride
3CH₃OH +PCl₃  -Δ⟶ 3CH₃Cl +H₃PO₃
methanol        chloromethane + phosphorous acid

Since PBr₃ and PI₃ are unstable compounds. So they are prepared in the reaction mixture (In-situ form) by the action of red phosphorous with Br₂ or I₂.

P₄ + 6Br₂ -Δ⟶4PBr₃
CH₃CH₂OH+ PBr₃ -Δ⟶ CH₃CH₂-Br+ H₃PO₃
ethanol                  bromoethane
Similarly,
P₄ + 6I₂ -Δ⟶ 4PI₃
CH₃CH₂OH+PI₃ -Δ⟶ CH₃CH₂-I+ H₃PO₃
ethanol             iodoethane

(c) Reaction with thionyl chloride (SOCl₂)
(Darzen’s reaction)

The chloroalkanes are prepared by heating alcohol with SOCl₂ in presence of pyridine. Only chloroalkane is prepared by this method. From this method, pure chloroalkane can be prepared because SO₂ and HCl evolved as gases.

Darzen's reaction (reaction with thionyl chloride) alcohol to chloroalkane or ethanol to chloro ethane
Darzen's Reaction or Reaction of alcohol with thionyl chloride.

Physical properties of haloalkanes

  • Lower members of haloalkane methyl chloride and methyl bromide are colorless gases, higher are colorless and sweet-smelling liquids and next higher are colorless solids.
  • They are insoluble in water and soluble in almost all organic solvents like ether, alcohol, etc.
  • They burn with green-edged flame in the air.
  • The boiling point of haloalkanes is higher than corresponding parent alkanes.
  • The boiling point of haloalkane having the same alkyl group is RI>RBr > RCl due to the large size of the halogen atom.
  • Branched-chain haloalkane has a lower boiling point than straight-chain haloalkane due to its spherical nature.
  • The B.P. increase as the increase in the alkyl group.

Chemical properties of haloalkanes

The haloalkanes are more reactive than alkanes due to the presence of polar C-X bonds. The polarity arises due to the difference in electronegativity value between carbon and a halogen atom.

[A] Nucleophilic substitution reaction

The nucleophile is electron-rich species having lone pairs of electrons or negative charges and can attack to electron-deficient center. When a nucleophile is substituted by another nucleophile then the reaction is called a nucleophilic substitution reaction.

Nuc: + R-LG → R-Nuc + LG:

Nuc- nucleophile LG- Leaving group

Example: R-Br + OH → R-OH + Br− 

Here, the existing nucleophile has been substituted by an incoming nucleophile.

The alkyl halides undergo nucleophilic substitution reaction (SN- reaction ) by following two mechanisms.

S stands for Substitution

N stand for Nucleophile

The number represents Kinetic order

SN1 reaction:

SN1 stands for nucleophilic substitution unimolecular. When the rate of SN depends upon the concentration of substrate only (alkyl halide), then the reaction follows first-order kinetics and is represented as SN1.
The alkaline hydrolysis of t-butyl bromide by aq. NaOH to give t-butyl alcohol is an example of SN1. The reaction completes in two steps.

Step 1)
Alkyl halide ionizes to give carbocation. Then step is slow and hence it is the rate-determining step.
one nucleophile to carbonium ion in SN1 reaction
The rate-determining step of SN1 Reaction
 
Step 2)
In the second step, the nucleophile attacks the carbonium ion to give t-butyl alcohol. (ionic reaction, fast)
Carbonium ion to product formation of product in SN1 reaction
Formation of product in SN1 Reaction

SN2 reaction:

SN2- stands for nucleophilic substitution bimolecular. When the rate of SN-reaction depends upon the concentration of substrate (alkyl halide) and nucleophile (Nu), then the reaction follows second-order kinetics and is represented as SN2.
Consider the alkaline hydrolysis of methyl bromide by aq. NaOH to give alcohol. It completes in one step through the formation of the intermediate.

SN2 reaction mechanism

Difference Between SN1 and SN2 Reaction

SN1SN2
This follows the Unimolecular Rate of Reaction mechanismThis follows the Bimolecular Rate of Reaction mechanism
Follows 1st order Kinetic ReactionFollows 2nd order Kinetic Reaction
Two-Step MechanismOne Step Mechanism
A carbocation is formed as an intermediate partNo Carbocation
Racemization occursInversion occurs
Order: 3°>2°>1°Order: 1°>2°>3°
RoR∝ [ substituent ]RoR∝ [ substituent ].[ Nucleophile ]

1. Reaction with aqueous NaOH or KOH (Formation of alcohol)

When haloalkane reacts with an aqueous solution of  NaOH or KOH then alcohol is formed.

R-X+aq.NaOH -Δ⟶ R-OH+NaX
haloalkane     alcohol
CH₃CH₂Cl+ aq.KOH -Δ⟶ CH₃CH₂OH+KCl
chloroethane(1⁰)     ethanol (1 ̊)

Ambident Nucleophile

Those nucleophiles that consist of possible two attacking sites on the electron-deficient center are called ambident nucleophiles. For example, NO₂⁻, CN⁻, etc. Cyanide ion is an ambident nucleophile because both carbon and nitrogen can supply a pair of electrons during the nucleophilic attack.
                     ⟶
 -C≡N & -N=C

Similarly, NO₂⁻has two attacking sites.

-NO & -ONO
R-X+CN⁻ ⟶ R-CN (Attack by carbon)
R-X+CN⁻ ⟶ R-NC (Attack by nitrogen)

2. Reaction with alcoholic NaCN or KCN

When haloalkane is heated with an alcoholic solution of NaCN or KCN then alkane nitrile (Cyanides) are formed. This reaction is largely used to increase the number of carbon atoms during organic conversion.

R-X+alc.KCN -Δ⟶ R-CN+KX
haloalkane  alkanenitrile(cyanide)
CH₃CH₂Cl+ alc.KCN -Δ⟶ CH₃CH₂CN+ KCl
chloroethane  propane nitrile (ethyl cyanide)
(2 carbon atoms) (3 carbon atoms)

Alkane nitrile(Cyanides) is a beneficial chemical that gives various products when treated with different reagents.

(a) Reduction Reaction

CH₃-CN+ 4[H] Ni/Pt/Pd or LiAlH4 CH₃CH₂NH₂
ethane nitrile (C2H5OH/Na, mendius rxn) ethanamine

A reaction in which an organic nitrile is reduced by nascent hydrogen (e.g. from sodium in ethanol) to a primary amine is REDUCTION REACTION.

b) Complete hydrolysis

CH₃-CN+ H₂O + dil.HCl -Δ⟶  CH₃COOH+ NH₄Cl
ethane nitrile                      ethanoic acid

c) partial hydrolysis

CH₃-CN+Conc.HCl (Δ + alc. H2O2⟶  CH₃CONH₂
ethane nitrile                                 ethanamide

Q. Convert methane to ethanoic acid


3. Reaction with alcoholic AgCN

When haloalkane is heated with an alcoholic solution of AgCN then alkyl isocyanide is formed.

R-X+alc.AgCN -Δ⟶ R-NC+AgX
haloalkane      alkyl isocyanide
CH₃CH₂Cl+ alc.AgCN -Δ⟶ CH₃CH₂-NC+AgCl
chloroethane      ethyl isocyanide

Here, AgCN is a covalent compound. So it does not dissociate easily. Therefore the lone pair of electrons in the nitrogen atom attacks haloalkane to form isocyanides.

Similarly, isocyanide forms different compounds as:

(a)Reduction

CH₃-NC+ 4[H] Ni/Pt/Pd or LiAlH4-> CH₃-NH-CH₃
methyl isocyanide (C2H5OH/Na) N-methylmethanamine

(b)Acidic hydrolysis

CH₃-NC + H₂O+ dil.HCl -Δ⟶ CH₃NH₂+ HCOOH
methyl isocyanide          methenamine

4. Formation of amines

When haloalkane is heated with alc. ammonia then amines are formed.

R-X + alc.NH3 -Δ R-NH2+HX
Alkane  alc. Ammonia        Amine
CH₃CH₂-Cl + alc.NH3 -Δ⟶ CH₃CH₂-NH2+HCl

5. Reaction with sodium alkoxide(R-ONa) (Williamson’s ether synthesis/ Formation of ether)

When haloalkane is heated with sodium alkoxide then ether is formed. This reaction is called Williamson’s etherification reaction.

R-OH+ Na -Δ⟶R-ONa+ ½H₂↑
alcohol sodium alkoxide
R-X+R-ONa -Δ⟶ R-O-R+NaX
haloalkane ether
CH₃CH₂Cl+ CH₃CH₂-ONa -Δ⟶CH₃CH₂-O-CH₂CH₃+NaCl
chloro ethane ethyoxyethane (diethyl ether)

Both symmetrical and unsymmetrical ether can be prepared by this method.

6. Formation of thioether

Thioether is (R-S-R”) analog of ether.
Name sulfides like ethers, replacing ”sulfide” for “ether” in the common name, or “alkylthio” for “alkoxy” in the IUPAC system.

CH3-Cl -Δ⟶ C2H5-S-CH3
Chloromethane     ethyl methyl sulfide
Formation of Thioether , haloalkanes notes
Formation of ThioEther

7. Carbylanime

When primary animes are heated with alcoholic potassium hydroxide (KOH) and chloroform forms a product which is a foul-smelling substance called carbylanime reaction.

R-NH2 + CHCl3 + 3KOH → RNC (Carbylamine) + 3KCl + 3H2O
Amine, Chloroform, alc. potassium hydroxide -ΔCarbylanimes
CH₃CH₂-NH2 + CHCl3 + 3KOH → CH₃CH₂NC + 3KCl + 3H2O

8. Reaction with aqueous NaNO₂ or KNO₂

When haloalkanes are heated with aqueous NaNO₂ or KNO₂ solution then alkyl nitrite is formed.

R-X+aq.NaNO₂ -Δ⟶R-ONO+NaX
haloalkane         alkyl nitrite
CH₃CH₂-Cl +aq.NaNO₂ -Δ⟶ CH₃CH₂-ONO+NaCl
chloroethane         ethyl nitrite

Here, NaNO₂ is an ionic compound. Hence Na−O bond breaks easily and negatively charged oxygen attacks haloalkane to form alkyl nitrite.[Na-O-N=O]→[Na⁺+ ONO⁻]

9. Reaction with alcoholic silver nitrite (AgNO₂)

When haloalkanes are heated with alcoholic AgNO₂ solution then nitroalkanes are formed.

R-X+alc.AgNO₂ -Δ⟶R-NO₂+AgX
haloalkane          nitroalkane
CH₃-Cl+alc.AgNO₂ -Δ⟶CH₃-NO₂+AgCl
chloromethane         nitromethane

Here, AgNO₂ is a covalent compound. Hence the lone pair of electrons on the nitrogen atom attacks an alkyl group of haloalkane to form nitroalkane.[Ag-O-N=O]→[Ag−NO₂]

[B] Elimination reaction (ᵦ- elimination reaction) Dehydrohalogenation reaction

When haloalkane is boiled with an alcoholic solution of NaOH or KOH then alkene is formed. In this reaction, one hydrogen and halogen atom are removed from adjacent carbon. So this reaction is called dehydrohalogenation reaction.

R-CH₂CH₂X+alc.NaOH-Δ⟶R-CH=CH₂+HX +H₂O
haloalkane                  alkene
CH₃CH₂Br+ alc. KOH-Δ⟶CH₂=CH₂+KBr+ H₂O
bromo ethane                 ETHENE

This reaction is also called β-elimination or 1,2-elimination.

Saytzeff’s rule

If dehydrohalogenation of haloalkane gives two or more alkenes then alkene containing a greater number of the alkyl group on double bonded carbon is the major product. This rule is called Saytzeff ’s rule.

saytzeff's rule or saytzeff's reaction
Saytzeff's rule
Q. Convert 1-bromopropane to 2-bromopropane.

[C] Reaction with metal

Reaction with sodium (Wurtz’s reaction)

When alkyl halide is heated with sodium metal in presence of dry ether, then alkane having a double number of carbon atoms is formed. Therefore it is used to increase carbon length.
Reaction with sodium (Wurtz’s reaction)
Reaction with sodium ( Wurtz's reaction )

[D] Reduction reaction of Haloalkane

1. Catalytic reduction

CH₃CH₂Cl+H₂ (Ni/Pt/Pd) ⟶CH₃CH₃+HCl
chloroethane ⟶ETHANE

2. Reduction with metal hydride

CH₃CH₂Br +2[H] ( Lialh4 or NaBH4 )⟶ CH₃CH₃+ HBr
bromoethane     ⟶        Ethane

3. Reduction with metallic solution

  1. Sn-Zn-Fe/HCl 
  2. C₂H₅OH/Na
  3. Red.P₄/HI
CH₃CH₂Cl+ 2[H] (Sn/ HCl ) ⟶ CH₃CH₃+HCl
chloroethane ⟶  ethane


Reaction question of class 12 haloalkanes
Reaction summary of haloalkanes

Preparation of Chloroform

The chloroform is prepared in the lab by heating ethanol or acetone with the aqueous paste of bleaching powder. In this process, the bleaching powder acts as an oxidizing agent, chlorinating agent as well as the hydrolyzing agent.

CaOCl₂+ H₂O -Δ⟶ Ca(OH)₂+ Cl₂
Bleaching powder     calcium hydroxide

1. From ethanol (ethyl alcohol)

(a) Oxidation of ethanol:

Chlorine oxidizes ethanol into ethanal.

CH₃CH₂OH+Cl₂ -Δ⟶ CH₃CHO+2HCl
ethanol                 ethanal

(b) Chlorination of ethanal:

Excess chlorine reacts with ethanal to give chloral.

CH₃CHO+3Cl₂ -Δ CCl₃CHO+ 3HCl
ethanal  choral(2,2,2-trichloroethanal)

(c) Hydrolysis of chloral:

The chloral is hydrolyzed with Ca(OH)₂ to form chloroform.

2CCl₃CHO+ Ca(OH)₂ -Δ 2CHCl₃+ (HCOO)₂Ca
choral ⟶ chloroform  calcium formate

2. From propanone (acetone)

(a) Chlorination of acetone

Acetone is chlorinated by passing excess chlorine through forming tri chloroacetone.

CH₃COCH₃+3Cl₂ -Δ⟶ CCl₃COCH₃+3HCl
acetone ⟶ tri chloroacetone

(b) Hydrolysis of tri chloroacetone

At last, tri chloroacetone is hydrolyzed with calcium hydroxide to form chloroform.

2CCl₃COCH₃+Ca(OH)₂ -Δ 2CHCl₃+ (CH₃COO)₂Ca
tri-chloroacetone ⟶ chloroform (trichloromethane)

Physical properties of Chloroform

  • It is a colorless mobile oily liquid.
  • Its boiling point is 61 ̊C and melting point is -60 ̊C.
  • It is heavier than water having an sp. gravity of 1.48.
  • It has a characteristic sweet smell and taste.
  • It is insoluble in water and soluble in almost all organic
  • solvents like benzene, ether, etc.
  • It is a good solvent for dissolving fats, oils, resins, waxes, etc.
  • The Vapour of chloroform causes temporary unconsciousness when taken in small amounts. So, it is used as an anesthetic drug. *Why it happen?

Chemical properties of chloroform

1. Action with air (Oxidation)

When chloroform is exposed to air in presence of sunlight, a highly poisonous phosgene gas (Carbonyl chloride) is formed.

2CHCl₃+ O₂  (sunlight) Hv 2COCl₂+ 2HCl
chloroform   phosgene gas

Therefore, the following precautions are taken while storing the chloroform.

  • It is always stored in a dark brown colored bottle to protect it from sunlight.
  • It is completely filled up in the bottle to keep out air.
  • A small amount (1%) of ethyl alcohol is added to the bottle of chloroform. The ethyl alcohol reacts with phosgene gas formed during storage to give non-toxic harmless diethyl carbonate.

phosgene gas react with ethyl alcohol

2. Reaction with silver powder

When chloroform is heated with silver powder then acetylene is formed.

2CHCl₃+ 6Ag -Δ⟶ H-C≡C-H +6AgCl
chloroform   acetylene

3. Reaction with conc.HNO₃(Nitration)

When chloroform is treated with conc. nitric acid then chloropicrin is formed which is used as an insecticide and war gas (Tear gas).

CHCl₃+ Conc.HNO₃  CCl₃-NO₂+ H₂O
chloroform (HO-NO₂)   chloropicrin (Trichloronitromethane)

4. Reaction with acetone

When chloroform is the heated presence of aqueous NaOH or KOH then with acetone in a crystalline solid of chloretone is formed which is used hypnotic drug (sleep-inducing).

Reaction with acetone and chloroform

5. Reduction

i)Acidic medium(Zn/HCl)

When chloroform is reduced in an acidic medium, methylene chloride is formed.

CHCl₃+Zn/HCl (C2H5OH +heat) -Δ  CH₂Cl₂ + HCl
chloroform  methylene chloride (dichloromethane)

ii)Basic medium(Zn/H₂O)

On reduction in neutral medium, methane is formed.

CHCl₃+Zn/H₂O -Δ CH₄+ 3HCl
chloroform ⟶ methane

Purity test of chloroform

6. Reaction with silver nitrate (AgNO₃)

i) With Pure Chloroform

Pure chloroform does not give white ppt. with AgNO₃ solution because the C-Cl bond in chloroform is a strong covalent bond and can not give Cl⁻ ion.

CHCl₃ + AgNO₃--->No white ppt.
(pure)

ii) With impure Chloroform

But, impure chloroform gives white ppt. of AgCl with AgNO₃ due to the presence of Cl⁻ ion after the oxidation of chloroform in the air.

CHCl₃+½O₂  COCl₂+ HCl
HCl+AgNO₃  AgCl↓ +HNO₃
                  (white ppt)

Read More: Haloarenes Notes Class 12 Chemistry

Important Question For Haloalkane and Chloroform

Haloalkanes Syllabus Class 12 NEB Chemistry
Fig: Haloalkanes whole syllabus/course content

Frequently Asked Questions

• What do you mean by haloalkanes?
Haloalkanes and haloarenes are hydrocarbons in which one or more hydrogen atoms have been replaced with halogen atoms.

• What haloalkanes called?

The haloalkanes, also known as alkyl halides, are a group of chemical compounds comprised of an alkane with one or more hydrogens replaced by a halogen atom (fluorine, chlorine, bromine, or iodine).

• What are haloalkanes with examples?

The haloalkanes are a group of chemical compounds comprised of an alkane with one or more hydrogens replaced by a halogen atom (fluorine, chlorine, bromine, or iodine). Example: Chloroethane (CH3CH2Cl).

• What are the uses of haloalkanes and Haloarenes?

Haloalkanes and haloarenes are used for many industrial and day to day purposes. They are used as flame retardants, propellants, solvents, pharmaceuticals, refrigerants, fire extinguishants, and many more. They are used as solvents for non-polar compounds.

• How many types of haloalkanes are there? 

Three different kinds
Halogenoalkanes are also called haloalkanes or alkyl halides. All halogenoalkanes contain a halogen atom - fluorine, chlorine, bromine or iodine - attached to an alkyl group. There are three different kinds of halogenoalkanes: Primary, secondary and tertiary.

• Why haloalkanes are more reactive than Haloarenes?

Greater the dipole moment, greater is the polarity and more is the reactivity. Thus, C−X bond of haloalkane is more polar than the C−X bond of haloarene. Hence, haloarenes are less reactive than haloalkanes.

• What is the difference between haloalkanes and Haloarenes?

When hydrogen atoms in aliphatic hydrocarbons(alkanes) are replaced by halogen atoms ,the compounds formed are known as haloalkanes. Similarly, when hydrogen atoms attached to benzene rings are replaced by halogen atoms the compounds that are formed are known as haloarenes.

• What is the haloalkanes formula?

CnH2n+2= Alkanes, CnH2n−2= Alkynes, CnH2n= Alkene, and CnH2n+1X is haloalkanes.

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