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163 
 
CHAPTER 13 
HYDROCARBON 
? Hydrocarbons are composed of Carbon and hydrogen. 
? The important fuels like Petrol, kerosene, coal gas, CNG, LPG etc. are all 
hydrocarbons or their mixture. 
Sources: 
 Petroleum and natural gas are the major sources of aliphatic hydrocarbon while coal is an 
important source of aromatic hydrocarbons. The oil trapped inside the rocks is known as 
petroleum. PETRA – ROCK, OLEUM – OIL. The oil in the petroleum field is covered with 
a gaseous mixture known as natural gas. The main constituents of the natural gas are 
methane, ethane, propane and butane. 
CLASSIFICATION OF HYDROCARBONS: 
                                  HYDROCARBON 
 
 
 
 Acyclic or Aliphatic                        Carbocyclic or Cyclic 
    ( Open chain)     
 
 
 Alicyclic  Aromatic 
Alkanes    Alkenes  Alkyne 
 
 
 Cycloalkanes   Cycloalkenes     Cycloalkynes 
Alkanes:- 
? Paraffins  
? General formula C
n
H
2n+2
 
? sp
3
 hybridisation  
? C–C bond length 1.15 4 A
0
  
? Chemically unreactive 
? Show chain, position and optical isomerism. 
? Heptane has 9 isomer, Octane 18 and Decane 75. 
Nomenclature: 
 
 
 
 
 
 
 
 
 
 
 
  
Page 2


163 
 
CHAPTER 13 
HYDROCARBON 
? Hydrocarbons are composed of Carbon and hydrogen. 
? The important fuels like Petrol, kerosene, coal gas, CNG, LPG etc. are all 
hydrocarbons or their mixture. 
Sources: 
 Petroleum and natural gas are the major sources of aliphatic hydrocarbon while coal is an 
important source of aromatic hydrocarbons. The oil trapped inside the rocks is known as 
petroleum. PETRA – ROCK, OLEUM – OIL. The oil in the petroleum field is covered with 
a gaseous mixture known as natural gas. The main constituents of the natural gas are 
methane, ethane, propane and butane. 
CLASSIFICATION OF HYDROCARBONS: 
                                  HYDROCARBON 
 
 
 
 Acyclic or Aliphatic                        Carbocyclic or Cyclic 
    ( Open chain)     
 
 
 Alicyclic  Aromatic 
Alkanes    Alkenes  Alkyne 
 
 
 Cycloalkanes   Cycloalkenes     Cycloalkynes 
Alkanes:- 
? Paraffins  
? General formula C
n
H
2n+2
 
? sp
3
 hybridisation  
? C–C bond length 1.15 4 A
0
  
? Chemically unreactive 
? Show chain, position and optical isomerism. 
? Heptane has 9 isomer, Octane 18 and Decane 75. 
Nomenclature: 
 
 
 
 
 
 
 
 
 
 
 
  
164 
 
 
Preparation:- 
? Wurtz reaction:- 
 
 
 
? Follow mainly free radical mechanism  
?  Useful in preparing an alkane containing 
  even number of carbon atoms 
?  Stepping up reaction 
Frankland reaction 
 
 
?From Grignard reagent (RMgX) 
 
 
 
 
?From unsaturated hydrocarbons:- 
     Sabatier-Senderens reduction 
 
 
 
 
4. From carboxylic acids- 
 Decarboxylation.-   
   
 Kolbe’s electrolytic method- 
   
 
 
? Physical Properties:- 
(1) Nature:- Non-Polar due to covalent nature of C—C bond and C—H bond. C—
C bond enrgy = 83 kj/mole and C—H bond energy = 99 kj/mole. 
C
1
—C
4
 = gases,  C
5
—C
17
 = colourless odourless liquid and > C
17 
=  Solid. 
(2) Solubility:- Like dissolve like 
Viz, Polar compounds dissolve in polar solvent and Non-Polar compound dissolve in 
non polar solvent. 
(3) Boiling point:- Low boiling point due to non polar in nature.  
Dry
3 2 3 2 2 3
ether
2CH CH Br 2Na CH CH CH CH 2NaBr
 
2
R X + Zn + R x R – R + ZnX
 
RMgX+HOH RH+Mg(OH)X
 
RMgX+R'OH RH+Mg(OR')X
 
2
RMgX+R'NH RH+Mg(NHR')X
 
Ni/
2 2 3
R C CH H R CH CH
 
Ni/
2 2 2 3
R CH CH H R CH CH
 
Page 3


163 
 
CHAPTER 13 
HYDROCARBON 
? Hydrocarbons are composed of Carbon and hydrogen. 
? The important fuels like Petrol, kerosene, coal gas, CNG, LPG etc. are all 
hydrocarbons or their mixture. 
Sources: 
 Petroleum and natural gas are the major sources of aliphatic hydrocarbon while coal is an 
important source of aromatic hydrocarbons. The oil trapped inside the rocks is known as 
petroleum. PETRA – ROCK, OLEUM – OIL. The oil in the petroleum field is covered with 
a gaseous mixture known as natural gas. The main constituents of the natural gas are 
methane, ethane, propane and butane. 
CLASSIFICATION OF HYDROCARBONS: 
                                  HYDROCARBON 
 
 
 
 Acyclic or Aliphatic                        Carbocyclic or Cyclic 
    ( Open chain)     
 
 
 Alicyclic  Aromatic 
Alkanes    Alkenes  Alkyne 
 
 
 Cycloalkanes   Cycloalkenes     Cycloalkynes 
Alkanes:- 
? Paraffins  
? General formula C
n
H
2n+2
 
? sp
3
 hybridisation  
? C–C bond length 1.15 4 A
0
  
? Chemically unreactive 
? Show chain, position and optical isomerism. 
? Heptane has 9 isomer, Octane 18 and Decane 75. 
Nomenclature: 
 
 
 
 
 
 
 
 
 
 
 
  
164 
 
 
Preparation:- 
? Wurtz reaction:- 
 
 
 
? Follow mainly free radical mechanism  
?  Useful in preparing an alkane containing 
  even number of carbon atoms 
?  Stepping up reaction 
Frankland reaction 
 
 
?From Grignard reagent (RMgX) 
 
 
 
 
?From unsaturated hydrocarbons:- 
     Sabatier-Senderens reduction 
 
 
 
 
4. From carboxylic acids- 
 Decarboxylation.-   
   
 Kolbe’s electrolytic method- 
   
 
 
? Physical Properties:- 
(1) Nature:- Non-Polar due to covalent nature of C—C bond and C—H bond. C—
C bond enrgy = 83 kj/mole and C—H bond energy = 99 kj/mole. 
C
1
—C
4
 = gases,  C
5
—C
17
 = colourless odourless liquid and > C
17 
=  Solid. 
(2) Solubility:- Like dissolve like 
Viz, Polar compounds dissolve in polar solvent and Non-Polar compound dissolve in 
non polar solvent. 
(3) Boiling point:- Low boiling point due to non polar in nature.  
Dry
3 2 3 2 2 3
ether
2CH CH Br 2Na CH CH CH CH 2NaBr
 
2
R X + Zn + R x R – R + ZnX
 
RMgX+HOH RH+Mg(OH)X
 
RMgX+R'OH RH+Mg(OR')X
 
2
RMgX+R'NH RH+Mg(NHR')X
 
Ni/
2 2 3
R C CH H R CH CH
 
Ni/
2 2 2 3
R CH CH H R CH CH
 
165 
 
The molecules are held together only by weak Van der Waalls’ forces. 
Since we known that the magnitude of Van der Waalls’ forces is directly 
proportional to the molecular size. Therefore, the boiling point increases with 
increase the molecular size i.e. with increase in number of carbon atoms.  
Noted:- the boiling points of the branched chain Alkanes are less than the straight 
chain isomers.  
            This is due to the fact that branching of the chain makes the molecule more 
compact and thereby decreases the surface aria and consequently, the magnitudes of 
Van der Waalls’ forces also decrease.  
 
 
 
(4) Melting point:- the melting point of Alkanes do not show 
 regular variation with increase in molecular size. The Alkanes with even number of 
carbon atoms having higher melting point as  compared to those Alkanes having 
immediately next lower and immediately next higher odd number of carbon atoms. 
 
? Chemical properties 
? Combustion:- 
 
? Oxidation:- 
 
 
 
 
 
? Substitution:- 
? Halogenation:- 
 
                    CH
4
   +  Cl
2
                         CH
3
Cl   +   HCl 
 
       CH
3
Cl                    CH
2
Cl
2
                       CHCl
3
                     CCl
4 
Noted:- Iodination is a reversible reaction. So it is carried out by heating alkane in 
the presence of some oxidizing agent like iodic acid (HIO
3
) or nitric acid (HNO
3
) or 
mercuric oxide (HgO) which oxidizes HI formed during the reaction. 
 
                   CH
4
   +  I
2
                               CH
3
I  +   HI 
 
                  5HI  +  HIO
3
                          3H
2
O  +  3I
2 
 
                  2HI  +  2HNO
3
                      2H
2
O  +  I
2
    +  2NO
2 
 
Noted:- Fluorination of alkane takes place explosively resulting even in the rupture 
of C—C bond in higher alkanes. 
4 2 2 2
CH 2O CO 2H O
H 217.0 K cal/mole
 
Cu
4 2 3
573 K
CH O 2CH OH
 
23
Mo O
4 2 2
Methanal
CH O HCHO H O
 
CH
3
CH
2
CH
2
CH
2
CH
3
n-pentane
boiling point = 309 K
 
H
3
C — CH — CH
2
CH
3
CH
3
iso-pentane
boiling point = 301 K
 
H
3
C — C — CH
3
CH
3
CH
3
neo-pentane
boiling point = 282.5 K
 
UV 
UV UV 
UV 
Heat 
 H
e
a
t 
 
Page 4


163 
 
CHAPTER 13 
HYDROCARBON 
? Hydrocarbons are composed of Carbon and hydrogen. 
? The important fuels like Petrol, kerosene, coal gas, CNG, LPG etc. are all 
hydrocarbons or their mixture. 
Sources: 
 Petroleum and natural gas are the major sources of aliphatic hydrocarbon while coal is an 
important source of aromatic hydrocarbons. The oil trapped inside the rocks is known as 
petroleum. PETRA – ROCK, OLEUM – OIL. The oil in the petroleum field is covered with 
a gaseous mixture known as natural gas. The main constituents of the natural gas are 
methane, ethane, propane and butane. 
CLASSIFICATION OF HYDROCARBONS: 
                                  HYDROCARBON 
 
 
 
 Acyclic or Aliphatic                        Carbocyclic or Cyclic 
    ( Open chain)     
 
 
 Alicyclic  Aromatic 
Alkanes    Alkenes  Alkyne 
 
 
 Cycloalkanes   Cycloalkenes     Cycloalkynes 
Alkanes:- 
? Paraffins  
? General formula C
n
H
2n+2
 
? sp
3
 hybridisation  
? C–C bond length 1.15 4 A
0
  
? Chemically unreactive 
? Show chain, position and optical isomerism. 
? Heptane has 9 isomer, Octane 18 and Decane 75. 
Nomenclature: 
 
 
 
 
 
 
 
 
 
 
 
  
164 
 
 
Preparation:- 
? Wurtz reaction:- 
 
 
 
? Follow mainly free radical mechanism  
?  Useful in preparing an alkane containing 
  even number of carbon atoms 
?  Stepping up reaction 
Frankland reaction 
 
 
?From Grignard reagent (RMgX) 
 
 
 
 
?From unsaturated hydrocarbons:- 
     Sabatier-Senderens reduction 
 
 
 
 
4. From carboxylic acids- 
 Decarboxylation.-   
   
 Kolbe’s electrolytic method- 
   
 
 
? Physical Properties:- 
(1) Nature:- Non-Polar due to covalent nature of C—C bond and C—H bond. C—
C bond enrgy = 83 kj/mole and C—H bond energy = 99 kj/mole. 
C
1
—C
4
 = gases,  C
5
—C
17
 = colourless odourless liquid and > C
17 
=  Solid. 
(2) Solubility:- Like dissolve like 
Viz, Polar compounds dissolve in polar solvent and Non-Polar compound dissolve in 
non polar solvent. 
(3) Boiling point:- Low boiling point due to non polar in nature.  
Dry
3 2 3 2 2 3
ether
2CH CH Br 2Na CH CH CH CH 2NaBr
 
2
R X + Zn + R x R – R + ZnX
 
RMgX+HOH RH+Mg(OH)X
 
RMgX+R'OH RH+Mg(OR')X
 
2
RMgX+R'NH RH+Mg(NHR')X
 
Ni/
2 2 3
R C CH H R CH CH
 
Ni/
2 2 2 3
R CH CH H R CH CH
 
165 
 
The molecules are held together only by weak Van der Waalls’ forces. 
Since we known that the magnitude of Van der Waalls’ forces is directly 
proportional to the molecular size. Therefore, the boiling point increases with 
increase the molecular size i.e. with increase in number of carbon atoms.  
Noted:- the boiling points of the branched chain Alkanes are less than the straight 
chain isomers.  
            This is due to the fact that branching of the chain makes the molecule more 
compact and thereby decreases the surface aria and consequently, the magnitudes of 
Van der Waalls’ forces also decrease.  
 
 
 
(4) Melting point:- the melting point of Alkanes do not show 
 regular variation with increase in molecular size. The Alkanes with even number of 
carbon atoms having higher melting point as  compared to those Alkanes having 
immediately next lower and immediately next higher odd number of carbon atoms. 
 
? Chemical properties 
? Combustion:- 
 
? Oxidation:- 
 
 
 
 
 
? Substitution:- 
? Halogenation:- 
 
                    CH
4
   +  Cl
2
                         CH
3
Cl   +   HCl 
 
       CH
3
Cl                    CH
2
Cl
2
                       CHCl
3
                     CCl
4 
Noted:- Iodination is a reversible reaction. So it is carried out by heating alkane in 
the presence of some oxidizing agent like iodic acid (HIO
3
) or nitric acid (HNO
3
) or 
mercuric oxide (HgO) which oxidizes HI formed during the reaction. 
 
                   CH
4
   +  I
2
                               CH
3
I  +   HI 
 
                  5HI  +  HIO
3
                          3H
2
O  +  3I
2 
 
                  2HI  +  2HNO
3
                      2H
2
O  +  I
2
    +  2NO
2 
 
Noted:- Fluorination of alkane takes place explosively resulting even in the rupture 
of C—C bond in higher alkanes. 
4 2 2 2
CH 2O CO 2H O
H 217.0 K cal/mole
 
Cu
4 2 3
573 K
CH O 2CH OH
 
23
Mo O
4 2 2
Methanal
CH O HCHO H O
 
CH
3
CH
2
CH
2
CH
2
CH
3
n-pentane
boiling point = 309 K
 
H
3
C — CH — CH
2
CH
3
CH
3
iso-pentane
boiling point = 301 K
 
H
3
C — C — CH
3
CH
3
CH
3
neo-pentane
boiling point = 282.5 K
 
UV 
UV UV 
UV 
Heat 
 H
e
a
t 
 
166 
 
 Features of Halogenations:- 
(i) The reactivity of Halogens:-    F
2
 > Cl
2
 > Br
2
 > I
2
. 
(ii) The rate of replacement of Hydrogens of alkanes is: 
                                         3° > 2° > 1° 
 
             
 
 
 
 
 
 
 
 
 
 
 
 
Mechanism:- halogenations reaction take place by free radical mechanism.  The 
reaction proceeds in the following steps: 
Initiation  
(i) Chain initiation step:-  
 
 
 
(ii) Chain Propagation step:- 
 
 
 
 
(iii) Chain Termination step:- 
 
 
 
 
 
 
? Nitration:-  
? The reaction takes places by free radicals mechanism at high temp (450
0
C). 
? At high temp C—C bond is also broken so that mixture of nitroalkanes is obtained.  
 
 
 
 
Cl — Cl
h
2Cl
 
3 3 3 3
CH CH CH CH
 
2
Cl Cl Cl
 
33
CH Cl CH Cl
 
CH
3
CH
2
CH
2
CH
3
CH
3
CH
2
CH
2
CH
2
Cl + CH
3
CH
2
CHCH
3
hv
Cl
2
Cl
n - Butane
 
1
°
CH - CH
3
Cl
2
C
CH - CH
2
 Cl
CH
3
CH
3
CH
3
CH
3
Cl
CH
3
CH
3
1
°
3
°
1
° CH
3
36%
64%
Isobutane
(3°)
(1°)
h
 
43
CH Cl CH HCl
 
3 2 3
CH Cl CH Cl Cl
 
CH
3
CH
2
CH
3
450°C
Conc. HNO
3
 
CH
3
CH
2
CH
2
NO
2
 + CH
3
CHCH
3
 + CH
3
CH
2
NO
2
+ CH
3
NO
2
NO
2
 
25% 40% 10% 25% 
Page 5


163 
 
CHAPTER 13 
HYDROCARBON 
? Hydrocarbons are composed of Carbon and hydrogen. 
? The important fuels like Petrol, kerosene, coal gas, CNG, LPG etc. are all 
hydrocarbons or their mixture. 
Sources: 
 Petroleum and natural gas are the major sources of aliphatic hydrocarbon while coal is an 
important source of aromatic hydrocarbons. The oil trapped inside the rocks is known as 
petroleum. PETRA – ROCK, OLEUM – OIL. The oil in the petroleum field is covered with 
a gaseous mixture known as natural gas. The main constituents of the natural gas are 
methane, ethane, propane and butane. 
CLASSIFICATION OF HYDROCARBONS: 
                                  HYDROCARBON 
 
 
 
 Acyclic or Aliphatic                        Carbocyclic or Cyclic 
    ( Open chain)     
 
 
 Alicyclic  Aromatic 
Alkanes    Alkenes  Alkyne 
 
 
 Cycloalkanes   Cycloalkenes     Cycloalkynes 
Alkanes:- 
? Paraffins  
? General formula C
n
H
2n+2
 
? sp
3
 hybridisation  
? C–C bond length 1.15 4 A
0
  
? Chemically unreactive 
? Show chain, position and optical isomerism. 
? Heptane has 9 isomer, Octane 18 and Decane 75. 
Nomenclature: 
 
 
 
 
 
 
 
 
 
 
 
  
164 
 
 
Preparation:- 
? Wurtz reaction:- 
 
 
 
? Follow mainly free radical mechanism  
?  Useful in preparing an alkane containing 
  even number of carbon atoms 
?  Stepping up reaction 
Frankland reaction 
 
 
?From Grignard reagent (RMgX) 
 
 
 
 
?From unsaturated hydrocarbons:- 
     Sabatier-Senderens reduction 
 
 
 
 
4. From carboxylic acids- 
 Decarboxylation.-   
   
 Kolbe’s electrolytic method- 
   
 
 
? Physical Properties:- 
(1) Nature:- Non-Polar due to covalent nature of C—C bond and C—H bond. C—
C bond enrgy = 83 kj/mole and C—H bond energy = 99 kj/mole. 
C
1
—C
4
 = gases,  C
5
—C
17
 = colourless odourless liquid and > C
17 
=  Solid. 
(2) Solubility:- Like dissolve like 
Viz, Polar compounds dissolve in polar solvent and Non-Polar compound dissolve in 
non polar solvent. 
(3) Boiling point:- Low boiling point due to non polar in nature.  
Dry
3 2 3 2 2 3
ether
2CH CH Br 2Na CH CH CH CH 2NaBr
 
2
R X + Zn + R x R – R + ZnX
 
RMgX+HOH RH+Mg(OH)X
 
RMgX+R'OH RH+Mg(OR')X
 
2
RMgX+R'NH RH+Mg(NHR')X
 
Ni/
2 2 3
R C CH H R CH CH
 
Ni/
2 2 2 3
R CH CH H R CH CH
 
165 
 
The molecules are held together only by weak Van der Waalls’ forces. 
Since we known that the magnitude of Van der Waalls’ forces is directly 
proportional to the molecular size. Therefore, the boiling point increases with 
increase the molecular size i.e. with increase in number of carbon atoms.  
Noted:- the boiling points of the branched chain Alkanes are less than the straight 
chain isomers.  
            This is due to the fact that branching of the chain makes the molecule more 
compact and thereby decreases the surface aria and consequently, the magnitudes of 
Van der Waalls’ forces also decrease.  
 
 
 
(4) Melting point:- the melting point of Alkanes do not show 
 regular variation with increase in molecular size. The Alkanes with even number of 
carbon atoms having higher melting point as  compared to those Alkanes having 
immediately next lower and immediately next higher odd number of carbon atoms. 
 
? Chemical properties 
? Combustion:- 
 
? Oxidation:- 
 
 
 
 
 
? Substitution:- 
? Halogenation:- 
 
                    CH
4
   +  Cl
2
                         CH
3
Cl   +   HCl 
 
       CH
3
Cl                    CH
2
Cl
2
                       CHCl
3
                     CCl
4 
Noted:- Iodination is a reversible reaction. So it is carried out by heating alkane in 
the presence of some oxidizing agent like iodic acid (HIO
3
) or nitric acid (HNO
3
) or 
mercuric oxide (HgO) which oxidizes HI formed during the reaction. 
 
                   CH
4
   +  I
2
                               CH
3
I  +   HI 
 
                  5HI  +  HIO
3
                          3H
2
O  +  3I
2 
 
                  2HI  +  2HNO
3
                      2H
2
O  +  I
2
    +  2NO
2 
 
Noted:- Fluorination of alkane takes place explosively resulting even in the rupture 
of C—C bond in higher alkanes. 
4 2 2 2
CH 2O CO 2H O
H 217.0 K cal/mole
 
Cu
4 2 3
573 K
CH O 2CH OH
 
23
Mo O
4 2 2
Methanal
CH O HCHO H O
 
CH
3
CH
2
CH
2
CH
2
CH
3
n-pentane
boiling point = 309 K
 
H
3
C — CH — CH
2
CH
3
CH
3
iso-pentane
boiling point = 301 K
 
H
3
C — C — CH
3
CH
3
CH
3
neo-pentane
boiling point = 282.5 K
 
UV 
UV UV 
UV 
Heat 
 H
e
a
t 
 
166 
 
 Features of Halogenations:- 
(i) The reactivity of Halogens:-    F
2
 > Cl
2
 > Br
2
 > I
2
. 
(ii) The rate of replacement of Hydrogens of alkanes is: 
                                         3° > 2° > 1° 
 
             
 
 
 
 
 
 
 
 
 
 
 
 
Mechanism:- halogenations reaction take place by free radical mechanism.  The 
reaction proceeds in the following steps: 
Initiation  
(i) Chain initiation step:-  
 
 
 
(ii) Chain Propagation step:- 
 
 
 
 
(iii) Chain Termination step:- 
 
 
 
 
 
 
? Nitration:-  
? The reaction takes places by free radicals mechanism at high temp (450
0
C). 
? At high temp C—C bond is also broken so that mixture of nitroalkanes is obtained.  
 
 
 
 
Cl — Cl
h
2Cl
 
3 3 3 3
CH CH CH CH
 
2
Cl Cl Cl
 
33
CH Cl CH Cl
 
CH
3
CH
2
CH
2
CH
3
CH
3
CH
2
CH
2
CH
2
Cl + CH
3
CH
2
CHCH
3
hv
Cl
2
Cl
n - Butane
 
1
°
CH - CH
3
Cl
2
C
CH - CH
2
 Cl
CH
3
CH
3
CH
3
CH
3
Cl
CH
3
CH
3
1
°
3
°
1
° CH
3
36%
64%
Isobutane
(3°)
(1°)
h
 
43
CH Cl CH HCl
 
3 2 3
CH Cl CH Cl Cl
 
CH
3
CH
2
CH
3
450°C
Conc. HNO
3
 
CH
3
CH
2
CH
2
NO
2
 + CH
3
CHCH
3
 + CH
3
CH
2
NO
2
+ CH
3
NO
2
NO
2
 
25% 40% 10% 25% 
167 
 
 
 
 
 
 
  
 
? Sulphonation:- replacement of hydrogen atom of alkane by –SO
3
H group. 
 
 
 
 
 
 
 
 
 
 
? Isomerization:- 
 
 
 
 
?Aromatization:- 
 
 
 
 
This method is also called dehydrogenation or hydroforming  
Similarly, heptane gives toluene, n-Octane give o-xylene and 2, methyl heptane give 
m-xylene. 
?Thermal decomposition or Pyrolysis or cracking or Fragmentation: - when higher 
alkanes are heated at high temp (about 700-800k) in the presence of alumina or silica 
catalysts, the alkanes break down to lower alkanes and alkenes.  
    CH
3
-CH
2
-CH
3
                        CH
3
-CH-CH
2
  +  CH
3
-CH
3
   +   C
2
H
4
    +   CH
4
          
? Action of steam:-   catalyst:   nickel, alumina Al
2
O
3
 
  1000 
0
C 
             CH
4
  +  H
2
O(Steam)                          CO  +  3H
2
 
This reaction is used for the industrial preparation of hydrogen from natural gas. 
8. Isomerisation:- 
The reaction occurs as: 
                            HO-NO2                                   HO
o
  +  
o
NO2 
                            
                             RH  +  
0
OH                           R
o 
  +  HOH 
                             R
o   
  +  
o
NO2                         RNO2 
450
0
C 
Homolytic fission 
CH
3
CH
3
CH
3
CH CH
3
SO
3
H
CH
3
CH
3
C
oleum
isobutane tert butyl sulphonic acid
 
The reaction occurs as: 
                            HO-SO3                                   HO
o
  +  
o
SO3H 
                            
                             RH  +  
0
OH                           R
o 
  +  HOH 
                             R
o   
  +  
o
SO2H                         RSO 2H 
450
0
C 
Homolytic fission 
H
3
C(CH
2
)
3
CH
3
AlCl
3
 / HCl
H
3
CCHCH
2
CH
3
CH
3
n-Pentane
2-Methyl butane
 
H
3
C(CH
2
)
4
CH
3
Cr
2
O
3
Hexane
773 K
10-20 atm
Benzene
 
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FAQs on Chemistry : Hydrocarbon - Class 11

1. What is a hydrocarbon?
Ans. A hydrocarbon is a compound composed of hydrogen and carbon atoms. It is a type of organic compound and is the simplest form of organic compounds. Hydrocarbons can be classified into two main types: saturated hydrocarbons (alkanes) and unsaturated hydrocarbons (alkenes and alkynes).
2. How are hydrocarbons classified?
Ans. Hydrocarbons are classified based on their structure and the type of bonds present between carbon atoms. Saturated hydrocarbons, also known as alkanes, have single bonds between carbon atoms and are characterized by the general formula CnH2n+2. Unsaturated hydrocarbons, such as alkenes and alkynes, have double or triple bonds between carbon atoms.
3. What are the properties of hydrocarbons?
Ans. The properties of hydrocarbons depend on their structure and the type of bonds present. Generally, hydrocarbons are nonpolar compounds with low melting and boiling points. They are insoluble in water but soluble in nonpolar solvents. Hydrocarbons are flammable and are used as fuels due to their high energy content.
4. How are hydrocarbons used in everyday life?
Ans. Hydrocarbons play a crucial role in our everyday life. They are the main components of fossil fuels such as gasoline, diesel, and natural gas, which are used for transportation and heating. Hydrocarbons are also used as raw materials in the production of plastics, polymers, solvents, lubricants, and various other chemicals.
5. What are the environmental impacts of hydrocarbons?
Ans. The combustion of hydrocarbons releases carbon dioxide, a greenhouse gas, which contributes to climate change. Hydrocarbon spills can contaminate soil and water, causing harm to ecosystems. Additionally, the extraction and processing of hydrocarbons can have negative impacts on the environment, including habitat destruction and air and water pollution.
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