CHEMISTRY
Hydrocarbons
yarocarbons are compounds which contain only carbon and hydrogen
Example: Methane (CH,)
Ethane(CH,-CH,)
Benzene (CH)
supposed to be derived froom
nese are fundamental organic compounds. All other organic compounds
are
hydrocarbons.
Hydrocarbons
open chain compounds closed chain compounds
Aromatic
saturated unsaturated
Alicyclic (characteristc smell
(only single bond (double bond or majority have benzene
between carbon triple bond between ring)
atoms) carbon atoms) saturated unsaturated
Benzenoid Non
alkanes eg. Benzene benzenoid
alkene alkyne cycloalkene cycloalkyne eg pyridine,
Eg. CH-CH (double bond) (triple bond) furan
eg. CH-CH) eg CH= CH
Toluine
CH3
O
Nomenclature of alkanes
Aliphatic compounds
Formulae Common name IUPAC name
Open chain compounds & alicyclic compounds are
collectively known as aliphatic compounds.
CH, Methane Methane
Openchain + Alicyclic > Aliphatic
CH-CH Ethane Ethane
(together)
ALKANES (Paraffins) CH,-CH-CH Propane Propane
with only single bond
Open chain hydrocarbon
between carbon atoms is called alkanes
CH-CH-CH,-CH, n-Butane Butane
General formula: C,H22 CH-CH-CH3
Iso-Butane 2-Methyl propane
Eg CH, (Methane) CH3
CH-CH, (Ethane) CH CHCHCH-CH, n-pentane pentane
CH-CHCH, (Propane) CH-CH - CH-CH3
lso-pentane 2-Methyl butane
These are also known as paraffins due to theirlow CH
reactivity (paraffins means low affinity)
In alkane, the carbon-carbon bond length is 154 CH3
pm and that of C- H bond is 112 pm CH-C-CH Neo-pentane 22-Diethyl propane
H 112pm
154pm CH
c-C
, Preparation of Alkanes b. By Kolbe's electrolysis
Alkanes can be produced by the electrolysis of
From unsaturated hydrocarbons.
sodium or potassium salts of carboxylic acids.
(From alkenes and alkynes)
Unsaturated hydrocarbons can be converted This is known as Kolle's electrolysis.
into alkanes by adding hydrogen in presence 2CH,COONa + 2H,O cirolyis
of catalyst like nickel, platinum, palladium Sodiuniethanoate
This process of addition of hydrogen is called
CH-CH, +2C0, +2NaOH+H2
hydrogenation. Ethane
CH =CH+H, t o PCH -CH MECHANISM
Ethene Ethane
CH,COONa->CH, -CO0 +Na
CH-C CH+2H Ni Ptor PdCH -CH2 -CH3
Propyne Propane Anode
. Fromalkyl halides
There are 3 methods for conversion of CH-CO0>CH,-COO+le"
alkylhalides to alkanes. CH-CO 0->CH3 +CO2
a. By reduction
CH +CH>CH3-CH
Alkyl halides are reduced to alkanes using Zn/ Cathode
HCI.
H,0+le >OH+H
CH-CH2 -Br+ Zn-HCCH,-CH, +HBr
Ethylbromide Nascent or
hydrogenZn-Cu/HC)
Ethane
H+HH2
Methane cannot be prepared by Kolle's electrolysis.
b. By Wurtz reaction
When alkyl halides are treated with metallic Iv. Using Grignard reagent
sodium in dry ether higher alkanes are formed Alkyl magnesium halides are known as
Dryether grignard reagent.
CH-CH-Cl+2Na
Ethylchlonde
+C1 -CH, -CH
R-X+ Mg R-MgX
Alkylhalide AlkylMagnesium halide
CH-CH2 -CH2 -CH +2NaCl
Butane
C. By Frankland reaction Eg: CH-CH2 - Br + Mg CH, -CH2 -
Mg Br
Ethyl magnesium bromide
Alkanes can be prepared by the reaction of alkyl Grignard reagent on hydrolysis form alkanes
hatide with metallic zinc.
CH-CH2 -MgBr+H,Oydrolysis
CH-CH, -Br+ Zn+Br-CH2-CH, Ethylmagnesiunbromide
Ethylbromide OH
CH3-CH2 -CH2 -CH, +ZnBr
Butane
CH,-CH++Mg, Br
III. From carboxylic acids Physical properties of Alkanes
In alkanes, the intermolecular forces are weak
Carboxylic acids can be converted to alkanes dispersion forces. Due to these weak forces alkanes
by 2 methods.
with C, to C, are gases,
By decarboxylation using sodalime
C to C,are liquids,
[NaOH+CaO]
When sodium or potassium salt of carboxylic C and above are solids
acid on heating with soda lime, alkanes are The boiling point of alkanes regularly increases
formed. with molecular mass. This can be explained on
the basis of vanderwaal forces. As carbon
CH-CH, -COONa + NaOHCa0
number increases, molecular size increases and
Sodium propanoate
surface area increases.
CH-CHy+NajCO3
Ethane Therefore the magnitude of vanderwaal forces
increases.
Here, carbon no decreases by one unit. This
process is called "STEPPING DOWN". Among isomeric alkanes, the branched chain
isomers have relatively low boiling point.
Hydrocarbons
yarocarbons are compounds which contain only carbon and hydrogen
Example: Methane (CH,)
Ethane(CH,-CH,)
Benzene (CH)
supposed to be derived froom
nese are fundamental organic compounds. All other organic compounds
are
hydrocarbons.
Hydrocarbons
open chain compounds closed chain compounds
Aromatic
saturated unsaturated
Alicyclic (characteristc smell
(only single bond (double bond or majority have benzene
between carbon triple bond between ring)
atoms) carbon atoms) saturated unsaturated
Benzenoid Non
alkanes eg. Benzene benzenoid
alkene alkyne cycloalkene cycloalkyne eg pyridine,
Eg. CH-CH (double bond) (triple bond) furan
eg. CH-CH) eg CH= CH
Toluine
CH3
O
Nomenclature of alkanes
Aliphatic compounds
Formulae Common name IUPAC name
Open chain compounds & alicyclic compounds are
collectively known as aliphatic compounds.
CH, Methane Methane
Openchain + Alicyclic > Aliphatic
CH-CH Ethane Ethane
(together)
ALKANES (Paraffins) CH,-CH-CH Propane Propane
with only single bond
Open chain hydrocarbon
between carbon atoms is called alkanes
CH-CH-CH,-CH, n-Butane Butane
General formula: C,H22 CH-CH-CH3
Iso-Butane 2-Methyl propane
Eg CH, (Methane) CH3
CH-CH, (Ethane) CH CHCHCH-CH, n-pentane pentane
CH-CHCH, (Propane) CH-CH - CH-CH3
lso-pentane 2-Methyl butane
These are also known as paraffins due to theirlow CH
reactivity (paraffins means low affinity)
In alkane, the carbon-carbon bond length is 154 CH3
pm and that of C- H bond is 112 pm CH-C-CH Neo-pentane 22-Diethyl propane
H 112pm
154pm CH
c-C
, Preparation of Alkanes b. By Kolbe's electrolysis
Alkanes can be produced by the electrolysis of
From unsaturated hydrocarbons.
sodium or potassium salts of carboxylic acids.
(From alkenes and alkynes)
Unsaturated hydrocarbons can be converted This is known as Kolle's electrolysis.
into alkanes by adding hydrogen in presence 2CH,COONa + 2H,O cirolyis
of catalyst like nickel, platinum, palladium Sodiuniethanoate
This process of addition of hydrogen is called
CH-CH, +2C0, +2NaOH+H2
hydrogenation. Ethane
CH =CH+H, t o PCH -CH MECHANISM
Ethene Ethane
CH,COONa->CH, -CO0 +Na
CH-C CH+2H Ni Ptor PdCH -CH2 -CH3
Propyne Propane Anode
. Fromalkyl halides
There are 3 methods for conversion of CH-CO0>CH,-COO+le"
alkylhalides to alkanes. CH-CO 0->CH3 +CO2
a. By reduction
CH +CH>CH3-CH
Alkyl halides are reduced to alkanes using Zn/ Cathode
HCI.
H,0+le >OH+H
CH-CH2 -Br+ Zn-HCCH,-CH, +HBr
Ethylbromide Nascent or
hydrogenZn-Cu/HC)
Ethane
H+HH2
Methane cannot be prepared by Kolle's electrolysis.
b. By Wurtz reaction
When alkyl halides are treated with metallic Iv. Using Grignard reagent
sodium in dry ether higher alkanes are formed Alkyl magnesium halides are known as
Dryether grignard reagent.
CH-CH-Cl+2Na
Ethylchlonde
+C1 -CH, -CH
R-X+ Mg R-MgX
Alkylhalide AlkylMagnesium halide
CH-CH2 -CH2 -CH +2NaCl
Butane
C. By Frankland reaction Eg: CH-CH2 - Br + Mg CH, -CH2 -
Mg Br
Ethyl magnesium bromide
Alkanes can be prepared by the reaction of alkyl Grignard reagent on hydrolysis form alkanes
hatide with metallic zinc.
CH-CH2 -MgBr+H,Oydrolysis
CH-CH, -Br+ Zn+Br-CH2-CH, Ethylmagnesiunbromide
Ethylbromide OH
CH3-CH2 -CH2 -CH, +ZnBr
Butane
CH,-CH++Mg, Br
III. From carboxylic acids Physical properties of Alkanes
In alkanes, the intermolecular forces are weak
Carboxylic acids can be converted to alkanes dispersion forces. Due to these weak forces alkanes
by 2 methods.
with C, to C, are gases,
By decarboxylation using sodalime
C to C,are liquids,
[NaOH+CaO]
When sodium or potassium salt of carboxylic C and above are solids
acid on heating with soda lime, alkanes are The boiling point of alkanes regularly increases
formed. with molecular mass. This can be explained on
the basis of vanderwaal forces. As carbon
CH-CH, -COONa + NaOHCa0
number increases, molecular size increases and
Sodium propanoate
surface area increases.
CH-CHy+NajCO3
Ethane Therefore the magnitude of vanderwaal forces
increases.
Here, carbon no decreases by one unit. This
process is called "STEPPING DOWN". Among isomeric alkanes, the branched chain
isomers have relatively low boiling point.
