Physical property of alkane PPT Chemistry Class 12

 Page 1


SAME TREND AND REASON FOR BOTH ?ANES? AND ?ENES?
ALL NON POLAR AND HAVE WEAK VAN DER WALLS FORCES
Melting point general increase with molecular mass
the trend is not as regular as that for boiling point.
Solubility alkanes are non-polar so are immiscible with water
they are soluble in most organic solvents.
PHYSICAL PROPERTIES OF 
ALKANES and ALKENES
Page 2


SAME TREND AND REASON FOR BOTH ?ANES? AND ?ENES?
ALL NON POLAR AND HAVE WEAK VAN DER WALLS FORCES
Melting point general increase with molecular mass
the trend is not as regular as that for boiling point.
Solubility alkanes are non-polar so are immiscible with water
they are soluble in most organic solvents.
PHYSICAL PROPERTIES OF 
ALKANES and ALKENES
Introduction - fairly unreactive
2 REACTIONS:
1) Combustion CH
4
(g)    +    2O
2
(g)      ——>    CO
2
(g)   +    2H
2
O(l)
2) Substitution (FREE RADICAL)
Equation:    CH
4
(g)   +   Cl
2
(g)    (uv light)——>   HCl(g)    +   CH
3
Cl(g)
chloromethane
_______________________Free Radical Substitution__________________
Initiation Cl
2
——>   2Cl• RADICALS CREATED
Propagation Cl• +  CH
4
——>    CH
3
• +   HCl RADICALS USED
Cl
2
+  CH
3
•  ——>   CH
3
Cl +   Cl•
Termination Cl• +  Cl• ——>    Cl
2
RADICALS REMOVED
Cl• +  CH
3
• ——>    CH
3
Cl
CH
3
• +  CH
3
• ——>    C
2
H
6
CHEMICAL PROPERTIES OF ALKANES
Page 3


SAME TREND AND REASON FOR BOTH ?ANES? AND ?ENES?
ALL NON POLAR AND HAVE WEAK VAN DER WALLS FORCES
Melting point general increase with molecular mass
the trend is not as regular as that for boiling point.
Solubility alkanes are non-polar so are immiscible with water
they are soluble in most organic solvents.
PHYSICAL PROPERTIES OF 
ALKANES and ALKENES
Introduction - fairly unreactive
2 REACTIONS:
1) Combustion CH
4
(g)    +    2O
2
(g)      ——>    CO
2
(g)   +    2H
2
O(l)
2) Substitution (FREE RADICAL)
Equation:    CH
4
(g)   +   Cl
2
(g)    (uv light)——>   HCl(g)    +   CH
3
Cl(g)
chloromethane
_______________________Free Radical Substitution__________________
Initiation Cl
2
——>   2Cl• RADICALS CREATED
Propagation Cl• +  CH
4
——>    CH
3
• +   HCl RADICALS USED
Cl
2
+  CH
3
•  ——>   CH
3
Cl +   Cl•
Termination Cl• +  Cl• ——>    Cl
2
RADICALS REMOVED
Cl• +  CH
3
• ——>    CH
3
Cl
CH
3
• +  CH
3
• ——>    C
2
H
6
CHEMICAL PROPERTIES OF ALKANES CHEMICAL PROPERTIES OF ALKENES
Equation C
2
H
4
(g)    +    HBr(g)    ———>    C
2
H
5
Br(l) bromoethane
Mechanism
ELECTROPHILIC ADDITION 
Double bond breaks and the 
2e- instead bond to Hydrogens
That leaves a carbon devoid 
Of an e-
Page 4


SAME TREND AND REASON FOR BOTH ?ANES? AND ?ENES?
ALL NON POLAR AND HAVE WEAK VAN DER WALLS FORCES
Melting point general increase with molecular mass
the trend is not as regular as that for boiling point.
Solubility alkanes are non-polar so are immiscible with water
they are soluble in most organic solvents.
PHYSICAL PROPERTIES OF 
ALKANES and ALKENES
Introduction - fairly unreactive
2 REACTIONS:
1) Combustion CH
4
(g)    +    2O
2
(g)      ——>    CO
2
(g)   +    2H
2
O(l)
2) Substitution (FREE RADICAL)
Equation:    CH
4
(g)   +   Cl
2
(g)    (uv light)——>   HCl(g)    +   CH
3
Cl(g)
chloromethane
_______________________Free Radical Substitution__________________
Initiation Cl
2
——>   2Cl• RADICALS CREATED
Propagation Cl• +  CH
4
——>    CH
3
• +   HCl RADICALS USED
Cl
2
+  CH
3
•  ——>   CH
3
Cl +   Cl•
Termination Cl• +  Cl• ——>    Cl
2
RADICALS REMOVED
Cl• +  CH
3
• ——>    CH
3
Cl
CH
3
• +  CH
3
• ——>    C
2
H
6
CHEMICAL PROPERTIES OF ALKANES CHEMICAL PROPERTIES OF ALKENES
Equation C
2
H
4
(g)    +    HBr(g)    ———>    C
2
H
5
Br(l) bromoethane
Mechanism
ELECTROPHILIC ADDITION 
Double bond breaks and the 
2e- instead bond to Hydrogens
That leaves a carbon devoid 
Of an e-
CHEMICAL PROPERTIES OF ALKENES
ELECTROPHILIC ADDITION OF HYDROGEN BROMIDE
ANIMATED MECHANISM
Animation repeats continuously after every 10 seconds
Page 5


SAME TREND AND REASON FOR BOTH ?ANES? AND ?ENES?
ALL NON POLAR AND HAVE WEAK VAN DER WALLS FORCES
Melting point general increase with molecular mass
the trend is not as regular as that for boiling point.
Solubility alkanes are non-polar so are immiscible with water
they are soluble in most organic solvents.
PHYSICAL PROPERTIES OF 
ALKANES and ALKENES
Introduction - fairly unreactive
2 REACTIONS:
1) Combustion CH
4
(g)    +    2O
2
(g)      ——>    CO
2
(g)   +    2H
2
O(l)
2) Substitution (FREE RADICAL)
Equation:    CH
4
(g)   +   Cl
2
(g)    (uv light)——>   HCl(g)    +   CH
3
Cl(g)
chloromethane
_______________________Free Radical Substitution__________________
Initiation Cl
2
——>   2Cl• RADICALS CREATED
Propagation Cl• +  CH
4
——>    CH
3
• +   HCl RADICALS USED
Cl
2
+  CH
3
•  ——>   CH
3
Cl +   Cl•
Termination Cl• +  Cl• ——>    Cl
2
RADICALS REMOVED
Cl• +  CH
3
• ——>    CH
3
Cl
CH
3
• +  CH
3
• ——>    C
2
H
6
CHEMICAL PROPERTIES OF ALKANES CHEMICAL PROPERTIES OF ALKENES
Equation C
2
H
4
(g)    +    HBr(g)    ———>    C
2
H
5
Br(l) bromoethane
Mechanism
ELECTROPHILIC ADDITION 
Double bond breaks and the 
2e- instead bond to Hydrogens
That leaves a carbon devoid 
Of an e-
CHEMICAL PROPERTIES OF ALKENES
ELECTROPHILIC ADDITION OF HYDROGEN BROMIDE
ANIMATED MECHANISM
Animation repeats continuously after every 10 seconds
5 ADDITION REACTIONS (ALL GO BACKWARDS)
1) Addition Hydrogenation (H
2
) 
C
2
H
4 (g)   
+     H
2 (g)    
—Ni—>    C
2
H
6 (g)
2)   Addition Halogenation (Cl
2
, Br
2
, I
2
) 
C
2
H
4 (g)   
+     Cl
2 (g)    
——>    C
2
H
4
Cl
2 (g)
3) Addition Hydrogenhalides 
C
3
H
6
(g)    +    HBr(g)    ———>    C
3
H
7
Br(l)
4)     Addition Hydration (H
2
O or HOH)   Le Chatieler (*BOTH WAYS) 
C
2
H
4 (g) 
+   H
2
O
(g) (or HOH)   
?
H
2
SO
4
?
C
2
H
5
OH
(g)      
?
H - -45 KJ/mol
5)  Addition Polymerization