4 - 25 Alkenes
● Homologous series of hydrocarbons, containing C＝C bond
● C＝C bond is functional group of alkenes
● ***More reactive than alkanes, as C＝C double bond is relatively weaker
than C-C single bond, easier to react and undergo addition reactions (C＝C
broken down to C-C)
● General formula - CnH2n (all alkenes have same empirical formula - CH2)
●
Unsaturated hydrocarbons
● Reason why alkenes are unsaturated: they contain C＝C bond (saturated
compounds contain SINGLE C-C bonds, whereas unsaturated compounds contain
one or more double/triple C-C bonds)***More reactive than alkanes, as C＝C
double bond…
●
● Combustion - Alkenes burn in air/oxygen, giving carbon dioxide and water
(although this reaction is wasteful, as alkenes are much too useful to waste by
burning them):
C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (l)
1
● Homologous series of hydrocarbons, containing C＝C bond
● C＝C bond is functional group of alkenes
● ***More reactive than alkanes, as C＝C double bond is relatively weaker
than C-C single bond, easier to react and undergo addition reactions (C＝C
broken down to C-C)
● General formula - CnH2n (all alkenes have same empirical formula - CH2)
●
Unsaturated hydrocarbons
● Reason why alkenes are unsaturated: they contain C＝C bond (saturated
compounds contain SINGLE C-C bonds, whereas unsaturated compounds contain
one or more double/triple C-C bonds)***More reactive than alkanes, as C＝C
double bond…
●
● Combustion - Alkenes burn in air/oxygen, giving carbon dioxide and water
(although this reaction is wasteful, as alkenes are much too useful to waste by
burning them):
C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (l)
1
