| Shapes of alkanes | every single carbon has 4 bonds so tetrahedral 109.5 degrees |
| General formula of alkanes | Cn H2n+2 |
| Bonding in Alkanes | -single covalent
-overlapping orbitals so sigma bonds |
| Effect of chain length and branching | - CHAIN LENGH INCREASES = MORE LONDON FORCES = SO MORE ENERGY REQUIRED = HIGHER BOLING POINT
-BRANCHES = MORE SURFACE CONTACT POINTS= LESS ENERGY REQUIRED TO OVERCOME THE INTERMOLECULAR FORCES= LOWER BOILING POINT |
| The combustion of alkanes | The moles of CO2 tell you the number of carbon atoms in the alkane
The moles of water tell you half the amount their is of Hydrogen in the alkane |
| Incomplete combustion example | C6H14 + 7/202 ---> 6CO + 7H20 |
| Complete combustion example | CH4 + 202 ----> C02 + 2H20 |
| Heterolytic fission | bond breaks unevenly
CL - Cl = CL+ AND CL-
as one gains and both electrons |
| Homolytic fission | Bonds break evenly
CL-CL = CL- AND CL-
each takes one electron so it is unpaired leaving a very reactive RADICAL |
| Halogenation of alkanes | Alkanes react with halogens under UV light
-radical substitution |
| Chlorination steps | Initiation:
The halogen (cl-cl) bond is broken by homolytic fission forming two radicals
CL* + CL*
Propagation:
1. CH4 + Cl* ---> CH3 * + HCL
2.CH3* + CL2 ----> CH3Cl + CL*
Termination:
The cancellations of radicals for the initiation eq
1. CL* + CL* = CL2
2.CH3* + CH3*= C2H6
3.CH3* + CL* =CH3CL |
