Chapter 12 - Alkanes Flashcards
1
Q
Bonding
A
Single covalent bonds - sigma bonds
each atom has 4 sigma bonds
2
Q
Sigma bonds
A
formed as a result of overlap of orbitals
density of bond is on line between two atoms
3
Q
general formula
A
CnH2n+2
4
Q
bond angle & shape
A
109.5 & tetrahedral
5
Q
what affects boiling points
A
- chain length - as it increases, more SA of contact & london forces so b.p. increases
- branching - as it increases, less SA of contact & london forces so b.p. decreases
6
Q
why are alkanes generally unreactive
A
- C-C & C-H sigma bonds strong
- C-C bonds are non-polar
- C-H bonds are considered non polar
7
Q
Alkanes reactions
A
- complete combustion
- incomplete combustion
- radical substitution
8
Q
radical substitution conditions & 3 steps
A
- UV light
- Initiation
- Propagation
- Termination
9
Q
Initiation
A
Bromine molecule breaks into radicals
- homolytic fission
10
Q
propagation
A
- radical collides with methane making HBr
- CH3 radical reacts with bromine making CH3Br and Bromine radical
- process continues
11
Q
termination
A
radicals react ending reaction
(3 combinations)
12
Q
limitations of radical substitution
A
- with longer chains substitution can occur at different points during the molecule
- further substitution can occur
