Chapter 12 Flashcards
Sigma bond
The result of two overlapping orbitals
Pair of electrons shared between bonding atoms
Alkanes shape
109.5
Tetrahedral shape
Why does more carbon atoms = ^ boiling point
More carbons
Larger surfaces area of contact points between molecules
More London forces
Higher strength of attraction between alcane chains
More heat need to overcome forces
Why does more branching = lower bp
More branching
Less surface area of contact points between molecules
Less London forces
Lower strength of attraction between molecules
Less energy needed to overcome forces
Complete combustion of alkanes
Alkane + oxygen –> carbon dioxide + water
Incomplete combustion of alkanes
Limited supply of oxygen
Alkane + oxygen –> carbon monoxide / carbon (soot) + water
Alkanes undergo radical substitution (halogénation)
Presence of uv radiation
Initiation propagation termination
Initiation of radical substitution
Halogen molecule absorbs uv radiation
Undergoes homolytic fission
2 highly reactive radicals
Propagation radical substitution 2 steps
Step 1
Halogen reacts with hydrogen in h-c bond
Producing an alkane radical and a hydrogen halide compound
Step 2
Alkane radical reacts with another halogen molecule
Producing an haloalkane and halogen radical
Termination - radical substitution
2 radicals collide
Producing a molecule with all electron pairs
The radicals are removed from the reaction mixture - stopping the reaction
What are the limitations of radical substitution and why does it happen
Produces a mixture of Of products, that may be unwanted and need to be filtered
If there is too much halogen
The hydrogen on wanted product with react with the halide forming an unwanted product
To stop this make sure there is an excess of alkane so there is a greater chance of the halogen radical colliding with alkane
