M4 B2 Alkanes
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Which type of intermolecular force exists between alkane molecules?
Induced dipole-dipole/ London forces
As carbon chain length INCREASES, so does mpt/ bpt. Why is this? (2)
• There are more electrons • The strength of induced dipole-dipole interactions increases.
As the carbon chain becomes MORE branched, the mpt/bpt DECREASES. Why is this? (2)
• Molecules cannot pack together as closely- therefore there is less surface contact. • Weaker and fewer induced dipole-dipole interactions/ London forces between molecules.
Why are alkanes and cycloalkanes so unreactive?
• C-H to C-C bonds have a high bond enthalpy • C-H and C-C are non-polar so do not attract attacking species.
General equation for the combustion of alkanes?
Alkane + oxygen = Carbon dioxide + water
What are the two possible different products (other than water) formed from incomplete combustion?
• Carbon monoxide • Carbon (soot)
What happens during carbon monoxide poisoning?
It prevents the Fe2+ ion in harmoglobin in red blood cells from binding with oxygen and the bodys tissues become starved of oxygen. This can be fatal.
What pollutants are produced when hydrocarbons are burned? (4)
• Carbon monoxide • Nitrogen oxide • Sulphur dioxide • Carbon dioxide
What is radical substitution?
A type of substitution reaction where a radical replaces (substitutes) a different atom or group of atoms.
What is a radical?
A species with an unpaired electron
What type of bond fission occurs to produce radicals?
Homolytic
What is one of the main conditions necessary to produce radicals?
UV radiation (light)
What is initiation?
The formation of radicals (using UV radiation)
What is propagation?
When radicals are used up and regenerated
What is termination?
Radicals are used up.
What is a sigma bond?
The overlap of two orbitals, directly/ head-on.
What is the shape and bond angle of a sigma bond?
Shape- Tetrahedral Angle- 109.5