Chapter 12 - Alkanes Flashcards
What is an alkane?
A saturated hydrocarbon containing C-H bonds only
What is the general formula of an alkane?
CnH2n+2
What is the polarity of alkane bonds, and why?
They are non polar
Carbon and hydrogen have similar electronegativities
What is the shape and bond angle of an alkane?
Tetrahedral
109.5°
What is a sigma bond?
A covalent bond which has a direct overlap of two orbitals
What type of intermolecular forces do alkanes have?
London dispersion forces/induced dipole dipole interactions
Because the bonds are non polar
What happens to the boiling point as chain length increases?
The boiling point increases because there is a larger surface area contact so stronger induced dipole dipole interactions - which take more energy to overcome
Does a branched molecule have a higher or lower boiling point than its equivalent straight chain?
Branched molecule has a lower boiling point as it cannot pack as tightly together and has less surface contact points therefore less energy to overcome induced dipole dipole interactions
Are alkanes soluble in water?
No, because the hydrogen bonds in water are stronger than the alkanes induced dipole dipole interactions
What reactions do alkanes undergo and are they reactive?
Alkanes undergo combustion reactions and react with halogens but are very unreactive
Why are alkanes so unreactive?
C-C and C-H sigma bonds are strong
C-C bonds are non-polar
C-H bonds are considered non polar due to similarity of electronegativity of C and H
What is complete combustion and what are the products of a complete combustion reaction with alkanes?
Complete combustion occurs with a plentiful supply of oxygen
Alkane + oxygen → carbon dioxide + water
What is incomplete combustion and what products are formed in the incomplete combustion of alkanes?
Incomplete combustion occurs in a limited supply of oxygen
Alkane + oxygen → carbon dioxide + water (and some carbon or carbon monoxide may be formed)
What type of hydrocarbon are most likely to undergo incomplete combustion?
Longer chains
How are haloalkanes formed from alkanes?
Free radical substitution
