alcohols Flashcards
1
Q
what are alcohols
A
- they contain the functional group -oh
2
Q
what are the physical properties of alcohols
A
- have higher boiling points than alkanes
- less volatile (forms a gas less easily)
- polar
- can form hydrogen bonds with other molecules
3
Q
explain an alcohols solubility in water
A
- greater water solubility than alkanes
- oh group can form hydrogen bonds with the water molecules
- solubility decreases as the chain length increases
4
Q
explain the viscosity in alcohols
A
- viscosity is a measure of a fluids resistance to flow
- low = flows easily
- high = doesn’t flow easily
- the viscosity increases as the length of the chain increases
- more hydrogen bonds form which require more energy to overcome
5
Q
how do you classify an alcohol
A
- primary = the oh group is only directly bonded to one carbon atoms in the hydrocarbon chain, or, 2 hydrogen atoms are bonded to the carbon on the hydrocarbon chain
- secondary = the oh group is directly bonded to 2 carbon atoms on the hydrocarbon chain, or, 1 hydrogen atom is attached to the carbon atom
- tertiary = the oh group is directly bonded to 3 carbon atoms on the hydrocarbon chain, or, there are no hydrogen atoms attached to the carbon atom
6
Q
explain the oxidation of alcohols
A
- this is the main reaction an alcohol will undergo
- oxidise the OH group
- using potassium dichromate solution acidified with sulfuric acid
- primary and secondary alcohols can be oxidised but tertiary alcohols cannot
7
Q
what will a primary alcohol form when oxidised
A
- under reflux, it will form ethanoic acid
- under distillation, it will form an aldehyde
8
Q
what does a secondary alcohol form when oxidised
A
- under reflux, it will form a ketone
9
Q
what is an aldehyde
A
- has the functional group -CHO
- the functional group is at the end of the hydrocarbon chain
- the suffix is -al
10
Q
what is a ketone
A
- has the same functional group as an aldehyde
- the functional group is in the middle of the chain
- the suffix is -one
11
Q
what is a carboxylic acid
A
- has the functional group -COOH
12
Q
what is an elimination reaction
A
- a reaction in which a smaller molecule is removed from a larger molecule leaving behind an unsaturated molecule
13
Q
what is a dehydration reaction with alcohols
A
- a water molecule is removed from the starting material
- heat the alcohol in reflux, in the presence of an acidic catalyst
14
Q
describe the differences between reflux and distillation
A
- reflux = allows continuous heating of volatile reactants, the vapourised reactants condense back into a reaction vessel to continue the reaction
- distillation = uses a side mounted condenser to separate liquids according to their boiling points
