Module 4 - [ch14,15] (alcohols, haloalkanes)
No description yet. This curated deck is ready for daily study.
Card preview (24)
why is methanol useful
efficient combustion - used as a high performance fuel starting material in many industrial syntheses (e.g to produce paint, adhesives ect.)
physical properties of alcohols in comparison to alkanes
higher melting points more soluble in water
why are alcohols more soluble than alkanes in water
can form hydrogen bonds with water molecules
why do alcohols have a higher boiling points than alkanes
alcohol has hydrogen bonds stronger than london forces in alkanes require more energy to overcome less volatile than alkanes
describe hydrogen bonding in alcohols
alcohols have a polar O-H bond due o difference in electronegativity of the oxygen and hydrogen atoms therefore polar -OH groups form strong hydrogen bonds
how does solubility of alcohols differ to that of alkanes as chain length increases
as hydrocarbon chain length increases, the influence of the -OH decreases solubility of longer-chain alcohols becomes to similar to hydrocarbons
how are alcohols classified
primary, secondary and tertiary based on number of hydrogen atoms and alkyl groups attached to the carbon atom with the -OH group
what are the two primary alcohols
methanol, ethanol
what do you call an alcohol where the carbon with the -OH group is bonded to no hydrogen atoms and 3 alkyl groups
tertiary
combustion of alcohol
alcohol + oxygen -> carbon dioxide + water
oxidation of alcohols
alcohol + oxidising agent -> carboxylic acid
which alcohols can be oxidised
primary and secondary
the example of oxidation you need to know
potassium dichromate(VI) K2Cr2O7 acidified with dilute sulfuric acid H2SO4 oxidised - orange -> green orange ( dichromate(VI) ions) green (chromium(III) ions)
what are primary alcohols oxidised to
aldehydes or carboxylic acids
how do you prepare an aldehyde
gentle heating of primary alcohol with acidified potassium dichromate
why is aldehyde is distilled out of the reaction mixture as it forms
to prevent further reaction with the oxidising agent aldehydes can be oxidised to carboxylic acids
how do you prepare carboxylic acids
heat primary alcohol strongly under reflux with an excess of acidified potassium dichromate(VI)
why is an excess of acidified potassium dichromate (VI) used in preparation of a carboxylic acid
ensures all of the alcohol is oxidised
why do you heat under reflux when preparing a carboxylic acid from a primary alcohol
ensures any aldehyde formed initially in the reaction also undergoes oxidation to become a carboxylic acid
oxidation of secondary alcohols
ketones
what is done to ensure the oxidation of secondary alcohols goes to completion
the secondary alcohol is heated under reflux with the oxidising mixture dichromate, orange-.green
what is done to ensure the oxidation of secondary alcohols goes to completion
the secondary alcohol is heated under reflux with the oxidising mixture dichromate, orange-.green
oxidation of tertiary alcohols
do not undergo oxidation reactions acidified dichromate remains orange
describe dehydration of alcohols
alcohol heated under reflux in the presence of an acid catalyst (H2SO4, H3PO4) to form an alkene + water