14 - Alcohols Flashcards
physical properties
- less volatile, higher mp and greater water solubility than alkanes
- alcohols have a polar OH bonds
- so they are polar molecules
- has hydrogen bonding between OH groups
1’ alcohol
Oh group attached to carbon that is bonded to 2 hydrogens and 1 alkyl group
2’ alcohol
Oh group attached to carbon that is bonded to 1 hydrogens and 2 alkyl group
3’ alcohol
Oh group attached to carbon that is bonded to no hydrogens and 3 alkyl group
1’ Oh to aldehyde
gentle heating with K2Cr2O7/H2SO4
-> distil the aldehyde so no further oxidation to form COOH
1 OH to COOH
heat strongly under reflux with excess K2Cr2O7/H2SO4
- reflux ensures aldehyde undergoes oxidation to COOH
- excess is used to ensure alcohol is oxidised
order of oxidation of primary alcohols
primary alcohols -> aldehyde -> carboxylic acid
what happens when oxidise a 2nd OH. how?
a ketone forms
- cannot further oxidise a ketone
- reflux withK2Cr2O7/H2SO4
orange to green
Dehydration of alcohols
heat under reflux with an acid catalyst like H2SO4 or H3PO4
- forms an alkene
- elimination
alcohol to haloalkane
- write the equation
heat under reflux with H2SO4 and NaBr
NaBr + H2SO4 -> NaHSO4 + HBr
- HBr firmed reacts with the alcohols to produce haloalkane
- OH replaced by Br
volatility and Tb of alcohols vs alkanes
- more energy is required to break the hydrogen bonds in an alcohol than the weaker London forces in an alkane
solubility of alcohols
- a molecule that can form H bonds with water is more soluble than one that cant
- alcohols are completely soluble in water as H bonds form between OH group and water molecules
- as chain length increases, the influence of OH bond becomes relatively smaller, so solubility of a longer chain alcohol is more like of a hydrocarbon
oxidation of tertiary alcohols
they do not undergo oxidation
- acidified potassium dichromate remains orange
