alcohols chapter 15 oxford aqa

uses of alcohols

solvents , intermediates in reactions, cosmetics, alcoholic drinks, antifreeze

general formula

CnH2n+1 OH

naming alcohols

suffix: alkane + ol

e.g propan-2-ol or methanol

which alchohol is used in antifreeze

ethane,1,2diol

what factors affect reactivity of alcohols

• polarity

• strength of bonds

shape of alcohols

tetrahedron because there are 2 lone pairs on O

classification of alcohols

• primary

• secondary

• tertiary

carbons in a primary alcohol

1 carbon bonds to the OH- functional group

carbons in a secondary alcohol

2 carbons bonded to the OH- functional group

carbons in a tertiary alcohol

3 carbons bonded to the OH- fucntional group

physical properties

• hydrogen bonding

• higher MP/BP than alkanes

• Similar relative molecular mass to alkanes

solubility of alcohols

• soluble in water =short chain

• insoluble in water = long chain

complete combustion of alcohols

• burn completely in the presence of oxygen

uses of alcohols

• fuel

• methylated spirits

elimination reactions in alcohol

dehydration where a small molecular leaves the alcohol to form water

dehydration step

• forming an alkene

reagents used for dehydration

• excess concentration sulfuric acid

• alminium oxide as a catalyst

condition for dehydration of alcohol

600 kelvins

mechanism for dehydration

• oxygen lone pair attack h+ proton

• oxygen cation gains an electron

• forming H2O and an alkene

isomeric alkenes

• Dehydration of longer chain alcohols can produce a mixture of alkenes which can exhibit E / Z isomerism with a number of different products

products formed when primary alcohols are oxidised

aldehydes

second oxidation of primary alcohols(aldehydes)

carboxylic acid

oxidation of secondary alcohol products

ketones

oxidation of tertiary alcohols

no product formed because they are not easily oxidised

reagents used in the first oxidation of ethanol

concentrated sulfuric acid potassium dichromate

role of sulfuric acid

proton donor/oxidising agent

why are anti bumping granules are added

gentle boiling

why is a pear shaped flask used

even distribution of heat

what happens during distillation of alcohols

ethanal evaporates and gets condensed in the condenser and is collected in a flask that gets cooled in ice

product formed when oxidising ethanol in reflux

carboxylic acid (ethanoic acid)

reflux

the ethanol vapour condenses back into the same flask until fully oxidised

reagents used for reflux

excess sulfurix acid and excess potassium dichromate

conditions for reflux

291k or 118 degrees celsius

symbol equation for reflux of ethanol

(O) is the oxidising agent

ethanol + 2O → ethanoic acid + water

apparatus used for reflux

• pear shaped flask

• condenser

• tubes

• blue flame bunsen burner

product formed when oxidising secondary alcohols

ketones

similarities of aldehydes and ketones

carbonyl group or C=O bond

aldehydes

at the end of the hydrocarbon chain

ketones

in the middle of the hydrocarbon chain

suffix for ketone

-one

suffixe for aldehydes

-al

test for aldehydes

gentle oxidation until an acid is formed

test for ketones result when oxidised

no visible change

silver mirror test

positive: colourless to silver

negative: no visible change in colour

what does the tollens silver mirror test for

aldehydes

colour change of fehling’s test

positive: blue → brick red of CuO (aldehyde present)

negative: remains blue (ketone present)

what does fehling’s test contain

blue Cu+ ions

role of the copper ions

gentle oxidising agent