alcohols part 2 Flashcards
what three important reactions do alcohols take part in
- combustion
- elimination
- oxidation
what do alcohols burn in oxygen to form
co2 and water
why do alcohols combust more efficiently than alkanes
presence of O atom
what does an alcohol react to form in an elimination reaction
an alkene
elimination
a reaction in which an atom/group of atoms is removed from a reactant
why do elimination reactions of alcohol involve dehydration
water is eliminated
reagent elimination
conc h2so4
conditions elimination
heat
elimination of alchools what happens
- oh group always removed
- h atom from an adjacent c also removed
- double bond forms between 2 c atoms
what can alcohols be oxidised by
oxidising agents such as acidifed potassium dichromate
what happens to acidified potassium dichromate when it acts as an oxidising agent
changes orange to green
half equation oxidation of alcohols
Cr2O72- + 14H+ + 6e- > 2Cr3+ + 7h2o
what is a primary alcohol oxidised to
an aldehyde and then to a carboxylic acid
general equation oxidation of primary alcohol
RCH2OH + {O} > RCOH + H2O
reagent and conditions oxidation primary
acidified potassium dichromate/ H+
gentle heat and distil
observation oxidation primary
orange to green
why is the product of oxidation of primary alcohol likely to be an aldehyde
aldehyde will have lower boiling point than alcohol it was formed from
reaction hasn’t been given chance to go any further
oxidation of ethanol symbol equation
CH3CH2OH + [O] > CH3CHO + H2O
oxidation to carboxylic acid general equation
RCH2OH + 2[O] > RCOOH + H2O
why is it 2[O] in symbol equation oxidation to carboxylic acid
alcohol being oxidised further
conditions oxidation to carboxylic acid
cr2o72-/H+ heat and reflux
why is product likely to be carboxylic acid
- reaction given chance to go to completion
- no products able to condense and separate
how can the carboxylic acid be removed from the reaction mixture when the reaction is complete
distillation
oxidation of ethanol to carboxylic acid symbol equation
CH3CH2OH + 2[O] > CH3COOH H2O
what is a secondary alcohol oxidised to
a ketone
can ketones be oxidised
no
general equation oxidation secondary alcohols
RCOHR1 + [O] > RCOR1 + H2O
reagents and conditions oxidation secondary alcohol
acidified potassium dichromate
heat and relflux
symbol equation oxidation of propan-2-ol (seoncdary)
CH3CHOHCH3 + [O] > CH3COCH3 + H2O
Apparatus for oxidation to a carboxylic acid
Reflux
Apparatus oxidation of primary alcohols
Immediate distillation
How can the presence of an aldehyde functional group be confirmed
Using mild oxidising agents such as tollens or fehlings
Observations tollens reagent
Silver mirror seen
Organic product silver mirror test
Carboxylic acid
Observations fehlings solution
Blue solution to brick red pot
How can the presence of a carboxylic acid functional group be confirmed
Using sodium carbonate
Observations carboxylic acid and sodium carbonate
Effervescence
Organic product sodium carbonate and carboxylic acid
Carboxylate salt
RCOO-Na+
General equation carboxylic acid and sodium carbonate
2RCOOH+ Na2CO3 > 2RCOONa + CO2 + H2O
