carbonyls and carboxylic acids Flashcards
why are aldehydes easy to oxidise?
as H atom is attached to the carbonyl group
what happens to solubility of carboxylic acids as chain length increases?
decreases - as hydrocarbon tails ‘get in the way’, breaking h bonds between carbon and water, reducing solubility
tollen’s test
Ag+ ins oxidise aldehyde, reducing Ag+ to Ag
other name for Brady’s solution
2,4 - dinitrophenylhydrazine
what is Brady’s test for
aldehyde and ketone
positive Brady’s result
orange ppt.
esterification
- conditions
reaction of alcohol with carboxylic acid to form and ester - in presence of H2SO4 (conc)
hydrolysis of ester - product and conditions
- hot aqueous acid –> parent carb. acid
- hot aqueous alkali –> carboxylate ion
acid hydrolysis
- reverse reaction of esterfication
acid hydrolysis - conditions - - explain products
- ester refluxed with dilute aqueous acid
- broken down by water with acid acting as catalyst
- carb. acid and alcohol
alkaline hydrolysis
ester refluxed with aqueous alkali
products of alkaline hydrolysis
carboxylate ion and alcohol
acyl chloride + alcohol =
HCl and ester
acyl chloride + phenol =
HCl and ester
acyl chloride + water =
HCl and carboxylic acid
acyl chloride + ammonia =
ammonium chloride and primary Amide
carbonyl functional group
C=O
carboxylic acid + … –> acyl chloride
SOCl2
acyl chloride + amine =
secondary amide
ester functional group
COO
advantages of using acid anhydrides instead of carboxylic acids to make esters
- position of equilibrium is further right so yield is higher
- no conc. acid catalyst required
disadvantages of using acid anhydrides instead of carboxylic acids to make esters
- lower atom economy
differences between acid and alkaline hydrolysis of esters
alkane hydrolysis produces carboxylate salt instead of carb acid
naming esters
alcohol gives first part of name
carboxylic acid gives second part
acyl chlorides formed form..
carboxylic acid and sulfonyl chloride
how to form alcohol from aldehyde
- what type of alcohol formed?
warm w. aq. NaBH4
- primary
how to form alcohol from ketone
- what type of alcohol formed?
warm w. aq. NaBH4
- secondary
what chemicals are used in the lab provide HCN in a reaction?
NaCN and H2SO4
what is useful about reaction between carbonyls and HCN
increases carbon chain length
how to identify aldehyde or ketone by 2,4-DNP (Bradys)
- filter solution to collect yellow/range ppt.
- solid then recrystallised to produce pure sample of crystals
- melting point is measured and recorded
- compare melting point to database to identify carbon compound
maximum number of carbon atoms in a carboxylic acid which is soluble in water
4
2 types of acid reactions of carboxylic acids
- redox with metals
- neutralisation with bases (eg. metal oxides, carbonates, alkalis)
carb. acid + metal ->
H2 + Carboxylate salt
carb. acid + metal oxide ->
salt + water
carb. acid + alkali ->
salt + water
carb. acid + carbonates ->
salt + water + carbon dioxide
carb acid derivative?
compound which can he hydrolysed to form parent carb. acid
common group of atoms all carb. acid derivatives share
acyl group
R - C = O
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carb acid derivatives (4)
- esters
- acyl chlorides
- acid anhydrides
- amides
product of alkaline hydrolysis with NaOH
sodium ethanoate salt
method for esterification (from acid and alcohol)
- 2cm3 ethanol + 2cm3 propanoic acid -> boiling tube
- add drops conc. H2SO4
- hot water bath at 80C - 5 mins
- pour into beaker w. Na2CO3 (aq)
[oily ester will float on surface]
why does radical substitution result in mixture of products
- further substitution can occur
- substitution at different places along the chain
