carboxylic acids Flashcards
where is the carbonyl group ( c=o) in aldehydes
at the end of the carbon chain , CHO
where is the carbonyl group in ketones?
joined to 2 carbon atoms
what is octanal in nature
CH3(CH2)7CHO , a colourless fragrant liquid found in oranges
used to attract mates for birds during breeding season
what happens in oxidation of aldehydes
oxidised to carboxylic acid when refluxed with acidified potassium dichromate ion, K2CR2O7^, and dilute sulfuric acid
what are the conditions for oxidation of aldehydes
refluxed with acidified potassium dichromate ion, K2CR2O7^, and dilute sulfuric acid
why dont ketones undergo oxidation reactions
lack of reactivty
why is reactivity of alkenes and carbonyl groups different?
double bond ( c=o) in carbonyls are polar as oxygen is more electronegative
double bond ( c=c) in alkenes are non-polar
what type of reaction does carbonyls undergo
nucleophilic addition , nucleophiles are attracted to positive carbon atom
what type of reactions does alkenes undergo
electrophilic addition
what is used to reduce aldehydes and ketones to alcohols?
NaBH4
what are aldehydes reduced to
primary alcohols
what are ketones reduced to
secondary alcohols
why is hydrogen cyanide used to react to aldehydes and ketones
to increase length of carbon chain
why is hydrogen cyanide (HCN) dangerous
colourless and poisonous liquid that boils slightly above room temperature
how is hydrogen cyanide formed
sodium cyanide and sulfuric acid are reacted together
what is the nucleophile for reduction of aldehydes and ketones
the hydride ion , H-, from NaBH4
what is the mechanism for reaction of aldehydes and ketones with NaB4
lone pair of electrons from hydride ion is attracted to and donated to slightly positive carbon atom. A dative covalent bond is formed between hydride ion and aldehyde/ketone. The pi bond in the c=o breaks by heterolytic fission forming a negatively charged intermediate ( oxygen) which donates a lone pair of electrons to a hydrogen atom in a water molecule to form an alcohol.
what is the nucleophile in NaCN/H+
cyanide ion , CN-
what is the mechanism for reaction of aldehydes/ketone with NaCN/H+
lone pair of electrons from cyanide ion is attracted to slightly positive carbon atom forming dative covalent bond. The pi bond in c=o breaks by heterolytic fission forming a negatively charged intermediate ( oxygen) which donates a lone pair of electrons to a hydrogen ion to form the product ( hydroxynitrile)
what is brady reagent
2,4 DNP with sulfuric acid
what is brady reagent used for
detect presence of carbonyl group in aldehydes and ketones forming orange precipitate
what is DNPH used for
reacts with carbonyl group in a nucleophilic addition-elimination reaction called condensation. NH2 adds across double bond and water is removed
what is used to distinguish an aldehyde and a ketone
tollens reagent
what does tollens reagent contain
solution of silver nitrate in aqueous ammonia
what happens when tollens reagent is added to an aldehyde
silver ions ( acts as oxidising agent is presence of ammonia) is reduced to form silver mirror
aldehyde oxidised to carboxylic acid
what functional group does carboxylic acid contain
carboxyl group
what is carboxylic acid used for
medicine,painkillers,fruit juices,vinegar
why are carboxylic acids soluble in water?
C=O and C-H bonds are polar allowing hydrogen bonds to form in water
why are carboxylic acids with over 4 carbon atoms not soluble in water
as number of carbon atoms increase, solubility decreases as non-polar carbon chain has a greater effect on overall polarity
what are properties of dicarboxylic acid
have 2 polar carboxyl groups to form hydrogen bonds. Solid at room temperature and dissolve readily in water
what do carboxylic acids react with in redox
metals
what do carboxylic acids react with in neutralisation
bases, alkalis , metal oxides , carbonates
what is formed when carboxylic acids react in redox or neutralisation
carboxylate salts
