carbonyl compound reactions Flashcards
describe the carbonyl group structure
C = O
- C is partially positive
- O is partially negative
- making it very polar
- small aldehydes and ketones are completely miscible (dissolve) with water
what is an aldehyde group?
C=O on the end
what is a ketone?
C=O in the chain
describe benzaldehyde
- simplest aromatic aldehyde
- benzene with H-C=O
describe phenylethanone
- simplest aromatic ketone
- benzene with H-C=O(CH3)
primary alcohols are oxidised to …. by ….
aldehydes
heating and distilling
secondary alcohols are oxidised to… by ….
ketones
heating under reflux
aldehydes are oxidised to …. by ….
carboxylic acids
heating under reflux
what is the reagent for alcohol oxidation?
acidified potassium dichromate
what colour does potassium dichromate turn during oxidation?
orange to green
aldehydes and ketones are reduced to …
their respective alcohols
what is the reducing agent used to reduce aldehydes and ketones?
NaBH4
what are the reagents and conditions for reducing aldehydes and ketones?
- NaBH4
- warm using water or ethanol as a solvent
- represented by [H]
how does NaBH4 act as a nucleophile?
1) hydride attacks delta positive carbon on the carbonyl and forms a bond
- arrow from H 2 e- to the C and then from double bond to the delta negative O
2) an intermediate forms and then reacts with a water molecule
- arrow from O 2 e- to the H of water and then from bond to O of water
3) organic product is an alcohol
- other product = the hydroxide ion
which bonds make up a double bond?
pi and sigma
what is the difference between a pi and sigma bond?
pi = p orbitals overlap above and below the planes of adjacent carbon atoms
sigma = p / s orbitals overlap on the same plane of adjacent carbon atoms
what property do carbonyl double bonds have, that alkenes don’t? what does this mean?
they are polar
- attract negative charged species
- act as nucleophiles
what reaction do carbonyls undergo?
nucleophilic substitution
what does an aldehyde reduce to?
primary alcohol
what does a ketone reduce to?
secondary alcohol
what is the first step in a reduction mechanism?
protonation
why are the electrons on H- ion attracted to the carbonyl?
- dipole on carbonyl attracts a pair of electrons on the hydride ion
- the electron pair in the pi bond are repelled onto the oxygen
the hydroxide ion is only in the…. not the ….
mechanism
equation
what is the role of the H- ion?
nucleophile
