carbonyl compounds

Question 1

define aldehyde

Answer 1

at least one H attached to the carbonyl group

Question 2

define ketone

Answer 2

at least 2 carbon attached to the carbonyl group

Question 3

define carbonyl group

Answer 3

a functional group with a C=O double bond

Question 4

define nucleophile

Answer 4

an atom/group of atoms attracted to an electron deficient centre

Question 5

give 3 examples of nucleophiles

Answer 5

Br -
OH -
NH3

Question 6

When oxidising aldehydes what is used as the oxidising agent

Answer 6

acidified potassium dichromate

(K2CrO7/ H2SO4)

Question 7

explain the mechanism for the nucleophilic addition of aldehydes and ketones

Answer 7

1. dipole present on carbonyl so susceptible to nucleophilic attack
2. nucleophile donates pair of e- to the carbon which is electron deficient
3. simultaneously the Pi electrons in the C=O bond break forming the intermediate
4. extra e- pair are donated to neighbouring H+ to form the alcohol which is stable

Question 8

what is the reducing agent in the reduction of carbonyls to give alcohols

Answer 8

NaBH4

sodium borohydride

Question 9

why do cyanide ions react with carbonyls

Answer 9

CN- ions need to be acidified to react directly with C=O. This makes the compound more reactive as the C=O becomes more polar. The pH should be no lower than 4