REACTIONS OF ALDEHYDES AND KETONES

Question 1

what is the reducing agent that reduces carbonyl compounds into alcohols

Answer 1

• Tetrahydridoborate(111)

Question 2

draw the structure of the reducing agent and describe it

Answer 2

• NaBH4 readily loses hydride ions
• a hydride ion is a negetatively charged hydrogen ion with a lone pair of electrons

Question 3

what are aldehydes(ethanal) and ketones(propanone) reduced to by tetrahydridoborate(111)

Answer 3

• primary alchols and secondary alchols

Question 4

what is a nucleophile

Answer 4

an atom or group of atoms that is attracted to a elctron deficient centre where is donates a pair of elctrons to form a new covalent bond

Question 5

what are curly arrows

Answer 5

show the movement of an electron pair in the breaking or formation of a covalent bond.

Question 6

outline the mechanism of nucleophilic addition reactions of aldehydes and ketones with hydride ions.

Answer 6

1. Electron deficient carbon atom in the polar C=0 doublebond is attacked by the hydride ion which acts as the nucleophile
2. the lone pair of electrons from the hydride ion forms a bond with carbon atom
3. at the same time the pi bond in the C=O bond breaks to produce a negativley charged intermediate
4. the intermediate donates an electron pair to a hydrogen atom in water molecule,forming a dative covalent bond and a hydroxide ion
5. the organic addition product is an alcohol.