17.2 3 Nucleophilic addition reactions

Question 1

reaction with hydrogen cyanide

Answer 1

reagent =hydrogen cyanide (HCN)
carried out in aqueous alkaline solution containing potassium cyanide (KCN)
Involve hydrogen atom attaching to the oxygen of carbonyl group and cyanide group attaching to carbon atom of carbonyl group
hydroxynitriles e.g 2-hydroxylbutanenitrile

Question 2

Addition of hydrogen cyanide to propanal

Answer 2

CH3CH2CHO+HCN=CH3CH2CH(OH)CN

Question 3

Addition to butanone

Answer 3

CH3COCH2CH3+HCN=CH3C(CN)(OH)CH2CH3

Question 4

SEE BOOK FOR

Answer 4

MECHANISM

Question 5

Using optical activity as evidence

Answer 5

arrangement of two atoms or group joined to C=0 is planar in step 1 of mechanism is an equal chance of cyanide ion attacking from each side of plane carbon is chrial centre equal amounts of both dextrorotatory and laevorotatory enantiomers fromed giving a product with no optical activity formation of a racemic mixture

Question 6

Brady’s reagent

Answer 6

2,4-dinitrophenylhydrazine
NEED TO KNOW STRUCTURE SEE PG 181
reacts with most carbonyl compounds to form a brightly coloured orange solid so appearence of an orange precipitate is a postive result

Question 7

Use of reaction with bradys reagent

Answer 7

postive result presence of a carbonyl compound
can find out individual compounds due to products called derivatives can be filtered purified and dried and their melting temperatures measured derivatives have the ending one
carbonyl compounds who have a similar boiling point can be identified as derivatives will have different boiling point