Reactions of the carbonyl group

Question 1

Draw the mechanism for the nucleophillic addition reactions

Answer 1

Question 2

How is hyrogen cyanide ion prepared for the addition reaction?

Answer 2

• sodium / potassium cyanide is used as a source for cyanide ions
• followed by the addition of dilute hydrochloric acid
  
  • source of H+ in reaction

Question 3

What are the products of the addition of hydrogen cyanide?

Answer 3

hydroxynitriles

Question 4

Why are hydroxynitriles useful?

Answer 4

useful in synthesis because both the -OH and -CN groups are reactive and can be converted into other functional groups

Question 5

How is a cyanide ion shown?

Answer 5

:CN^-

Question 6

What is the ovarall balanced equation for the addition of hydrogen cyanide with an aldehyde?

Answer 6

RCHO + HCN → RC(CN)(OH)H

Question 7

Why is the addition of hydrogen cyanide important?

Answer 7

it increases the length of the carbon chain by one carbon

reaction will produce racemix mixture of two optical isomers (anantiomers) when carried out with an aldehyde or an unsymmetrical ketones

because the cyanide ion may attack from above or below the flat C=O group

Question 8

How is KCN dangerous?

Answer 8

• irritant
• dangerous if ingested or inhaled
• react with moisture to form HCN
  
  • highly toxic gas

Question 9

How are the risks of using KCN minimised?

Answer 9

• wear gloves, safety goggles and a lab coat
• fume cuboard