Organic Synthesis

Question 1

When planning a synthetic route what must we consider

Answer 1

• reagents required to convert 1 FG > another
• presence of other function groups
• conditions required
• rate of reaction
• yield
• atom economy
• safety
  -financial economy
• problems of purification
  -isomer formations

Question 2

How can we extend a carbon chain

Answer 2

Reacting HCN wth aldehydes and ketones
Reacting KCN with haloalkanes
Alkylation of benzene ring
Acylation of benzene rings

Question 3

Reaction of aldehydes/ ketones with HCN
Reagents
Conditions
Product
Equation
Mechanism

Answer 3

Reagents :
Potassium cyanide and dilute acid
Condition:
Reflux
Product:
Hydroxynitrile
Equation:
CH3CHO + HCN —> CH3CH(OH)CN
Mechanism
Nucleophilic addition with CN- ion

Question 4

Why Be careful when reacting HCN and aldehyde/ ketone

Answer 4

Possibility for optical isomerism in hydroxylnitriles
But
This is an excellent method for adding an extrac C atom to a chain the CN group can be converted to COOH OR amine

Question 5

Converting Hydroxylnitrile to carboxylic acid C2H5CN + ? —> ?

Answer 5

Reacting with dilute acid in hydrolysis reaction
C2H5CN + 2H2O —> C2H5COOH + NH3

Question 6

Converting hydroxylnitrile to amine
C2H5CN + ? —> ?

Answer 6

React with H2 gas and nickel catalyst
C2H5CN + 4[H] —> C2H5CH2NH2

Question 7

Reaction of haloalkanes + KCN
Reagents
Conditions
Product
Equation
Mechanism

Answer 7

Reagents:
Aqueous alcoholic potassium cyanide
Conditions:
Reflux on aqueous alcoholic solution
Product:
Nitrile
Equation:
C2H5Br + KCN (aq/alc) —> C2H5CN + KBr
Mechanism:
Nucleophilic substitution with CN-

Question 8

Converting Nitrile to carboxylic acid
C2H5CN + ? —> ?

Answer 8

Reacted with dilute acid in hydrolysis reaction
C2H5CN + 2H20 —> C2H5COOH + NH3

Question 9

Converting Nitrile to amine
C2H5CN + ? —> ?

Answer 9

Reacting with H2 gas/ nickel catalyst
C2H5CN + 4[H] —> C2H5CH2NH2

Question 10

Why do chiral form during aldehyde/ketones reaction with cyanide ions

Answer 10

• the C=O bonds is planar
• Nucleophilic can attack from above and below
• equal chance of each possibility
• a mixture of optically active isomers produced
• only occurs if different groups are attached to the carbonyl groups

Question 11

Consequences of forming chiral molecules during synthesis

Answer 11

• isomers have to be separated to obtain the one that is effective
• separation can be expensive and complicated
• non-separation could lead to larger dose having possible dangerous side effects