4.2.7 : synthetic routes in organic synthesis

Question 1

Alkane to haloalkane

Answer 1

Radical substitution

halogen/UV

Question 2

Alkane to alkene

Answer 2

Cracking

Question 3

Alkene to alkane

Answer 3

Hydrogenation

H2, Ni catalyst, 150 dc

Question 4

Alkene to haloalkane (1 step)

Answer 4

Halogenation

Hydrogen halide (e.g. HBr)

Question 5

Alkene to haloalkane (2 steps)

Answer 5

Alkene -> alcohol -> haloalkane

1. Alkene -> alcohol
   - Hydration
   - H2O (g) / H3PO4 (phosphoric acid) catalyst
2. Alcohol -> haloalkane
   - Halide substitution
   - Sodium halide and H2SO4 (sulfuric acid)

OR

Alkene -> alkane -> haloalkane

1. alkene -> alkane
   - hydrogenation
   - H2, Ni cat, 150 dc
2. alkane -> haloalkane
   - radical substitution
   - halogen/UV

Question 6

Haloalkane to alkene (2 steps)

Answer 6

Haloalkane -> alcohol -> alkene

1. Haloalkane -> alcohol
   - Hydrolysis
   - NaOH/ethanol, reflux
2. Alcohol -> alkene
   - Dehydration
   - conc. H2SO4 (sulfuric acid)

Question 7

Haloalkane to alcohol (1 step)

Answer 7

Hydrolysis

NaOH/ethanol
reflux

Question 8

Primary alcohol to carboxylic acid

Answer 8

Oxidation : K2Cr2O7/H2SO4
reflux

Question 9

Primary alcohol to aldehyde

Answer 9

Oxidation : K2Cr2O7/H2SO4
distil immediately

Question 10

Secondary alcohol to ketone

Answer 10

Oxidation : K2CrO7/H2SO4
reflux

Question 11

Haloalkane to carboxylic acid (2 steps)

Answer 11

Haloalkane -> alcohol -> carboxylic acid

1. haloalkane -> alcohol
   - hydrolysis
   - NaOH/ethanol, reflux
2. alcohol -> carboxylic acid
   - oxidation: K2Cr2O7/H2SO4
   - reflux

Question 12

Alkene to aldehyde (2 steps)

Answer 12

Alkene -> alcohol -> aldehyde

1. Alkene -> alcohol
   - hydration
   - H2O (g) /H3PO4 catalyst
2. alcohol -> aldehyde
   - oxidation: K2Cr2O7/H2SO4
   - distil immediately

Question 13

Alkene to ketone (3 steps)

Answer 13

Alkene -> haloalkane -> alcohol -> ketone

1. alkene -> haloalkane
   - halogenation
   - hydrogen halide
2. haloalkane -> alcohol
   - hydrolysis
   - NaOH/ethanol, reflux
3. alcohol -> ketone
   - oxidation: K2Cr2O7/H2SO4
   - reflux

Question 14

Alcohol to haloalkane (1 step)

Answer 14

Halide substitution

Sodium halide and H2SO4

Question 15

Alcohol to haloalkane (2 steps)

Answer 15

Alcohol -> alkene -> haloalkane

1. alcohol -> alkene
   - dehydration
   - conc H2SO4
2. alkene -> haloalkane
   - halogenation
   - hydrogen halide