28 Organic synthesis

Question 1

Haloalkane + NaCN –>

Answer 1

Nitrile + X-

Question 2

Haloalkane + NaCN –>

Answer 2

Nitrile + X-

Question 3

Aldehyde + HCN –>

Answer 3

Nitrile + OH-

Question 4

Ketone + HCN –>

Answer 4

Nitrile + OH-

Question 5

What does the reduction of a nitrile make?

Answer 5

Amine

Question 6

What does the hydrolysis of a nitrile make?

Answer 6

Carboxylic acid

Question 7

What is used in the reduction of nitriles?

Answer 7

H2 + Ni catalyst

Question 8

What is used in the hydrolysis of nitriles?

Answer 8

Heating with dilute (aq) acid

Question 9

How do you prepare a solid from a liquid reaction mixture? (4 marks)

Answer 9

• Set up Buchner pressure apparatus
• Put filter paper inside the funnel, and wet with solvent
• Pour reaction mixture into funnel
• Rinse beaker and add too
• Leave under suction for a few minutes to dry

Question 10

Describe how you would recrystallise an impure solid to increase purity? (3 marks)

Answer 10

• Dissolve the impure sample in a minimum volume of warm solvent
• Allow solution to cool to room temperature, then place in a water bath until crystals reform
• Filter using Buchner apparatus

Question 11

How do you evaluate the purity of the sample from its melting point range?

Answer 11

Pure samples have a very small melting range.

Question 12

How do you determine the melting point range of a sample? (3 marks)

Answer 12

• Seal the end of a capillary tube using a Bunsen burner
• Fill with crystals to about 3mm depth
• Use electrically heated melting point apparatus to take its melting point

Question 13

What are two benefits of using reflux?

Answer 13

Speeds up the reaction.
Prevents reagents being lost.

Question 14

What method should be used to separate soluble and insoluble products?

Answer 14

-Add mixture to separating funnel
- Add water, shake
- Let settle
- If could contain trace amounts of acid, add NaHCO3
- Run off lower layer
- Add anhydrous CaCl2 to organic layer (drying agent)