Chapter 28 - Organic synthesis

Question 1

What is filtration under reduced pressure used for? What equipment is needed?

Answer 1

Technique for seperating a solid product from a solvent or liquid reaction mixture

You need:

• Buchner flask
• Buchner funnel
• Pressure tubing
• Filter paper
• Access to filter or vacuum pump

Question 2

How do you carry out filtartion under reduced pressure

Answer 2

Question 3

What is recrystallisation used for? What does pruification by recrystallisation depend on?

Answer 3

Solid product obtained after filtartion will contain impurities which can be removed by carrying out recrystallisation.

Depends upon the desired product and the impurities having different solubilities in the chosen solvent

Question 4

How do you carry out recrystallisation?

Answer 4

Question 5

What is melting point determination used for and how are the results analysed?

Answer 5

Melting points/melting ranges (difference between temp at which the sample starts to melt and the temp at which melting is complete) of solids determined to identify whether a solid compound is pure.

The melting range of a pure organic substance is very sharp (of one or two degrees)

If the compound contains impurities, the solid melts over a wide range of temperatures. Also has a lower melting point than a pure sample.

Question 6

What are the 2 types of melting point determination techniques?

Answer 6

• Using electrically heated melting point apparatus
• Using an oil bath or thiele tube method

Question 7

How do you carry out the procedure for mellting point determination using electrically heated melting point apparatus?

Answer 7

Question 8

How do you carry out the procedure for mellting point determination using an oil bath or Thiele tude method?

Answer 8