Question

Hi anyone can answar these questions or only part of them ?

1-What are the advantages of using thionyl chloride rather than other available chlorination agents?

2-When an oil bath is used to reflux a solution, why is it recommended ?

3-If charcoal is used in a recrystallization, how and why might Celite then be used subsequently?

4-Why is thionyl chloride removed by distillation at reduced pressure rather than at atmospheric pressure?

5-Illustrate the mechanism for the reaction of thionyl chloride and; (a) water and (b) a chiral alcohol.

6-Illustrate the mechanism of the reaction of cholesterol with PCl5 to yield 3-chloro-5-cholestene.

Answer 1

1-What are the advantages of using thionyl chloride rather than other available chlorination agents?

Ans: When thionyl chloride is used, the by products obtained are SO2 and HCl. These are gaseous and escape out from the reaction mixture and alkyl chloride formed is pure.

Note: Thionyl chloride converts alcohols to alkyl chlorides.

2-When an oil bath is used to reflux a solution, why is it recommended ?

Ans: When an oil bath is used to reflux a solution, localised heating is prevented. It gives uniform heating. If we use a hot plate or a heating mantle, localised heating occurs which is dangereous.

3-If charcoal is used in a recrystallization, how and why might Celite then be used subsequently?

Ans: A layer (or bed) of Celite is formed on filter cloth present in Buchner funnel. The solution containing charcoal is passed through this. Charcoal particles remains on the top of the Celite layer and the solution passes through. The compound to be crystalized remains in the solution and the colour impurites remains absorbed on the charcoal.

4-Why is thionyl chloride removed by distillation at reduced pressure rather than at atmospheric pressure?

Ans: If we remove thionyl chloride from the reaction mixture by distillation at atmospheric pressure, then the distillation will occur at high temperture. At that temperature, the products of the reaction will decompose or there is possibility of side reactions. To avoid this, vacuum distillation at lower temperature is carried out.