Question

Discuss the reduction of acetophenone with sodium borohydride and a workup of ethanol. My % yield is 21.5% . Analyze why is this result and relate to the theories and concepts. Please provide a descriptive paragraph, please

Answer 1

In the reaction between acetophenone and sodium borohydride product formed is 1 - Phenylethanol and boron salts.

In this reaction firstly we take sodium borohydride in beaker and then add ethanol. Reaction between acetophenone and sodium borohydride is highly exothermic so it must be carried out in fumehood and the reaction temperature must be maintained by ice bath. After the reaction is completed then the excess borohydride and ethoxyborohydride destroyed by aqeous acid.Ethanol is water soluble so in this reaction organic and inorganic products formed cannot be seperated by simple extraction with water and diethyl ether so lost of product is more. So first work is to boil off much of the ethanol. And then add water and diethyl ether to seperate the organic and inorganic products.

The pecentage yeild = Actual yeild / Theoritical yeild X 100%

Actual yeild is the actual amount produced when the experiment or reaction is carried out.

Theoritical yeild is the amount of product calculated from the limiting reactant.

Percentage yeild is less because of factors like:

1) The reaction may not produce stiochiometric amount of product. This can be possible because of slow rate, equilibrium set up, decomposition of reactant or product or evaporation.

2) During work of solvent extraction or crystallization, product is not completely seperated and it is discarded so there is loss of product occurs, then the percentage yeild is less.

3) Some product may remain inside the reaction, purification vessel.

4) In our case if temperature is not properly maintained then reactant will not completely react and product form is less in yeild.

Beacause of these factors percentage yeild is less.