Question

#11 If a three-step synthesis has the following percent yield what is the overall percent yield of the experiment? Step 1: 25% Step 2: 100% Step 3: 25% A 25% B 100% C 75% D 6.3% #12 What is the disadvantage of doing a reaction without a solvent? A economics B ease of purification C reactants should mix to a homogeneous system D environmentally friendly E all of the above

Answer 1

#11 The percent yield of a reaction is given by -

For this particular three step reaction, overall percentage yield can be calculated by using the formula given below-

actual yield percent yield = 2 theoretical vield X 100%

% yield for step (1&2) = step 1 × step 2 / 100

= 25% × 100 % / 100 = 25% = A
  

Overall yield = A × step 3 / 100 = 25% × 25% /100

= 6.25 % ~ 6.3%

#12 C. reactant should mix to a homogeneous system.

We will consider the options one by one -

A. Economics (Advantage)

---> Ofcourse the reaction without solvent will be economical as they are of high price, needs processing and also separation.

B) Ease of purification ( Advantage)

---> Whole solid phase synthesis relies on this basis.

C) Reactant should mix to a homogeneous system (Disadvantage)

---> The whole point of using the solvent in any reaction is to make reactant more soluble and make up a homogeneous system needed to carry out the reaction. Often solvent workups are required for the purification and separation of the desired products!!

D) environmentally friendly (Advantage)

---> Green chemistry implies to avoid the use of toxic solvents and reduce pollution.

Hope it clears your concept!