Unit 2 - Green Metrics

Question 1

What five components are usually assessed when comparing the sustainability of reactions?

Answer 1

Raw materials

Reaction types (additions, eliminations)

Reagents (including catalysts)

Reaction conditions (including solvents)

Toxicity of products (including waste by-products)

Question 2

What is the atom efficiency of a rearrangement (such as Claisen rearrangement)?

Answer 2

100%

Question 3

What is the atom efficiency of an addition reaction (such as hydrogenation and carbonylation)?

Answer 3

100%

Question 4

What is the atom efficiency of a Diels-Alder reaction?

Answer 4

100%

Question 5

What is the atom efficiency of substitution and elimination reactions?

Answer 5

Less than 100%.

Question 6

During the synthesis of phenol, what are the two routes used and what are their atom economies?

Answer 6

1) The sulfonation of benzene. Atom economy = 20.4%

2) The oxidation of cumene. Atom economy = 62%. However, if the acetone is used as a useful product then this increases to 100%.

Question 7

What are the advantages of using the E-factor metric?

Answer 7

Takes into account solvent use.

Question 8

What are the disadvantages of using the E-factor metric?

Answer 8

Large uses of water as solvent or benign dilute inorganics will inflate the E factor with very little environmental effect.

Concentrates on waste rather than hazard.

Question 9

What are the disadvantages of using the atom economy metric?

Answer 9

They are theoretical and do not include the reaction yield, selectivity or the hazard of the waste stream.

Only includes stoichiometric reagents, and does not include catalysts or solvents.

Do not include anything about energy intensiveness or toxicity.

Question 10

What is effective mass yield and how is it calculated?

Answer 10

The proportion of the mass of desired product and the mass of harmful reagents.

EMY = (mass of desired product / mass of non-benign reagents) x 100

Question 11

What is a disadvantage of effective mass yield?

Answer 11

It is difficult to judge whether a reagent is benign or not.

Question 12

How is RME calculated?

Answer 12

RME = (mass of desired product / mass of starting reactants) x 100

Question 13

How is CE calculated?

Answer 13

CE = (mass of carbon in product / mass of carbon in process) x 100

Question 14

How is MI calculated and what is it a measure of?

Answer 14

MI = total mass in process / mass of product

It is a measure of intensity.

Question 15

How is MP calculated and what is it a measure of?

Answer 15

MP = mass of product / total mass in process

It is a measure of productivity.

Question 16

What were the problems with the old synthesis of ibuprofen?

Answer 16

It had a low atom efficiency (40%) but the largest problem was the loss of CCl₄ solvent at 1-2 kg per day when the limit was 5 mL per day.

Question 17

What is the atom efficiency of the new synthesis of ibuprofen?

Answer 17

77%.