PH3S58 Provide answers for the following questions as a Word or pdf file via the submission link on Blackboard by 12:00 pm Monday 28th November 2022.
Consider the route to tafenoquine (Compound 9) outlined below, and with consideration of the 12 principles of green chemistry, identify any significant hazards or limitations associated with the synthetic route.
In particular, identify;
a. Five hazardous chemicals and state their associated risks.
b. One fundamental limitation of the process with regards to its atom efficiency.
c. Two instances of reaction conditions which are undesirable for further process development.
d. Two instances where waste streams from reactions would require processing.
(Total of 20 marks)
Identify two instances where control in large-scale reactions is more difficult than the corresponding small- scale laboratory reactions and suggest strategies that can be used to overcome these difficulties.
(a) The hydrolysis reaction of phosphorous trichloride (PCl3) in water at 10 oC proceeds under adiabatic reaction conditions with a heat of reaction of -275 kJ/mol. Given the following data:
Mass of water used: 10 Kg
Mass of phosphorous trichloride used: 10 Kg
Molecular weight of phosphorous trichloride = 137 g/mol Specific heat capacity (CpH O) of water = 4.2 J/g/oC
Specific heat capacity (CpPCl3) of phosphorous trichloride = 1.8 J/g/oC Calculate:
(i) the total amount of heat liberated (Qrxn) in the hydrolysis reaction.
(ii) the specific heat capacity of the final reaction mixture (Cpmix).
(iii) the adiabatic temperature rise (Tad).
(iv) the maximum temperature of the synthetic reaction (MTSR) assuming complete reaction of phosphorous trichloride.
(v) Is the severity in the case of a thermal runaway “high”, “medium” or “low”? Explain your answer.
(b) Subsequent DSC calorimetry studies of the final reaction mixture indicated that an additional exothermic reaction was observed with an onset temperature of 350 oC producing a gaseous product. Suggest why it would be inherently unsafe to carry out the hydrolysis reaction of phosphorous trichloride at 50 oC, and what would be the potential consequences of a loss of thermal control.
(3 marks) (Total of 20 marks)
Design and Methods