use of large scale equipment (see section 11.2.1). These changes, waste disposal
and the hazards associated with carrying out the synthesis using larger amounts
of the reagents should be evaluated before the conversion is made (see section
11.2.2). The pilot plant should produce sufficient quantities of the drug to carry
out the comprehensive tests that are required by the regulating authority. Once a
licence to manufacture the drug has been granted, the pilot plant synthesis is
converted to the full manufacturing process. The main considerations in this
conversion are chemical engineering issues, environmental impact, waste dis-
posal, safety, quality control and cost.
11.2.1 Chemical engineering issues
Initially, the chemical engineers will have to decide whether the reactions can be
safely carried out in the existing plant or whether it will be necessary to
construct a new plant. Since the latter could be very expensive, they should
also consider whether it is possible to modify the synthesis so that it could utilize
existing equipment. The standard large scale reaction vessel is a stainless steel
container. It is usually equipped with a stirring paddle, a heating jacket for
controlling the reaction temperature, openings that allow solids and liquids to
be placed in or removed from the vessel and provision for either distilling or
refluxing liquids (Figure 11.2). Reaction vessels are usually connected by
Out-flow to other
equipmentTo receiverStirrerLiquids inHeating jacket using
hot or cold liquidsThree-way valveSolid in
(Charge-hole)CondenserFigure 11.2 A diagramatic representation of a typical reaction vessel. The three way valve
enables the condenser to be used to either reflux or distil the liquids in the reaction vessel
CHEMICAL DEVELOPMENT 225