Safety and Selectivity in the Scale-Up of Chemical Reactions

Introduction

The aim of the course is to give lab chemists an understanding of the issues that need to be considered during the early stages of scale up to large laboratory scale equipment (10-20 litre vessels) / kilo lab. The course will concentrate on chemical safety and selectivity issues and include information on what safety testing equipment is available and the uses and limitations of this equipment. Attendees will learn how to identify potential problems whether they be thermal hazards or selectivity issues. Methods used by other companies for handling hazardous reagents and reactions will be described as well as alternative chemistry to circumvent these reactions and/or reagents.

Course Outline

Introduction

a) The safety literature
b) Functional groups which can cause problems on scale up

Improving safety and selectivity in chemical reactions

a) Inherent safety, choosing the right synthetic route
b) Reaction criticality classes (Stoessel diagrams)
c) Solvent selection
d) Choosing the right reagent
e) Catalysis - the plusses and minuses
f) Choosing the right reaction conditions, the effect of concentration

Thermal Hazard Testing and Runaway Reactions

a) Introduction and overview of safety issues in the chemical industry
b) Heat loss considerations
c) Desk screening - unstable groups, Oxygen balance equation etc
d) Principles of hazard testing - equipment and uses
e) Effect of changes to reaction variables

Solvent Selection and Solvent Effects

a) Reasons for choosing a solvent
b) The effect of solvents on chemical reactions
c) Useful solvent parameters
d) Phase transfer catalysis
e) Water as a solvent
f) Solvent free reactions
g) Alternative solvents - supercritical fluids, ionic liquids, fluorous solvents

Oxidation and Reduction

a) Choice of reagent(s)
b) Stoichiometric versus catalytic
c) Reagent stability
d) Safety issues

Hazardous Reactions and Reagents

a) Azides
b) Making triazoles and tetrazoles
c) Diazo compounds, including diazomethane
d) Petasis methylenation
e) Grignard Reagents and Organolithiums
f) Use of cyanide

Work Up

a) Quenching reactions
b) Minimising work up - Telescoping
c) Catalyst removal
d) Product isolation

Scaling up Chemical reactions

a) What can go wrong - it's not what you do but the way that you do it
b) Heat transfer areas
c) Importance of dose control and in process analysis
d) Reactions with initiation periods
e) Simple do's and don't's
f) Flammability issues

Case studies

a) Grignard reaction
b) Azide chemistry
c) Oxidation and reduction