Process design

Examples of variables and responses for a chemical process

Table 1 provides examples of the types of variables and responses for a chemical process.  A continuous variable is a factor whose values can easily be adjusted over a range (quantitative factor). A categorical variable is a factor that is non-continuous (qualitative factor).

Table 1
VariablesResponses
ContinuousCategorical
Substrate A/B ratio Substrate A/ Substrate B Conversion
Reagent quality Regioselectivity
Temperature Stereoselectivity
Concentration Reagent Enatioselectivity
Rate of addition Solvent Rate or rate constant
pH Order of addition Purity / impurities
Time Type of equipment Isolated yield
Pressure Particle size
Agitation rate Density

When selecting factors to study, use prior knowledge where available (previous observations, literature knowledge, related chemistry, etc.) and choose factors that are likely to answer the experimental objectives.