NOTE: Students who had taken UPC2201 Chemicals and Us in or before AY2011-2 are not eligible to read this module.

Whether it is a simple acid-base neutralization reaction or a complex series of reactions in the biosynthesis of cholesterol, the initiation of any reaction is the interaction between two separate reacting species or two separate reacting sites in a molecule. The interaction is molecular courtship similar to human courtship, i.e. between two species or two sites of opposite nature. This molecular courtship can stay in close proximity for a long time, or it can result in molecular marriage, i.e. forming a bond. On the contrary if conditions turn out to be unfavorable, the courtship may terminate or the marriage may end with a divorce.

Acid-base neutralization: H + + OH → H2O

molecular courtship

Sequence of concerted reactions in the biosynthesis of cholesterol


If the molecular courtship is favorable, it governs the resulting combined properties of the two interacting species, quite similar to human courtship moderating the human behavior of the individuals and promoting mutual understanding.