Drug stability - lecture 3

Question 1

what is the definition of poly functional ?

Answer 1

It is when one group may affect the behaviour of another.

Question 2

what causes polarisation ?

Answer 2

Electronegativity leads to polarisation the greater the electronegativity the more polarised it is.

Question 3

What can influence the rate of hydrolysis ?

Answer 3

Inductive and mesomeric effects

Question 4

What is oxidation ?

Answer 4

Oxidation is loss of electron. Loss of 2 hydrogen atoms.

Question 5

What is reduction ?

Answer 5

Reduction is gain of electrons. Gain of 2 hydrogen.

Question 6

How to control hydrolysis ?

Answer 6

Determine pH of maximum stability from kinetic experiments and formulate at this pH. So then alter the dielectric constant by addition of nonaqueous solvents.

Question 7

What is the process of oxidation ?

Answer 7

the removal of the electropositive atom (e.g H). the removal of a radical or an electron. An increase in oxidation number.

Question 8

What is autoxidation ?

Answer 8

Its a slow oxidation in the presence of atmospheric O2. Also a chain process of three steps initiation, propagation and termination involving free radicals.

Question 9

Factors effecting autoxidation ?

Answer 9

Light, sensitisers, catalyst, hydrogen ion concentration (pH) and temperature.

Question 10

What are the two types of free radicals ?

Answer 10

Heterolytic bond cleavage - both electrons making the bond move together when the bond is broken.
homiletic bond cleavage - the two electrons making up the bond get distributed equally between two atoms so each atom gets 1 electrons.