Drug Stability - Lecture 2

Question 1

What must be measured to see the pH?

Answer 1

The hydrolytic rate profile must be measured

Question 2

what type of graphs can be plotted for pH?

Answer 2

V-plott grpahs. where log K versus pH will shows the minimum rate at about neutrality.

Question 3

Describe an acid catalysed hydrolysis.

Answer 3

Protonation of a carbonyl oxygen will occur. Then the water molecule will attack the nucleophile.

Question 4

Is acid hydrolysis reversible?

Answer 4

Yes and its called esterification.

Question 5

Describe a base catalysed hydorlysis

Answer 5

A nucleophile will attack a hydroxide ion (OH). the reaction takes places because of the polarisation of the carbonyl group. The carboxylate salt is isolated.

Question 6

Is base catalysed hydrolysis reversible?

Answer 6

NO since the carboxylate anion shows little tendency to react with an acid.

Question 7

How does temperature affect hydrolysis?

Answer 7

An increase in temperature increases the hydrolysis rate.

Question 8

What equation can be used to measure the rate of hydrolysis?

Answer 8

The Arrhenius equation

Question 9

What is the best way to reduce the rate of hydrolysis ?

Answer 9

To replace all or most of the water with a solvent such as alcohol or propylene glycol.

Question 10

What effect does temperature have on solids ?

Answer 10

• Melting on temperature increase
• Changing of polymorphic form
• May be loosely bound to water which is lost at higher temperature