determination of the chloroform-water partition co-efficient of barbiturates

Question 1

what are barbiturates

Answer 1

they act as central nervous system depressants and by virtue of this they produce a wide spectrum of effects , from mild sedation to total anaesthesia. they can be used as hypnotics , sedatives , anticonvulsants and anaesthetics , although they are probably most familiar as sleeping pils. barbiturates are solvable in both organic and aqueous environments dependent on solution PH. they behave as weak acids due to the resonance stability of the conjugated ring systems.

Question 2

What is a diuretic acid

Answer 2

an acid with 2 pKa values

Question 3

what is a butabarbital

Answer 3

a short acting barbiturate which is more lipophilic so more readily crosses the blood brain barrier , inducing anaesthetic effects more rapidly . it has a pKa value of 8.48.

Question 4

Chloroform

Answer 4

chloroform is heavier than water so will sink to the bottom

Question 5

Papp

Answer 5

Papp is a measure of the total amount of drug partitioned between the organic and aqueous layer. This is greatly affected by changes in pH.

Question 6

Papp is calculated by

Answer 6

(conc.in organic layer)/(cons.in aqueous layer)

Question 7

PTrue is

Answer 7

Ptrue is a measure of how the unionised drug partitions between the organic and aqueous layers. It is unaffected by changes in pH

Question 8

PTrue can be calculated by

Answer 8

ptrue=papp x fraction unionised