Question

Two related barbiturates, barbital and secobarbital have the following properties:

Barbital: pK =7.8, Oil/water Partition Coefficient =1

Secobarbital: pK = 7.9, Oil/water Partition Coefficient = 52

When administered orally, secobarbital is passively absorbed 6-times more readily by stomach cells than is barbital. Using the information given here, provide an explanation for the difference in stomach absorption rates for these two molecules.

Answer 1

AS the pK Barbital and Secobarbital of both are quite equal hence stomach absorption rates is don't depend on pK in this case it depends on Oil/water Partition Coefficient .

AS  Oil/water Partition Coefficient of  Secobarbital is greter than Barbital there fore we can say that Secobarbital is more soluble in oil as compare to Barbital . Hence the stomach will absorb that thing which is less soluble in water and that is Secobarbital .

hence its   is absorbed 6-times more readily by stomach cells than the barbital