Question

Compound A has a partition coefficient of 3.0 when it is partitioned between Ch2Cl2 and water. If 2.0 g of compound A is partitioned between 100 mL of Ch2Cl2 and 50 mL of water, calculate how much will be in the upper layer and how much will be in the lower layer?

Answer 1

The distribution co-efficient is 3.0. We know that

K = C_O/C_AQ

whre K = partition co-efficient; C_O is the concentration in the organic layer (in g/mL ) and C_AQ is the concentration in the aqueous layer (in g/mL).

Given,

K = 3.0,

we have,

C_O/C_AQ = 3.0

====> C₀ = 3.C_AQ

We have 100 mL dichloromethane (DCM), i.e, V_O = 100 mL and 50 mL water, i.e, V_AQ = 50 mL.

Let x g be in the organic layer and y g be in the aqueous layer.

Therefore,

x = V_O*C_O =100*3*C_AQ = 300*C_AQ

Y = V_AQ*C_AQ = 50*C_AQ

Therefore,

300*C_AQ +50*C_AQ = 4

====> 350*C_AQ = 4

====> C_AQ = 4/350 = 0.01143

Therefore, y = 50*C_AQ = (50 mL)*(0.01143 g/mL) = 0.5715 g

Therefore, 0.57 g compound will go into the aqueous phase.

The amount in the organic phase = (100 mL)*3*(0.01143 g/mL) = 3.429.

Ans: The amounts present in the organic and aqueous layers are 3.429 g and 0.5715 g