1 Acetaminophen is a weaker acid than carbonic acid, but aspirin is a stronger a

Question

1 Acetaminophen is a weaker acid than carbonic acid, but aspirin is a stronger acid than carbonic acid. Prepare a flow diagram like the one in this this experiment, showing a procedure that can be used to separate a mixture of sucrose, aspirin and acetaminophen.

2. Supposed a reaction mixture when diluted with water, afforded 300mL of aqueous solution of 30g of the reaction product malononitrile which is isolated by extraction with ether. The solubility of malononitrile in ether at room temperature is 20g /100mL and in water is 13.3g /100mL. Keeping in mind that the Kd is the ratio of the solubilties in two solvent. What weight of malononitrile would be recovered by extraction by 100mL of portion of ether.   

Explanation / Answer

1. Separation of sucrose, aspirin and acetaminophen.

Of the three sucrose is soluble in water but not in organic solvents, The other two dissolve in organic solvent.

Procedure for separation:

(i). Add dichloromethane to the mixture of three compounds. Sucrose will remain indissolved. Do a gravity filtration to separate sucrose as residue.

(ii) To the dichloromethane solution add aqueous NaOH. aspirin will form salt of sodium and dissolves in water. Separate the aqueous layer from organic dichlormethane layer.

(iii) Acidify aqeuous layer to reprecipitate aspirin.

(iv) Evaporate the dichloromethane layer to isolate acetaminophen.

2. Kd = solute in organic phase/solute in aqueous phase

         = (20/100)/(13.3/100)

         = 1.504

Now, let x be the amount of malononitrile in organic phase, then 30-x would be the amount present in aqeous phase, that is,

Kd = (x/100)/(30-x/300)

with, volume of ether = 100 mL

volume fo aqueous phase = 300 mL

solve for x,

1.504 = 3x/(30-x)

45.12 - 1.504x = 3x

x = 10.02 g

So, the amount of malononitrile present in organic phase after extraction with 100 mL ether is 10.02 g

amount left in aqueous phase = 30 - 10.02 = 19.98 g

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