a) The distribution constants for acompound are as follows: Kcyclohexane/water =

Question

a) The distribution constants for acompound are as follows:

Kcyclohexane/water = 1.5

Kdiethyl ether/water = 5.1

You have an aqueous mixture of thecompound. Which solvent system, cyclohexane/water, pentane/water,or diethyl ether/water, would give the most efficient extractioninto the organic solvent?

b) You have prepared an organiccompound by reacting it with strong aqueous acid. The work-up callsfor extraction into methylene chloride, then a wash with 5%NaHCO3. What is the purpose of the NaHCO3wash?

Explanation / Answer

a . Since the distribution constant of the compound ismore in pentane / water system , it can be used for most efficientextraction into organic solvent .    Distribution constant, K = concentration ofcompound in organic solvent / concentrtion of compound of inwater    Higher value of K indicates thatconcentraion of compund is more in oraganic solvent than itsconcentration in water ,so    the system with larger K is preferable for mostefficeint extration . b.   5% NaHCO3 is used toneutralize the system so as to get solid compound .        At sufficient pH thesoluble compound comes to solid state in the system .

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