RESULTS: Amount of crude cholesterol extracted from gallstones Percent (%) chole
ID: 694165 • Letter: R
Question
RESULTS: Amount of crude cholesterol extracted from gallstones Percent (%) cholesterol in 2.0 g of gallstones Amount of purified cholesterol obtained Percent recovery of purified cholesterol Melting point of crude cholesterol Melting point of purified cholesterol CONCLUSIONS: Comment on how well this procedure isolated and purified cholesterol. POST LAB QUESTIONS 1. Although cholesterol is an alcohol, why is it not soluble in water? What type of solvents isit soluble enough in to be extracted from natural sources? Why? 2. Why is the ethereal solution of cholesterol after debromination washed with 10% sodium hydroxide solution and then with saturated sodium chloride solution? What simple chemical test can be used to show that cholesterol is unsaturated? Explain. Why might old zinc dust not react in the debromination reaction? 3. 4. 92Explanation / Answer
2
we typcally wash the solution with NaOH , a base, in order to favour deprotonation of any grup in the products
NaOH is very basic, so H+ is not readily available, protonatino of groups will not occur
it also icnreases activity coefficients and ionic strneght which favours separation of phases
3
Hydrogenation of the species
which will occur, since double bonds can be broken to form Hydrogen rich species
4
Old zinc dust might be oxidized already, so ZnO will not react as Zn(s)
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