The main objectives of this lab are to isolate cholesterol from gallstone and observing the reactions that took place in the transformations. There will be three major steps to transform gallstone into 4-Cholesten-3-one cholesterol. The cholesterol that is obtained from gallstone is a 5-Cholesten-3β-ol. For the first step, this compound was added with bromine to get ts dibromide derivative, 5α,6β-Dibromocholestan-3β-ol. In this experiment we got 71.3% of recovery yield of cholesterol. Next, this cholesterol compound is oxidized into dibromocholestanone by sodium dichromate and then debrominated by zinc to form 5-cholesten-3-one and we obtained 68% of them. The final step is to get the stable state of cholesterol, 4-cholesten-3-one by treating the previous product with oxalic acid. The final product percentage yield was 78%. In this lab, we failed to produce the intermediate compound, 5-cholesten-3-one but succeed in producing isolated cholesterol and 4-cholesten-3-one.
There are three major reactions essential for this lab; bromination, oxidation and isomerization. In the bromination sequence, bromine is first added to the cholesterol in the first step to get rid of the double bond forming cholesterol dibromide. The double bond is replaced by the two bromine atoms. However, the double bond is reestablished later when zinc is used to remove the two bromine atoms. The bromination of cholesterol is important in order to avoid the double bond from any possible reaction between the steps of oxidation. In addition, it purifies the compound because other steroid will not undergo easy bromination thus, will not precipitate with the cholesterol dibromide.
For the oxidation reactions, sodium dichromate, Na2Cr2O7, and zinc are the oxidants. In the first oxidation step, cholesterol dibromide is oxidized into ketone; dibromocholestanone. The OH functional group is replaced with O double bond. Zinc is then replaced the bromine atoms to reestablish...