Bromination of Cholesterol Introduction In this experiment, you will carry out t

Question

Bromination of Cholesterol Introduction In this experiment, you will carry out the bromination of cholesterol. IH NMR analysis of cholesterol and dibromocholesterol will allow you to elucidate" the structure of dibromocholesterol and to make some conclusions about the mechanism of the bromination reaction. 21 18 Brz H H 15 Zn H dibromocholesterol cholesterol Cholesterol ag, 2.6 mmol) is in methyl (7ml) in a 25 ml Erlenmeyer flask. To this solution is added dropwise a solution (c. 8 ml) of bromine in a acid containing sodium acetate via syringe. The dibromocholesterol should crystalize out as a a plastic white paste. Allow the mixture to cool in an ice bath for several minutes. Prepare a solution of ether ml) and acetic acid (12 ml) and allow to cool in an ice bath. Collect the cholesterol dib by suction filtration, and wash the solid material carefully with the cold ether/ac acid mixture to remove traces of Continue to apply suction until the solid is reasonably dry, transfer it to a weighed vial and dry by high vacuum for 15 minutes. Submit a sample for HNMR in CDCls This solution has been prepared beforehand. It consists of acetic acid (100 ml, bromine (9 g) and anhydrous sodium acetate g). Based on the NMR-results, draw the exact stereochemical structure of the product, using the provided templates for the four alternative structures (Br can be in either "x" or "Y" position).

Explanation / Answer

Based on the NMR data, we have pure compund formed as the product with only one conformation for the compound structure.

Based on the NMR the hydrogen on the carbon next to the -OH group is in the axial position as it is more downfiled shifted due to 1,3-diaxial interaction with the Br at the 3-position of the ring.

Based on the NMR, the hydrogen on the carbon next to -Br is in the equatorial position as it is shifted more downfield in position due to disielding effect.

The structure based on the NMR data would be thus,similar to B, with Y as Hydrogen and X as the Br group.

Related Questions

Navigate

• Browse (All)
• Browse B
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.