Bromination/Debromination of Cholesterol

1) On page 363, The NMR shows a peak at 2.3 ppm. What set of H’s do you think this peak represents? It’s tough to see the splitting for it, so use what you know about chemical shifts.

2) If 3b-cholestanol is an impurity in Cholesterol, why doesn’t it also react with Br₂? What happens to it after bromination of Cholesterol takes place? (ie- why is it that bromination allows you to separate it from cholesterol?)

3) Assign the IR peaks on page 364 for the starting material cholesterol.

4) What is the % by mass of 4.5 M NaOH? (SHOW ME THE ENTIRE CALCULATION)

5) What is the density of methyl t-butyl ether? In an extraction with water, would it be the top or bottom layer?

CHARACTERISTIC INFRARED ABSORPTION FREQUENCIES
Bond	Compound Type	Frequency range, cm^-1
C-H	Alkanes	2960-2850(s) stretch
		1470-1350(v) scissoring and bending
	CH3 Umbrella Deformation	1380(m-w) - Doublet - isopropyl, t-butyl
C-H	Alkenes	3080-3020(m) stretch
		1000-675(s) bend
C-H	Aromatic Rings	3100-3000(m) stretch
	Phenyl Ring Substitution Bands	870-675(s) bend
	Phenyl Ring Substitution Overtones	2000-1600(w) - fingerprint region
C-H	Alkynes	3333-3267(s) stretch
		700-610(b) bend
C=C	Alkenes	1680-1640(m,w)) stretch
CºC	Alkynes	2260-2100(w,sh) stretch
C=C	Aromatic Rings	1600, 1500(w) stretch
C-O	Alcohols, Ethers, Carboxylic acids, Esters	1260-1000(s) stretch
C=O	Aldehydes , Ketones, Carboxylic acids, Esters	1760-1670(s) stretch
O-H	Monomeric -- Alcohols, Phenols	3640-3160(s,br) stretch
	Hydrogen-bonded -- Alcohols, Phenols	3600-3200(b) stretch
	Carboxylic acids	3000-2500(b) stretch
N-H	Amines	3500-3300(m) stretch
		1650-1580 (m) bend
C-N	Amines	1340-1020(m) stretch
CºN	Nitriles	2260-2220(v) stretch
NO2	Nitro Compounds	1660-1500(s) asymmetrical stretch
		1390-1260(s) symmetrical stretch

v - variable, m - medium, s - strong, br - broad, w - weak