Cholesterol specific rotation

Cholesterol when isolated from natural sources is obtained as a single enantiomer The observed rotation a of a 0 3 g sample of cholesterol in 15 ml of chloroform solution contained in a 10 cm polarimeter tube is -0 78° Cal culate the specific rotation of cholesterol... 

From the previous problem, the specific rotation of natural cholesterol is [a] = 39°. The mixture... 

A-6. (a) The specific rotation of pure (-)-cholesterol is -39°. What is the specific rotation of a... 

SampiG ProbiGm 5.5 Pure cholesterol has a specific rotation of-32. A sample of cholesterol prepared in the lab had a... 

PROBLEM 7.5 A sample of synthetic cholesterol was prepared consisting entirely of the enantiomer of natural cholesterol. A mixture of natural and synthetic cholesterol has a specific rotation [a] o of -13°. What fraction of the mixture is natural cholesterol ... 

Problem 5.4 A 0.5-g sample of cholesterol isolated from an atherosclerotic arterial specimen yields an observed rotation of -0.76° when dissolved in 20 mL of chloroform and placed in a 1-dm cell. Determine the specific rotation [a] of cholesterol for (a) the entities as defined above (b) an increase in solute from 0.5 g to 1.0 g (c) an increase in solvent from 20 mL to 40 mL and (d) an increase in path length from 1 dm to 2 dm. 

From the previous problem, the specific rotation of natural cholesterol is [a] = -39°. The mixture of natural ( )-cholesterol and synthetic (+)-cholesterol specified in this problem has a specific rofation [a] of 13°. 

The concentration of cholesterol dissolved in chloroform is 6.15 g per 100 ml of solution. (a) A portion of this solution in a 5-cm polarimeter tube causes an observed rotation of - 1.2 . Calculate the specific rotation of cholesterol. (b) Predict the observed rotation if the same solution were placed in a 10-cm tube. (c) Predict the observed rotation if 10 ml of the solution were diluted to 20 ml and placed in a 5-cm tube. 

For solutions it is necessary to specify the solvent, since solvent-solute interactions can affect not only the magnitude of optical activity, but perhaps the direction of the rotation as well. ° For example, the specific rotation of (-)-a-methylbenzylamine was found to be -31.86° in benzene and -52.29° in Specific rotations are usually reported in an abbreviated format. The specific rotation of cholesterol is given as [a]D-31.5° (c = 2 in ether) [a]D°-39.5° (c = 2 in chloroform). Note that in this format, the concentration of a solution is usually taken to mean grams per 100 mL. ° It is also possible to define a molecular rotation (O) when molecular weight is known, as shown in equation 2.2. Calculating molecular rotation makes it easier to determine the effect of the same chromophore in different molecules. 

When 0.095 g of cholesterol is dissolved in 1.00 ml of ether and placed in a sample cell 10.0 cm in length, the observed rotation at 20°C (using the D line of sodium) is -2.99°. Calculate the specific rotation of cholesterol. 

The melting point of cholesterol is 147-148 °C, and its specific optical rotation is —40 . 

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