Once a compound has been isolated, a chemist needs to make sure that it is the d

Question

Once a compound has been isolated, a chemist needs to make sure that it is the desired product and that it is pure. Using the mass of a solid isolated to determine a percent yield is meaningless if it is not the desired product! You will check the purity of your compound by determining its melting point and comparing it to the literature value for cholesterol nominate. You must find the literature values for 2-acetonaphthone, cholesterol and cholesterol nominate (also known as cholesterol pelargonate), as quoted by one of the chemical companies who regularly make them: Sigma Aldrich. Once you found these values, you should entered them into page E4-8 of your worksheets. Based on the information on the Sigma website, what is the melting point for cholesterol nominate (also called cholesterol pelargonate)? Give your answer in degree C, but do not include units in your answer. The value reported for melting point refers only to one of the possible phase transitions for cholesterol nominate. As a liquid-crystal forming compound, cholesterol nominate has several phase transitions, including two liquid-crystal mesophases. Based on the information on the Sigma website, what is the temperature range over which the cholesterol nominate will change from ordered, crystalline solid to a disordered (Isotropic") liquid? Give your answer in degree C, but do not include units in your answer. As you record these values on your worksheet, consider which temperature range you expect to match more closely with your observed data. Again, based on the information on the Sigma catalog, what is the melting point of 2-acetonaphthone? Give your answer in degree C, but do not include units in your answer. Finally, what is the melting point for cholesterol? Give your answer in degree C, but do not include units in your answer.

Explanation / Answer

Cholestryl nonanoate mp= 74-77 0C

Chloestericphase to isotropic phase= 90 0C

2-Acetonaphthone mp= 52-56 0C

Cholesterol mp = 147-149 0C

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