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Pre lab questions

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1. Why is sulfuric acid, rather than hydrochloric acid, used to catalyze the dehydration of alcohols?

2. A sample of 150 mg of an organic compound is dissolved in 7.5 ml of water. The solution is paced in a 20-cm polarimeter tube and the rotation measured in a polarimeter. The rotation observed was +2.676 degrees. Distilled water, in the same tube, gave a reading of +0.016 degrees. Calculate the specific rotation of the compound.

3. Which of the following compounds have a meso form?

2,3- Dibromopentane
2,4-Dibromopentane
2,3-Dibromobutane

Why is it a meso form?

4. Compounds such naphthalene and 1,4-dichlorobenzene fine use as mothballs since they sublime at a slow rate at atmospheric pressure. Explain this behavior in terms of the structure of the molecules.

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1. Why is sulfuric acid, rather than hydrochloric acid, used to catalyze the dehydration of alcohols?

In a dehydration the alcohol becomes charged (R-OH2+) then it can leave (a double bond is formed) the acid provides the extra H+ for the alcohol. Then the resulting anion (HSO4-) can do the elimination reaction creating the double bond. HCl still provides the H+ and still could do the elimination, but could also (more likely) just substitute giving R-Cl and not the double bond desired.

2. A sample of 150 mg of an organic compound is ...

Solution Summary

Pre lab questions for organic chemistry lab, role of sulfuric acid, polarimetry,

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