Problem set 3: Chem. 127/227, Fall quarter 2007 1. Formulate a mechanism (arrow pushing will do) that illustrates the acid catalyzed formation of the THP ether of ethanol, starting from ethanol and dihydropyran. 2. Illustrate the reverse process, that is, the acid catalyzed (H 3 O + /H 2 O) conversion of the THP ether referred to above, to ethanol and dihydropyran. 3. Draw the diastereoisomers formed from the acid catalyzed reaction of dihydropyran with (R)-2-butanol. 4. The process wherein the first formed intermediate in a photochemically initiated process, generally a singlet excited state, is converted to the triplet state is referred to as intersystem crossing. This can occur rapidly. With acetone, for example, the rate of intersystem crossing is 5 x 10 8 s-1 . Molecular oxygen, a molecule that exists as a triplet ground state, can react with other triplet species, e.g., a triplet excited state. When this occurs, the excited state is said to be quenched. In principle, singlets can also react with oxygen. Suppose that (a) the concentration of oxygen dissolved in a
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