Chem436ProbSetKey2 - Chemistry436:ProblemSet2KEY Name TA...

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Chemistry 436: Problem Set 2 KEY Name: ________________ TA: ___________________ Problem #1.) Please predict the major product from the following reactions. J. Org. Chem. , 28 , 1940 (1963) J. Am. Chem. Soc., 94 , 7159 (1972) b. Explain the difference in stereoselectivity seen above. An axial attack results in steric interactions with the 1,3 diaxial hydrogens on the ring. This steric interaction is not present with an equatorial attack. However, an equatorial attack forces the carbonyl oxygen to become fully eclipsed with the equatorial hydrogen on the adjacent carbon. For small nucleophiles, such as LiAlH 4 , the steric interaction is lower in energy that this torsional strain and an axial attack is favored. For bulky nucleophiles, such as LiBH(s‐Bu) 3 , the steric interactions with the 1,3 diaxial hydrogens is larger than the torsional strain and an equatorial attack is favored. Problem #2.) The Felkin‐Ahn model for additions to carbonyl compounds can be used to accurately determine the stereochemistry of the product. Given what you know of this model, please explain the difference in stereoselectivity seen below.
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Chem436ProbSetKey2 - Chemistry436:ProblemSet2KEY Name TA...

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