10-24-08 - promote/disfavor each of these four reaction...

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We begin by contrasting the E2 versus E1 mechanisms. For the E2 mechanism, elimination is stereospecific because it is concerted. For the E1 mechanism, elimination is not stereospecific because it is not concerted. One important aspect of the E2 elimination is the following: If there are two different C-H bonds that can adopt the required anti-periplanar geometry, the elimination will occur to give the more substituted alkene. Thus, Zaitsev’s rule applies to both E1 and E2. The underlying physical basis for Zaitsev’s rule was reviewed. Upon exposure of an alkyl halide to a nucleophile, four possible outcomes may result: S N 2, E2, S N 1, E1. In class, we discussed the factors that promote each pathway. Based on a given set of conditions, you should be able to predict the major products that would result. In class, we reviewed the factors that
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Unformatted text preview: promote/disfavor each of these four reaction pathways. Multi-Step Synthesis : Now that we have a modest arsenal of transformations at our disposal, we can perform sequences of transformations. In class, we were given a starting material and product and were asked to devise a synthetic sequence that enables the overall transformation. For example, we converted cyclohexane to cis-1,2-cyclohexane diol in three steps. A number of other examples were given. When devising synthetic sequences, it is helpful to think backwards in terms of functional group interconversions. Make 3 x 5 cards and roadmaps to gain a command of functional group interconversions and corresponding reaction mechanisms. Next time : Begin reactions of alcohols...
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