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Unformatted text preview: Understanding how the number of equivalents of base used will affect an aldol or Claisen reaction 1) Remember that the amount of carbonyl compound present is defined to be 1.0 equivalent, so the number of equivalents of base are really describing a ratio of the amount of base to the amount of carbonyl compound added at the beginning of the reaction. 0.5 equivalents of base means there only half as many base molecules as carbonyl compound molecules added to the reaction. 2) Determine how much base is consumed in the overall reaction mechanism (i.e. is a catalytic amount or are 0.5 equivalents required?) by seeing if base is consumed (i.e. the last step of the Claisen condensation) or not (i.e. aldol mechanism). If base is consumed, calculate the ratio of number of molecules of base consumed versus the number of starting carbonyl compounds consumed in the reaction. For example, in the Claisen condensation, one molecule of base is consumed for every product molecule created (due to the last step). However, each product molecule requires two ester molecules. Therefore, the ratio of base to ester consumed 1 molecule of base for every two molecules of ester. Since the amount of ester is by definition 1.0 equivalents, this means you need at minimum of 0.5 equivalents of base....
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- Spring '10
- Chemistry, Amide, Claisen