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Question 7 (12 points) For the decarboxylation of 5-nitro-3-carboxbenzisoxazole (reaction shown below), a carbon isotope (k12/13) effect was measured to be 1.046 in aqueous buffer at 20 oC (Lewis, C-Paneth, P.: O'Leary, M. H.; Hilvert, D. J. Am. Chem. Soc., 1993, 115, 1410-1413). ON ON CEN CO2 N 2 Na a. (8 points) Propose a reasonable mechanism for the above reaction that is consistent with the KiE observed and clearly give the structure of the transition state for your rate-determine step. Explain the significance of the KiE in determining your mechanism b. (4 points) It was reported that with increasing dioxane (a non polar aprotic solvent) ration in the aqueous medium, that there was a four fold increase in the rate of the reaction. Briefly explain this observation.