Aspirin laboratory synthesis

Reactions 5.14 and 5.15 illustrate two specific examples. In another example, the laboratory synthesis of aspirin (Reaction 5.16), using acetic anhydride, gives excellent yields of the ester. 

In a laboratory synthesis, a student begins with 3.00 mL of acetic anhydride (density = 1.08 g/mL) and 1.25 g of salicylic acid. Once the reaction is complete, the smdent collects 1.22 g of aspirin. Determine the limiting reactant, theoretical yield of aspirin, and percent yield for the reaction. 

Higher aspirin doses of 900 to 1,500 mg per day have not been shown to have increased efficacy in arterial thromboembolism prevention when compared with 300 mg per day or lower doses. In one metaanalysis of 19 antiplatelet trials in several thrombotic disorders, the issue of aspirin dosage was indirectly analyzed (44). It was found that trials employing 900 to 1,500 mg of daily aspirin versus placebo had similar outcomes to trials employing doses of 300 to 325 mg per day versus placebo. Patients treated with 900 to 1,500 mg experienced a 23% reduction in new vascular events, whereas those taking 320 mg showed a decrease of 24%. Thus a dose-response plateau appears to exist in aspirin s antithrombotic effect. Clinical and laboratory observations are complimentary in this reqrect since aspirin inhibition of in vitro platelet PG synthesis shows a similar dose-re nse plateau with maximal blockade at micromolar concentrations (2,25,28). 

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