Aspirin isotopes

The deuterium kinetic isotope effect (fejjjo/ 030) for the hydrolysis of aspirin is 2.2. What does this tell you about the kind of catalysis exerted by the ort/io-carboxyl substituent Hint It is easier to break an O—H bond than an O—D bond.)... 

Calculations of the spectra of the closely related compounds—acetylsalicylic acid (aspirin) and salicylaldehyde, at different temperatures and with selective deuteration, have been published for acetylsalicylic acid in Ref. 54 and for salicylaldehyde in Ref. 53. In the acetylsalicylic acid crystal there are no intramolecular hydrogen bonds—only intermolecular hydrogen bonds are present. The molecules of acetylsalicylic acid form hydrogen-bonded dimeric cyclic structures, similar to those present in salicylic acid. The IR spectra of the acetylsalicylic acid and the salicylic acid crystals in the region of the O—H(D) stretching vibrations are similar, excluding peaks due to intramolecular hydrogen bonds. Spectra of the acetylsalicylic acid crystal were calculated at two temperatures 300 and 77K. The experimental spectra and the observed temperature and isotopic effects are reproduced in these calculations reasonably well [54]. 

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