In part I, the students observe anhydride formation and decomposition using 1 H NMR spectroscopy. An NMR tube is charged with KSBA and NaOH (0.5 equiv) in D 2 O; dimethylacetamide (DMA) is also included as an internal standard for the determination of absolute concentrations of KSBA-An. The reaction mixture is then treated with EDC (0.3 equiv) immediately before acquisition of spectra is started. Generation of KSBA-An is typically fast enough that it is already formed by the time the first spectrum is acquired (we usually find it convenient to shim the instrument on a blank sample first so that acquisition can be started without delay after the EDC is added). The anhydride concentrations are easily determined from the integration of new signals appearing in the 1 H NMR spectra. The full 1 H NMR spectroscopy experiment can be conveniently carried out in about 20 min. pD of the reaction mixture changes slightly as the carboxylic acid is initially consumed and then regenerated. A plot of ln[KSBA-An] against time, shown in Figure , can be used to determine the rate constant k for the (pseudo-first-order) hydrolysis from a linear fit.