techniques are more commonly utilized on inorganic or organometallic systems than on purely organic reactions, and examples include exploration of the samarium Barbier reaction. Reaction calorimetry Calorimetry may be used to monitor the course of a reaction, since the instantaneous heat flux of the reaction, which is directly related to the enthalpy change for the reaction, is monitored. Reaction calorimetry may be classified as a differential technique since the primary data collected are proportional to rate vs. time. From these data, the starting material or product concentration over time may be obtained by simply taking the integral of a polynomial fit to the experimental curve. While reaction calorimetry is less frequently employed than a number of other techniques, it has found use as an effective tool for catalyst screening. Reaction calorimetry has also been applied as an efficient method for mechanistic study of individual reactions including the prolinate-catalyzed α-amination of aldehydes and the palladium catalyzed Buchwald-Hartwig amination reaction. Further techniques While Gas Chromatography, HPLC, and Mass Spectrometry are all excellent techniques for distinguishing mixtures of compounds (and sometimes even enantiomers), the time resolution of these measurements is less precise than that of the techniques described above. Regardless, these techniques have still seen use, such as in the investigation of the Heck reaction where the heterogeneous nature of the reaction precluded utilization of the techniques described above. and SOMO-activation by organocatalysts Despite their shortcomings, these techniques may serve as excellent calibration methods. Data manipulation and presentation Reaction progress data may often most simply be presented as plot of substrate concentration ([A]t) vs. time (t) or fraction conversion (F) vs. time (t). The latter requires minor algebraic manipulation to convert concentration/absorbance values to fractional conversion (F), by: F = where [A]0 is the amount, absorbance, or concentration of substrate initially present and [A]t is the amount, absorbance, or concentration of that reagent at time, t. Normalizing data to fractional conversion may be particularly helpful as it allows multiple reactions run with different absolute amounts or concentrations to be compared on the same plot. Data may also commonly be presented as a plot of reaction rate (v) vs. time (t). Again, simple algebraic manipulation is required; for example, calorimetric experiments give: v = where q is the instantaneous heat transfer, ΔH is the known enthalpy change of the reaction, and V is the reaction volume. Data from reaction progress kinetics experiments are also