High-throughput physical organic chemistry - Hammett parameter evaluation

High-throughput analysis techniques were developed to allow the rapid assessment of a range of Hammett parameters utilizing positive electrospray mass spectrometry (ESI+-MS) as the sole quantitative tool, with the core of the approach being a so-called "analytical construct". Hammett substituent parameters were determined for a range of meta- and para-substituted anilines by high-throughput ( HT) assessment of relative reaction rates for competitive amide bond formation reaction with up to five parameters determined in a single pot reaction. Sensitivity of the reaction to substituents' effects ( materialized by Hammett's rho parameter) was determined in the first instance, with HT Hammett's sigma substituent parameter assessment then carried out successfully for over 30 anilines, with excellent correlation observed between the HT ESI+-MS method of determination and literature values.