Heterocyclic Mesomeric Betaines and Mesoionic Compounds, Volume 137 in the Advances in Heterocyclic Chemistry series, highlights new advances in the field, with this new volume presenting interesting chapters on a variety of topics, including Heterocyclic Mesomeric Betaines, Type A Mesoionic Compounds (1980-2020), Type B Mesoionic Compounds (1980-2020), Recent Developments in the Chemistry of Heteroporphyrins, Carbaporphyrins and Related Systems, Heterocyclic Zwitterions Based on Coupled Polymethines, Meso-ionic Compounds reproduced from Adv. Heterocycl. Chem. 1976, 19, 1-122., and Meso-ionic Heterocycles (1976-1980) reproduced from Tetrahedron, 1982, 38, 2965-3011. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in Advances in Heterocyclic Chemistry series Updated release includes the latest information on Betaine