CXLIX.—The mutarotation of camphorquinonehydrazone and mechanism of simple desmotropic change

Abstract

OF the various types of isomeric change, that which involves a change of position of one hydrogen atom only, as in a simple desmotropic change, would, for various reasons, appear to be the most simple, and probably the most easy to investigate.We do not intend to review the many important contributions already made to this subject, in particular since such a course would involve, for the most part, a repetition of much with which Lowry has somemhat recently dealt in his suggestive paper on mutarotation and

Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

“…Tautomerization is defined as ''the addition of a H-atom (proton) at one molecular site and its removal from another'' [64], and it leads to changes of the molecular skeleton, electron density distribution, and chemical properties. Although tautomerism is a long-standing research topic in organic chemistry, for example, one of the pioneering studies has been reported by Claisen in 1896 [65], it still remains a challenging subject.…”

Tautomerism: Introduction, History, and Recent Developments in Experimental and Theoretical Methods

“…Laar [35] had proposed a so-called oscillatory model, where a hydrogen atom vibrates continuously between the two possible positions. Other early observations include dielectric effects: the polarity of the solvent could help release a proton from one position, thus making a transfer possible [1]. Although a tautomerization reaction is not an ionization (Section 1.1), an ionization step does play a crucial role, and may in many cases be the rate-determining step.…”

Fluorescence of isatin N‐phenylsemicarbazones: aggregation and hydrazide–hydrazonol tautomerism

“…Solution fluorescence was measured in a 1 cm cuvette with an FSP 920 (Edinburgh Instruments, UK) spectrofluorimeter in front-face arrangement to avoid self-absorption effect. 1 H NMR spectra were recorded on Varian NMR System spectrometer (Palo Alto, CA, USA) operating at 600 MHz for 1 H in DMSO-d 6 with TMS (tetramethylsilane) as the internal standard. The fluorescent quantum yield (Φ F ) of Ia in benzene was determined by Eqns.…”

“…Prototropic tautomerism, defined as 'the addition of a proton at one molecular site and its removal from another' and hence clearly distinguished from ionization, is one of the most important phenomena in organic chemistry despite the relatively small proportion of molecules in which it can occur. [1,2] Tautomers are rapidly interconverted constitutional isomers, usually distinguished by a different bonding location for a labile hydrogen atom and a differently located double bond. (Micro)Environment surrounding the individual tautomer has an important influence on tautomer stability and thus on the overall ratio of individual tautomeric forms in equilibrium.…”