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Chemicals from Aromatic Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
The molecule can exist in different tautomers resulting in different crystalline solids. By way of definition, a tautomer is each of two or more isomers of a compound that exist together in equilibrium, and are readily interchanged by migration of an atom or group within the molecule. Thus, tautomers are constitutional isomers of organic compounds that readily interconvert and the reaction commonly results in the relocation of a proton. Tautomerism is, for example, relevant to the behavior of amino acids and nucleic acids, two of the fundamental building blocks of life.
Enolate Anions and Condensation Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Tautomers are two or more isomers of a compound that exist together in equilibrium and are readily interchanged by migration of an atom or group within the molecule. Tautomerism is the ability of some compounds to exist as a mixture of two interconvertible isomers that are in equilibrium What is the Hell–Volhard–Zelinsky Reaction?
Regium bonds formed by MX (M═Cu, Ag, Au; X═F, Cl, Br) with phosphine-oxide/phosphinous acid: comparisons between oxygen-shared and phosphine-shared complexes
Published in Molecular Physics, 2019
Baishu Zheng, Yi Liu, Zhaoxu Wang, Fengxiang Zhou, Yuan Liu, XunLei Ding, Tian Lu
To our knowledge, few studies have been made to characterise coinage metals Cu, Ag and Au interacting with P as lone-pair donate. Phosphonates hold a critically important position in the process of organic synthesis [26–33]. For example, phosphonates are widely used in preparing olefins by reaction of Horner–Wadsworth–Emmons, while trivalent phosphorus derivatives play a key role as ligands in metal catalysed reactions [34,35]. As we all know, phosphonates are multifunctional molecules with a lone pair on the P atom and a lone pair on the O atom. Consequently, P(O) group is able to ligate to a variety of metal ions and acids to form complexes [36–38]. In addition, phosphonates could be presented by two tautomeric forms, phosphine oxide and phosphinous acid [39]. The tautomerism plays important roles in many chemical and biological processes because different tautomers often have different properties, especially when their active sites are considered. For example, Chatt et al. [40] showed that only phosphinous acid forms could be captured by coordination with transition metal complexes. It is useful to analyse the geometries, stability, and particularly the mechanism underlying the strength of the metal–ligand bond in typical phosphonates metallic complexes acting as efficient catalysts.
Comparison of the stability of thymine tautomers and the interaction of its tautomers with Na+, K+, Mg2+ and Ca2+ in gas and solvent phases
Published in Molecular Physics, 2020
Marzyeh Mohammadi, Shapour Ramazani
The smallest was recorded for T6 (2.79 kJmol−1) and the largest for T13 (118.76 kJmol−1). The free energy rating of other tautomers in the solvent phase is as follows: T1 < T6 < T2 < T7 < T14 < T12 < T9 < T15 < T16 < T5 < T18 <T17 <T4 <T11 < T10 <T8< T3< T13. Due to the stability of the thymine tautomers in gas and solvent phases, it is safe to say that certain tautomers in the solvent phase become more stable than the gas phase.
Quantum chemical study of tautomeric equilibriums, intramolecular hydrogen bonds, and π-electron delocalization in the first singlet and triplet excited states of 2-selenoformyl-3-thioxo-propionaldehyde
Published in Journal of Sulfur Chemistry, 2023
Ramin Rafat, Ebrahim Nakhaei, Farshid Zargari, Faezeh Gorgichi, Alireza Nowroozi
A tautomeric process is an equilibrium between two and more tautomers with different arrangements of atoms and chemical bonds. The most obvious example of the tautomeric process is the equilibrium between the keto and enol forms of β-dicarbonyl compounds. Evidently, the tautomeric process usually leads to a more unstable structure with respect to the initial one. For instance, the enol forms of acetaldehyde compound in the tautomeric process at MP2/6–311++G (d,p) level of computations are approximately 50 kJ/mol less stable than the initial keto form, which is symbolized by tautomeric energy change (ΔETE) [28]. Similar treatment is also observed for other tautomeric processes.