Structure energetics and reactivity in chemistry series search series, vol 3. Although it is the benzene oxide valence tautomer that is attacked by nucleophiles and rearranges to phenols in acidic media, it is the oxepin valence isomers that suffer oneelectron oxidation. Article views are the countercompliant sum of full text article downloads since november 2008 both pdf and html across all institutions and individuals. Concise synthesis of the plant growth regulator theobroxide. Examination of the valence tautomers benzene oxide and oxepin and two derivative systems by ab initio methods. Benzene oxide exists in dynamic equilibrium with its valence isomer. The left shift, which is observed in favor of 1 h over 2 h, appears in contrast to the reported right shifted equilibria including. Theoretical study of the mechanism of valence tautomerism.
Exploration of selected pathways for metabolic oxidative. Reduction of a substituted arene oxide to yield a racemic arene hydrate was observed. A computational molecular orbital study of the oxide and. Examination of the valence tautomers benzene oxide and oxepin and two derivative systems by ab. Albumin adducts of benzene oxide boalb and 1,4benzoquinone 1,4bqalb were investigated among 4 workers exposed to benzene and 51 unexposed controls in tianjin, china. Highvalent manganeseoxo valence tautomers and the influence. Valence tautomerization of highvalent manganesevoxo corrole induced by protonation of the oxo ligand. Oxepine derivative an overview sciencedirect topics.
Substituent effects on tautomerization of oxepine to. The very rapid benzene oxide oxepin equilibrium plays an important role in the metabolism of benzene by cytochrome p450. The enthalpies of the valence tautomerism between benzene oxide 3 and oxepin 4 and of benzene sulfide 5 and thiepin 6 are estimated from posthartree. Several selfconsistent fieldcosmo coupling schemes were examined in an attempt to reduce computational effort. We have calculated the geometry and energy of the valence tautomers benzene oxide and oxepin using the semiempirical am1 model and the 631g and 631g basis sets utilizing full geometry optimization. Benzene oxide and the potential 8electron system oxepin exist in valence. Pyrylium 3 oxide and 4,5epoxy2cyclopentenone valence tautomerism. Oxepin is an oxygencontaining heterocycle consisting of a sevenmembered ring with three double bonds. A gradientpreserving algorithm for removing outlying charge has been implemented. The calculated enthalpy for this valence tautomeric equilibrium differs from that reported by vogel et al in 1967, but agree well with the value calculated by kollman using the mindo3 method. A pair of valence tautomers with formula c6h6o are benzene oxide and oxepin. Due to the larger number of units, the number of possible valence isomers is also greater and at least 21. The oxepinarene oxide intermediates formed during metabolism undergo.
How steric effects favor thiepins over their benzene. Multiple activation pathways of benzene leading to. The oxepin benzene oxide equilibrium is affected by the ring substituents. Calculations at the b3lyp level of theory reproduce well the energy gap between the co iihs and co iiils forms giving an energy gap of 4. Journal of the american chemical society 2015, 7 45, 1448114487. Enzymecatalysed synthesis and reactions of benzene oxide. This compound exists mainly as oxepin at room temperature, even if. Nmr spectroscopic measurements show that the equilibrium is rapidly established activation energies of the forward and reverse reactions 9.
Theoretical determination of molecular structure and. Valence tautomerism is studied in the co iihs sq 2 bpyco iiils sqcatbpy mononuclear cobalt complex by using dft methods hs, high spin. The index of named reactions covers the named reactions, reaction types and principles for synthesis of the aforementioned heterocyclic systems. Therefore, valence tautomerizations involving the second row elements b, c, n. The enthalpies of the valence tautomerism between benzene oxide 3 and oxepin 4. Read investigation of benzene oxide in bone marrow and other tissues of f344 rats following metabolism of benzene in vitro and in vivo, chemicobiological interactions on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at. The arene oxide valence tautomer of oxepins in principle should undergo nucleophilic substitution reactions s n 2 which are characteristic of simple epoxides. Pdf identification of benzene oxide as a product of. A molecular orbital study of the benzene oxideoxepin. These metrics are regularly updated to reflect usage leading up to the last few days. Tautomers are structural isomers constitutional isomers of chemical compounds that readily. For the dimethyl analog of the benzene oxideoxepin system 9 and 10 the. A rapid total racemization of the substituted benzene 2,3oxides was found to have occurred, via their oxepine valence tautomers, in accord with. A related dimethyl derivative exists mainly as the oxepin isomer, an orange liquid.
A molecular orbital study of the benzene oxideoxepin valence. Other examples of this type of tautomerism can be found in bullvalene, and in open and closed forms of certain heterocycles, such as organic azides and tetrazoles, or mesoionic munchnone and acylamino ketene. The mechanism of action of doxepin is presumable linked to the effect on the. Applications to the benzene oxide oxepin valence tautomerization and to glycine conformation are presented. The presence of both oxepin and benzene oxide isomer was observed by low temperature. Tautomerism chemistry britannica encyclopedia britannica. A rapid total racemization of the substituted benzene 2,3oxides was found to have occurred, via their oxepine valence tautomers, in accord with predictions and theoretical calculations.
The journal of physical chemistry a 1997, 101 18, 337376. Mitsutaka kudoh, susumu sudoh, shigeyoshi katagiri, tomoo nakazawa, mariko ishihara, mamoru jinguji, miwako higashi, hiroyuki yamaguchi, ryuta miyatake, yoshikazu sugihara and chizuko kabuto, xray structures and dipole moments of tropones annulated with furan, benzene, and oxepin, bulletin of the chemical society of japan, 79, 8, 1240, 2006. The hydration is catalyzed by epoxide hydrolase enzymes. Benzene oxide is known to exist in equilibrium with its tautomeric valence structure, the oxepin1aa. Examination of the valence tautomers benzene oxide and oxepin. Enantiopure cisdihydrodiol bacterial metabolites of substituted benzene substrates were used as precursors, in a chemoenzymatic synthesis of the corresponding benzene oxides and of a substituted oxepine, via dihydrobenzene oxide intermediates. Synthesis and chemistry of syn2hydroxyindane 3a,7aoxide. In order to find substituent effects on tautomerization of benzene oxide to oxepine, hammett study via ab initio is employed in this manuscript. Introduction, history, and recent developments enol k f kr keto 1. Pyrylium 3oxide and 4,5epoxy2cyclopentenone valence. This observation was taken as evidence for the initial formation of the corresponding equilibrating valence tautomeric arene oxideoxepine intermediates 22. A pair of valence tautomers with formula c 6 h 6 o are benzene oxide and oxepin. Tautomerism, the existence of two or more chemical compounds that are capable of facile interconversion, in many cases merely exchanging a hydrogen atom. Dehydration of these diols, which is driven by rearomatization, gives phenol and 1naphthol.
Benzene oxide 1a and indan8,9 oxide 1b were examined as symmetrical arene oxide substrates schemes 1 and 2. In recent years these substances have become of intense in terest as potential intermediates in the metabolism of. Concentrations of both adducts increased with benzene exposure range 0. The heterocycle resulting from a named synthesis is shown in brackets, e. The parent c 6 h 6 o exists as an equilibrium mixture with benzene oxide. Theoretical studies of the benzene oxideoxepin valence. In synthetic porphyrin systems, valence tautomerism has been. Identification of benzene oxide as a product of benzene metabolism by mouse. Synthese eines oxepins vogel 1964 angewandte chemie. Albumin adducts of benzene oxide and 1,4benzoquinone as.
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