Originally, hammett study was based on ionizations of m and pxc 6 h 4 y, where log kk 0 was introduced as the hammett equation. Theoretical studies of the benzene oxideoxepin valence. Benzene oxide 1a and indan8,9 oxide 1b were examined as symmetrical arene oxide substrates schemes 1 and 2. Multiple activation pathways of benzene leading to. 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. Highvalent manganeseoxo valence tautomers and the influence. Dehydration of these diols, which is driven by rearomatization, gives phenol and 1naphthol.
The very rapid benzene oxide oxepin equilibrium plays an important role in the metabolism of benzene by cytochrome p450. Synthese eines oxepins vogel 1964 angewandte chemie. This observation was taken as evidence for the initial formation of the corresponding equilibrating valence tautomeric arene oxideoxepine intermediates 22. Albumin adducts of benzene oxide and 1,4benzoquinone as. 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. For the dimethyl analog of the benzene oxideoxepin system 9 and 10 the. A molecular orbital study of the benzene oxideoxepin. These metrics are regularly updated to reflect usage leading up to the last few days.
Reduction of a substituted arene oxide to yield a racemic arene hydrate was observed. The valence isomers are not restricted to isomers of benzene. Tautomers are structural isomers constitutional isomers of chemical compounds that readily. Due to the larger number of units, the number of possible valence isomers is also greater and at least 21. Valence tautomerism is studied in the co iihs sq 2 bpyco iiils sqcatbpy mononuclear cobalt complex by using dft methods hs, high spin. Synthesis and chemistry of syn2hydroxyindane 3a,7aoxide. 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. The oxepinarene oxide intermediates formed during metabolism undergo. Theoretical study of the mechanism of valence tautomerism. 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. Oxepine derivative an overview sciencedirect topics. Valence tautomers are of fundamental interest because of their distinct optical.
The mechanism of action of doxepin is presumable linked to the effect on the. Introduction, history, and recent developments enol k f kr keto 1. Attempts have been made to assess the degree of electron delocahzation. Pdf identification of benzene oxide as a product of. Article views are the countercompliant sum of full text article downloads since november 2008 both pdf and html across all institutions and individuals. The arene oxide valence tautomer of oxepins in principle should undergo nucleophilic substitution reactions s n 2 which are characteristic of simple epoxides. Examination of the valence tautomers benzene oxide and oxepin and two derivative systems by ab initio methods. The presence of both oxepin and benzene oxide isomer was observed by low temperature. Oxepin is an oxygencontaining heterocycle consisting of a sevenmembered ring with three double bonds. A pair of valence tautomers with formula c 6 h 6 o are benzene oxide and oxepin. 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. Bock department of chemistry, philadelphia college of textiles and science, philadelphia, pa 19144 u. Stark a and rastetter w 1996 structureactivity relationships in the mutagenicity and cytotoxicity of putative metabolites and related analogs of benzene derived from the valence tautomers benzene oxide and oxepin, environmental and molecular mutagenesis, 10. 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.
Examination of the valence tautomers benzene oxide and oxepin and two derivative systems by ab. 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. A molecular orbital study of the benzene oxideoxepin valence. In order to find substituent effects on tautomerization of benzene oxide to oxepine, hammett study via ab initio is employed in this manuscript. A computational molecular orbital study of the oxide and. In synthetic porphyrin systems, valence tautomerism has been. Benzene oxide and the potential 8electron system oxepin exist in valence. The enthalpies of the valence tautomerism between benzene oxide 3 and oxepin 4. Chemoenzymatic synthesis of monocyclic arene oxides and. 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. Structure energetics and reactivity in chemistry series search series, vol 3.
Several selfconsistent fieldcosmo coupling schemes were examined in an attempt to reduce computational effort. Tautomerism chemistry britannica encyclopedia britannica. How steric effects favor thiepins over their benzene sulfide tautomers at theoretical levels article in journal of molecular structure theochem 861. Tautomerism, the existence of two or more chemical compounds that are capable of facile interconversion, in many cases merely exchanging a hydrogen atom. 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. A pair of valence tautomers with formula c6h6o are benzene oxide and oxepin. A related dimethyl derivative exists mainly as the oxepin isomer, an orange liquid. The heterocycle resulting from a named synthesis is shown in brackets, e. Exploration of selected pathways for metabolic oxidative. A gradientpreserving algorithm for removing outlying charge has been implemented. Pyrylium 3oxide and 4,5epoxy2cyclopentenone valence. Benzene oxide and naphthalene1,2 oxide hydrate to give dihydroxydihydrobenzene and 1,2dihydroxydihydronaphthalene, respectively. Concise synthesis of the plant growth regulator theobroxide.
The oxepin benzene oxide equilibrium is affected by the ring substituents. Benzene oxide exists in dynamic equilibrium with its valence isomer. Both alternatives of nelectron delocalization have been discussed in con nection with measured properties of cht l, azp i, and oxp 3. Nmr spectroscopic measurements show that the equilibrium is rapidly established activation energies of the forward and reverse reactions 9. Identification of benzene oxide as a product of benzene metabolism by mouse. The hydration is catalyzed by epoxide hydrolase enzymes. This compound exists mainly as oxepin at room temperature, even if.
Theoretical determination of molecular structure and. Enzymecatalysed synthesis and reactions of benzene oxide. In reality oxepin benzene oxide 7 is resistant to attack by hard nucleophiles such as oh. Substituent effects on tautomerization of oxepine to. The parent c 6 h 6 o exists as an equilibrium mixture with benzene oxide.
How steric effects favor thiepins over their benzene. 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. In recent years these substances have become of intense in terest as potential intermediates in the metabolism of. Examination of the valence tautomers benzene oxide and oxepin. A rapid total racemization of the substituted benzene 2,3oxides was found to have occurred, via their oxepine valence tautomers, in accord with. 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. Concentrations of both adducts increased with benzene exposure range 0.