Dimesityldioxirane

Sander, Wolfram; Schroeder, Kerstin; Muthusamy, Sengodagounder; Kirschfeld, A.; Kappert, W.; Boese, Roland; Kraka, Elfi; Sosa, Carlos; Cremer, Dieter

doi:10.1021/ja964280n

Cited by 62 publications

(58 citation statements)

References 47 publications

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“…26, 27 Calculations correctly reproduce the planar arrangement of the nearest neighbors of the C atom and the key bond lengths and bond angles, in particular, the O-OH bond length, which most often lies between 1.43 and 1.47 Å (see Refs 9,10). It should also be noted that the O(4)-O(5) bond length in the D form, obtained from our calculations is similar to that in dioxiranes RR´CO 2 (R = H, Me), being in agreement with the mi crowave and X ray diffraction data 28, 29 and with the re sults of calculations. [13][14][15] Both tautomers have an additional intramolecular H bond (see Table 2).…”

Section: Resultssupporting

confidence: 88%

Tautomerism of peroxyacetic acid derivatives: a quantum chemical study

et al. 2005

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The electronic and molecular structures and the relative stabilities of organic peracids X=C(R)-COOH and their cyclic tautomers, dioxiranes , with R = Me, CF 3 ; X = O, NH, were studied using the ab initio Hartree-Fock method and the density functional theory (B3LYP version) as well as at the MP2 MP4 Møller-Plesset levels of perturbation theory. Geometry optimization was performed by the UHF and B3LYP methods with the 6 31G** basis set and at the MP2/cc pvtz level of theory. The acyclic form of the peracid is more stable than the cyclic dioxirane form irrespective of the nature of the substitu ent. The energy difference between these tautomers increases as the CF 3 and NH groups are replaced by Me and O, respectively. Parameters of the activation barrier to tautomeric conver sion increase in parallel with enhancement of the electron accepting properties of both sub stituents. The transition state of tautomeric interconversion, which is topologically similar to the acyclic structure of the carbonyl oxide derivative R(HX)C=O + -O -, was found and char acterized taking peroxyacetic acid as an example. The characteristic features of the transition state are an intramolecular "multicenter" H bond and the charge distribution that is inconsis tent with the canonical structure mentioned above. An appropriate reaction coordinate for the transformation of the quasi tetrahedral dioxirane structure into a planar peroxyacetic acid structure is provided by the dihedral angle. Deprotonated anionic systems are characterized by much smaller differences between the relative stabilities of the open and closed forms of isomers and by much lower activation barriers to isomeric conversions.

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Section: Resultssupporting

confidence: 88%

Tautomerism of peroxyacetic acid derivatives: a quantum chemical study

et al. 2005

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“…UV/Vis spectra were recorded with a diode array spectrometer (Hewlett-Packard, HP 8452) in the spectral range between 200 ± 600 nm with a resolution of 2 nm. [56] Fluorescence quenching: Various concentrations of LipSS and DHLA were dissolved in spectroscopic grade solvent CH 3 OH solutions of riboflavin. Each sample solution was purged with N 2 or Ar for 20 min, placed in a quartz cuvette, sealed with a septum, lined with Teflon tape to prevent contamination, and then subjected to the measurement of the fluorescence spectrum.…”

Section: Methodsmentioning

confidence: 99%

Photoinduced Interactions Between Oxidized and Reduced Lipoic Acid and Riboflavin (Vitamin B₂)

Bucher

Sander

2004

ChemPhysChem

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As a powerful natural antioxidant, lipoic acid (LipSS) and its reduced form dihydrolipoic acid (DHLA) exert significant antioxidant activities in vivo and in vitro by deactivation of reactive oxygen and nitrogen species (ROS and RNS). In this study the riboflavin (RF, vitamin B2) sensitized UVA and visible-light irradiation of LipSS and DHLA was studied employing continuous irradiation, fluorescence spectroscopy, and laser flash photolysis (LFP). Our results indicate that LipSS and DHLA quench both the singlet state (1RF*) and the triplet state (3RF*) of RF by electron transfer to produce the riboflavin semiquinone radical (RFH.) and the radical cation of LipSS and DHLA, respectively. The radical cation of DHLA is rapidly deprotonated twice to yield a reducing species, the radical anion of LipSS (LipSS.-). When D2O was used as solvent, it was confirmed that the reaction of LipSS with 3RF* consists of a simple electron-transfer step, while loss of hydrogen occurs in the case of DHLA oxidation. Due to the strong absorption of RFH. and the riboflavin ground state, the absorption of the radical cation and the radical anion of LipSS can not be observed directly by LFP. N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and N,N,N',N'-tetramethyl benzidine (TMB) were added as probes to the system. In the case of LipSS, the addition resulted in the formation of the radical cation of TMPD or TMB by quenching of the LipSS radical cation. If DHLA is the reducing substrate, no formation of probe radical cation is observed. This confirms that LipSS.- is produced by riboflavin photosensitization, and that there is no oxidizing species produced after DHLA oxidization.

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“…For the latter the comparison of the calculated one with the X-ray crystallographic structure reveals a good agreement of the calculated and experimental bond angles of the dioxirane ring and the CϪO bond lengths (Table 1). [32] Only the calculated OϪO distance of 1.491 Å is slightly shorter than the experimental value of 1.503 Å . With 1.494 Å the calculated OϪO distance in 2b is slightly larger than that in 2a which indicates a smaller steric pressure (buttressing effect) on the dioxirane ring.…”

Section: Pathway C Concerted O Insertionmentioning

confidence: 71%

Sterically Hindered Carbonyl O‐Oxides and Dioxiranes − (6‐tert‐Butyl‐2,3,4‐trimethylphenyl)phenylcarbonyl O‐Oxide and (6‐tert‐Butyl‐2,3,4‐trimethylphenyl)phenyldioxirane

Schroeder

Sander

2005

Eur J Org Chem

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(6-tert-Butyl-2,3,4-trimethylphenyl)phenylcarbonyl O-oxide (1b) was generated by photooxidation of diazo compound 6b in an organic glass and in solution and characterized by UV/ Vis spectroscopy and by its photo-and thermochemistry. With 4.5 min at 230 K the half-life of 1b is considerably smaller than that of dimesityl ketone O-oxide (1a). The only clearly detected thermal product of 1b is the corresponding ketone 3b. The isomeric (6-tert-butyl-2,3,4-trimethylphenyl)-

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Dimesityldioxirane

Cited by 62 publications

References 47 publications

Tautomerism of peroxyacetic acid derivatives: a quantum chemical study

Tautomerism of peroxyacetic acid derivatives: a quantum chemical study

Photoinduced Interactions Between Oxidized and Reduced Lipoic Acid and Riboflavin (Vitamin B₂)

Sterically Hindered Carbonyl O‐Oxides and Dioxiranes − (6‐tert‐Butyl‐2,3,4‐trimethylphenyl)phenylcarbonyl O‐Oxide and (6‐tert‐Butyl‐2,3,4‐trimethylphenyl)phenyldioxirane

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Dimesityldioxirane

Cited by 62 publications

References 47 publications

Tautomerism of peroxyacetic acid derivatives: a quantum chemical study

Tautomerism of peroxyacetic acid derivatives: a quantum chemical study

Photoinduced Interactions Between Oxidized and Reduced Lipoic Acid and Riboflavin (Vitamin B2)

Sterically Hindered Carbonyl O‐Oxides and Dioxiranes − (6‐tert‐Butyl‐2,3,4‐trimethylphenyl)phenylcarbonyl O‐Oxide and (6‐tert‐Butyl‐2,3,4‐trimethylphenyl)phenyldioxirane

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Photoinduced Interactions Between Oxidized and Reduced Lipoic Acid and Riboflavin (Vitamin B₂)