489-01-0Relevant articles and documents
Organochalcogen substituents in phenolic antioxidants
Amorati, Riccardo,Pedulli, Gian Franco,Valgimigli, Luca,Johansson, Henrik,Engman, Lars
scheme or table, p. 2326 - 2329 (2010/07/20)
Little is known about the ED/EW character of organochalcogen substituents and their contribution to the O-H bond dissociation enthalpy (BDE) in phenolic compounds. A series of ortho- and para-(S,Se,Te)R-substituted phenols were prepared and investigated by EPR, IR, and computational methods. Substituents lowered the O-H BDE by >3 kcal/mol in the para position, while the ortho-effect was modest due to hydrogen bonding (～3 kcal/mol) to the O-H group.
Transformations of organic molecules with F-TEDA-BF4 in ionic liquid media
Pavlinac, Jasminka,Zupan, Marko,Stavber, Stojan
experimental part, p. 2394 - 2409 (2009/12/03)
The transformations of organic molecules with F-TEDA-BF4 (1) were investigated in the hydrophilic ionic liquid (IL) 1-butyl-3-methyl- imidazolium tetrafluoroborate ([bmim][BF4], 2) and the hydrophobic IL 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF6], 3). The range of substrates included alkyl substituted phenols 4a-c, 9, 13, 1,1-diphenylethene (15), alkyl aryl ketones 19-22, aldehydes 23-25 and methoxy-substituted benzene derivatives 26-30. The evaluation of the outcome of reactions performed in IL media in comparison to those of the corresponding reactions in conventional organic solvents revealed that the transformations in IL are less efficient and selective. The effect of the presence of a nucleophile (MeOH, H2O, MeCN) on the course of reaction was also studied.
Mild and reliable cleavage sequence for phenoxy acetates
Mirk, Daniela,Waldvogel, Siegfried R.
, p. 7911 - 7914 (2007/10/03)
A novel combination of reliable transformations like ester saponification and subsequent Curtius-rearrangement employing mild reaction conditions, offers the first synthetically interesting strategy for the removal of methoxycarbonylmethyl groups from phenolic oxygens. This methodology gives also access to labile iodosubstituted phenols. A novel combination of reliable transformations like ester saponification and subsequent Curtius-rearrangement employing mild reaction conditions, offers the first synthetically interesting strategy for the removal of methoxycarbonylmethyl groups from phenolic oxygens. This methodology gives also access to labile iodosubstituted phenols.
Modeling the Co-Antioxidant Behavior of Monofunctional Phenols. Applications to Some Relevant Compounds
Amorati, Riccardo,Ferroni, Fiammetta,Pedulli, Gian Franco,Valgimigli, Luca
, p. 9654 - 9658 (2007/10/03)
A study on the regeneration of α-tocopherol (vitamin E) by phenolic co-antioxidants in homogeneous hydrocarbon solution is reported. The behavior of some relevant phenols such as BHA, BHT, and trans-resveratrol appears to be nicely predicted by a model based on the knowledge of kinetic and thermochemical data concerning the various reactants. Despite its good reputation as an antioxidant, trans-resveratrol was found only moderately effective (kinh = 2.0 × 105 M-1 s -1 in chlorobenzene at 303 K) and unable to recycle vitamin E.
4-Formyl amino-n-methylpiperidine derivatives, the use thereof as stabilisers and organic material stabilised therewith
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, (2008/06/13)
The present invention relates to 4-formylamino-N-methylpiperidine derivatives of the formula (I) where the variables are as defined in the Description, to a process for preparing these piperidine derivatives, to the use of these piperidine derivatives of the invention, or prepared according to the invention, for stabilizing organic material, in particular for stabilizing plastics or coating materials, and also to the use of these piperidine derivatives of the invention, or prepared according to the invention, as light stabilizers or stabilizers for wood surfaces. The present invention further relates to stabilized organic material which comprises these piperidine derivatives of the invention or prepared according to the invention.
Thioether substituted hydroxybenzophenones and stabilized compositions
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, (2008/06/13)
2-Hydroxybenzophenone derivatives substituted in the 4′-position by a thioether moiety exhibit enhanced absorption in the UV at longer wavelength. Compositions comprising organic material subject to actinic degradation are beneficially stabilized with such derivatives.
Hydrogen-bonding effects on the properties of phenoxyl radicals. An EPR, kinetic, and computational study
Lucarini, Marco,Mugnaini, Veronica,Pedulli, Gian Franco,Guerra, Maurizio
, p. 8318 - 8329 (2007/10/03)
The effect of 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP) on the properties of phenoxyl radicals has been investigated. HFP produces large variations of the phenoxyl hyperfine splitting constants indicative of a large redistribution of electron spin density, which can be accounted for by the increased importance of the mesomeric structures with electric charge separation. The conformational rigidity of phenoxyl radicals with electron-releasing substituents is also greatly enhanced in the presence of HFP, as demonstrated by the 2 kcal/mol increase in the activation energy for the internal rotation of the p-OMe group in the p-methoxyphenoxyl radical. By using the EPR equilibration technique, we have found that in phenols the O-H bond dissociation enthalpy (BDE) is lowered in the presence of HFP because it preferentially stabilizes the phenoxyl radical. In phenols containing groups such as OR that are acceptors of H-bonds, the interaction between HFP and the substituent is stronger in the phenol than in the corresponding phenoxyl radical because the radical oxygen behaves as an electron-withdrawing group, which decreases the complexating ability of the substituent. In phenols containing OH or NH2 groups, EPR experiments performed in H-bond accepting solvents showed that the interaction between the solvent and the substituent is much stronger in the phenoxyl radical than in the parent phenol because of the electron-withdrawing effect of the radical oxygen, which makes more acidic, and therefore more available to give H-bonds, the OH or NH2 groups. These experimental results have been confirmed by DFT calculations. The effect of HFP solvent on the reactivity of phenols toward alkyl radicals has also been investigated. The results indicated that the decrease of BDE observed in the presence of HFP is not accompanied by a larger reactivity. The origin of this unexpected behavior has been shown by DFT computations. Finally, a remarkable increase in the persistency of the α-tocopheroxyl radical has been observed in the presence of HFP.
Efficient synthesis of 2,5-di-t-butyl-4-fluorophenol
Bandgar,Kasture,Dudhmal, Chaya
, p. 81 - 83 (2007/10/03)
When 4-fluorophenol was refluxed with excess of t-butyl chloride in the presence of various catalysts, e.g. Envirocat EPZG, EPZ10, EPIC, sulfated zirconia, natural kaolinitic clay, zirconium nitrate, zinc chloride and bismuth nitrate, the product obtained was 2,5,di-t-butyl 4-fluorophenol in excellent yield.
Synthesis of 2,5- and 2,6-di-t-butyl-4-halo- or -4-methoxy-phenols using silica, lithium perchlorate and lithium bromide as neutral catalysts
Bandgar,Uppalla,Sadavarte
, p. 582 - 583 (2007/10/03)
When a mixture of 4-halo- or 4-methoxy-phenol and excess of t-butyl chloride in the presence of neutral catalyst such as silica or lithium perchlorate or lithium bromide was refluxed, 2,5-and 2,6-di-t-butyl-4-halo or 4-methoxy phenols were obtained in good yields.
