Showing papers on "Bond cleavage published in 1996"
TL;DR: The reactivities of various antioxidative compounds including catechol derivatives and endogenous radical scavengers toward hydroxyl radical (.OH) were investigated by an electron spin resonance-spin trapping method, thiobarbituric acid method, and DNA strand scission assay.
191 citations
TL;DR: A comparison study of Ether Cleavage Systems using data from Y2K and Y2M to evaluate the efficiency and efficiency of these systems against known barriers, such as high temperatures and high pressures.
190 citations
TL;DR: In this paper, the C−C triple bond was cleaved in the presence of the carbonyl complex with the formation of the toluene and the 1-alkyne to vinylidene tautomerism.
Abstract: The hydration of phenylacetylene in the presence of the complex mer,trans-(PNP)RuCl2(PPh3) in THF at 60 °C leads to the cleavage of the C−C triple bond with formation of the carbonyl complex fac,cis-(PNP)RuCl2(CO) and toluene [PNP = CH3CH2CH2N(CH2CH2PPh2)2]. A study under different experimental conditions, the use of model and isotope labeling experiments, and the detection of several intermediates, taken altogether, show that the C−C bond cleavage reaction comprises a number of steps, among which the most relevant to the mechanism are 1-alkyne to vinylidene tautomerism, conversion of a vinylidene ligand to hydroxycarbene by intramolecular attack of water, deprotonation of hydroxycarbene to σ-acyl, deinsertion of CO from the acyl ligand, and hydrocarbon elimination by protonation of the metal-alkyl moiety. The following intermediate species have been isolated and characterized: the vinylidene fac,cis-(PNP)RuCl2{CC(H)Ph}, the (aquo)(σ-alkynyl) complex fac-(PNP)RuCl(C⋮CPh)(OH2), and the (benzyl)carbonyl me...
159 citations
TL;DR: In this article, a calculation of the energy barrier against RNO 2 scission in 26 molecules showed that there is a correlation between the size of energy barrier and the susceptibility to high-rate exothermic reaction (detonation).
Abstract: A calculation of the energy for bond rupture for a number of energetic molecules using MNDO/3 indicates that the weakest bond is generally that between the NO 2 and the remainder of the molecule. A calculation of the energy barrier against RNO 2 scission in 26 molecules shows that there is correlation between the size of the energy barrier and the susceptibility to high-rate exothermic reaction (detonation). The correlation seems to be independent of bond type (CN, NN, ON) and thus independent of chemical family. The results suggest that RNO 2 rupture may be the rate-controlling step in the initiation of detonation of many energetic molecules.
138 citations
TL;DR: The results showed that in the acyl-carbon bond cleavage step (i.e. the deformylation process) the original carbonyl oxygen at C-32 of the precursor is retained in formic acid and the second oxygen of formate is derived from molecular oxygen; precisely the same scenario that has previously been observed for the acyll-carbon cleavage steps catalyzed by aromatase and 17α-hydroxylase-17,20-lyase.
134 citations
TL;DR: The main photosensitized oxidation product in aqueous solution of 8-oxo-7,8-dihydro-2'-deoxyguanosine (1) has been isolated by HPLC and characterized as 1-(2deoxy-β-d-erythro-pentofuranosyl)-cyanuric acid (7) as mentioned in this paper.
Abstract: The main photosensitized oxidation product in aqueous solution of 8-oxo-7,8-dihydro-2‘-deoxyguanosine (1) has been isolated by HPLC and characterized as 1-(2-deoxy-β-d-erythro-pentofuranosyl)-cyanuric acid (7) and its precursor, 1,3,5-triazine-1(2H)-carboximidamide, 3-(2-deoxy-β-d-erythro-pentofuranosyl)tetrahydro-2,4,6-trioxo- (6). This was achieved by carrying out extensive spectroscopic measurements including FAB mass spectrometry, 1H and 13C NMR analyses. The formation of the photooxidized nucleoside 7 is accounted for by a type II mechanism through initial [2+2] cycloaddition across the C-4−C-5 ethylenic bond of 1. The 1,2 bond cleavage of the transient dioxetanes gives rise to the modified nucleoside 6 through a nine-membered ring oxidized intermediate nucleoside. The derivative 6 further decomposes into the stable cyanuric acid nucleoside 7 by the hydrolysis of the guanidino residue with the concomitant release of urea 8. Photosensitizers such as methylene blue and rose Bengal were found to efficie...
115 citations
TL;DR: X-ray crystal structures of the Yersinia tyrosine phosphatase in complex with tungstate and nitrate have been solved to 2.4-Å resolution and are consistent with a general acid-catalyzed, in-line displacement of the phosphate moiety to Cys403 on the enzyme, followed by attack by a nucleophilic water molecule to release orthophosphate.
114 citations
TL;DR: A steady-state and pre-steady-state kinetic analysis of the conversion of a number of substrates of the dehalogenase found that brominated substrates had a lower Km, but a similar kcat than the chlorinated analogs and nematocide 1,2-dibromoethane.
107 citations
TL;DR: In this article, the dissociation energy of the C−H bond in benzene was predicted at the BLYP/6-311G level of theory, and the results showed that the removal of hydrogens is accompanied by highly regular changes in the molecular geometries, namely a widening of the ipso bond angle by 6.0° and a concomitant shortening of adjacent C−C bonds by ca. 0.02 A.
Abstract: Electronic structure calculations carried out at the BLYP/6-311G** level of theory accurately predict the dissociation energy of the C−H bond in benzene. The analogous energies of the homolytic C−H bond cleavage in the other nine polycyclic aromatic hydrocarbons (PAHs) are found to be governed almost entirely by steric factors, the hydrogens from congested regions of the PAHs being removed preferentially. The removal of hydrogens is accompanied by highly regular changes in the molecular geometries, namely a widening of the ipso bond angle by ca. 6.0° and a concomitant shortening of the adjacent C−C bonds by ca. 0.02 A. These observations suggest an almost complete localization of the unpaired σ electrons on single carbon atoms and the separation of the local σ and π effects in the aryl radicals under study. This localization is confirmed by the computed charges and spin populations of atoms in the phenyl, 1-naphthalenyl, and 2-naphthalenyl radicals. In contrast with their UHF counterparts, the UBLYP elect...
95 citations
TL;DR: In this paper, an iron-peroxo complex PcS-FeOOH was shown to be the active species responsible for the epoxidation of 2,6-dichloro-1,4-benzoquinone and the C-C bond cleavage of 3,5-diclomeric acid.
Abstract: 2,4,6-trichlorophenol (TCP) is oxidized by potassium monopersulfate or hydrogen peroxide in the presence of iron or manganese tetrasulfonatophthalocyanines (FePcS or MnPcS) to yield not only the corresponding 2,6-dichloro-1,4-benzoquinone but also ring-cleavage products. Catalytic oxidation of the TCP ring by hydrogen peroxide is more efficient than by potassium monopersulfate, despite a slower substrate conversion, suggesting that different mechanisms are involved for these two catalytic systems: a metal-oxo mechanism for FePcS/KHSO5 and a metal-peroxo mechanism for FePcS/H2O2. Eight different final oxidation products and four quinone intermediates have been identified in the oxidation of TCP by the FePcS/H2O2 catalytic system. Chloromaleic acid is the main product of the oxidative ring cleavage. An iron-peroxo complex PcS-FeOOH is probably the active species responsible for the epoxidation of 2,6-dichloro-1,4-benzoquinone and the C–C bond cleavage of 3,5-dichloro-2-hydroxy-1,4-benzoquinone ring, both intermediates generated during the catalytic TCP degradation. The oxidation of pentachlorophenol (PCP) is also catalyzed by FePcS or MnPcS with KHSO5 or H2O2.
93 citations
TL;DR: In this paper, the reaction mechanism for Cu[9]aneN3Cl2-catalyzed hydrolysis of ethyl 4-nitrophenyl phosphate was probed using kinetic isotope effects and isotope exchange experiments.
Abstract: The reaction mechanism for Cu[9]aneN3Cl2-catalyzed hydrolysis of ethyl 4-nitrophenyl phosphate was probed using kinetic isotope effects and isotope exchange experiments. The solvent deuterium isotope effect (Dk = 1.14), combined with the absence of 18O incorporation into 4-nitrophenol, suggests that hydrolysis proceeds through intramolecular attack of the metal-coordinated hydroxide at the phosphorus center. The secondary 15N isotope effect (15k = 1.0013 ± 0.0002) implies that loss of the leaving group occurs at the rate-limiting step with approximately 50% bond cleavage in the transition state. This study is one of the first applications of the secondary 15N isotope effect to simple metal-promoted hydrolysis reactions, and the result is consistent with concerted bond formation and cleavage. A mechanism consistent with the isotope studies is presented.
TL;DR: In this article, the authors show that the (2R)-2-acetoxy-2-phenylethanoate derivatives (2-34 mCi) can be converted into their 2-acetoxylacetoxy derivatives with complete retention of configuration, i.e., with 100% stereoselection.
Abstract: The ethanol samples in the isolated alcohol/water mixtures were converted into their (2R)-2-acetoxy-2-phenylethanoate derivatives (2-34 mCi). Examination of the well-resolved {sup 3}H NMR spectra for these derivatives produced an exceptionally consistent set of stereochemical data. When corrected for the enantiomeric purity of the ethyl tosylate starting materials, the data clearly show that the reaction occurs with complete retention of configuration, i.e., with 100% stereoselection. Barring substantial slowing of the carbon-carbon bond rotation of the ethyl radical when bound to the enzyme, this result rules out mechanisms proceeding via alkyl radical (and/or cation) structures, even very short-lived ones, as such intermediates would have to have a lifetime of < 1 x 10{sup -14} s in order not to undergo any detectable C-C bond rotation, i.e., the capture reaction would have to be much faster than the decay of a transition state. The data instead point to a mechanism in which C-H bond cleavage is preceded by bond formation at the alkyl carbon, i.e., one proceeding through a pentacoordinated carbon species. 29 refs., 1 fig., 1 tab.
Journal Article•
TL;DR: In this article, an iron-peroxo complex PcS-FeOOH was shown to be the active species responsible for the epoxidation of 2,6-dichloro-1,4-benzoquinone and the C-C bond cleavage of 3,5-diclomeric acid.
Abstract: 2,4,6-trichlorophenol (TCP) is oxidized by potassium monopersulfate or hydrogen peroxide in the presence of iron or manganese tetrasulfonatophthalocyanines (FePcS or MnPcS) to yield not only the corresponding 2,6-dichloro-1,4-benzoquinone but also ring-cleavage products. Catalytic oxidation of the TCP ring by hydrogen peroxide is more efficient than by potassium monopersulfate, despite a slower substrate conversion, suggesting that different mechanisms are involved for these two catalytic systems: a metal-oxo mechanism for FePcS/KHSO5 and a metal-peroxo mechanism for FePcS/H2O2. Eight different final oxidation products and four quinone intermediates have been identified in the oxidation of TCP by the FePcS/H2O2 catalytic system. Chloromaleic acid is the main product of the oxidative ring cleavage. An iron-peroxo complex PcS-FeOOH is probably the active species responsible for the epoxidation of 2,6-dichloro-1,4-benzoquinone and the C–C bond cleavage of 3,5-dichloro-2-hydroxy-1,4-benzoquinone ring, both intermediates generated during the catalytic TCP degradation. The oxidation of pentachlorophenol (PCP) is also catalyzed by FePcS or MnPcS with KHSO5 or H2O2.
TL;DR: In this article, the adsorption and reaction of methanol and ethanol on a preoxidised Cu(100) surface was studied with Reflection-Absorption Infra-Red Spectroscopy (RAIRS).
TL;DR: In this article, a laser flash photolysis of S-nitroso complexes of glutathione and bovine serum albumin via excitation at 355 nm has been used to investigate the photogeneration of nitric oxide (NO) and subsequent radical reactions.
Abstract: — Laser flash photolysis of S-nitroso complexes of glutathione (GSNO) and bovine serum albumin (BSANO) via excitation at 355 nm has been used to investigate the photogeneration of nitric oxide (NO) and subsequent radical reactions. In the case of GSNO, liberation of NO was confirmed by its oxidation of oxyhemoglobin to met hemoglobin. Initial NO release is via homolytic cleavage of the S-N bond to produce the glutathione thiyl radical, GS, which can subsequently react with (a) ground-state GSNO (k= 1.7 × 109M−1/i> s−1) to yield additional NO and oxidized glutathione, GSSG; and (b) oxygen (k= 3.0 × 109M−1 s−1) to give the glutathione peroxy radical, GSOO, which subsequently reacts with ground-state GSNO (k= 3.8 × 108M−1 s−1), also producing additional NO and GSSG. The relative concentrations of oxygen and GSNO in the system determine the major pathway for removal of G'. These secondary reactions occur at such high rates that they preclude radical recombination under low-intensity irradiation conditions. The quantum yield of overall loss of GSNO thus varies with both GSNO and oxygen concentrations; a value of 0.66 was determined for an aerated solution of GSNO (0.86 mM). In the case of GSNO, therefore, generation of NO is not due solely to homolysis of the S-N bond; secondary reactions of the radicals formed lead to further NO liberation. In rationalizing the known phototoxicity of GSNO, possible contributions from thiyl and thiyl-derived radicals should be considered. In contrast to GSNO, direct excitation of BSANO (containing one bound NO group per molecule) led to photodecomposition with a quantum yield of 0.09 but no evidence was obtained for liberation of NO into the bulk medium.
TL;DR: In this article, a practical synthesis of (E)-1-stannylalk-1-enes containing a range of oxygen and nitrogen functionality is highlighted, involving hydro stannylation followed by palladium-catalysed carbon bromine bond cleavage reactions of 1-bromoalkynes.
Abstract: A practical synthesis of (E)-1-stannylalk-1-enes containing a range of oxygen and nitrogen functionality is highlighted, involving hydrostannylation followed by palladium-catalysed carbon–bromine bond cleavage reactions of 1-bromoalkynes.
TL;DR: In this paper, the utilization of bismuth compounds in oxidation reactions of organic derivatives was discussed and both the pentavalent and trivalent states of Bismuth were found to display oxidizing power.
TL;DR: In this article, the authors studied the oxidation of aliphatic acids by radicals resulting from the protolysis of hydrogen peroxide and showed that the carboxylic group is slow to oxidize and the hydroxyl group of alphatic acids activates the adjacent CH bond and leads, after hydrogen atoms abstraction, O2 addition and HO2 removal, to the carbonyl group.
Abstract: The aim of this work was to study the oxidation of aliphatic acids by radicals resulting from the protolysis of hydrogen peroxide. Experiments carried out in dilute aqueous solutions (pH = 2.9−3.5) of mono and dicarboxylic acids with 1 to 4 carbon atoms showed (i) the oxidation of the carboxylic group is slow, (ii) the hydroxyl group of hydroxylated acids activates the adjacent CH bond and leads, after hydrogen atoms abstraction, O2 addition and HO2 removal, to the carbonyl group, (iii) a CC bond cleavage occurs after hydrogen atom abstraction and oxygen addition for unsubstituted dicarboxylic acids. Except for oxalic acid, the mechanism of oxidation into CO2 of the acids studied involves oxygen consumption and O2−/HO2 release.
TL;DR: Rate constants are consistent with arginine 38 having two roles in catalysing compound I formation: firstly, promotion of proton transfer to the imidazole group of histidine 42 to facilitate peroxide anion binding to the haem, and secondly, stabilisation of the transition state for the heterolytic cleavage of the oxygen-oxygen bond.
Abstract: Horseradish peroxidase isoenzyme C (HRPC) mutants were constructed in order to understand the role of two key distal haem cavity residues, histidine 42 and arginine 38, in the formation of compound I and in substrate binding. The role of these residues as general acid-base catalysts, originally proposed for cytochrome c peroxidase by Poulos and Kraut in 1980 was assessed for HRPC. Replacement of histidine 42 by leucine [(H42L)HRPC*] decreased the apparent bimolecular rate constant for the reaction with hydrogen peroxide by five orders of magnitude (k1 = 1.4×102 M–1s–1) compared with both native-glycosylated and recombinant forms of HRPC (k1 = 1.7×107 M–1s–1). The first-order rate constant for the heterolytic cleavage of the oxygen-oxygen bond to form compound I was estimated to be four orders of magnitude slower for this variant. Replacement of arginine 38 by leucine [(R38L)HRPC*] decreased the observed pseudo-first-order rate constant for the reaction with hydrogen peroxide by three orders of magnitude (k1 = 1.1×104 M–1s–1), while the observed rate constant of oxygen bond scission was decreased sixfold (k2 = 142 s–1). These rate constants are consistent with arginine 38 having two roles in catalysing compound I formation: firstly, promotion of proton transfer to the imidazole group of histidine 42 to facilitate peroxide anion binding to the haem, and secondly, stabilisation of the transition state for the heterolytic cleavage of the oxygen-oxygen bond. These roles for arginine 38 explain, in part, why dioxygen-binding globins, which do not have an arginine in the distal cavity, are poor peroxidases. Binding studies of benzhydroxamic acid to (H42L)HRPC* and (R38L)HRPC* indicate that both histidine 42 and arginine 38 are involved in the modulation of substrate affinity.
TL;DR: Findings suggest that P450eryF utilizes the substrate to assist in the acid-catalysed dioxygen bond cleavage reaction.
Abstract: A highly conserved threonine in the active site of cytochromes P450 has been proposed to participate in O2 binding and cleavage. Cytochrome P450eryF is unusual in having alanine in place of this threonine and an ordered active site water molecule (Wat 519) which is hydrogen bonded to the substrate 5-hydroxyl group and is in position to operate as an acid catalyst required for cleaving dioxygen. To asses the role of this alanine residue and Wat 519 in catalysis, two mutant forms of P450eryF (Ala --> Ser,Ala --> Thr) and a substrate analogue lacking a 5-hydroxyl group were examined using kinetic, spectral and crystallographic techniques. In each case decreased catalytic activity was correlated with a loss or repositioning of Wat 519. These findings suggest that P450eryF utilizes the substrate to assist in the acid-catalysed dioxygen bond cleavage reaction.
TL;DR: Diphenyl-2-thienylphosphine, Ph2PC4H3S (1), reacts with Ru3(CO)12] in refluxing toluene to give the compound [Ru3(μ2-H)(μ3-Ph2PC 4H2S)(CO)9] (2) (59%), cyclometalated at the thiophene ring, with sm...
TL;DR: O-transfer to ancillary phosphine ligand to give R(3)P=O selectively involves the Rh-linked O atom of the peroxo group of RhCl(CO(4))(P)(3).
Abstract: Extended labeling experiments have shown that formation of rhodium peroxocarbonate from CO2 and [RhCl(η2-O2)(P)3] (P is PEt2Ph or PEtPh2) proceeds through O−O bond cleavage and CO2 insertion. O-transfer to ancillary phosphine ligand to give R3PO selectively (>85%) involves the Rh-linked O atom of the peroxo group of RhCl(CO4)(P)3.
TL;DR: In this article, the oxidation of MnIII2(2-OHsalpn)2, 1 (2-HOsalpn = 1,3-bis(salicylideneamino)-2-propanol), with tert-butyl hydroperoxide was studied in organic media.
Abstract: The oxidation of MnIII2(2-OHsalpn)2, 1 (2-OHsalpn = 1,3-bis(salicylideneamino)-2-propanol), with tert-butyl hydroperoxide was studied in organic media. A one-electron reaction occurs resulting in i...
TL;DR: The results clearly demonstrate that the distal histidine of H93C Mb is hardly involved in the O-O bond cleavage step and are in good agreement with the role of thiolate ligation for the formation of the reactive intermediate, equivalent to compound I, in the catalytic cycle of P-450 reactions.
Abstract: We have reported that H93C human myoglobin (Mb), in which proximal histidine (His93, F8) was replaced by cysteine, gave nearly identical spectroscopic features of P-450 [Adachi, S., Nagano, S., Ishimori, K., Watanabe, Y., Morishima, I., Egawa, T., Kitagawa, T., & Makino R. (1993) Biochemistry 32, 241-252]. More importantly, the thiolate ligand enhanced its oxygenation activities when supported by H2O2 due to the exclusive encouragement of heterolytic O-O bond cleavage of peroxides. While we have attributed the enhanced heterolysis to the electron donation from the thiolate ligand, possible participation of the distal histidine (H64, E7) in H93C Mb cannot be eliminated. In addition, the racemic product formation catalyzed by H93C Mb implied that its distal cavity could prevent substrates from accessing to the heme and the reactions may proceed other than by the P-450 type mechanism (ferryl oxygen transfer). In order to clarify whether the distal histidine is involved in the O-O bond cleavage step and to improve accessibility of substrates, the distal histidine of H93C Mb is replaced by smaller and nonpolar residues, glycine (H64G/H93C Mb) and valine (H64V/H93C Mb), by site-directed mutagenesis. Various spectroscopic studies on these double-mutated Mbs revealed the ligation of cysteine to the ferric heme as a thiolate form. In the reaction with cumene hydroperoxide, the anionic nature of the proximal cysteine in H64G/H93C and H64V/H93C Mbs was found to encourage the heterolytic O-O bond cleavage as observed for H93C Mb. The results clearly demonstrate that the distal histidine of H93C Mb is hardly involved in the O-O bond cleavage step and are in good agreement with the role of thiolate ligation for the formation of the reactive intermediate, equivalent to compound I, in the catalytic cycle of P-450 reactions. In the oxygenation of methyl p-tolyl sulfide, the ratios of ferryl oxygen transfer increased in H64G/H93C Mb (58%) and H64V/H93C Mb (78%) as compared to H93C Mb (53%). The increased ratios of ferryl oxygen transfer imply the active site of H64G/H93C and H64V/H93C Mbs being more accessible for substrates; however, the sulfoxidation by the ferric mutant Mbs/H2O2 system was much slower than that by H93C Mb. The poor activities of these mutant Mbs are attributed to the significantly discouraged binding of H2O2.
TL;DR: The thermal reaction of enyne-allenes 1 with large substituents (tert-butyl, trimethylsilyl) at the acetylene terminus leads to C2C6 cyclization products presumably via an intermediate benzo-fulvene biradical, whereas with a hydrogen substituent the expected Myers-Saito cycloaromatization product is formed.
TL;DR: The photochemistry of N-hydroxypyridine-2(1H)-thione (N-HPT) has been investigated in aqueous and organic solvents using laser flash photolysis (λexc = 308 or 355 nm) as discussed by the authors.
Abstract: The photochemistry of N-hydroxypyridine-2(1H)-thione (N-HPT) has been investigated in aqueous and organic solvents using laser flash photolysis (λexc = 308 or 355 nm). Independent of the environment, UV excitation of N-HPT causes homolytic N−O bond cleavage, which leads to formation of the 2-pyridylthiyl (PyS•) and hydroxyl (•OH) radicals. In aqueous media, this process occurs efficiently from both the anionic and neutral forms (ΦN-O ≈ 0.20−0.30). In addition to N−O bond scission, N-HPT undergoes other primary photoprocesses which are pH-dependent. At pH = 7, photoionization (Φe− = 0.09 (λexc = 308 nm) and 0.05 (λexc = 355 nm)) of the anionic form generates the hydrated electron as well as the semioxidized radical of N-HPT. Fast rearrangement of the latter species produces the N-oxy-2-pyridylthiyl radical. At pH = 2, where the uncharged structure predominates, formation of an excited triplet state (ET ≥ 59.5 kcal mol-1) is observed (ΦT ≥ 0.05 using λexc = 355 nm) but photoionization does not take place. T...
TL;DR: In this paper, the photo-induced rearrangement at room temperature yielded the imido complexes [η5-C5H4]-Si(CH3)2-N(CH 3)2]M(=NR)[N(Ch3) 2]2]2 as a result of SiN bond cleavage.
TL;DR: In this paper, the first synthetic thiolato-iron porphyrin (SR complex) which retains its structure during catalytic oxidation was presented, which greatly accelerates the rate of the OO bond cleavage and its heterolysis even in highly hydrophobic media.
Abstract: (1) A distinctive structural feature of P450 is the unusual thiolate coordination to heme. We have succeeded in the preparation of the first synthetic thiolato-iron porphyrin ( SR complex) which retains its structure during catalytic oxidation. Experiments using SR complex have revealed that the thiolate ligand greatly accelerates the rate of the OO bond cleavage and its heterolysis even in highly hydrophobic media. (2) Heteroaromatic N -oxides were found to be excellent oxidants in the presence of ruthenium porphyrin. 2,6-disubstituted pyridine N -oxides plus a catalytic amount of Ru porphyrin oxidized olefins and sulfides to afford epoxides and sulfoxides, respectively, in high yields. The system in the presence of hydrogen halide effectively oxidized unactivated alkanes and arenes to give alcohols (or ketones) and p -quinones in high yields with high selectivity and an extremely high catalyst turnover number (up to 1.2 × 10 5 ). (3) A polypeptide-bound porphyrinatoiron complex was prepared. The polymer complex exhibited greater P450-like activity than non-bound Fe(TPP)Cl in the oxidation of olefin and aniline derivatives. (4) P450 mimics were applied to drug metabolism studies. These model systems were effective for one-step preparation of unstable metabolic intermediates, ‘candidate metabolites’, and for the discovery of novel modes of metabolism.
TL;DR: In this article, the effects of alkyl chain structure on the rate of carbon−halogen bond dissociation and β-hydride elimination were studied under ultra-high-vacuum conditions.
Abstract: The effects of alkyl chain structure on the rate of carbon−halogen bond scission in alkyl chlorides, bromides, and iodides on a Cu(100) surface and on the rates of β-hydride elimination by the alkyl products of these carbon−halogen bond scission reactions have been studied under ultra-high-vacuum conditions. It is found that the carbon−halogen bond dissociation rates increase in the order: C−Cl < C−Br < C−I and C(1°)−X < C(2°)−X < C(3°)−X, where X denotes the halogen and 1°, 2°, 3° refer to the number of alkyl substituents at the halogen-substituted carbon. β-Hydride elimination by the corresponding alkyl groups shows the following trends: (1) alkyl chain length (greater than three carbons) does not significantly affect the rate of β-hydride elimination; (2) the rate increases with alkyl substitution at the α-carbon in the order primary alkyls < secondary alkyls, (3) the rate of increase is substantially larger than expected on the basis of the increase in the number of β-hydrogens, and (4) for C5 and C...