Formation Of Phenoxide Research Articles

Reactivity of 3- and 4-pyridinylnitrene-n-oxide radical anions

Ion–molecule reactions in a flowing afterglow are used to examine the electronic structure of 3- and 4-pyridinylnitrene-n-oxide radical anions. Reactions with nitric oxide are generally similar to those reported previously for other aromatic nitrene radical anions. In particular, phenoxide formation by nitrogen–oxygen exchange is observed with both isomers. Oxygen atom abstraction by NO is also observed with both isomers. Very significant differences in the reactivity are observed in the reactions of the two isomers with carbon disulfide. The reactivity of the 3-n-oxide isomer with CS2 is similar to that observed previously for nitrene radical anions, and reactions of the n-oxide moiety are not observed, similar to what is expected based on solution chemistry. The 4-n-oxide isomer, however, undergoes many reactions, including oxygen atom and oxygen ion transfer and sulfur–oxygen exchange, that involve the n-oxide oxygen. The increased reactivity of the oxygen is attributed to increased charge density at the oxygen due to pi electron donation of the nitrene anion in the para position.

Characterization of multiple fragmentation pathways initiated by collision‐induced dissociation of multifunctional anions formed by deprotonation of 2‐nitrobenzenesulfonylglycine

The correlation of anion structure with the fragmentation behavior of deprotonated nitrobenzenesulfonylamino acids was investigated using tandem mass spectrometry, isotopic labeling and computational methods. Four distinct fragmentation pathways resulting from the collision-induced dissociation (CID) of deprotonated 2-nitrobenzenesulfonylglycine (NsGly) were characterized. The unusual loss of the aryl nitro substituent as HONO was the lowest energy process. Subsequent successive losses of CO, HCN and SO2 indicated that an ortho cyclization reaction had accompanied loss of HONO. Other pathways involving rearrangement of the ionized sulfonamide group, dual bond cleavage and intramolecular nucleophilic displacement were proposed to account for the formation of phenoxide, arylsulfinate and arylsulfonamide product ions at higher collision energies. The four distinct fragmentation pathways were consistent with precursor-product relationships established by CID experiments, isotopic labeling results and the formation of analogous product ions from 2,4-dinitrobenzenesulfonylglycine and the Ns derivatives of alanine and 2-aminoisobutyric acid. The computations confirmed a low barrier for ortho cyclization with loss of HONO and feasible energetics for each reaction step in the four pathways. Computations also indicated that three of the fragmentation pathways started from NsGly ionized at the carboxyl group. Overall, the pathways identified for the fragmentation of the NsGly anion differed from processes reported for anions containing a single functional group, demonstrating the importance of functional group interactions in the fragmentation pathways of multifunctional anions.

Reductive Dealkylation of Anisole and Phenetole: Towards Practical Lignin Conversion

We present and develop alternative catalysts for biomass conversion and specifically lignin conversion into aromatics. Unlike the conventional CoMo and NiMo formulations, our catalysts can convert low-sulfur feedstocks. A set of five magnesia–alumina mixed oxides were screened in the hydrodealkylation of alkyl phenyl ethers as lignin model compounds. The typical selectivity to phenol is 30–75 %. Interestingly, we saw that the more basic the catalyst, the higher the selectivity for phenol. The results concur with the formation of phenoxide (PhO–) and RH3+ fragments on the catalyst surface. These can then react with H+ and H– species formed by the hydrogen dissociation on the MgO surface, giving phenol and hydrocarbons. We conclude that magnesia–alumina mixed oxides are attractive candidates for catalyzing lignin breakdown. These catalysts are highly stable, inexpensive, and readily available.

The First Total Synthesis of (.+‐.)‐Annosqualine by Means of Oxidative Enamide—Phenol Coupling: Pronounced Effect of Phenoxide Formation on the Phenol Oxidation Mechanism.

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The first total synthesis of (±)-annosqualine by means of oxidative enamide–phenol coupling: pronounced effect of phenoxide formation on the phenol oxidation mechanism

The first total synthesis of a spiro-isoquinoline alkaloid, (±)-annosqualine, was established by employing an enamide–phenol coupling of a 1-methylene-1,2,3,4-tetrahydroisoquinoline derivative with a hypervalent iodine reagent, where the formation of the phenoxide was recognized to be an essential step for the reaction of the phenolic hydroxyl group with the hypervalent iodine reagent leading to the formation of the desired product.

Efficiency of enzymatic and non-enzymatic catalysts in the synthesis of insoluble polyphenol and conductive polyaniline in water

The present work analyzes the potential use of white-rot fungi (WRF) and hematin for phenol and aniline polymerization, as a low-cost alternative to horseradish peroxidase (HRPC). The objective is to evaluate the capability of these catalysts to produce tailor-made aniline as well as to eliminate phenols by precipitation from aqueous solution. 4-Aminoantypirine (4AAP) was used to test phenoxide formation by crude protein preparations of white-rot fungi at selected conditions. The crude extracts of Pleurotus sajor-caju (PSC) were selected because of the promising values obtained for the phenoxide formation rate. HRPC/H 2O 2 and P. sajor-caju derived enzymes/H 2O 2 (PSC/H 2O 2) systems produced soluble polyaniline in the presence of polystyrene sulphonated (PES), with high aniline conversions at 45 °C. For the case of insoluble polyphenol production, the PSC-derived enzymes, in absence of hydrogen peroxide, produced insoluble polyphenol with similar efficiencies as those found with HRPC or hematin in a one step phenol treatment (near 40% phenol conversion). For the aniline process, at least 75% aniline conversion was obtained when using PSC enzymes at room temperature. After long reaction times, the lignin-modifying enzymes derived from PSC only produced a conductive form of polyaniline (PANI) at lower temperatures than those required when employing HRPC. Fungal enzymes look promising for eliminating aniline/phenol from wastewaters since the obtained results demonstrated that they are able to polymerizate and precipitate them from aqueous solutions.

Evidence for heterodimers of 2,4,5-trichlorophenol on planar lipid layers. A FTIR-ATR investigation

Trichlorophenols are weak acids of high hydrophobicity and are able to transport protons across the mitochondrial membrane. Thus the proton motive force is dissipated and the ATP production decreased. In situ Fourier Transform Infrared-Attenuated Total Reflection (FTIR-ATR) experiments with 2,4,5-trichlorophenol (TCP) adsorbed to model membranes resulted in good evidence for the formation of the TCP-heterodimer. Two surfaces were examined: a dipalmitoyl phosphatidic acid (DPPA) monolayer and a planar DPPA/1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC) bilayer. TCP was adsorbed from 1 to 3 mM solutions at pH 6.0 to the lipid layers leading to surface layers at the water/lipid interface. Difference spectra showed an effect on DPPA acyl chains even when it was covered with POPC. Time-resolved measurements revealed two distinct adsorption processes, which were assigned to TCP and its deprotonated anion (phenoxide), respectively. For DPPA/POPC bilayers, the adsorption of TCP was faster than that of its phenoxide, whereas adsorption of both species to DPPA monolayers proceeded with similar velocity. In both cases, phenoxide formation at the membrane was found to be delayed with respect to phenol adsorption. Phenoxide and phenol were retained after replacing the TCP solution with buffer. For the retained species, we estimated a phenol/phenoxide molar ratio of 1 at pH 6.0 (p K a=6.94 for TCP), demonstrating strong evidence for heterodimer formation.

Evidence for heterodimers of 2,4,5-trichlorophenol on planar lipid layers. A FTIR-ATR investigation

Trichlorophenols are weak acids of high hydrophobicity and are able to transport protons across the mitochondrial membrane. Thus the proton motive force is dissipated and the ATP production decreased. In situ Fourier Transform Infrared-Attenuated Total Reflection (FTIR-ATR) experiments with 2,4,5-trichlorophenol (TCP) adsorbed to model membranes resulted in good evidence for the formation of the TCP-heterodimer. Two surfaces were examined: a dipalmitoyl phosphatidic acid (DPPA) monolayer and a planar DPPA/1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine (POPC) bilayer. TCP was adsorbed from 1 to 3 mM solutions at pH 6.0 to the lipid layers leading to surface layers at the water/lipid interface. Difference spectra showed an effect on DPPA acyl chains even when it was covered with POPC. Time-resolved measurements revealed two distinct adsorption processes, which were assigned to TCP and its deprotonated anion (phenoxide), respectively. For DPPA/POPC bilayers, the adsorption of TCP was faster than that of its phenoxide, whereas adsorption of both species to DPPA monolayers proceeded with similar velocity. In both cases, phenoxide formation at the membrane was found to be delayed with respect to phenol adsorption. Phenoxide and phenol were retained after replacing the TCP solution with buffer. For the retained species, we estimated a phenol/phenoxide molar ratio of 1 at pH 6.0 (p K a =6.94 for TCP), demonstrating strong evidence for heterodimer formation.

Challenges in the isolation of taxanes from Taxus canadensis by fast pyrolysis

The Waterloo Fast Pyrolysis Process (WFPP) was used to determine the feasibility of extracting taxanes from needles, twigs and whole clippings of Taxus canadensis. Purification techniques developed for solvent extracts were not suitable for achieving analytic chromatographic separation of taxanes from pyrolytic lignins and other pyrolysis products as these materials are in much higher quantities in pyrolysis oil than in solvent extracts. A number of separation techniques were attempted including liquid–liquid partitioning, silica gel chromatography, adsorption and sodium phenoxide formation. Pretreatment of the feedstock by deionization was also attempted. Taxol® was identified in pyrolysis oils of needles and whole clippings with 20% recovery compared to solvent extraction. Other taxanes were most likely present in higher concentrations but could not be analyzed because of interference by phenolic substances.

Poly(aryl ether phenylquinoxalines) via anionic ring opening polymerization of macrocycles

AbstractA cyclic poly(aryl ether phenylquinoxaline) was prepared via the self‐polymerization of 1 in an N‐methyl‐2‐pyrrolidone (NMP) solution containing base using a pseudo‐high dilution polymerization condition. The macrocycle formation of 1 was carried out in the presence of potassium carbonate in a NMP/toluene solvent mixture at a solids content of 1%. The water generated by phenoxide formation was removed as an azeotrope with toluene 170 °C. A concentrated solution of the macrocycle was added to the reaction mixture over an 8 hour period. The reaction was allowed to proceed for an additional 24h to ensure quantitative reaction. A number of characterization techniques were used to study the cyclization of 1 including GPC, HPLC, H NMR and matrix‐assisted laser desorption ionization (MALDI) mass spectroscopy. The MALDI‐TOF mass spectrum of the cyclization of 1 clearly showed that a mixture of macrocycles is obtained, with the expected distribution of molecular weights. Facile ring opening polymerization of the cyclic poly(aryl ether phenylquinoxaline) oligomers was accomplished with a nucleophilic initiator. High polymer was obtained for each polymerization temperature (η = 0.4–0.5 dl/g in NMP), however, prolonged reaction time resulted in significant gel formation. The Tg's were high and commensurate with the high molecular weight linear analog (250 °C).

Some reactions of cationic 16-electron molybdenum mononitrosyl complexes with phenols and arylamines

The complex [Mo(NO)LCl2]PF6(L =N,N′,N″-trimethyl-1,4,7-triazacyclononane) reacts with methanol to give [Mo(NO)L(Cl)(OMe)]PF6 but the reaction with 4-ferrocenylphenol results in reduction rather than phenoxide formation. The complex [Mo(NO)LBr2]PF6 reacts with 4-amino-2-methyl-4′-ferro-cenylazobenzene to give a bimetallic complex containing a seven-co-ordinate paramagnetic molybdenum centre (µeff= 3.13).

Gas-Phase reactions of NO 2− with nitrobenzenes and quinones. Electron transfer, clusters and formation of phenoxide and quinoxide negative ions. Use of NO 2 as a negative ion chemical ionization reagent

Negative-ion/molecule reactions in systems containing methane as the major gas (∼ 4 torr), with NO 2 and compounds A at mtorr pressures were studied in a pulsed electron, high pressure mass spectrometer. The compounds A were substituted nitrobenzenes and quinones. All these A compounds have positive electron affinities. Three types of reactions were observed and examined. (1) Electron transfer: A − + NO 2 = A + NO 2 −. The exothermic electron transfer reactions proceeded with ADO collision rates for exothermicities from 30 to ∼ 10 kcal mol −1. Lower exothermicities led to low collision yields. (2) Adduct formation: NO 2 − + A = NO 2 −·A. The equilibria for adduct formation were determined. Stable adducts are formed when A has hydrogens with partial protic character. The stability of the adducts NO 2 −·A increased with increase in the electron affinity of A, when A was a substituted nitrobenzene. Substituents that increase the electron affinity of nitrobenzene are electron-withdrawing groups which also increase the protic character of the hydrogens involved in bonding in NO 2 −·A. (3) Some of the compounds A were converted to phenoxy negative ions on reaction with NO 2 −. For example, para-dinitrobenzene leads to formation of the para-nitrophenoxide negative ion. The oxy-negative-ion-forming reaction can be isomer specific. The utility of reaction types (1)–(3) is examined from the standpoint of negative ion chemical ionization where the reagent gas is NO 2 in methane and the reagent ion is NO 2 −.