Phenyl Carbon Research Articles

Combination of a solid phase extraction and a two-dimensional LC-UV method for the analysis of vitamin D3 and its isomers in olive oil

The current HPLC methods for the quantification of vitamin D3 (VitD3) and its two isomers previtamin D3 (PreVitD3) and trans-vitamin D3 (trans-VitD3) in olive oil preparations present some limitations mainly due to peak overlapping of the oily matrix components with the compounds of interest. The use of two-dimensional liquid chromatography (2D-LC) with different retention mechanism can reach higher resolving power thus allowing the analysis of complex samples.The present paper proposes a new alternative method including a solid phase extraction sample preparation step and a two-dimensional liquid chromatographic analysis using routine instrumentation, fitting the needs of quality assurance and quality control laboratories of pharmaceutical companies. The extraction protocol was demonstrated to provide a clean-up of the sample and a quantitative recovery of the species of interest. The 2D method proved its suitability in the isolation of vitamins from oil components in the first dimension and the separation and quantification of the analytes in the second dimension thanks to the orthogonal selectivities of phenyl and porous graphitic carbon (PGC) stationary phases.The method was validated following ICH guidelines and possesses an adequate sensitivity to quantify the impurity trans-VitD3 in pharmaceuticals considering the limits imposed by regulatory agencies. The applicability of the phenyl x PGC 2D-LC-UV method to quality control of medicinal products based on VitD3 in olive oil was confirmed by the successful quantification of vitamins in olive oil formulations.

Hypercoordination by multiple dangling benzylmethoxy ligands in highly crowded triaryltin bromide [(2-MeOCH2C6H4)3]SnBr and diaryltin mixed halides [(2-MeOCH2C6H4)2]SnBrCl.

The reaction between the Grignard reagent formed between Mg and 2-bromobenzylmethyl ether and SnCl4 produced four products: [2-(MeOCH2)C6H4]3SnBr (1), [2-(MeOCH2)C6H4]2SnX2 (2, X2 = Br2 (a) and BrCl (b)), [{2-(MeOCH2)C6H4}3Sn]2 (3), and [{2-(MeOCH2)C6H4}2SnBr]2O (4). In the case of 1, two of the three dangling arm O atoms coordinate to the central tin atom with O-Sn internuclear distances of 2.53 (O1) and 2.91 (O2) Å, the shorter interaction being trans to the Br atom, the other trans to a phenyl carbon atom. In the case of 2 the resulting hexacoordinate structure exhibits two very short O---Sn interactions of 2.42 and 2.50 Å, well below the sum of the VdW radii of O and Sn, 3.69 Å. The sterically crowded ditin compound 3 was obtained in trace amounts and the structure demonstrates no dangling O---Sn interactions. General changes in structure compared to other distannane systems are reflective of the great steric crowding. Distannoxane 4, has a Sn-O-Sn bond angle of 148.1(2)o which is larger compared to other distannoxane structures. The intermolecular interactions between Sn---O 2.470(3) and 2.521(3)Å and 2.665(3) and 2.629(3)Å for Sn1 and Sn2 respectively are responsible for a distorted octahedral geometry around the two tin atoms.

Visible Light-Mediated Inactivation of H1N1 Virus UsingPolymer-Based Heterojunction Photocatalyst.

It is well known that viruses cannot replicate on their own but only inside the cells of target tissues in the organism, resulting in the destruction of the cells or, in some cases, their transformation into cancer cells. While viruses have relatively low resistance in the environment, their ability to survive longer is based on environmental conditions and the type of substrate on which they are deposited. Recently, the potential for safe and efficient viral inactivation by photocatalysis has garnered increasing attention. In this study, the Phenyl carbon nitride/TiO2 heterojunction system, a hybrid organic-inorganic photocatalyst, was utilized to investigate its effectiveness in degrading the flu virus (H1N1). The system was activated by a white-LED lamp, and the process was tested on MDCK cells infected with the flu virus. The results of the study demonstrate the hybrid photocatalyst's ability to cause the virus to degrade, highlighting its effectiveness for safe and efficient viral inactivation in the visible light range. Additionally, the study underscores the advantages of using this hybrid photocatalyst over traditional inorganic photocatalysts, which typically only work in the ultraviolet range.

Catalytic Pyrolysis of Waste Plastics over Industrial Organic Solid-Waste-Derived Activated Carbon: Impacts of Activation Agents

Renewable source-derived carbon is found to be a green alternative catalyst to zeolite for the pyrolysis of plastics. However, only polyethylene (PE) catalytic pyrolysis over biomass-derived carbon has been extensively studied. In this work, carbon was produced from industrial organic solid waste using different activation agents, and their catalytic performance on the thermal degradation of typical polymers, namely PE, polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were investigated. The degradation mechanisms and the roles of different active sites of the carbons are discussed. Steam failed to activate the carbon, which has a low specific surface area (6.7 m2/g). Chemical activation using H3PO4 and ZnCl2 produces carbons with higher specific surface area and more porosity. The pyrolysis characteristics of LDPE, PP, PS, and PET catalyzed by the carbons were studied using TGA and a fixed-bed reactor. The thermogravimetric results indicate that all three carbons reduce the pyrolysis temperature. The analysis of the products shows that the P- and Zn-involved acid sites on the AC-HP and AC-ZN change the reaction pathway of plastics and promote: (1) C-C cracking and aromatization of polyolefins; (2) the protonation of phenyl carbon of PS to yield higher benzene, toluene, and ethylbenzene; and (3) the decarboxylation of the terephthalic acid intermediate of PET, resulting in higher CO2 and benzene. In addition, the high-value chemicals, long-chain alkylbenzenes, were found in the liquids of AC-ZN and AC-HP. The long-chain alkylbenzenes are probably formed by acid-catalyzed alkylation of aromatic hydrocarbons. This study provides basic data for the development of a cheap catalyst for plastic pyrolysis.

The ion-neutral complex-mediated fragmentation reaction in electrospray ionization tandem mass spectrometric analysis of N-phenyl-3-(phenylthio)propanamides.

Amides are the fundamental units of both peptides and proteins, and also important functional groups of medical chemicals. Investigation of the fragmentation mechanism of amides in the gas phase is scientifically important for structural analysis. However, understanding of this problem is still elusive. Protonated N-phenyl-3-(phenylthio)propanamide and its derivatives were investigated using positive ion tandem mass spectrometry (ESI-MS/MS) with an LCQ mass spectrometer. Accurate mass analysis was conducted with a micrOTOF-QII mass spectrometer. Density functional theory (DFT) calculations using the Gaussian 03 program and deuterium-labelling (D-labelling) experiments were performed to verify the proposed fragmentation mechanism. Interpretation of the fragment ions in the collision-induced dissociation mass spectra showed that the ionizing proton in the protonated ion transferred from the most thermodynamically favorable carbonyl oxygen to the dissociative protonation site at amide nitrogen or sulfur atom upon collisional activation. The dissociation of the amide or the C-S bond was induced by such proton transfer. An ion-neutral complex (INC) was generated via the dissociation of the amide bond. In the INC, it was observed that the carbocation of the ionic part attacked the ortho phenyl carbon atom adjacent to the sulfur atom, and proton transfer from the carbon atom to the nitrogen atom led to the formation of protonated aniline. The fragmentation mechanism of protonated N-phenyl-3-(phenylthio)propanamide and its derivatives was proposed and elucidated. All the compounds studied showed similar fragmentation pathways, and the competitive formation of two ions, RC9 H9 OS+ and C6 H8 N+ , was observed. The generation of protonated aniline is mediated by INC in ESI-MS/MS.

Modification of High‐Density Polyethylene through the Grafting of Methyl Methacrylate Using RAFT Technique and Preparation of Its Polymer/Clay Nanocomposites**

AbstractA well‐defined method for discovering an easy and effective strategy through graft copolymer derived from poly (methylmethacrylate) (PMMA) as a monomer, high‐density polyethylene (HDPE) and its organoclay nanocomposite with physicochemical and mechanical properties was successfully prepared by reversible addition‐fragmentation transfer (RAFT) polymerization, and factors organoclay (Cloisite® 20 A) on the terminal features of the obtained graft copolymer were investigated. First, maleic anhydride (MA) was grafted onto HDPE directed by, the inauguration of an anhydride chain with ethanolamine to develop a hydroxylated high‐density polyethylene (HDPE‐OH). After that, the hydroxyl masses were esterified by using RAFT agent, 4‐cyano‐4‐[(phenyl carbon thionyl) sulfanyl valeric acid to obtain HDPE‐CTA macroinitiator. Then, the MMA monomer was grafted onto HDPE via the RAFT method to obtain the HDPE‐g‐PMMA graft copolymer. In the end, HDPE‐g‐PMMA/clay nanocomposite by a solution intercalation method was synthesized. The structures of the, copolymer and nanocomposite were studied by Fourier transform infrared spectroscopy, X‐ray diffraction, and Transmission electron microscopy (TEM) techniques. It explores for the synthesis of HDPE‐g‐PMMA/clay nanocomposites, disclosed a foliated structure. Based on the thermic behavior, synthesized HDPE‐g‐PMMA/clay nanocomposites can display the above thermic solidity with just some extent (5) of organoclay.

4-Nitrophenol Efficient Photoreduction from Exfoliated and Protonated Phenyl-Doped Graphitic Carbon Nitride Nanosheets.

The photoreduction of 4-nitrophenol to 4-aminophenol by means of protonated and exfoliated phenyl-doped carbon nitride is reported. Although carbon nitride-based materials have been recognized as efficient photocatalysts, the photoreduction of 4-nitrophenol to 4-aminophenol is not allowed because of the high recombination rate of the photogenerated electron–hole pairs. In this paper, we show the morphology effects on the photoactivity in phenyl-doped carbon nitride. Structural (TEM, XRD, Raman) and optical characterization (absorption, photoluminescence) of the protonated and exfoliated phenyl-doped carbon nitride (hereafter pePhCN) is reported. The increased photocatalytic efficiency, with respect to the bulk material, is underlined by the calculation of the kinetic constant of the photoreduction process (2.78 × 10−1 min−1 and 3.54 × 10−3 min−1) for pePhCN and bulk PhCN, respectively. Finally, the detailed mechanism of the photoreduction process of 4-nitrophenol to 4-aminophenol by modified phenyl carbon nitride is proposed.

Unprecedented Treatment Strategy of Aquatic Environments: Oxidative Degradation of Penicillin G by Chromium Trioxide in Acidic Media and the Impact of Metal Ion Catalysts: Kinetics and Mechanistic Insights.

Degradation kinetics and pathways of the antibiotic penicillin G (Pen) have been examined via oxidation by chromium trioxide (CrVI) in aqueous sulfuric and perchloric acid media. The oxidation reactions were monitored by spectrophotometry at 298 K. In both acidic media, penicillin G oxidation was set to proceed through acid catalysis. The stoichiometry of the reactions designated that 3 moles of Pen required 2 moles of CrVI. The kinetics of Pen oxidation in both acids was of the first order with regard to [CrVI] and less-than unity order with regard to [Pen] and [H+] in their variation. The rates of reactions displayed negligible impacts upon altering ionic strengths or dielectric constants of the reaction media. There was no intrusion of free radicals throughout the redox reactions. Addition of low concentrations of Ni2+, Cu2+, and Zn2+ ions enhanced the oxidation rates, while addition of Cr3+ as a described product did not noteworthily alter the rates. Under comparable investigational circumstances, the oxidation rates in HClO4 were almost 2-fold greater than in H2SO4. The oxidation products of penicillin G were identified by spectral analysis and spot tests as phenyl acetic acid, 2-formyl-5,5-dimethyl-thiazolidine-4-carboxlate ion, ammonium ion, and carbon dioxide. Reliance of reaction rates on temperature has been explored, and the activation and thermodynamic parameters were estimated and debated. In view of the noted reactions’ orders and products’ identification, a plausible mechanism for the oxidation reactions was suggested. The derived rate law was set to be in accordance with the acquired results. This study offers an unprecedented simple and low-cost treatment method for removal or degradation of certain pollutants for protecting the environment and human health.

Highly efficient visible light phenyl modified carbon nitride/TiO2 photocatalyst for environmental applications

Eco-sustainable solutions for the neutralization of air and water pollutants have increasingly gravitated toward the use of heterogeneous photocatalysts. This approach, which transforms pollutants into harmless substances through a light-driven chemical reaction on a catalytic surface, must comply with eco-sustainability requirements and be easily applicable. Semiconductor-based photocatalysis is a promising pathway for the degradation of environmental pollutants and, among all the various semiconductors used, titanium dioxide has proved itself to be the foremost material for environmental remediation due to its highly desirable photocatalytic properties. Titanium dioxide, however, poorly exploits the visible part of the electromagnetic spectrum due to the relatively large band-gap of its anatase phase, and as such, the UV portion of the solar spectrum is largely responsible for its photocatalytic activity. Herein, we demonstrate a highly efficient visible light hybrid catalyst based on titanium dioxide and phenyl carbon nitride (PhCN). With the organic component providing a broad absorption up to 600 nm and fast charge exchange to the conduction band of TiO2, the combination allows for the highly efficient photocatalytic degradation of Rhodamine B under visible excitation.

Crystal structure of ipratropium bromide monohydrate, C20H30NO3Br(H2O)

The crystal structure of ipratropium bromide monohydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Ipratropium bromide monohydrate crystallizes in the space group P21/c (#14) with a = 8.21420(7) Å, b = 10.54617(13) Å, c = 24.0761(39) Å, β = 99.9063(7) °, V = 2054.574(22) Å3, and Z = 4. Both hydrogen atoms of the water molecule act as donors to the bromide cation, forming a ring with the graph set R2,4(8). The hydroxyl group also acts as a donor to Br. Several C–H⋯Br hydrogen bonds are present. The water molecule acts as an acceptor in two C–H⋯O hydrogen bonds from methyl groups. The ketone acts as an acceptor in C–H⋯O hydrogen bonds from methyl groups, a methylene group, and a methyne group. The hydroxyl group acts as an acceptor in a C–H⋯O hydrogen bond from a phenyl carbon atom. The powder pattern is included in the Powder Diffraction File™ as entry 00-066-1611.

Understanding hydroxide reactions with guanidinium-based anion exchange polymers under conditions relevant to bipolar membrane electrodialysis

Anion exchange polymers are susceptible to loss of cationic functionality as a result of nucleophilic attack by hydroxide ions. This research investigated the stability of two guanidinium-based cations as anion exchange functional groups under conditions relevant to bipolar membrane electrodialysis. Density functional theory simulations were performed to investigate reaction energies and activation barriers for reactions of hydroxide ions with pentamethylguanidinium (PMG) and hexamethylguanidinium (HMG) cations bound to a diaryl ketone polymer backbone. The effect of physically adsorbed chloride and hydroxide ions, and chemically adsorbed hydroxide ions, on reaction energetics were determined. Fukui functions for nucleophilic attack were used to identify locations most likely to undergo reactions with hydroxide ions. For the PMG species, the most likely bond cleavage reactions were highly exergonic, with ΔGrxno values as large as −46 kcal/mol and activation barriers less than 10 kcal/mol. Chemisorption of hydroxide ions on both PMG and HMG cations was energetically favorable, with activation barriers of 5.3 and 2.7 kcal/mol, and resulted in loss of cationic functionality. Anion adsorption changed the reactivity of both PMG and HMG structures towards nucleophilic attack. For nucleophilic attack at the phenyl carbon atom, adsorption of OH− on the guanidinium carbon atom made PMG less reactive, while adsorption of Cl− made HMG less reactive. Bond cleavage and loss of cationic functionality was a two or three step process involving addition of OH− to the phenyl or guanidinium carbon atoms, followed by bond stretching or deprotonation of the added hydroxide species. For PMG species, deprotonation of the hydroxide resulted in bond cleavage or produced metastable species that decomposed with activation barriers less than 2 kcal/mol. HMG species were more stable with respect to this degradation mechanism, having activation barriers for bond cleavage ranging from 17 to 29 kcal/mol.

Picket fence porphyrin challenges. Unexpected atropisomerism

The synthesis and structural analysis of two new bis imidazole-ligated iron(II) porphyrinates are reported. The reacting porphyrin used in the studies was the four-coordinate [Formula: see text] atropisomer of [Fe(TpivPP)] (picket fence porphyrin); the axial ligands are 2-methylimidazole and 1,2-dimethylimidazole. Crystal structure analysis revealed that the [Fe(TpivPP)(2-MeHIm)[Formula: see text]] complex had a strongly ruffled porphyrin core that accommodated the hindered ligands on both the picket side and the open face of the porphyrin. Reaction with 1,2-dimethylimidazole with the four-coordinate [Fe(TpivPP)] starting material led to an isomerized form of the picket fence porphyrin. The structure analysis showed that the product obtained was the [Formula: see text] atropisomer. Strong ruffling caused by the bulky 1,2-dimethylimidazole ligand must allow the requisite rotation about the methine carbon to phenyl carbon single bond and yields what is probably the most stable form of the complex. The relative orientation of the two axial ligands in both complexes are approximately perpendicular to each other. Other structural parameters are in general accord with six-coordinate iron(II) porphyrinates.

Synthesis, spectral, structural, photoluminescence, thermal and DFT studies of phenylmercury(II) and Ni(II) complexes of 3-methoxycarbonyl-piperidine-1-carbodithioate

Two new complexes [PhHg(mpc)] (1) and [Ni(mpc)2] (2) {mpc = 3-methoxycarbonyl-piperidine-1-carbodithioate} have been synthesized and characterized by elemental analyses, IR, NMR, UV–Vis and single crystal X-ray diffraction data. Both the complexes crystallize in triclinic system with space group P1¯. The geometry around the Hg(II) ion bonded with phenyl carbon and dithiosulfur atom of mpc is almost linear. Complex 2 is square planar having two unit of mpc ligand. Potassium salt of mpc and complex 1 emit violet light upon excitation at about 293 nm, while complex 2 emit blue light upon excitation at 323 nm wavelength. Cyclic voltammetry studies of free ligand (Kmpc) and its complexes 1 and 2 shows irreversible redox behaviour. Thermal behaviour of the complexes 1 and 2 have been studied which indicate that complex 1 evaporates completely over 700 °C temperature where as complex 2 converts into nickel sulfide as final residue. Frontier molecular orbital analysis reveals that complex 2 is softer and more reactive than complex 1. In the solid state, crystal structures of complexes are stabilized by intermolecular interactions.

Catalytic co-aromatization of methane and heptane as an alkane model compound over Zn-Ga/ZSM-5: A mechanistic study

The joint conversion of methane and heptane, a model compound of paraffin-rich raffinate oil, over a Zn-Ga modified zeolite catalyst has been investigated at various reaction times. In comparison with the performance from a N2 environment, the introduction of methane highly promotes the formation of light aromatic compounds with a single phenyl ring, and increased carbon number and substitution index of chemical constituents formed are indicative of methane incorporation into the liquid product. In addition, with prolonged time, the interaction between catalyst and methane molecules is enhanced. Through cleavage of methane molecules, the formed moieties likely participate in the aromatization reaction, which results in the growth of larger aromatic components through further condensation. According to the NMR spectra, witnessing methane engagement into the phenyl carbon and alkyl carbon sites of the formed liquid aromatics along with increasing reaction time is evidenced 13C-methane incorporation into aromatics. The excellent catalytic performance of Zn-Ga/ZSM-5 might be ascribed to the greatly dispersed metal species on the catalyst surface as well as a certain amount of medium and weak acid sites. With regards to the spent catalyst, the presence of methane could inhibit the aggregation of loaded active metals and coke formation during the co-aromatization process. The elucidation on the co-conversion of methane and high alkane provides great potential for the utilization of natural gas resources and intermediates formed from petrochemical industries.

Carbon Kinetic Isotope Effects and the Mechanisms of Acid-Catalyzed Decarboxylation of 2,4-Dimethoxybenzoic Acid and CO2 Incorporation into 1,3-Dimethoxybenzene.

The rate of decarboxylation of 2,4-dimethoxybenzoic acid (1) is accelerated in parallel to the extent that the carboxyl group acquires a second proton (1H+). However, the conjugate acid would resist C-C bond breaking as that would lead to formation of doubly protonated CO2. An alternative via formation of a higher-energy protonated phenyl tautomer (2H+) prior to C-C bond breaking would produce protonated CO2, an energetically inaccessible species that can be avoided by transfer of the carboxyl proton to water in the same step. Headspace sampling of CO2 that evolves in the acid-catalyzed process and analysis by GC-IRMS gives a smaller than expected value of 1.022 for the carbon kinetic isotope (CKIE), k12/k13. While this value establishes that C-C cleavage is part of the rate-determining process, intrinsic CKIEs for decarboxylation reactions are typically greater than 1.03. Computational analysis of the C-C bond cleavage from 2H+ gives an intrinsic CKIE of 1.051 and suggests two partially rate-determining steps in the decarboxylation of 1: transfer of the second carboxyl proton to the adjacent phenyl carbon and C-C cleavage in which the carboxyl proton is also transferred to water. Applying the principle of microscopic reversibility to fixation of CO2 in acidic solutions reveals the importance of proton transfers to both carbon and oxygen in the overall fixation process.

Oxidative coupling of sp2 and sp3 carbon\u2013hydrogen bonds to construct dihydrobenzofurans

Metal-catalyzed cross-couplings provide powerful, concise, and accurate methods to construct carbon–carbon bonds from organohalides and organometallic reagents. Recent developments extended cross-couplings to reactions where one of the two partners connects with an aryl or alkyl carbon–hydrogen bond. From an economic and environmental point of view, oxidative couplings between two carbon–hydrogen bonds would be ideal. Oxidative coupling between phenyl and “inert” alkyl carbon–hydrogen bonds still awaits realization. It is very difficult to develop successful strategies for oxidative coupling of two carbon–hydrogen bonds owning different chemical properties. This article provides a solution to this challenge in a convenient preparation of dihydrobenzofurans from substituted phenyl alkyl ethers. For the phenyl carbon–hydrogen bond activation, our choice falls on the carboxylic acid fragment to form the palladacycle as a key intermediate. Through careful manipulation of an additional ligand, the second “inert” alkyl carbon–hydrogen bond activation takes place to facilitate the formation of structurally diversified dihydrobenzofurans.

Methane Upgrading of Acetic Acid as a Model Compound for a Biomass-Derived Liquid over a Modified Zeolite Catalyst

The technical feasibility of coaromatization of acetic acid derived from biomass and methane was investigated under mild reaction conditions (400 °C and 30 bar) over silver-, zinc-, and/or gallium-modified zeolite catalysts. On the basis of GC-MS, Micro-GC, and TGA analysis, more light aromatic hydrocarbons, less phenol formation, lower coke production, and higher methane conversion are observed over 5%Zn-1%Ga/ZSM-5 catalyst in comparison with catalytic performance over the other catalysts. Direct evidence of methane incorporation into aromatics over 5%Zn-1%Ga/ZSM-5 catalyst is witnessed in 1H, 2H, and 13C NMR spectra, revealing that the carbon from methane prefers to occupy the phenyl carbon sites and the benzylic carbon sites, and the hydrogen of methane favors the aromatic and benzylic substitutions of product molecules. In combination with the 13C NMR results for isotopically labeled acetic acid (13CH3COOH and CH313COOH), it can be seen that the methyl and carbonyl carbons of acetic acid are equally i...

Bitumen partial upgrading over Mo/ZSM-5 under methane environment: Methane participation investigation

Bitumen extracted from oil sands which is abundant in Canada needs to be partially upgraded in order to meet pipeline specifications before being sent to downstream refineries. Hydrotreating where expensive hydrogen is involved at high pressure (15∼20MPa) is commonly employed as the technique to satisfy the upgrading requirement. In this study it is reported that a partially upgraded crude oil can be readily produced from bitumen under methane environment at mild conditions (400°C and 3MPa) without H2 engagement under the facilitation of 5%Mo/ZSM-5 (SiO2/Al2O3=23:1). The methane participation into the upgrading process was evidenced by analyzing the products obtained from the methanotreating of styrene and n-butylbenzene, the model compounds to represent heavy oil, as well as the heat effect during upgrading. Direct evidence of methane incorporation into the product molecules is observed on 1H, 2D and 13C NMR spectra, revealing that the carbon and hydrogen from methane occupy the phenyl carbon sites and aromatic and benzylic hydrogen sites, respectively, in the product molecules. Through extensive catalyst characterizations using TEM, XRD, and XPS, the excellent catalytic upgrading performance might be closely related to the highly dispersed molybdenum oxide particles on the zeolite support at partially reduced oxidation state for better methane activation. The outcomes from this research could not only create an innovative route for more profitable natural gas utilization, but also benefit bitumen partial upgrading in a more economical and environmentally friendly way.

Stimuli-Responsive Frustrated Lewis-Pair-Type Reactivity of a Tungsten Iminoazaphosphiridine Complex.

Reactions of 3-imino-azaphosphiridine complexes 1 a,b with carbodiimides 2 a,b, isocyanates 3 a,b, and carbon dioxide are described. Whereas exchange of the carbodiimide unit occurs in the first case, an overall ring expansion takes place with phenyl isocyanate (3 a) and carbon dioxide to yield complexes 4 and 5 bearing novel 1,3,5-oxazaphospholane ligands; the isopropyl derivative 3 b did not react under these conditions. DFT calculations provide insight into the pathway of the reaction with carbon dioxide with model complex 1 c, revealing effects of initial non-covalent interactions with the substrate onto the ring bonding, thus triggering an initially masked frustrated Lewis-pair-type behavior.

Gas-phase Smiles rearrangement reactions of deprotonated N-phenylbenzamides studied by electrospray ionization tandem mass spectrometry.

Electrospray ionization tandem mass spectrometry (ESI-MS(n)) is an invaluable tool for the study of gas-phase reactions. When N-phenylbenzamide is analyzed in negative ion mode, the nucleophilic deprotonated site of nitrogen or oxygen, together with the adjacent electrophilic phenyl carbon in the same molecule, provides a useful opportunity to study the intramolecular nucleophilic reaction in the gas phase. All MS(n) experiments of deprotonated N-phenylbenzamides were conducted on an ion trap mass spectrometer using ESI in negative ion mode. The accurate masses of fragments were measured on an ESI quadrupole time-of-flight mass spectrometer in negative ion mode. Theoretical calculations were conducted at the B3LYP/6-31++G(d,p) level of density functional theory using the Gaussian 03 program. When the polarity of the substituent on the aniline ring was changed, gas-phase Smiles rearrangement reactions could be initiated by different atoms in the anionic center. Upon collisional activation, loss of CO from deprotonated N-phenylbenzamides could be observed, which can be interpreted as a nitrogen anion triggering the Smiles rearrangement reaction through a three-membered ring transition state. As the aniline ring was substituted by a strong electron-withdrawing group (e.g., NO(2), COCH(3), or CF(3)) at the para position, a characteristic phenolate anion was obtained, which was derived from the Smiles rearrangement reaction initiated by the oxygen anion through a four-membered ring transition state. In the fragmentation of deprotonated N-phenylbenzamides, the gas-phase Smiles rearrangement reaction initiated by either the nitrogen or the oxygen atom can proceed. The findings in this study have not only enriched knowledge on the gas-phase Smiles rearrangement reactions, but also provided valuable information for understanding the rearrangements of deprotonated aromatic amides in gas phase.