Loss Of Ethylene Research Articles

Ligand and Metal Effects in the Gas‐Phase Fragmentation of Thiomethoxymethyl Complexes

While the collision‐induced dissociation (CID) of the mass‐selected cation [(Ph3P)2Pt(CH2SCH3)]+ selectively liberates PPh3, the diphosphine complex [(dppe)Pt(CH2SCH3)]+ (dppe = 1,2‐bis(diphenylphosphino)ethane) ejects C2H4, CH2S, and (CH3)2S instead. The analogous palladium complexes [(Ph3P)2Pd(CH2SCH3)]+ and [(dppe)Pd(CH2SCH3)]+ show similar reactivity, except that C–H‐bond activation is completely lacking. For other bidentate diphosphine ligands such as dppm, dppv, dppp, dppb, dppbz, dppf, and xantphos, a correlation of the dominant reaction channels with the bite angle is observed. For bite angles > 90°, hydrogen‐atom transfer is favored, as evidenced by an increase in dimethyl‐sulfide loss. For smaller bite angles (< 90°), intramolecular activation of the thiomethoxymethyl ligand predominates, thus resulting in increased losses of thioformaldehyde and ethene. The results of the CID experiments are compared with those for [(bipy)Pt(CH2SCH3)]+, for which the loss of C2H4 is observed as the main process. DFT calculations for the complexes [(dppe)Pt(CH2SCH3)]+ and [(bipy)Pt(CH2SCH3)]+ together with the experimental findings uncover subtle differences in the underlying reaction mechanisms.

Demonstration of Capture, Cooling, Tagging, and Spectroscopic Characterization of UV Photoproduct Ions in a Cryogenic Ion Trap: Application to 266 nm Photofragment Ions from Rhodamine 6G.

We demonstrate a method to determine the structures of the primary photodissociation products from a cryogenically cooled parent ion. In this approach, a target ion is cooled by a pulse of buffer gas and tagged in a 20 K Paul trap. The cold ion is then photodissociated by pulsed (∼5 ns) UV laser excitation, and the ionic products are trapped, cooled, and tagged by introduction of a second buffer gas pulse in the same trap. The tagged fragments are then ejected into a triple focusing, UV/vis/IR time-of-flight photofragmentation mass spectrometer which yields vibrational and electronic spectra of the mass-selected photofragments. These methods are demonstrated by application to the 266 nm photodissociation of the Rhodamine 6G cation to yield the R575 fragment ion based on loss of ethene as well as to a weaker secondary fragment arising from loss of m/z 43.

Zur Dekarbonisierung N‐Heterocyclischer Carbene (NHCs): Die einfachen Alan‐Addukte (NHC) ⋅ AlR3 (R=H, Me, Et)

AbstractDie Reaktion des Amin‐stabilisierten Alans (NMe3) ⋅ AlH3 1 mit dem Rückgrat‐gesättigten N‐heterocyclischen Carben (NHC) SIDipp (SIDipp=1,3‐Bis‐{2,6‐di‐iso‐propyl‐phenyl}‐imidazolidin‐2‐yliden) bei 0 °C ergab das NHC‐stabilisierte Alan‐Addukt (SIDipp) ⋅ AlH3 2. Erhöhte Temperaturen oder verlängerte Reaktionszeiten bei Raumtemperatur führten zum Produkt einer Ringerweiterungs‐Reaktion (RER) des NHCs, (NMe3) ⋅ AlH(RER‐SIDippH2), 3 ⋅ (NMe3). Die anschließende Reaktionen mit den sterisch weniger anspruchsvollen NHCs (IMeMe {=1,3,4,5‐Tetramethyl‐imidazolin‐2‐yliden}, IiPrMe {=1,3‐Di‐iso‐propyl‐4,5‐dimethyl‐imidazolin‐2‐yliden} und IiPr {=1,3‐Di‐iso‐propyl‐imidazolin‐2‐yliden}) lieferten die NHC‐stabilisierten RER‐Produkte (NHC) ⋅ AlH(RER‐SIDippH2) 3 ⋅ (NHC) (NHC=IMeMe, IiPrMe, IiPr), während mit den sterisch anspruchsvolleren NHCs IDipp (=1,3‐Bis‐{2,6‐di‐iso‐propyl‐phenyl}‐imidazolin‐2‐yliden), SIDipp und ItBu (=1,3‐Di‐tert‐butyl‐imidazolin‐2‐yliden) keine Reaktion beobachtet wurde. Die Verbindungen 3 ⋅ (NHC) wurden ebenfalls ausgehend von (SIDipp) ⋅ AlH3 2 und NHC bei Raumtemperatur erhalten. Das Erhitzen von Lösungen von (SIDipp) ⋅ AlH3 2 ohne zusätzliche Base auf 95 °C führte unter Verlust von Ethen zu einer Dekarbonisierung des NHCs und somit zur Substitution des Carben‐Kohlenstoffatoms durch Aluminiumhydrid. Die anschließende Dimerisierung ergab cis‐[AlH{μ‐N(Dipp)CH2CH2N(Dipp)}]2 4_dimer. Das Erhitzen von Lösungen der NHC‐stabilisierten Aluminiumalkyle (SIDipp) ⋅ AlR3 2R (R=Me, Et) auf 145 °C führte stattdessen unter Freisetzung von Ethen zur vollständigen Spaltung des NHC‐Grundgerüstes und Isolierung der Dialkylaluminium(III)‐Amidinate {DippNC(R)NDipp}AlR2 5R (R=Me, Et).

How to Decarbonize N-Heterocyclic Carbenes (NHCs): The simple Alane Adducts (NHC) ⋅ AlR3 (R=H, Me, Et).

The reaction of the amine-stabilized alane (NMe3) ⋅ AlH3 1 with the backbone-saturated N-heterocyclic carbene (NHC) SIDipp (SIDipp=1,3-bis-{2,6-di-iso-propyl-phenyl}-imidazolidin-2-ylidene) at 0 °C yielded the NHC alane adduct (SIDipp) ⋅ AlH3 2. Reaction at elevated temperatures or prolonged reaction at room temperature gave the product of a ring expansion reaction (RER) of the NHC, (NMe3) ⋅ AlH(RER-SIDippH2) 3 ⋅ (NMe3). Subsequent reaction of the latter with sterically less hindered NHCs (IMeMe {=1,3,4,5-tetramethyl-imidazolin-2-ylidene}, IiPrMe {=1,3-di-iso-propyl-4,5-dimethyl-imidazolin-2-ylidene}, and IiPr {=1,3-di-iso-propyl-imidazolin-2-ylidene}) afforded the NHC-stabilized RER-products (NHC) ⋅ AlH(RER-SIDippH2) 3 ⋅ (NHC) (NHC=IMeMe, IiPrMe, IiPr), while no reaction was observed with the sterically more demanding NHCs IDipp (=1,3-bis-{2,6-di-iso-propyl-phenyl}-imidazolin-2-ylidene), SIDipp and ItBu (=1,3-di-tert-butyl-imidazolin-2-ylidene). The compounds 3 ⋅ (NHC) were also obtained starting from (SIDipp) ⋅ AlH3 2 and NHC at room temperature. Heating solutions of (SIDipp) ⋅ AlH3 2 without additional base to 95 °C resulted in decarbonization of the NHC and substitution of the carbene carbon atom with aluminum hydride under loss of ethene. Subsequent dimerization afforded cis-[AlH{μ-N(Dipp)CH2CH2N(Dipp)}]2 4_dimer. Heating solutions of the NHC-ligated aluminum alkyls (SIDipp) ⋅ AlR3 2R (R=Me, Et) to 145 °C instead led to complete scission of the NHC backbone with evolution of ethene and isolation of the dialkylaluminium(III) amidinates {DippNC(R)NDipp}AlR2 5R (R=Me, Et).

Reaction dynamics of S(3P) with 1,3-butadiene and isoprene: crossed-beam scattering, low-temperature flow experiments, and high-level electronic structure calculations.

Sulfur atoms serve as key players in diverse chemical processes, from astrochemistry at very low temperature to combustion at high temperature. Building upon our prior findings, showing cyclization to thiophenes following the reaction of ground-state sulfur atoms with dienes, we here extend this investigation to include many additional reaction products, guided by detailed theoretical predictions. The outcomes highlight the complex formation of products during intersystem crossing (ISC) to the singlet surfaces. Here, we employed crossed-beam velocity map imaging and high-level ab initio methods to explore the reaction of S(3P) with 1,3-butadiene and isoprene under single-collision conditions and in low-temperature flows. For the butadiene reaction, our experimental results show the formation of thiophene via H2 loss, a 2H-thiophenyl radical through H loss, and thioketene through ethene loss at a slightly higher collision energy compared to previous observations. Complementary Chirped-Pulse Fourier-Transform mmWave spectroscopy (CP-FTmmW) measurements in a uniform flow confirmed the formation of thioketene in the reaction at 20 K. For the isoprene reaction, we observed analogous products along with the 2H-thiophenyl radical arising from methyl loss and C3H4S (loss of ethene or H2 + acetylene). CP-FTmmW detected the formation of thioformaldehyde via loss of 1,3-butadiene, again in the 20 K flow. Coupled-cluster calculations on the pathways found by the automated kinetic workflow code KinBot support these findings and indicate ISC to the singlet surface, leading to the generation of various long-lived intermediates, including 5-membered heterocycles.

In situ studies of reversible solid-gas reactions of ethylene responsive silver pyrazolates.

Solid-gas reactions and in situ powder X-ray diffraction investigations of trinuclear silver complexes {[3,4,5-(CF3)3Pz]Ag}3 and {[4-Br-3,5-(CF3)2Pz]Ag}3 supported by highly fluorinated pyrazolates reveal that they undergo intricate ethylene-triggered structural transformations in the solid-state producing dinuclear silver-ethylene adducts. Despite the complexity, the chemistry is reversible producing precursor trimers with the loss of ethylene. Less reactive {[3,5-(CF3)2Pz]Ag}3 under ethylene pressure and low-temperature conditions stops at an unusual silver-ethylene complex in the trinuclear state, which could serve as a model for intermediates likely present in more common trimer-dimer reorganizations described above. Complete structural data of three novel silver-ethylene complexes are presented together with a thorough computational analysis of the mechanism.

Intramolecular interactions and the neutral loss of ammonia from collisionally activated, protonated ω-aminoalkyl-3-hydroxyfurazans.

Gas phase fragmentation reactions of monoprotonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan were investigated to examine potential interactions between functional groups. The two heterocyclic alkyl amines were ionized by electrospray ionization (ESI, positive mode) and fragmented using tandem mass spectrometry (MS/MS). The fragmentation pathways were characterized using pseudo MS3 experiments, precursor-ion scans, and density functional computations. For both heterocyclic ions, loss of ammonia was the only fragmentation process observed at low collision energies. Computational analysis indicated that the most feasible mechanism was intramolecular nucleophilic displacement of ammonia from the protonated ω-aminoalkyl side chain by N5 of the furazan ring. The alkylated nitrogen in the resulting bicyclic product ion facilitated N-O bond cleavage; subsequent neutral losses of nitric oxide (NO) and carbon monoxide (CO) occurred by homolytic bond cleavages. Next in the multistep sequence, neutral loss of ethylene from a radical cation was observed. A less favorable, competing fragmentation pathway of protonated 4-(3-aminopropyl)-3-hydroxyfurazan was consistent with cleavage of the 3-hydroxyfurazan ring and losses of NO and CO. Overall, the similar fragmentation behavior found for protonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan differed from that previously characterized for furazan analogs with shorter alkyl chains. These observations demonstrate that a small change in the structure of multifunctional, heterocyclic alkyl amines may significantly influence interactions between distinct functional groups and the nature of the fragmentation process.

Characterization of photochemical losses of volatile organic compounds and their implications for ozone formation potential and source apportionment during summer in suburban Jinan, China

Volatile organic compounds (VOCs) undergo substantial photochemical losses during their transport from emission sources to receptor sites, resulting in serious implications for their source apportionment and ozone (O3) formation. Based on the continuous measurements of VOCs in suburban Jinan in August 2022, the effects of photochemical losses on VOC source contributions and O3 formation were evaluated in this study. The observed and initial concentrations of total VOCs (TVOC) were 12.0 ± 5.1 and 16.0 ± 7.4 ppbv, respectively. Throughout the observation period, alkenes had the most prominent photochemical losses (58.2%), followed by aromatic hydrocarbons (23.1%), accounting for 80.6% and 6.9% of the total losses, respectively. During high O3 episodes, the photochemical loss of VOCs was 6.9 times higher than that during the cleaning period. Alkene losses (exceeding 67.3%), specifically losses of isoprene, propylene, ethylene, and n-butene, dominated the total losses of VOCs during the O3 increase period. Eight sources of VOCs were identified by positive matrix factorization (PMF) based on the observed and initial concentration data (OC-PMF and IC-PMF, respectively). Concentrations of all emission sources in the OC-PMF were underestimated by 2.4%–57.1%. Moreover, the contribution of each emission source was over- or underestimated compared with that in case of the IC-PMF. The contributions of biogenic and motor vehicle exhaust emissions were underestimated by 5.3 and 2.8 percentage points, respectively, which was associated with substantial oxidation of the emitted high-reactive species. The contributions of coal/biomass burning and natural gas were overestimated by 2.4 and 3.9 percentage points, respectively, which were related to the emission of low-reactive species (acetylene, ethane, and propane). Based on our results, the photochemical losses of VOCs grossly affect their source apportionment and O3 formation. Thus, photochemical losses of VOCs must be thoroughly accounted to establish a precise scientific foundation for air-pollution control strategies.

Qualitative Analysis of Novel Flavonoid Adducts from Nerve Agent Tabun-Exposed Arabidopsis thaliana (L.) Based on Quadrupole-Time of Flight Mass Spectrometry.

Flavonoids are a kind of secondary metabolite which widely exist in plants. They contain a lot of active hydroxyls, which can react with toxic chemicals to produce potential exposure biomarkers. In this article, the model plant Arabidopsis thaliana (L.) was exposed to the nerve agent O-Ethyl N,N-dimethyl phosphoramidocyanidate (Tabun). By comparing with the plant not exposed to Tabun, some characteristic ions were identified by quadrupole-time of flight mass spectrometry in the acetonitrile extract of the exposed leaves. These characteristic ions were selected as parent ions to produce product ion mass spectra (PIMS). Some interesting fragmentation pathways were revealed, including neutral loss of glucoside, rhamnose and ethylene. O-Ethyl N,N-dimethyl phosphoryl modified flavonoids were deduced from assignment of the PIMS. The element components and the accurate mass of the product ions from each parent ion matched well with those of the proposed fragmentation pathways. Through comparison with the PIMS of structurally closely related chemical of Isobutyl methylphosphonyl modified flavonoids, the structures and the fragmentation pathways of the O-Ethyl N,N-dimethyl phosphoryl modified flavonoids were finally confirmed. Successfully finding and identifying these three specific exposure biomarkers in plants provided a new strategy for the retrospective analysis of organophosphorus exposure and forensic analysis.

Study of the gas-phase decomposition pathways of poly(ethylene glycol) by Electron Transfer Dissociation

Tandem mass spectrometry involving electron transfer dissociation (ETD) could be very useful for polymer characterization. However, parameters influencing gas-phase decomposition pathways are poorly understood and this method is rarely applied. In this report, precursor ions [polyether + cation(s)]2+ generated from three poly(ethylene glycol) (PEG), which differ only in their chain ends (dimethoxy PEG, monomethoxy/monohydroxy PEG or dihydroxy PEG), were submitted to ETD conditions to study the influence of the cationizing agent, and that of the chain ends on the dissociation pathways. Experiments were carried out using various cationization agents: H+, alkali metals (Li+, Na+ and Cs+), an alkaline earth (Ba2+) and transition metals (Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+). The gas phase interaction of a fluoranthene anion with precursor ions [PEG24Me2+cation(II)]2+ or [PEG24Me2+2 cation(I)]2+ gives very variable results depending on the metal. Bond dissociation is not always observed, because competitive reactions can lead to the formation of sufficiently stable species (by addition of fluoranthene, simple reduction of the complex, elimination of the metal, or by addition of O2), to the detriment of fragmentation reactions (in particular with the monovalent cations Na+ and Cs+). In contrast, from [PEG24Me2+cation(II)]2+ all divalent cations lead to bond cleavages. These cations can be classified according to their ability to cause the highest fragmentation: Fe2+ > Ba2+ > Mn2+ ≈ Ni2+ > Co2+ > Cu2+ > Zn2+. Although the Fe2+ adduct presents the highest fragmentation rate, the spectrum is dominated by the loss of a small molecule (ethylene), the Ni2+ cation gives the richest fragmentation (the number of fragment series was the most important). Within the same family of cationization agents (alkaline or transition metals), the processes implemented under ETD conditions can sometimes be very different. Some fragment ions are common to a set of metals (e.g. the an ion series is generated from all adducts), while others are more specific (e.g. the loss of ethylene from Mn2+, Fe2+ and Co2+ adducts). The C–O bond is the most frequently broken bond. From monomethoxy/monohydroxy PEG and dihydroxy PEG, the presence of a hydroxyl function at one end of the chain can compromise bond dissociation along the carbon skeleton if H+ loss is favored, but the use of a transition metal such as Mn and Fe, induces nevertheless fragmentation. This work establishes that ETD of polyether backbone is possible if a suitable cation is chosen (Fe (II), Mn (II) for example), regardless of the chain end (-OCH3 or –OH).

Comparison of aliphatic polyesters prepared by acyclic diene metathesis and thiol‐ene polymerization of α,ω‐polyenes arising from oleic acid‐based 9‐decen‐1‐ol

AbstractDevelopment of more sustainable and environmentally friendly polymers as alternatives to petroleum‐based polymers is a priority. We report the synthesis of six linear, aliphatic, renewable polymers by acyclic diene metathesis (ADMET) and thiol‐ene polymerization of α,ω‐polyenes resulting from thermal esterification of adipic, azelaic, and itaconic acids with 9‐decen‐1‐ol. ADMET homopolymerization was performed with 1.0 mol% Hoveyda–Grubbs second generation metathesis catalyst. Thiol‐ene copolymerization was conducted photochemically with 1 wt% 2,2‐dimethoxy‐2‐phenyl‐acetophenone and stoichiometric 1,2‐ethanedithiol (EDT). Although the thiol‐ene copolymers exhibited carbon and atom economies of 100%, the ADMET‐derived polyesters possessed superior renewable carbon content (100%) and environmental factors (<4). These results were attributed to incorporation of non‐renewable EDT into poly(thioether‐ester)s and loss of ethene during production of ADMET polyesters. The Mn (>26 kDa), Mw (>92 kDa), and dispersities (>3.4) of the poly(thioether‐ester)s were higher than the corresponding polyesters, which in part explained why the poly(thioether‐ester)s gave higher melting (>61°C), crystallization (>49°C) and glass transition (>−31°C) temperatures. The cross‐linked itaconate polymers did not melt or crystallize, thereby suggesting amorphous morphology. Lastly, the ADMET polyesters were more thermally stable (T50 > 408°C) than the poly(thioether‐ester)s (T50 < 377°C). In summary, the aliphatic biopolymers displayed a wide range of properties that were impacted by polymerization method as well as the nature of the monomer.

Chemical Characterization and Quantitation of Phenols in Fuel Extracts by Using Gas Chromatography/Methane Chemical Ionization Triple Quadrupole Mass Spectrometry

The ability to detect, characterize, and quantify phenols in aviation fuels is critical as these compounds can negatively affect the storage stability of the fuel. However, some phenols inhibit free-radical autoxidation and hence are beneficial. The development of a method based on gas chromatography coupled with positive-ion-mode methane chemical ionization/triple quadrupole mass spectrometry [GC/(methane CI) QqQ] for the characterization and quantitation of phenols in fuels is reported here. Sixteen phenols, ranging from phenol to phenols with up to three alkyl groups of different chain lengths, were studied. Natural phenols (defined as phenols without tert-butyl groups) were protonated upon methane CI, which was associated with diagnostic fragmentation. For example, upon protonation, 2-, 3-, and 4-ethylphenols fragmented via the loss of ethylene, which facilitated their distinction from the isomeric 2,4-, 2,5-, and 3,4-dimethylphenols. Furthermore, the natural phenols formed stable adducts with C2H5+ and C3H5+ ions generated from methane upon CI. In contrast, additive phenols (with one or more tert-butyl groups) were predominantly ionized via electron abstraction to yield molecular radical cations and did not form adduct ions and generated some diagnostic fragment ions, such as ions of m/z 57 (tert-butyl cation). Most of the molecular radical cations of additive phenols also exhibited a methyl radical loss, while protonated additive phenols exhibited water loss. The limit of detection and the limit of quantitation were determined to be 1.3 μM (0.33 ppm) and 4.2 μM (1.08 ppm), respectively, and the linearity of quantitation was between 5 and 160 μM. Measurements of equimolar mixtures composed of additive and natural phenols demonstrated similar (within 10%) but not identical ionization efficiencies for these two compound types. Intra- and interday measurements of the signal intensities of the phenols were highly repeatable, with average relative standard deviations of 1.7 and 5.2%, respectively. The same method was employed to successfully characterize and quantify unknown phenols in alternative and petroleum-based jet fuel extracts. The petroleum-based Jet A fuel was found to contain a 1.5 times greater concentration of phenols than the alternative fuel. Jet A contained monomethylated phenols (108 Da), while the alternative fuel did not. Several phenols with molecular weights of 122, 136, and 150 Da were detected in both Jet A and the alternative fuel. The CI mass spectra suggested that some of these phenols had multiple methyl substituents. The information that can be acquired by using the GC/(CI) QqQ method will facilitate establishing links between the chemical compositions of fuels and fuel properties. Overall, the method was found to be robust and repeatable.

Top-down formation of ethylene from fragmentation of superhydrogenated polycyclic aromatic hydrocarbons

Context. Fragmentation is an important decay mechanism for polycyclic aromatic hydrocarbons (PAHs) under harsh interstellar conditions and represents a possible formation pathway for small molecules such as H2, C2H2, and C2H4. Aims. Our aim is to investigate the dissociation mechanism of superhydrogenated PAHs that undergo energetic processing and the formation pathway of small hydrocarbons. Methods. We obtain, experimentally, the mass distribution of protonated tetrahydropyrene (C16H15+, [py + 5H]+) and protonated hex-ahydropyrene (C16H17+, [py + 7H]+) upon collision-induced dissociation (CID). The infrared (IR) spectra of their main fragments are recorded by infrared multiple-photon dissociation (IRMPD). Extended tight-binding (GFN2-xTB) based molecular dynamics (MD) simulations were performed in order to provide the missing structure information for this experiment and to identify fragmentation path ways. The pathways for fragmentation were further investigated at a hybrid density functional theory (DFT) and dispersion-corrected level. Results. A strong signal for loss of 28 mass units of [py + 7H]+ is observed both in the CID experiment and the MD simulation, while [py + 5H]+ shows a negligible signal for the product corresponding to a mass loss of 28. The 28 mass loss from [py + 7H]+ is assigned to the loss of ethylene (C2H4) and a good fit between the calculated and experimental IR spectrum of the resulting fragment species is obtained. Further DFT calculations show favorable kinetic pathways for loss of C2H4 from hydrogenated PAH configurations involving three consecutive CH2 molecular entities. Conclusions. This joint experimental and theoretical investigation proposes a chemical pathway of ethylene formation from fragmentation of superhydrogenated PAHs. This pathway is sensitive to hydrogenated edges (e.g., the degree of hydrogenation and the hydrogenated positions). The inclusion of this pathway in astrochemical models may improve the estimated abundance of ethylene.

Impact of the Acetaldehyde-Mediated Condensation on the Phenolic Composition and Antioxidant Activity of Vitis vinifera L. Cv. Merlot Wine.

Acetaldehyde is a critical reactant on modifying the phenolic profile during red wine aging, suggesting that the acetaldehyde-mediated condensation can be responsible for the variation of antioxidant activity during the aging of this beverage. The present study employs exogenous acetaldehyde at six levels of treatment (7.86 ± 0.10–259.02 ± 4.95 mg/L) before the bottle aging of Merlot wines to encourage phenolic modification. Acetaldehyde and antioxidant activity of wine were evaluated at 0, 15, 30, 45, 60 and 75 days of storage, while monomeric and polymeric phenolics were analyzed at 0, 30 and 75 days of storage. The loss of acetaldehyde was fitted to a first-order reaction model, the rate constant (k) demonstrated that different chemical reaction happened in wines containing a different initial acetaldehyde. The disappearance of monomeric phenolics and the formation of polymeric phenolics induced by acetaldehyde could be divided into two phases, the antioxidant activity of wine did not alter significantly in the first phase, although most monomeric phenolics vanished, but the second phase would dramatically reduce the antioxidant activity of wine. Furthermore, a higher level of acetaldehyde could shorten the reaction time of the first phase. These results indicate that careful vinification handling aiming at controlling the acetaldehyde allows one to maintain prolonged biological activity during wine aging.

Photoionization of Two Potential Biofuel Additives: γ-Valerolactone and Methyl Butyrate.

The photoionization of two potential biofuel additives, γ-valerolactone (GVL, C5H8O2) and methyl butyrate (MB, C5H10O2) has been studied by imaging photoelectron photoion coincidence spectroscopy (iPEPICO) at the VUV beamline of the Swiss Light Source (SLS). The vibrational fine structure in the photoelectron spectrum is compared with a Franck-Condon simulation for the electronic ground-state band of the GVL cation. In the lowest energy dissociative photoionization channel of GVL, CO2 is lost, resulting in a 1-butene fragment ion with a 0 K appearance energy of E0 = 10.35 ± 0.01 eV. A newly calculated 1-butene ionization energy of 9.595 ± 0.015 eV establishes the reverse barrier height to CO2 loss as 66.6 ± 4.3 kJ mol-1. Methyl butyrate cations undergo McLafferty rearrangement, which explains the missing ion signal at the computed adiabatic ionization energy of 9.25 eV. After H transfer, ethylene is lost in the lowest energy dissociation channel to yield the methyl acetate enol ion at E0 = 10.24 ± 0.04 eV. This value connects the energetics of methyl butyrate with that of methyl acetate enol ion, which is established at ΔfHo0K[CH2C(OH)OCH3+] = 502 ± 6 kJ mol-1. Parallel to ethylene loss, methyl loss is also observed from the enol tautomer of the parent ion. Both samples exhibit low-energy nonstatistical dissociative ionization channels. In GVL, the methyl-loss abundance rises quickly but levels off suddenly in the energy range of the first electronically excited states, indicating nonstatistical competition between CH3 and CO2 loss. In MB, the major parallel dissociation channel is the loss of a methoxy radical. Calculations indicate that McLafferty rearrangement is inhibited on the excited-state surface. Indeed, breakdown curve modeling of this and a sequential CO-loss channel confirms a second statistical regime in dissociative photoionization, decoupled from ethylene loss.

Design and economic analysis of industrial-scale methanol-to-olefins plants

The production of ethylene and propylene, which are the building blocks of the petrochemical industry, from methanol is attractive because of the possibility of green methanol generation or the availability of inexpensive natural gas for methanol production. Based on the reactor performance of UOP/Hydro MTO (Methanol-to-olefins) technology, a base design and an alternative design of the overall process for an industrial-scale MTO plant are presented. The design scope includes the reaction and conditioning section, product separation and recovery section, ethylene and propylene refrigeration cycles, and cold-box. The alternative design differs from the base design by the use of a cold-box. The design employs driving force analysis, column targeting analysis, and pinch design method for distillation train determination, column improvement, and energy integration. Based on the current prices of methanol and olefins, both designs are profitable with IRR higher than 26%. The alternative design is superior to the base design in ethylene loss, energy consumption, exergy loss, and economic profit.

Foliar resistance to Rhizoctonia solani in Arabidopsis is compromised by simultaneous loss of ethylene, jasmonate and PEN2 mediated defense pathways

Rhizoctonia solani causes damaging yield losses on most major food crops. R. solani isolates belonging to anastomosis group 8 (AG8) are soil-borne, root-infecting pathogens with a broad host range. AG8 isolates can cause disease on wheat, canola and legumes, however Arabidopsis thaliana is heretofore thought to possess non-host resistance as A. thaliana ecotypes, including the reference strain Col-0, are resistant to AG8 infection. Using a mitochondria-targeted redox sensor (mt-roGFP2) and cell death staining, we demonstrate that both AG8 and a host isolate (AG2-1) of R. solani are able to infect A. thaliana roots. Above ground tissue of A. thaliana was found to be resistant to AG8 but not AG2. Genetic analysis revealed that ethylene, jasmonate and PENETRATION2-mediated defense pathways work together to provide resistance to AG8 in the leaves which subsequently enable tolerance of root infections. Overall, we demonstrate a significant difference in defense capabilities of above and below ground tissue in providing resistance to R. solani AG8 in Arabidopsis.

Collision-induced dissociation of protonated fentanyl: A DFT study

The fragmentation pathways leading to the major products resulting from collision-induced dissociation of protonated fentanyl are investigated. Starting from a protonated fentanyl in a twist conformation, transfer of the proton from the piperidine to the amide nitrogen allows the lone pair of the piperidine nitrogen to assist in displacement of the amide group and results in ring-opening of the piperidine to yield an ion with m/z 188 (C13H18N+). This is the fragmentation pathway with the lowest energy barrier; the barrier to the loss of the phenethyl group as a phenonium or 1-phenylethyl cation from the nitrogen in the piperidine ring is 64 kJ mol−1 higher in energy. At even higher collision energies a bicyclic ion, also with nominal m/z 188 but with different elemental composition (C12H14NO+), is formed after sequential losses of ethene and phenethylamine from protonated fentanyl. Possible pathways to ring opening of the piperidine ring of N-protonated fentanyl include nucleophilic attack by the amide oxygen or the phenyl ring on the piperidine ring. The two m/z 188 ions give different dissociation products; minor products in the mass spectrum of protonated fentanyl at m/z 146, 134 and 132 are all generated from the dominant m/z 188 ion, C13H18N+, whereas only a product at m/z 132 is formed from the C12H14NO+ ion.

Syntheses of Molybdenum and Tungsten Imido Alkylidene Complexes that Contain a Bidentate Oxo/Thiolato Ligand

Abstract3,3′,5,5′‐Tetra‐tert‐butyl‐2′‐sulfanyl[1,1′‐biphenyl]‐2‐ol (H2[tBu4OS]) was prepared in 24 % yield overall from the analogous biphenol using standard techniques. Addition of H2[tBu4OS] to Mo(NAr)(CHCMe2Ph)(2,5‐dimethylpyrrolide)2 led to formation of Mo(NAr)(CHCMe2Ph)[tBu4OS], which was trapped with PMe3 to give Mo(NAr)(CHCMe2Ph)[tBu4OS](PMe3) (1(PMe3)). An X‐ray crystallographic study of 1(PMe3) revealed that two structurally distinct square pyramidal molecules are present in which the alkylidene ligand occupies the apical position in each. Both 1(PMe3)A and 1(PMe3)B are disordered. Mo(NAd)(CHCMe2Ph)(tBu4OS)(PMe3) (2(PMe3); Ad=1‐adamantyl) and W(NAr)(CHCMe2Ph)(tBu4OS)(PMe3) (3(PMe3)) were prepared using analogous approaches. 1(PMe3) reacts with ethylene (1 atm) in benzene within 45 minutes to give an ethylene complex Mo(NAr)(tBu4OS)(C2H4) (4) that is isolable and relatively stable toward loss of ethylene below 60 °C. An X‐ray study shows that the bond distances and angles for the ethylene ligand in 4 are like those found for bisalkoxide ethylene complexes of the same general type. Complex 1(PMe3) in the presence of one equivalent of B(C6F5)3 catalyzes the homocoupling of 1‐decene, allyltrimethylsilane, and allylboronic acid pinacol ester at ambient temperature. 1(PMe3), 2(PMe3), and 3(PMe3) all catalyze the ROMP of rac‐endo,exo‐5,6‐dicarbomethoxynorbornene (rac‐DCMNBE) in the presence of B(C6F5)3, but the polyDCMNBE that is formed has a random structure.

Multi-Scale Analysis of Integrated C1 (CH4 and CO2) Utilization Catalytic Processes: Impacts of Catalysts Characteristics up to Industrial-Scale Process Flowsheeting, Part II: Techno-Economic Analysis of Integrated C1 Utilization Process Scenarios

In the second part of this paper (Part II), the potentials and characteristics of an industrial-scale Oxidative Coupling of Methane (OCM) process integrated with CO2-hydrogenation, ethane dehydrogenation, and methane reforming processes are highlighted. This novel process concept comprises a direct conversion of methane to ethane and ethylene and further conversion of the resulted carbon dioxide and remaining unreacted methane, respectively, to methanol and syngas. In this context, the selected experimental results of the catalytic CO2-hydrogenation to methanol reported in the first part of this paper (Part I), were utilized to represent its industrial-scale performance. The experimental results of the mini plant-scale operation of an OCM reactor and CO2 removal units along with the experimental and industrial data available for representing the operation and performance of all process-units in the integrated process structures were utilized to perform a comparative techno-economic environmental analysis using Aspen-Plus simulation and an Aspen Economic Process Analyzer. The experimental procedure and the results of testing the sequence of OCM and CO2-hydrogenation reactors are particularly discussed in this context. It was observed that in the sequential operation of these reactors, ethylene will be also hydrogenated to ethane over the investigated catalysts. Therefore, the parallel-operation of these reactors was found to be a promising alternative in such an integrated process. The main assumptions and the conceptual conclusions made in this analysis are reviewed and discussed in this paper in the light of the practical limitations encountered in the experimentations. In the context of a multi-scale analysis, the contributions of the design and operating parameters in the scale of catalyst and reactor as well as in the process-scale represented by analyzing the type and operating conditions of the downstream-units and the process-flowsheets on the economic and environmental performance of the integrated process structures were studied. Moreover, the economic impacts of extra ethylene and methanol produced respectively via the integrated ethane dehydrogenation and CO2-hydrogenation sections were analyzed in detail. The required capital investment was found to be even smaller than the yearly operating cost of the plant. The environmental impacts and sustainability of the integrated OCM process were found to be enhanced by securing a minimum direct CO2-emission and energy-efficient conversion of CO2 and the unreacted CH4, respectively, to methanol and syngas. Besides producing such value-added by-products, efficient operation of downstream process-units was secured by minimizing the energy usage and ethylene losses. Under the considered conditions in this analysis, the specifications of the finally selected integrated OCM process structure, providing the fastest return of investments (less than 8 years), are highlighted.