Primary Reaction Products Research Articles

Potential energy curve for singlet-oxygen quenching reaction by vitamin E

The singlet-oxygen (1O2) quenching-reaction by vitamin E (α-tocopherol) was studied by using density functional theory, and the potential energy curve was calculated. On the basis of the computational results, the following mechanism was suggested for the quenching reaction. In the initial stage of the quenching reaction, 1O2 and α-tocopherol approach each other, a partial electron transfer takes place from α-tocopherol to 1O2, and an exciplex between the two molecules is formed. Further approach raises the potential energy of the exciplex and leads to a crossing point between the potential energy curves of the lowest singlet and triplet states. Then, physical quenching from 1O2 to 3O2 is caused by α-tocopherol. Even more approach of 1O2 and α-tocopherol yields a pseudo-stable 6,8a-endoperoxide of α-tocopherol after passing through a transition state. The 6,8a-endoperoxide could be transformed to the primary product (8a-hydroxyperoxy-α-tocopherone) of a chemical reaction between 1O2 and α-tocopherol. The geometries at the potential energy minima and the transition state in the lowest singlet state were optimized, and the geometry at the potential-energy curve crossing-point between the lowest singlet and triplet states was obtained besides stabilization and activation energies included in the potential energy curve. The geometry of the primary product of the chemical reaction was also optimized.

Production and evaluation of alkali-activated binders of low-calcium fly ash with slag replacement

Formulating alkali-activated binders requires a clear understanding of the role of activator concentration and source material composition on product formation and strength gain. Alkali activation of a low-calcium fly ash (FA) binder with slag replacements at 30% and 50% by mass was evaluated. The reactivity and compressive strength gain of the activated binders were evaluated using activating solutions with different sodium hydroxide molarities (SHMs). An increase in SHM produced a higher compressive strength of the activated binder. The primary reaction product formed in the activated binder was calcium silicate hydrate with aluminium substitution (C-(A)-S-H). An increase in SHM led to an increase in C-(A)-S-H content and a reduction in porosity. The slag contributed to early reactivity of the binder and the initial strength development, while the FA contributed to the later age strength by silica enrichment of the C-(A)-S-H. While increasing the SHM produced an increase in early reactivity, the sodium did not directly contribute to the formation of the reaction product. The sodium from the alkaline activator was not chemically bound to the C-(A)-S-H and could be removed by leaching in water. An increase in basicity with SHM enhanced the contribution of the low-calcium FA, leading to higher silica enrichment of the C-(A)-S-H.

Strength, microstructure, CO2 emission and economic analyses of low concentration phosphoric acid-activated fly ash geopolymer

Phosphoric acid (PA)-activated geopolymer is a potential construction material with superior mechanical performance and high temperature resistance. However, the synthesis of phosphoric acid-activated fly ash (FA) geopolymer (PAFG) usually requires high concentrations of PA. In this study, the mechanical properties and microstructure of PAFG samples prepared with varying low PA concentrations (LPA, 1–4 M), liquid/FA ratios (0.3–0.45), and curing temperatures (25, 60, 90 °C), as well as their effects on the environment and economy, were investigated. The compressive strengths of PAFG with activation of LPA were generally low. The PAFG prepared with a L/F = 0.35 and 4 M PA solution curing at 60 °C for 6 days obtained the highest compressive strength of 13.23 MPa. The formation of geopolymer gels of Si-O-Al-O-P, Al-O-P, or Si-O-P were the primary reaction products and strength gain for PAFG samples. The increase in PA concentration and L/F ratio accelerated the FA dealumination reaction and the polymerization reaction by increasing the H+ and P-O concentrations of solution. In comparison to low concentration NaOH-activated fly ash geopolymer and cement pastes, the CO2 emission intensity and energy consumption intensity of PAFG curing at 25 °C were reduced by 70.9% and 35.6%, and 90.6% and 90.6%, respectively. Albeit the cost increased by 87.4% and 30.7%, respectively. Therefore, it is essential to develop inexpensive chemical processes for the preparation of PA solutions.

Real-time NMR analysis of polyhydroxyalkanoate synthase reaction that synthesizes block copolymer comprising glycolate and 3-hydroxybutyrate

The sequence-regulating polyhydroxyalkanoate (PHA) synthase PhaCAR spontaneously synthesizes the homo-random block copolymer, poly[3-hydroxybutyrate (3HB)]-b-poly[glycolate (GL)-ran-3HB]. In this study, a real-time in vitro chasing system was established using a high-resolution 800 MHz nuclear magnetic resonance (NMR) and 13C-labeled monomers to monitor the polymerization of GL-CoA and 3HB-CoA into this atypical copolymer. Consequently, PhaCAR initially consumed only 3HB-CoA and subsequently consumed both substrates. The structure of the nascent polymer was analyzed by extracting it with deuterated hexafluoro-isopropanol. In the primary reaction product, a 3HB-3HB dyad was detected, and GL-3HB linkages were subsequently formed. According to these results, the P(3HB) homopolymer segment is synthesized prior to the random copolymer segment. This is the first report of its kind which proposes the application of real-time NMR to a PHA synthase assay, paving the way for elucidating the mechanisms of PHA block copolymerization.

A third polymorph of the zwitterionic complex trichlorido-((dimethylphosphoryl)methanaminium-κO)zinc(II)

Abstract By the reaction of (dimethylphosphoryl)methanamine (dpma) with one equivalent of zinc(II) chloride in a concentrated hydrochloric acid solution and subsequent slow evaporation of the solvent, the title compound (dpmaH)ZnCl3 was obtained in quantitative yield. The primary reaction product mainly consists of larger brick-shaped colorless and smaller cuboide colorless crystals. Long-time storage over several months of these crystals in the mother liquor yielded a third polymorph (P21/n; a = 9.6639(1); b = 10.0271(1); c = 11.2446(1) Å; β = 98.964(1)°) of this compound. Similar to the two other modifications, its crystal structure consists of a zwitterionic dpmaHZnCl3 complex containing the cationic dpmaH+ ligand, which coordinates the zinc atom through its oxygen atom. Hydrogen bonds connect neighboring zwitterionic complexes to a layered structure. The motif of a hydrogen bonded dimer, similar to that found in the chain structure of polymorph I, is also present, but in the title structure these dimers form hydrogen bonds in two dimensions.

What are the Tower's method products: Metal-hydroxides or metal-glycerolates?

It has been long believed that colloidal nickel hydroxide nanoparticles are produced by the reaction of nickel salts, glycerol and potassium hydroxide known as the Tower method. In the present work, we challenge this belief and reveal the reasons for error in identification of nickel products produced by the Tower method. We propose that Ni-based precursor complexes are the primary products of the Tower method reaction, and these precursors undergo transition to layered Ni-glycerolate derivatives upon thermal treatment. We demonstrated the presence of Ni2+ coordinated to different types of O-donor ligands (glycerol, glycerolate ion, acetate ion and/or OH−) forming Ni-complex precursors. Using in-situ transmission electron microscopy, we showed that Ni-based precursor complexes can be converted to nickel nanoparticles upon exposure to electron beam, but no evidence of nickel hydroxide nanoparticle formation was found. The nickel hydroxide nanoparticles are only formed upon further reaction of Ni-glycerolate precursors with an aqueous alkaline solution. Those new findings shed light on the nature of the metal derivatives obtained by the reaction of Ni2+ and glycerol in the Tower method and provide more solid foundation to design electrode materials for batteries, supercapacitors, electrocatalysts and electrochemical sensors.

Reactions O(3P, 1D) + HCCCN(X1Σ+) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments.

Cyanoacetylene (HCCCN), the first member of the cyanopolyyne family (HCnN, where n = 3, 5, 7, ...), is of particular interest in astrochemistry being ubiquitous in space (molecular clouds, solar-type protostars, protoplanetary disks, circumstellar envelopes, and external galaxies) and also relatively abundant. It is also abundant in the upper atmosphere of Titan and comets. Since oxygen is the third most abundant element in space, after hydrogen and helium, the reaction O + HCCCN can be of relevance in the chemistry of extraterrestrial environments. Despite that, scarce information exists not only on the reactions of oxygen atoms with cyanoacetylene but with nitriles in general. Here, we report on a combined experimental and theoretical investigation of the reactions of cyanoacetylene with both ground 3P and excited 1D atomic oxygen and provide detailed information on the primary reaction products, their branching fractions (BFs), and the overall reaction mechanisms. More specifically, the reactions of O(3P, 1D) with HCCCN(X1Σ+) have been investigated under single-collision conditions by the crossed molecular beams scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy, Ec, of 31.1 kJ/mol. From product angular and time-of-flight distributions, we have identified the primary reaction products and determined their branching fractions (BFs). Theoretical calculations of the relevant triplet and singlet potential energy surfaces (PESs) were performed to assist the interpretation of the experimental results and clarify the reaction mechanism. Adiabatic statistical calculations of product BFs for the decomposition of the main triplet and singlet intermediates have also been carried out. Merging together the experimental and theoretical results, we conclude that the O(3P) reaction is characterized by a minor adiabatic channel leading to OCCCN (cyanoketyl) + H (experimental BF = 0.10 ± 0.05), while the dominant channel (BF = 0.90 ± 0.05) occurs via intersystem crossing to the underlying singlet PES and leads to formation of 1HCCN (cyanomethylene) + CO. The O(1D) reaction is characterized by the same two channels, with the relative CO/H yield being slightly larger. Considering the recorded reactive signal and the calculated entrance barrier, we estimate that the rate coefficient for reaction O(3P) + HC3N at 300 K is in the 10-12 cm3 molec-1 s-1 range. Our results are expected to be useful to improve astrochemical and photochemical models. In addition, they are also relevant in combustion chemistry, because the thermal decomposition of pyrrolic and pyridinic structures present in fuel-bound nitrogen generates many nitrogen-bearing compounds, including cyanoacetylene.

A combined crossed molecular beam and theorerical study of the O(3P,1D) + acrylonitrile (CH2CHCN) reactions and implications for combustion and extraterrestrial environments.

Acrylonitrile (CH2CHCN) is ubiquitous in space (molecular clouds, solar-type star forming regions, and circumstellar envelopes) and is also abundant in the upper atmosphere of Titan. The reaction O(3P) + CH2CHCN can be of relevance in the chemistry of the interstellar medium because of the abundance of atomic oxygen. The oxidation of acrylonitrile is also important in combustion as the thermal decomposition of pyrrolic and pyridinic structures present in fuel-bound nitrogen generates many nitrogen-bearing compounds, including acrylonitrile. Despite its relevance, limited information exists on this reaction. We report a combined experimental and theoretical investigation of the reactions of acrylonitrile with both ground 3P and excited 1D atomic oxygen. From product angular and time-of-flight distributions in crossed molecular beam experiments with mass spectrometric detection at a collision energy, Ec, of 31.4 kJ mol-1, we have identified the primary reaction products and determined their branching fractions (BFs). Theoretical calculations of the relevant triplet and singlet potential energy surfaces (PESs) were performed to interpret the experimental results and elucidate the reaction mechanism. Adiabatic statistical calculations of product BFs for the decomposition of the main triplet and singlet intermediates have been carried out. Combining the experimental and theoretical results, we conclude that the O(3P) reaction leads to two main product channels: (i) CH2CNH (ketenimine) + CO (dominant with a BF of 0.87 ± 0.05), formed via efficient intersystem crossing from the entrance triplet PES to the underlying singlet PES, and (ii) HCOCHCN + H (minor, with a BF of 0.13 ± 0.05), occurring adiabatically on the triplet PES. Our study suggests the inclusion of this reaction as a possible destruction pathway of CH2CHCN and a possible formation route of CH2CNH in the interstellar medium. The O(1D) + CH2CHCN reaction mainly leads to the formation of CH2CNH + CO adiabatically on the singlet PES. This result can improve models related to the chemistry of interstellar ice and cometary comas, where O(1D) reactions can play a role. Overall, our results are expected to be useful for improving the models of combustion and extraterrestrial environments.

Reactions of nicotine and the hydroxyl radical in the environment: Theoretical insights into the mechanism, kinetics and products

Nicotine (NCT) is a prevalent and highly poisonous tobacco alkaloid found in wastewater discharge. Advanced oxidative processes (AOP) are radical interactions between harmful pollutants and ambient free radicals that, theoretically, result in less toxic compounds. For a better understanding of the chemical transformations and long-term environmental effects of toxic discharges, the study of these processes is crucial. Here, quantum chemical calculations are used to investigate the AOP of the NCT in aqueous and lipidic environments. It was found that NCT interacted with HO• in polar and nonpolar media, with an overall rate constant koverall = 106 − 1010 M−1 s−1. The computed kinetic data are reasonably accurate as seen by the comparison with the experimental rate constant in water (pH = 7.0), which results in a kcalculated/kexperimetal ratio of 1.4. The hydrogen transfer (C7, C9, C12)−single electron transfer pathways are the main mechanisms for the HO• + NCT reaction in pentyl ethanoate solvent to form the cations as the primary products of the two-step reaction. However, in aqueous environments, the degradation of NCT by HO• radicals increases with increasing pH levels. It is predicted that oxidation products are less toxic than nicotine itself, especially in an aqueous environment with a pH < 7.0.

Computational Study of the Gas-Phase Thermal Degradation of Perfluoroalkyl Carboxylic Acids.

Perfluoroalkyl carboxylic acids (PFCAs) are persistent and ubiquitous pollutants. Environmental remediation is often achieved by absorption on matrices followed by high-temperature thermal treatment to desorb and decompose the PFCAs. Detailed product studies of the thermal degradation of PFCAs have been hampered by the complex nature of product mixtures and associated analytical challenges. On the basis of high-level computational studies, we propose reaction pathways and mechanisms for the high-temperature mineralization of a series of linear PFCAs with a backbone length from C-4 to C-8. The favored initial reaction pathways are nonselective C-C bond homolytic cleavages (with bond dissociation energies of ∼75-90 kcal/mol), resulting in carbon-centered radicals which can undergo β-scissions (Ea ≈ 30-40 kcal/mol) which can be preceded by F atom shifts (Ea ≈ 30-45 kcal/mol). In competing barrierless processes, the carbon-centered radicals can lose •F, resulting in the formation of volatile perfluoroalkenes (ΔH ≈ 50-80 kcal/mol). A variety of competing fragmentation processes yield shorter chain perfluorinated PFCAs, isomeric alkenes, alkenoic acids, alkyl, and alkyloic acid radicals. The results provide the energetics for primary, secondary, and tertiary reaction products and insight into the fundamental understanding of the pyrolytic pathways of PFCAs leading to their mineralization.

One of Nature's Puzzles Is Assembled: Analog of the Earth's Most Complex Mineral, Ewingite, Synthesized in a Laboratory.

Through the combination of low-temperature hydrothermal synthesis and room-temperature evaporation, a synthetic phase similar in composition and crystal structure to the Earth’s most complex mineral, ewingite, was obtained. The crystal structures of both natural and synthetic compounds are based on supertetrahedral uranyl-carbonate nanoclusters that are arranged according to the cubic body-centered lattice principle. The structure and composition of the uranyl carbonate nanocluster were refined using the data on synthetic material. Although the stability of natural ewingite is higher (according to visual observation and experimental studies), the synthetic phase can be regarded as a primary and/or metastable reaction product which further re-crystallizes into a more stable form under environmental conditions.

Thermal decomposition pathways of phenylalanine and glutamic acid and the interaction mechanism between the two amino acids and glucose

Understanding the migration and transformation of nitrogen during biomass pyrolysis and the influence of cellulose components on the nitrogen-containing components of biomass is important for the clean and efficient utilization of biomass. In this study, we performed pyrolysis-photoionization time-of-flight mass spectrometry (Py-PI-TOF-MS), pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS), and closed U-tube pyrolysis to analyze phenylalanine, glutamic acid, and their mixtures, the product composition of the primary and secondary reactions of amino acids, and the effect of glucose on the pyrolysis products of the two amino acids. The experimental results were combined with density functional theory calculations to reveal the pyrolysis path of the two amino acids and the mechanism of the effect of glucose on amino acid pyrolysis. The results revealed that phenylalanine undergoes deamination and decarboxylation reactions during pyrolysis. The hydrogen on the carboxyl group is transferred during this process to release CO2 and generate phenethylamine. Phenylalanine generates a large amount of N-phenethylpropane-2-imine through a secondary reaction. Glucose may play a role in the hydrogen supply and promote the deamination of phenethylamine to produce styrene. The primary reaction product of glutamic acid is a nitrogen-containing heterocyclic ring. The pyrolysis product, l-pyroglutamic acid, generates 2-pyrrolidinone through a decarboxylation reaction. Glucose can reduce the reaction energy barrier for the formation of 2-pyrrolidinone.

Interfacial reactions in Ni/Se-90 at.%Te and Ni/Pb1-xSnxSe couples

Se-90 at.%Te and Pb1-xSnxSe (x = 0, 0.1, 0.2, 0.3) alloys are important thermoelectric elements. Ni is commonly used as a diffusion barrier layer in contact with thermoelectric elements. The interfacial reactions in the Ni/Se-90 at.%Te and Ni/Pb1-xSnxSe (x = 0, 0.1, 0.2, 0.3) couples reacted at 500 °C are examined to study the reaction phase formation and microstructural evolution at the reaction zones. In the solid Ni/liquid Se-90 at.%Te couples reacted at 500 °C, two reaction phase layers, Ni3Te2 and NiTe2-x, are formed at the contact interface. Dendritic (SeTe) and needle-shaped NiTe2-x precipitates are found on the thermoelectric side, showing the reaction path is Ni/Ni3Te2/NiTe2-x/liquid (SeTe) + NiTe2-x/liquid Se-90 at.%Te. In the solid Ni/solid Pb1-xSnxSe couples reacted at 500 °C, the Ni3Pb2Se2 ternary phase is the primary reaction product, regardless of the Sn solubility. Doping of Sn in the Pb1-xSnxSe alloys (x ≥ 0.1) causes additional phase formation of Ni5.62SnSe2, Ni–Sn, and PbSe, giving rise to an interlarded multilayer structure at the reaction zones. The phase formation in the two reaction couples is rationalized by the dominant diffusion species of Ni. The related phase diagrams are assessed and used for illustrating the above-mentioned interfacial reactions.

A Mechanistic Study of Thermal Decomposition of 1,1,2,2-Tetramethyldisilane Using Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry.

Thermal decomposition of 1,1,2,2-tetramethyldisilane was performed by flash pyrolysis in a SiC microreactor in the temperature range from 295 to 1340 K, followed by molecular beam sampling and vacuum ultraviolet photoionization mass spectrometry analysis. Density functional theory investigations on the energetics of reactants, intermediates, and products were carried out to support the experimental observations. Energetics for 1,1,2,2-tetramethyldisilane initiation decomposition reactions and important secondary reactions were calculated. Dimethylsilane, dimethylsilyl radicals, dimethylsilylene, trimethylsilane, and tetramethyldisilene were determined as the primary reaction products in the initiation thermal decompositions of 1,1,2,2-tetramethyldisilane. Further decomposition reactions of tetramethyldisilene, such as production of dimethylsilene (m/z = 72) and eventually SiC3H4 (m/z = 68) fragments, were examined. Other products from secondary reactions of dimethylsilane and dimethylsilylene such as SiC2H2-6 and SiCH0-4 were also observed. The comprehensive pyrolysis mechanism of 1,1,2,2-tetramethyldisilane was proposed.

Shear activation of ZDDP reaction films in the presence and absence of nanodiamonds

We explore the impact of shear stress and nanodiamond (ND) additives on the formation temperatures of thermal- and tribo- reaction films of steel samples immersed in basestock oils containing zinc dialkyl dithio-phosphate (ZDDP) additives. The measurements were performed in-situ using a quartz crystal microbalance (QCM) immersed in oil, oil plus ZDDP, and oil plus ZDDP-ND blends over the temperature range 25 200 °C. ZDDP reaction film formation temperatures were observed to decrease with contact stress and be similar in value to ZDDP-ND blends. ND were observed to be embedded in the reaction films, consistent with prior observations for Tricresyl phosphate (TCP) ND blends, and also consistent with the presence of both primary and secondary reaction products in the films. In addition, the ZDDP+ND reaction tribofilms were observed to be thicker, rougher and more adhesive than those formed with only ZDDP.

Simplified Enzymatic Synthesis of 2-Keto-3-Deoxy-D-Gluconate from D-Gluconate Using the Gluconate Dehydratase from Thermoproteus tenax.

Many research areas, e.g., basic research but also applied fields of biotechnology, biomedicine, and diagnostics often suffer from the unavailability of metabolic compounds. This is mostly due to missing easy and efficient synthesis procedures. We herein describe the biocatalytic/enzymatic production of 2-keto-3-deoxy-D-gluconate, an intermediate of central metabolic pathways in all three domains of life and also of bacterial polysaccharides, lipopolysaccharides, and cell wall components. The method is based on the gluconate dehydratase from the hyperthermophilic crenarchaeon Thermoproteus tenax, which can be easily recombinantly overproduced in Escherichia coli and-due to its intrinsic thermostability-rapidly be purified by two precipitation steps. The enzyme completely converts D-gluconate to solely stereochemically pure KDG, taking benefits from the enol-keto-tautomerism of the primary reaction product. The final product can then easily be separated from the protein by ultrafiltration. The simple one-step procedure, which is suitable at least for the lab-scale/gram-scale production of KDG, replaces lengthy multi-step reactions and is easily scalable. This approach also illustrates the great application potential of Archaea with their unusual metabolic pathways and enzymes for the synthesis of added value products.

Tetrazene-Characterization of Its Polymorphs.

The reinvestigation of tetrazene single crystalline material by means of X-ray methods resulted in a slightly different structure when compared to previously published data. Reaction conditions responsible for different crystalline modification formation were investigated. Newly described C form was found to be the primary reaction product and the combined action of temperature and the presence of water over time is required for the transition to the A form. Both forms were described by X-ray powder diffraction. Tetrazene was also subjected to infrared and Raman spectroscopy, which allowed differentiating between the forms. The molecule was isotopically labeled with 15N atoms at two different locations (ring and nitrogen sidechain) and employed in assigning vibrational modes to the resulting bands. Differences between sensitivities to mechanical stimuli of the two modifications were investigated and found industrially insignificant. In the same vein, the performance of either modification in primer composition and primer was identical.

Rate coefficient and mechanism of the OH-initiated degradation of cyclobutanol: A combined experimental and theoretical study

The degradation process of cyclobutanol (cButOH) by hydroxyl radical (OH), under atmospheric conditions, (750 ± 10) Torr of air and (296 ± 2) K, has been studied. The rate coefficient for the title reaction (k296K = (7.3 ± 0.6) x 10−12 cm3 molecule−1 s−1) was determined at 296 K by the conventional relative-rate method. Electronic structure calculations with uCCSD(T)/uBHandHLYP/aug-cc-PVDZ were conducted to study the reaction mechanism. The global rate coefficient was also calculated using the transition state theory with tunnelling corrections, obtaining a value of 5.4 × 10−12 cm3 molecule−1 s−1 in agreement with the experimental determination. Additionally, reaction products identification in clean and NOx-contaminated atmospheres was performed for the first time. The identified reaction products and their corresponding yields (YP) depend on the environment composition in which the reaction is studied. In the absence of NOx, cyclobutanone (cButanone) was the only identified product, with YcButanone = (0.66 ± 0.08). In NOx-contaminated atmospheres, in addition to cButanone, tetrahydrofuran (THF), 2-nitro-1-butanol (2N1B), 3-nitro-2-butanol (3N2B) and 2-methyl-2-nitro-1-propanol (2M2N1P), were also identified as primary reaction products. Under this condition, we were able to determine only the yields of cButanone and THF (YcButanone = 0.38 ± 0.05 and YTHF = 0.28 ± 0.02). A likely reaction mechanism for the observed products is proposed and the atmospheric implications are discussed.

Ozone Initiates Human-Derived Emission of Nanocluster Aerosols.

Nanocluster aerosols (NCAs, particles <3 nm) are important players in driving climate feedbacks and processes that impact human health. This study reports, for the first time, NCA formation when gas-phase ozone reacts with human surfaces. In an occupied climate-controlled chamber, we detected NCA only when ozone was present. NCA emissions were dependent on clothing coverage, occupant age, air temperature, and humidity. Ozone-initiated chemistry with human skin lipids (particularly their primary surface reaction products) is the key mechanism driving NCA emissions, as evidenced by positive correlations with squalene in human skin wipe samples and known gaseous products from ozonolysis of skin lipids. Oxidation by OH radicals, autoxidation reactions, and human-emitted NH3 may also play a role in NCA formation. Such chemical processes are anticipated to generate aerosols of the smallest size (1.18-1.55 nm), whereas larger clusters result from subsequent growth of the smaller aerosols. This study shows that whenever we encounter ozone indoors, where we spend most of our lives, NCAs will be produced in the air around us.

A crossed molecular beam investigation of the N(2D) + pyridine reaction and implications for prebiotic chemistry

The reactivity of the prototypical aromatic six-membered N-heterocyclic pyridine is of relevance in atmospheric/combustion chemistry, as well as astrochemistry and prebiotic chemistry. Yet, experimental/theoretical studies of elementary reactions involving pyridine are scarce, with little information on primary reaction products and their branching fractions (BFs). Here, we report crossed molecular beam studies of the reaction of electronically excited atomic nitrogen, N(2D), with pyridine. This reaction can proceed via ring-contraction (BF≈0.35) or H-displacement (BF≈0.65) mechanisms, while the inclusion of N(2D) into the ring leads to pyrimidine + CH. Implications for prebiotic chemistry and the chemistry of Saturn’s moon Titan are noted.