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The formation of CN and its isotopologue C15N through radiative association has been investigated. We considered two processes for the collisions of ground state C(3P) and N(4S) atoms (A2Π → X2Σ+ and b4Π → a4Σ+), as well as, for the first time, we investigated the radiative association of ground state C(3P) and excited N(2D) atoms (B2Σ+ → X2Σ+). The cross-sections for the three processes have been calculated using semi-classical, quantum mechanical, and Breit–Wigner theories. The rate constants, derived from the combination of semi-classical and Breit–Wigner results, have been fitted to the Kooij formula to be used in astrochemical modeling. The rate constant for the B2Σ+ → X2Σ+ process dominates in the investigated temperature range (10–10 000 K), when its own asymptotic energy is used as a reference level. Moreover, the B2Σ+ → X2Σ+ process presents the most pronounced isotope effect on the rate constant. We suggest considering these newly investigated radiative association processes for the formation of CN and C15N in the interstellar medium.

The dynamics of the radical–radical reaction O(3P) + C3H5 has been investigated by means of the crossed molecular beam technique with mass spectrometric detection at a collision energy of 73.0 kJ mol−1; the reaction mechanism of the H-displacement channel has been elucidated, while experimental evidence of the occurrence of one or more C–C bond-breaking channels at this collision energy has been obtained. [ABSTRACT FROM AUTHOR]

We report new interferometric images of cyclopropenylidene, c-C3H2, toward the young protocluster OMC-2 FIR 4. The observations were performed at 82 and 85 GHz with the NOrthern Extended Millimeter Array (NOEMA) as part of the project Seeds Of Life In Space (SOLIS). In addition, IRAM-30 m data observations were used to investigate the physical structure of OMC-2 FIR 4. We find that the c-C3H2 gas emits from the same region where previous SOLIS observations showed bright HC5N emission. From a non-LTE analysis of the IRAM-30 m data, the c-C3H2 gas has an average temperature of ∼40 K, a H2 density of ∼3 × 105 cm−3, and a c-C3H2 abundance relative to H2 of (7 ± 1) × 10−12. In addition, the NOEMA observations provide no sign of significant c-C3H2 excitation temperature gradients across the region (about 3–4 beams), with Tex in the range 8 ± 3 up to 16 ± 7 K. We thus infer that our observations are inconsistent with a physical interaction of the OMC-2 FIR 4 envelope with the outflow arising from OMC-2 FIR 3, as claimed by previous studies. The comparison of the measured c-C3H2 abundance with the predictions from an astrochemical PDR model indicates that OMC-2 FIR 4 is irradiated by an FUV field ∼1000 times larger than the interstellar one, and by a flux of ionizing particles ∼4000 times larger than the canonical value of 1 × 10−17 s−1 from the Galaxy cosmic rays, which is consistent with our previous HC5N observations. This provides an important and independent confirmation of other studies that one, or more, source inside the OMC-2 FIR 4 region emits energetic (≥10 MeV) particles. [ABSTRACT FROM AUTHOR]

Complex organic molecules have been observed for decades in the interstellar medium. Some of them might be considered as small bricks of the macromolecules at the base of terrestrial life. It is hence particularly important to understand organic chemistry in Solar-like star-forming regions. In this article, we present a new observational project: Seeds Of Life In Space (SOLIS). This is a Large Project using the IRAM-NOEMA interferometer, and its scope is to image the emission of several crucial organic molecules in a sample of Solar-like star-forming regions in different evolutionary stages and environments. Here we report the first SOLIS results, obtained from analyzing the spectra of different regions of the Class 0 source NGC 1333-IRAS4A, the protocluster OMC-2 FIR4, and the shock site L1157-B1. The different regions were identified based on the images of formamide (NH2CHO) and cyanodiacetylene (HC5N) lines. We discuss the observed large diversity in the molecular and organic content, both on large (3000–10,000 au) and relatively small (300–1000 au) scales. Finally, we derive upper limits to the methoxy fractional abundance in the three observed regions of the same order of magnitude of that measured in a few cold prestellar objects, namely –10−11 with respect to H2 molecules. [ABSTRACT FROM AUTHOR]

Despite the relevance of the reactions of the prototypical nitrogen-containing six-membered aromatic molecule (N-heterocyclic) of pyridine (C 6 H 5 N) in environmental science, astrochemistry, planetary science, prebiotic chemistry, and materials science, few experimental/theoretical studies exist on the bimolecular reactions involving pyridine and neutral atomic/molecular radicals. We report a combined experimental and theoretical study on the elementary reaction of pyridine with excited nitrogen atoms, N( 2 D), aimed at providing information about the primary reaction products and their branching fractions (BFs). From previous crossed molecular beam (CMB) experiments with mass-spectrometric detection and present synergistic calculations of the reactive potential energy surface (PES) and product BFs we have unveiled the reaction mechanism. It is found that the reaction proceeds via N( 2 D) barrierless addition to pyridine that, via bridged intermediates followed by N atom "sliding" into the ring, leads to 7-membered-ring structures. They further evolve, mainly via ring-contraction mechanisms toward 5-membered-ring radical products and, to a smaller extent, via H-displacement mechanisms toward 7-membered-ring isomeric products and their isomers. Using the theoretical statistical estimates, an improved fit of the experimental data previously reported has been obtained, leading to the following results for the dominant product channels: C 4 H 4 N (pyrrolyl) + HCN (BF = 0.61 ± 0.20), C 3 H 3 N 2 (1H-imidazolyl/1H-pyrazolyl) + C 2 H 2 (BF = 0.11 ± 0.06), and C 5 H 4 N 2 (7-membered-ring molecules or pyrrole carbonitriles) + H (BF = 0.28 ± 0.10). The ring-contraction product channels C 4 H 4 N (pyrrolyl) + HCN, C 3 H 3 N 2 (1H-imidazolyl) + C 2 H 2 , C 3 H 3 N 2 (1H-pyrazolyl) + C 2 H 2 , and C 5 H 5 (cyclopentadienyl) + N 2 have statistical BFs of 0.54, 0.09, 0.11, and 0.07, respectively. Among the H-displacement channels, the cyclic-CHCHCHCHNCN + H channel and cyclic-CHCHCHCHCN 2 + H are theoretically predicted to have a comparable BF (0.07 and 0.06, respectively), while the other isomeric 7-membered-ring molecule + H channel has a BF of 0.03. Pyrrole-carbonitriles and 1H-ethynyl-1H-imidazole (+ H) isomeric channels have an overall BF of 0.03. Implications for the chemistry of Saturn's moon Titan and prebiotic chemistry, as well as for understanding the N-doping of graphene or carbon nanotubes, are noted.

Despite extensive experimental and theoretical studies on the kinetics of the O( 3 P) + C 7 H 8 (toluene) reaction and a pioneering crossed molecular beam (CMB) investigation, the branching fractions (BFs) of the CH 3 C 6 H 4 O(methylphenoxy) + H, C 6 H 5 O(phenoxy) + CH 3 , and spin-forbidden C 5 H 5 CH 3 (methylcyclopentadiene) + CO product channels remain an open question, which has hampered the proper inclusion of this important reaction in the chemical modelling of various chemical environments. We report a CMB study with universal soft electron-ionization mass-spectrometric detection of the reactions O( 3 P, 1 D) + toluene at the collision energy of 34.7 kJ mol -1 . From CMB data we have inferred the reaction dynamics and quantified the BFs of the primary products and the role of intersystem crossing (ISC). The CH 3 -elimination channel dominates (BF = 0.69 ± 0.22) in the O( 3 P) reaction, while the H-displacement and CO-formation channels are minor (BF = 0.22 ± 0.07 and 0.09 ± 0.05, respectively), with ISC accounting for more than 50% of the reactive flux. Synergistic transition-state theory (TST)-based master equation simulations including nonadiabatic TST on ab initio coupled triplet/singlet potential energy surfaces were employed to compute the product BFs and assist in the interpretation of the CMB results. In the light of the good agreement between the theoretical predictions for the O( 3 P) + toluene reaction and the CMB results as well as the absolute rate constant as a function of temperature ( T ) (from literature), the so-validated computational methodology was used to predict channel-specific rate constants as a function of T at 1 atm.

Phosphorus (P) is a fundamental element for whatever form of life, in the same way as the other biogenic macroelements (SONCH). The prebiotic origin of P is still a matter of debate, as the phosphates present on earth are trapped in almost insoluble solid matrixes (apatites) and, therefore, hardly available for inclusion in living systems in the prebiotic era. The most accepted theories regard a possible exogenous origin during the Archean Era, through the meteoritic bombardment, when tons of reactive P in the form of phosphide ((Fe,Ni) 3 P, schreibersite mineral) reached the primordial earth, reacting with water and providing oxygenated phosphorus compounds (including phosphates). In the last 20 years, laboratory experiments demonstrated that the corrosion process of schreibersite by water indeed leads to reactive phosphates that, in turn, react with other biological building blocks (nucleosides and simple sugars) to form more complex molecules (nucleotides and complex sugars). In the present paper, we study the water corrosion of different crystalline surfaces of schreibersite by means of periodic DFT (density functional theory) simulations. Our results show that water adsorbs molecularly on the most stable (110) surface but dissociates on the less stable (001) one, giving rise to further reactivity. Indeed, subsequent water adsorptions, up to the water monolayer coverage, show that, on the (001) surface, iron and nickel atoms are the first species undergoing the corrosion process and, in a second stage, the phosphorus atoms also get involved. When adsorbing up to three and four water molecules per unit cell, the most stable structures found are the phosphite and phosphate forms of phosphorus, respectively. Simulation of the vibrational spectra of the considered reaction products revealed that the experimental band at 2423 cm -1 attributed to the P-H stretching frequency is indeed predicted for a phosphite moiety attached to the schreibersite (001) surface upon chemisorption of up to three water molecules., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

We report on a combined experimental and theoretical investigation of the N( 2 D) + C 6 H 6 (benzene) reaction, which is of relevance in the aromatic chemistry of the atmosphere of Titan. Experimentally, the reaction was studied (i) under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy ( E c ) of 31.8 kJ mol -1 to determine the primary products, their branching fractions (BFs), and the reaction micromechanism, and (ii) in a continuous supersonic flow reactor to determine the rate constant as a function of temperature from 50 K to 296 K. Theoretically, electronic structure calculations of the doublet C 6 N potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism. The reaction is found to proceed 6 barrierless addition of N( via barrierless addition of N( 2 D) to the aromatic ring of C 6 H 6 , followed by formation of several cyclic (five-, six-, and seven-membered ring) and linear isomeric C 6 N intermediates that can undergo unimolecular decomposition to bimolecular products. Statistical estimates of product BFs on the theoretical PES were carried out under the conditions of the CMB experiments and at the temperatures relevant for Titan's atmosphere. In all conditions the ring-contraction channel leading to C 6 N intermediates that can undergo unimolecular decomposition to bimolecular products. Statistical estimates of product BFs on the theoretical PES were carried out under the conditions of the CMB experiments and at the temperatures relevant for Titan's atmosphere. In all conditions the ring-contraction channel leading to C 5 H 5 (cyclopentadienyl) + HCN is dominant, while minor contributions come from the channels leading to o -C 6 N ( 5 -N-cycloheptatriene radical) + H, C o -N-cycloheptatriene radical) + H, C 4 N (pyrrolyl) + C 4 N (pyrrolyl) + C 2 H 2 (acetylene), C 5 H 5 CN (cyano-cyclopentadiene) + H, and p -C 6 N + H. Rate constants (which are close to the gas kinetic limit at all temperatures, with the recommended value of 2.19 ± 0.30 × 10 5 N + H. Rate constants (which are close to the gas kinetic limit at all temperatures, with the recommended value of 2.19 ± 0.30 × 10 -10 cm 3 s -1 over the 50-296 K range) and BFs have been used in a photochemical model of Titan's atmosphere to simulate the effect of the title reaction on the species abundances as a function of the altitude.

Acrylonitrile (CH 2 CHCN) 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( 3 P) + CH 2 CHCN 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 3 P and excited 1 D atomic oxygen. From product angular and time-of-flight distributions in crossed molecular beam experiments with mass spectrometric detection at a collision energy, E c , 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( 3 P) reaction leads to two main product channels: (i) CH 2 CNH (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 CH 2 CHCN and a possible formation route of CH 2 CNH in the interstellar medium. The O( 1 D) + CH 2 CHCN reaction mainly leads to the formation of CH 2 CNH + CO adiabatically on the singlet PES. This result can improve models related to the chemistry of interstellar ice and cometary comas, where O( 1 D) reactions can play a role. Overall, our results are expected to be useful for improving the models of combustion and extraterrestrial environments.

The reaction between the ground-state hydroxyl radical, OH( 2 Π), and ethylene, C 2 H 4 , has been investigated under single-collision conditions by the crossed molecular beam scattering technique with mass-spectrometric detection and time-of-flight analysis at the collision energy of 50.4 kJ/mol. Electronic structure calculations of the underlying potential energy surface (PES) and statistical Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of product branching fractions on the derived PES for the addition pathway have been performed. The theoretical results indicate a temperature-dependent competition between the anti -/ syn -CH 2 CHOH (vinyl alcohol) + H, CH 3 CHO (acetaldehyde) + H, and H 2 CO (formaldehyde) + CH 3 product channels. The yield of the H-abstraction channel could not be quantified with the employed methods. The RRKM results predict that under our experimental conditions, the anti - and syn -CH 2 CHOH + H product channels account for 38% (in similar amounts) of the addition mechanism yield, the H 2 CO + CH 3 channel for ∼58%, while the CH 3 CHO + H channel is formed in negligible amount (<4%). The implications for combustion and astrochemical environments are discussed.

Cyanoacetylene ( HCCCN), the first member of the cyanopolyyne family (HC n N, 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 3 P and excited 1 D 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( 3 P,  1 D) with HCCCN(X 1 Σ + ) 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, E c , 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( 3 P) 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 1 HCCN (cyanomethylene) + CO. The O( 1 D) 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( 3 N at 300 K is in the 10 3 N at 300 K is in the 10 -12 cm 3 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.

Two quantum effects can enable reactions to take place at energies below the barrier separating reactants from products: tunnelling and intersystem crossing between coupled potential energy surfaces. Here we show that intersystem crossing in the region between the pre-reactive complex and the reaction barrier can control the rate of bimolecular reactions for weakly coupled potential energy surfaces, even in the absence of heavy atoms. For O( 3 P) plus pyridine, a reaction relevant to combustion, astrochemistry and biochemistry, crossed-beam experiments indicate that the dominant products are pyrrole and CO, obtained through a spin-forbidden ring-contraction mechanism. The experimental findings are interpreted-by high-level quantum-chemical calculations and statistical non-adiabatic computations of branching fractions-in terms of an efficient intersystem crossing occurring before the high entrance barrier for O-atom addition to the N-atom lone pair. At low to moderate temperatures, the computed reaction rates prove to be dominated by intersystem crossing., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Atomic oxygen reactions can contribute significantly to the oxidation of unsaturated aliphatic and aromatic hydrocarbons. The reaction mechanism is started by electrophilic O atom addition to the unsaturated bond(s) to form "chemically activated" triplet oxy-intermediate(s), which can evolve adiabatically on the triplet potential energy surface (PES) and nonadiabatically via intersystem crossing on the singlet PES, forming intermediates that undergo unimolecular decomposition to a variety of bimolecular product channels. Here, we apply a combined crossed molecular beam (CMB)-theoretical approach to the study of the O( 3 P) + 1,3-butadiene reaction. Although the kinetics of this reaction have been extensively investigated, little is known about the primary products and their branching fractions (BFs). In the present work, a total of eight product channels were observed and characterized in a CMB experiment at a collision energy of 32.6 kJ mol -1 . Synergic ab initio transition-state theory-based master equation simulations coupled with nonadiabatic transition-state theory on coupled triplet/singlet PESs were employed to compute the product BFs and assist the interpretation of the CMB experimental results. The good agreement found between the theoretical predictions and CMB experiments supported the use of the adopted methodology for the prediction of channel-specific rate constants as a function of temperature and pressure suitable to be used for the kinetic modeling of 1,3-butadiene oxidation and of systems where 1,3-butadiene is an important intermediate.

We report on a combined experimental and theoretical investigation of the N( 2 D) + CH 2 CCH 2 (allene) reaction of relevance in the atmospheric chemistry of Titan. Experimentally, the reaction was investigated (i) under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy ( E c ) of 33 kJ/mol to determine the primary products and the reaction micromechanism and (ii) in a continuous supersonic flow reactor to determine the rate constant as a function of temperature from 50 to 296 K. Theoretically, electronic structure calculations of the doublet C 3 N potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism. The reaction is found to proceed via barrierless addition of N( 4 N potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism. The reaction is found to proceed via barrierless addition of N( 2 D) to one of the two equivalent carbon-carbon double bonds of CH 2 CCH 2 , followed by the formation of several cyclic and linear isomeric C 3 N intermediates that can undergo unimolecular decomposition to bimolecular products with elimination of H, CH 4 N intermediates that can undergo unimolecular decomposition to bimolecular products with elimination of H, CH 3 , HCN, HNC, and CN. The kinetic experiments confirm the barrierless nature of the reaction through the measurement of rate constants close to the gas-kinetic rate at all temperatures. Statistical estimates of product branching fractions (BFs) on the theoretical PES were carried out under the conditions of the CMB experiments at room temperature and at temperatures (94 and 175 K) relevant for Titan. Up to 14 competing product channels were statistically predicted with the main ones at E c C(N)CH + H (BF = 87.0%) followed by CHCCHNH + H (BF = 10.5%) and CH cyclic -CH 2 C(N)CH + H (BF = 87.0%) followed by CHCCHNH + H (BF = 10.5%) and CH 2 (vinyl) channels (overall BF < 1%). The dynamics and product distributions are dramatically different with respect to those observed in the isomeric reaction N( 2 H 3 (vinyl) channels (overall BF < 1%). The dynamics and product distributions are dramatically different with respect to those observed in the isomeric reaction N( 2 D) + CH 3 CCH (propyne), where at a similar E H (BF = 41%), c-C(N)CH + CH c the main product channels are CH 2 NH (methanimine) + C 2 H (BF = 41%), c-C(N)CH + CH 3 (BF = 32%), and CH 2 CHCN (vinyl cyanide) + H (BF = 12%). Rate coefficients (the recommended value is 1.7 (±0.2) × 10 -10 cm 3 s -1 over the 50-300 K range) and BFs have been used in a photochemical model of Titan's atmosphere to simulate the effect of the title reaction on the species abundance (including any new products formed) as a function of the altitude., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The reaction of electronically excited nitrogen atoms, N( 2 D), with vinyl cyanide, CH 2 CHCN, has been investigated under single-collision conditions by the crossed molecular beam (CMB) scattering method with mass spectrometric detection and time-of-flight (TOF) analysis at the collision energy, E c of the CMB experiment. According to our theoretical calculations, the reaction is found to proceed via barrierless addition of N( E c ═CH-CN, followed by the formation of cyclic and linear intermediates that can undergo H, CN, and HCN elimination. In competition, the N( 2 D) addition to the CN group is also possible via a submerged barrier, leading ultimately to N 2 ═CH-CN, followed by the formation of cyclic and linear intermediates that can undergo H, CN, and HCN elimination. In competition, the N( 2 D) addition to the CN group is also possible via a submerged barrier, leading ultimately to N 2 + C 3 H 3 N 3 isomeric products. Experimentally, no evidence of CN, HCN, and N 2 forming channels was observed. These findings were corroborated by the theory, which predicts a variety of competing product channels, following N( 2 isomeric products. Experimentally, no evidence of CN, HCN, and N 2 forming channels was observed. These findings were corroborated by the theory, which predicts a variety of competing product channels, following N( 2 -CH(N)CHCN + H (BF = 35.0%), E c = 31.4 kJ/mol, being six isomeric H forming channels: c -CH(N)CHCN + H (BF = 35.0%), c (N)CCN(cyano-azirine) + H (BF = 7.4%), 2 NCCN + H (BF = 26.3%), c -CH 2 (N)CCN(cyano-azirine) + H (BF = 7.4%), trans (N)CH(2H-azirine) + CN and cis -HNCCHCN + H (BF = 1.3%), while C-C bond breaking channels leading to c (N)C + HCN are predicted to be negligible (0.02% and 0.2%, respectively). The highly exothermic N 2 (N)CH(2H-azirine) + CN and c CCH (propargyl) channel is also predicted to be negligible because of the very high isomerization barrier from the initial addition intermediate to the precursor intermediate able to lead to products. The predicted product BFs are found to have, in general, a very weak energy dependence. The above cyclic and linear products containing an additional C-N bond could be potential precursors of more complex, N-rich organic molecules that contribute to the formation of the aerosols on Titan's upper atmosphere. Overall, the results are expected to have a significant impact on the gas-phase chemistry of Titan's atmosphere and should be properly included in the photochemical models.2 (N)C + HCN are predicted to be negligible (0.02% and 0.2%, respectively). The highly exothermic N 2 + CH 2 CCH (propargyl) channel is also predicted to be negligible because of the very high isomerization barrier from the initial addition intermediate to the precursor intermediate able to lead to products. The predicted product BFs are found to have, in general, a very weak energy dependence. The above cyclic and linear products containing an additional C-N bond could be potential precursors of more complex, N-rich organic molecules that contribute to the formation of the aerosols on Titan's upper atmosphere. Overall, the results are expected to have a significant impact on the gas-phase chemistry of Titan's atmosphere and should be properly included in the photochemical models.

The reaction between cyano radicals (CN, X 2 Σ + ) and cyanoethene (C 2 H 3 CN) has been investigated by a combined approach coupling crossed molecular beam (CMB) experiments with mass spectrometric detection and time-of-flight analysis at a collision energy of 44.6 kJ mol -1 and electronic structure calculations to determine the relevant potential energy surface. The experimental results can be interpreted by assuming the occurrence of a dominant reaction pathway leading to the two but-2-enedinitrile (1,2-dicyanothene) isomers ( E - and Z -NC-CH═CH-CN) in a H-displacement channel and, to a much minor extent, to 1,1-dicyanoethene, CH 2 C(CN) 2 . In order to derive the product branching ratios under the conditions of the CMB experiments and at colder temperatures, including those relevant to Titan and to cold interstellar clouds, we have carried out RRKM statistical calculations using the relevant potential energy surface of the investigated reaction. We have also estimated the rate coefficient at very low temperatures by employing a semiempirical method for the treatment of long-range interactions. The reaction has been found to be barrierless and fast also under the low temperature conditions of cold interstellar clouds and the atmosphere of Titan. Astrophysical implications and comparison with literature data are also presented. On the basis of the present work, 1,2-dicyanothene and 1,1-dicyanothene are excellent candidates for the search of dinitriles in the interstellar medium.

Glycine (Gly), NH 2 CH 2 COOH, is the simplest amino acid. Although it has not been directly detected in the interstellar gas-phase medium, it has been identified in comets and meteorites, and its synthesis in these environments has been simulated in terrestrial laboratory experiments. Likewise, condensation of Gly to form peptides in scenarios resembling those present in a primordial Earth has been demonstrated experimentally. Thus, Gly is a paradigmatic system for biomolecular building blocks to investigate how they can be synthesized in astrophysical environments, transported and delivered by fragments of asteroids (meteorites, once they land on Earth) and comets (interplanetary dust particles that land on Earth) to the primitive Earth, and there react to form biopolymers as a step towards the emergence of life. Quantum chemical investigations addressing these Gly-related events have been performed, providing fundamental atomic-scale information and quantitative energetic data. However, they are spread in the literature and difficult to harmonize in a consistent way due to different computational chemistry methodologies and model systems. This review aims to collect the work done so far to characterize, at a quantum mechanical level, the chemical life of Gly, i.e., from its synthesis in the interstellar medium up to its polymerization on Earth.

Ethanol (CH 3 CH 2 OH) is a relatively common molecule, often found in star-forming regions. Recent studies suggest that it could be a parent molecule of several so-called interstellar complex organic molecules (iCOMs). However, the formation route of this species remains under debate. In the present work, we study the formation of ethanol through the reaction of CCH with one H 2 O molecule belonging to the ice as a test case to investigate the viability of chemical reactions based on a "radical + ice component" scheme as an alternative mechanism for the synthesis of iCOMs, beyond the usual radical-radical coupling. This has been done by means of DFT calculations adopting two clusters of 18 and 33 water molecules as ice models. Results indicate that CH 3 CH 2 OH can potentially be formed by this proposed reaction mechanism. The reaction of CCH with H 2 O on the water ice clusters can be barrierless (because of the help of boundary icy water molecules acting as proton-transfer assistants), leading to the formation of vinyl alcohol precursors (H 2 CCOH and CHCHOH). Subsequent hydrogenation of vinyl alcohol yielding ethanol is the only step presenting a low activation energy barrier. We finally discuss the astrophysical implications of these findings., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Phosphorus is an element of primary importance for all living creatures, being present in many biological activities in the form of phosphate (PO 4 3- ). However, there are still open questions about the origin of this specific element and on the transformation that allowed it to be incorporated in biological systems. The most probable source of prebiotic phosphorus is the intense meteoritic bombardment during the Archean era, a few million years after the solar system formation, which brought tons of iron-phosphide materials (schreibersite) on the early Earth crust. It was recently demonstrated that by simple wetting/corrosion processes from this material, various oxygenated phosphorus compounds are produced. In the present work, the wetting process of schreibersite (Fe 2 NiP) was studied by computer simulations using density functional theory, with the PBE functional supplemented with dispersive interactions through a posteriori empirical correction. To start disentangling the complexity of the system, only the most stable (110) surface of Fe 2 NiP was used simulating different water coverages, from which structures, water binding energies, and vibrational spectra have been predicted. The computed (ana-)harmonic infrared spectra have been compared with the experimental ones, thus, confirming the validity of the adopted methodology and models., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The reaction of excited nitrogen atoms N( 2 D) with CH 3 CCH (methylacetylene) was investigated under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy ( E c of N( addition of N( 2 D) to the carbon-carbon triple bond of CH 3 of N( insertion of N( 2 D) into the CH bond of the methyl group, followed by the formation of cyclic and linear intermediates that can undergo H, CH 3 , and C 2 H elimination or isomerize to other intermediates before unimolecularly decaying to a variety of products. Kinetic calculations for addition and insertion mechanisms and statistical (Rice-Ramsperger-Kassel-Marcus) computations of product branching fractions (BFs) on the theoretical PES were performed at different values of total energy, including the one corresponding to the temperature (175 K) of Titan's stratosphere and that of the CMB experiment. Up to 14 competing product channels were statistically predicted, with the main ones, at E c = 31.0 kJ/mol, being the formation of CH 2 -C(N)CH + CH 2 H (ethylidyne) (BF = 0.41), c -C(N)CH + CH 3 (BF = 0.32), CH 2 C(N)CH + H (BF = 0.04). Of the 14 possible channels, seven correspond to H displacement channels of different exothermicity, for a total H channel BF of ∼0.25 at c = 31.0 kJ/mol. Experimentally, dynamical information could only be obtained about the overall H channels. In particular, the experiment corroborates the formation of acrylonitrile + H, which is the most exothermic of all 14 reaction channels and is theoretically calculated to be the dominant H-forming channel (BF = 0.12). The products containing a novel C-N bond could be potential precursors to form other nitriles (C 2 N E c N) or more complex organic species containing N atoms in planetary atmospheres, such as those of Titan and Pluto. Overall, the results are expected to have a potentially significant impact on the understanding of the gas-phase chemistry of Titan's atmosphere and the modeling of that atmosphere.2 N 2 , C 3 N) or more complex organic species containing N atoms in planetary atmospheres, such as those of Titan and Pluto. Overall, the results are expected to have a potentially significant impact on the understanding of the gas-phase chemistry of Titan's atmosphere and the modeling of that atmosphere.