Experimental identification of aminomethanol (NH2CH2OH)-the key intermediate in the Strecker Synthesis

In-depth exploration of catalytic sites on amorphous solid water: I. The astrosynthesis of aminomethanol

Chemical processes taking place on ice-grain mantles are pivotal to the complex chemistry of interstellar environments. In this study, we conducted a comprehensive analysis of the catalytic effects of an amorphous solid water (ASW) surface on the reaction between ammonia (NH3) and formaldehyde (H2CO) to form aminomethanol (NH2CH2OH) using density functional theory. We identified potential catalytic sites based on the binding energy distribution of NH3 and H2CO reactants, on a set-of-clusters surface model composed of 22 water molecules and found a total of 14 reaction paths. Our results indicate that the catalytic sites can be categorized into four groups, depending on the interactions of the carbonyl oxygen and the amino group with the ice surface in the reactant complex. A detailed analysis of the reaction mechanism using Intrinsic Reaction Coordinate and reaction force analysis, revealed three distinct chemical events for this reaction: formation of the C-N bond, breaking of the N-H bond, and formation of the O-H hydroxyl bond. Depending on the type of catalytic site, these events can occur within a single, concerted, albeit asynchronous, step, or can be isolated in a step-wise mechanism, with the lowest overall transition state energy observed at 1.3 kcal mol-1. A key requirement for the low-energy mechanism is the presence of a pair of dangling OH bonds on the surface, found at 5% of the potential catalytic sites on an ASW porous surface.

Unveiling the chemical kinetics of aminomethanol (NH2CH2OH): insights into O . H and O2 photo-oxidation reactions and formamide dominance

Aminomethanol is released into the atmosphere through various sources, including biomass burning. In this study, we have expounded the chemical kinetics of aminomethanol in the reaction pathways initiated by the hydroxyl radical (O ˙ H) with the aid of ab initio//density functional theory (DFT) i.e., coupled-cluster theory (CCSD(T))//hybrid-DFT (M06-2X/6-311++G (3df, 3pd). We have explored various possible directions of theO ˙ H radical on aminomethanol, as well as the formation of distinct pre-reactive complexes. Our computational findings reveal that the H transfer necessitates activation energies ranging from 4.1 to 6.5 kcal/mol from the -CH2 group, 3.5-6.5 kcal/mol from the -NH2 group and 7-9.3 kcal/mol from the -OH group of three rotational conformers. The H transfer from -CH2, -NH2 and -OH exhibits an estimated total rate constant (k OH) of approximately 1.97 × 10-11 cm3 molecule-1 s-1 at 300 K. The branching fraction analysis indicates a pronounced dominance of C-centered NH2C ˙ HOH radicals with a favorability of 77%, surpassing the N-centeredN ˙ HCH2OH (20%) and O-centered NH2CH2O ˙ (3%) radicals. Moreover, our investigation delves into the oxidation of the prominently favored carbon-centered NH2C ˙ HOH radical through its interaction with atmospheric oxygen molecules. Intriguingly, our findings reveal that formamide (NH2CHO) emerges as the predominant product in the NH2C ˙ HOH + 3O2 reaction, eclipsing alternative outcomes such as amino formic acid (NH2COOH) and formimidic acid (HN = C(H)-OH). At atmospheric conditions pertinent to the troposphere, the branching fraction value for the formation of formamide is about 99%, coupled with a rate constant of 5.5 × 10-12 cm3 molecule-1 s-1. Finally, we have scrutinized the detrimental impact of formamide on the atmosphere. Interaction of formamide with atmospheric hydroxyl radicals could give rise to the production of potentially perilous compounds such as HNCO. Further, unreactedN ˙ HCH2OH radicals may initiate the formation of carcinogenic nitrosamines when reacting with trace N-oxides (namely, NO and NO2). This, in turn, escalates the environmental risk factors.

Quantum Chemistry and Astrochemistry: A Match Made in the Heavens

Quantum chemistry can uniquely answer astrochemical questions that no other technique can provide. Computations can be parallelized, automated, and left to run continuously providing exceptional molecular throughput that cannot be done through experimentation. Additionally, the granularity of the individual computations that are required of potential energy surfaces, reaction mechanism pathways, or other quantum chemically derived observables produces a unique mosaic that make up the larger whole. These pieces can be dissected for their individual contributions or evaluated in an ad hoc fashion for each of their roles in generating the larger whole. No other scientific approach is capable of reporting such fine-grained insights. Quantum chemistry also works from a bottom-up approach in providing properties directly from the desired molecule instead of a top-down perspective as required of experiment where molecules have to be linked to observed phenomena. Furthermore, modern quantum chemistry is well within the range of "chemical accuracy" and is approaching "spectroscopic accuracy." As such, the seemingly difficult questions asked by astrochemistry that would not be asked initially for any other application require quantum chemical reference data. While the results of quantum chemical computations are needed to interpret astrochemical observation, modeling, or laboratory experimentation, such hard questions, regardless of the original need to answer them, produce unique solutions. While questions in astrochemistry often require novel developments in and implementations of quantum chemistry as outlined herein, the applications of these solutions will stretch beyond astrochemistry and may yet impact fields much closer to Earth.

Tandem Dual-Site PbCu Electrocatalyst for High-Rate and Selective Glycine Synthesis at Industrial Current Densities

Direct electrosynthesis of high-value amino acids from carbon and nitrogen monomers remains a challenge. Here, we design a tandem dual-site PbCu electrocatalyst for efficient amino acid electrosynthesis. Using oxalic acid (H2C2O4) and hydroxylamine (NH2OH) as the raw reactants, for the first time, we have realized the flow-electrosynthesis of glycine at the industrial current density of 200 mA cm-2 with Faradaic efficiency over 78%. In situ ATR-FTIR spectroscopy characterizations reveal a favorable tandem pathway on the dual-site catalyst. Specifically, the Pb site drives the highly selective electroreduction of H2C2O4 to form glyoxylic acid, and the Cu site accelerates the fast hydrogenation of oxime to form a glycine product. A glycine electrosynthesis (GES)-formaldehyde electrooxidation (FOR) assembly is further established, which synthesizes more valuable chemicals (HCOOH, H2) while minimizing energy consumption. Altogether, we introduce a new strategy to enable the one-step electrosynthesis of high-value amino acid from widely accessible monomers.

Hydrophobic Trinuclear Copper Cluster-Containing Organic Framework for Synergetic Electrocatalytic Synthesis of Amino Acids

Electrocatalytic synthesis of amino acids provides a promising green and efficient pathway to manufacture the basic substances of life. Herein, reaction of 2,5-perfluroalkyl-terepthalohydrazide and tris(4-µ2 -O-carboxaldehyde-pyrazolato-N, N')-tricopper affords a crystalline trinuclear copper cluster-containing organic framework, named F-Cu3 -OF. Incorporation of abundant hydrophobic perfluroalkyl groups inside the channels of F-Cu3 -OF is revealed to successfully suppress the hydrogen evolution reaction via preventing H+ cation with large polarity from the framework of F-Cu3 -OF and in turn increasing the adsorption of other substrates with relatively small polarity like NO3 - and keto acids on the active sites. The copper atoms with short distance in the trinuclear copper clusters of F-Cu3 -OF enable simultaneous activization of NO3 - and keto acids, facilitating the following synergistic and efficient C─N coupling on the basis of in situ spectroscopic investigations together with theoretical calculation. Combination of these effects leads to efficient electroproduction of various amino acids including glycine, alanine, leucine, valine, and phenylalanine from NO3 - and keto acids with a Faraday efficiency of 42%-71% and a yield of 187-957 µmol cm-2 h-1 , representing the thus far best performance. This work shall be helpful for developing economical, eco-friendly, and high-efficiency strategy for the production of amino acids and other life substances.

Enantiodetermining processes in the synthesis of alanine, serine, and isovaline

In this study, quantum chemical calculations were used to explore the synthesis of three chiral α-amino acids, specifically alanine, serine, and isovaline, from reactants found in interstellar space. Our focus is on the crucial step in the synthesis pathway that determines the chirality of the amino acids. The results indicate that in the case of alanine, the determination of enantiomer is primarily influenced by the direction of the collision of molecules or functional groups, which leads to the formation of a chirality center in a crucial intermediate. However, contrary to chemical expectations, the enantiodetermining/enantioselection step for serine and isovaline synthesis occurs prior to the creation of a chirality center.

Ultraviolet-Initiated Decomposition of Solid 1,1-Diamino-2,2-dinitroethylene (FOX-7)

FOX-7 (1,1-diamino-2,2-dinitroethylene) was photolyzed with 202 nm photons to probe reaction energies, leading to the decomposition of this energetic material and to compare results from irradiations using lower-energy 532 and 355 nm photons as well as higher-energy electrons. The photolysis occurred at 5 K to suppress thermal reactions, and the solid samples were monitored using Fourier transform infrared spectroscopy (FTIR), which observed carbon dioxide (CO2), carbon monoxide (CO), cyanide (CN-), and cyanate (OCN-) after irradiation. During warming to 300 K, subliming products were detected using electron-impact quadrupole mass spectrometry (EI-QMS) and photoionization time-of-flight mass spectrometry (PI-ReTOF-MS). Five products were observed in QMS: water (H2O), carbon monoxide (CO), nitric oxide (NO), carbon dioxide (CO2), and cyanogen (NCCN). The ReTOF-MS results showed overlap with electron irradiation products but also included three intermediates for the oxidation of ammonia and nitric oxide: hydroxylamine (NH2OH), nitrosamine (NH2NO), and the largest product at 76 amu with the proposed assignment of hydroxyurea (NH2C(O)NHOH). These results highlight the role of reactive oxygen intermediates and nitro-to-nitrite isomerization as key early reactions that lead to a diverse array of decomposition products.

Preparation of methanediamine (CH2(NH2)2)-A precursor to nucleobases in the interstellar medium

Although methanediamine (CH₂(NH₂)₂) has historically been the subject of theoretical scrutiny, it has never been isolated to date. Here, we report the preparation of methanediamine (CH₂(NH₂)₂)-the simplest diamine. Low-temperature interstellar analog ices composed of ammonia and methylamine were exposed to energetic electrons which act as proxies for secondary electrons produced in the track of galactic cosmic rays. These experimental conditions, which simulate the conditions within cold molecular clouds, result in radical formation and initiate aminomethyl (ĊH₂NH₂) and amino ([Formula: see text]₂) radical chemistry. Exploiting tunable photoionization reflectron time-of-flight mass spectrometry (PI-ReToF-MS) to make isomer-specific assignments, methanediamine was identified in the gas phase upon sublimation, while its isomer methylhydrazine (CH₃NHNH₂) was not observed. The molecular formula was confirmed to be CH₆N₂ through the use of isotopically labeled reactants. Methanediamine is the simplest molecule to contain the NCN moiety and could be a vital intermediate in the abiotic formation of heterocyclic and aromatic systems such as nucleobases, which all contain the NCN moiety.

Spectroscopic evidence for 1,2-diiminoethane - a key intermediate in imidazole synthesis

Simple imines and diimines are common building blocks in organic synthesis, but the compound class is spectroscopically not well characterized. Herein we report the formation of the simplest diimine, namely 1,2-diiminoethane, as well as spectroscopic characterization by cryogenic matrix isolation IR and UV/Vis spectroscopy. Three conformers of 1,2-diiminoethane form after UV irradiation of 1,2-diazidoethane by N₂ extrusion at 3 K in solid argon and can be photochemically interconverted. In a matrix isolation pyrolysis experiment at 600 °C with 1,2-diazidoethane as the starting material we observe hydrogen cyanide and formaldimine as the main decomposition products. All experimental findings are supported by deuterium labeling experiments and B3LYP/6-311++G(2d,2p) calculations. Irradiation of 1,2-diazidoethane in aqueous solution leads to the formation of imidazoles as indicated by NMR spectroscopy and GC-MS analysis. Our results underline the key role of diimines as building blocks in N-heterocyclic chemistry.

Photo-Induced Reactions between Glyoxal and Hydroxylamine in Cryogenic Matrices

In this paper, the photochemistry of glyoxal−hydroxylamine (Gly−HA) complexes is studied using FTIR matrix isolation spectroscopy and ab initio calculations. The irradiation of the Gly−HA complexes with the filtered output of a mercury lamp (λ > 370 nm) leads to their photoconversion to hydroxyketene−hydroxylamine complexes and the formation of hydroxy(hydroxyamino)acetaldehyde with a hemiaminal structure. The first product is the result of a double hydrogen exchange reaction between the aldehyde group of Gly and the amino or hydroxyl group of HA. The second product is formed as a result of the addition of the nitrogen atom of HA to the carbon atom of one aldehyde group of Gly, followed by the migration of the hydrogen atom from the amino group of hydroxylamine to the oxygen atom of the carbonyl group of glyoxal. The identification of the products is confirmed by deuterium substitution and by MP2 calculations of the structures and vibrational spectra of the identified species.

Nanostructured silicate catalysts for environmentally benign Strecker-type reactions: status quo and quo vadis

Chemical processes are usually catalytic transformations. The use of catalytic reagents can reduce the reaction temperature, decrease reagent-based waste, and enhance the selectivity of a reaction potentially avoiding unwanted side reactions leading to green technology. Chemical processes are also frequently based on multicomponent reactions (MCRs) that possess evident improvements over multistep processes. Both MCRs and catalysis tools are the most valuable principles of green chemistry. Among diverse MCRs, the three-component Strecker reaction (S-3-CR) is a particular transformation conducive to the formation of valuable bifunctional building blocks (α-amino nitriles) in organic synthesis, medicinal chemistry, drug research, and organic materials science. To be a practical synthetic tool, the S-3-CR must be achieved using alternative energy input systems, safe reaction media, and effective catalysts. These latter reagents are now deeply associated with nanoscience and nanocatalysis. Continuously developed, nanostructured silicate catalysts symbolize green pathways in our quest to attain sustainability. Studying and developing nanocatalyzed S-3-CR condensations as an important model will be suitable for achieving the current green mission. This critical review aims to highlight the advances in the development of nanostructured catalysts for technologically important Strecker-type reactions and to analyze this progress from the viewpoint of green and sustainable chemistry.

The innovations in the development of nanostructured silicate catalysts for Strecker reactions are analyzed discussing the advantages and drawbacks of existing protocols based on the use of nanocatalytic systems for α-amino nitrile formation.