Reaction Of CH3O2 Research Articles

Computational Insights into SN 2 and Proton Transfer Reactions of CH3 O- with NH2 Y and CH3 Y.

Bimolecular nucleophilic substitution (SN 2) reactions have been extensively studied in both theory and experiment. While research on C-centered SN 2 reactions (SN 2@C) has been ongoing, SN 2 reactions at neutral nitrogen (SN 2@N) have received increased attention in recent years. To recommend methods for dynamics simulations, the comparison for the properties of the geometries, vibrational frequencies, and energies is done between MP2 and six DFT functional calculations and experimental data as well as the high-level CCSD(T) method for CH3 O- +NH2 Cl/CH3 Cl reactions. The relative energy diagrams at the M06 method for CH3 O- with CH3 Y/NH2 Y reactions (Y=F, Cl, Br, I) in the gas and solution phase are explored to investigate the effects of the leaving groups, different reaction centers, and solvents. We mainly focus on the computational of inv-SN 2 and proton transfer (PT) pathways. The PT channel in the gas phase is more competitive than the SN 2 channel for N-center reactions, while the opposite is observed for C-centered reactions. Solvation completely inhibits the PT channel, making SN 2 the dominant pathway. Our study provides new insight into the SN 2 reaction mechanisms and rich the novel reaction model in gas-phase organic chemistry.

The influence of monomolecular water and bimolecular water on BrO + CH2O reaction

The catalytic influence of water molecules on BrO + CH2O reaction was discussed through the investigation of mechanism and kinetics. The potential energy surfaces and dynamic properties of the BrO + CH2O reaction were investigated at the CCSD(T)/aug-cc-pVTZ//B3LYP/cc-pVTZ level. The reaction generates four different products, respectively, through four pathways without water and nine pathways with water. The results have shown that the generation of HCO + HOBr occupied the entire reaction without water. The rate constants were obtained by employing the KisThelP program based on the Transition State Theory with Wigner tunneling correction. This rate constants of the naked reaction are lower than that in the presence of monomolecular water and are higher than that in the presence of bimolecular water. The current calculations indicated that monomolecular water could accelerate the BrO + CH2O reaction, while bimolecular water could not accelerate the BrO + CH2O reaction. The effective rate constants (in the presence of monomolecular water and bimolecular water) are much lower than that of the naked reaction.

Kinetics of the cross‐reaction of CH3O2 + HO2 radicals measured in the Highly Instrumented Reactor for Atmospheric Chemistry

AbstractThe sensitive Fluorescence Assay by Gas Expansion (FAGE) method has been used to detect methyl peroxy (CH3O2) and hydroperoxyl (HO2) radicals after their conversion by titration with excess NO to methoxy (CH3O) and hydroxyl (OH) radicals, respectively, to study the kinetics of the reaction of CH3O2 + HO2 radicals. The rate coefficient of the reaction was measured in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) at 1000 mbar of synthetic air at T = 268–344 K, selectively detecting both radicals. Using a numerical model to fit both CH3O2 and HO2 radical temporal decays globally at each temperature investigated, rate coefficients for the reaction have been obtained. The room temperature rate coefficient was found to be kCH3O2 +HO2(295 K) = (4.6 ± 0.7) × 10−12 molecule−1 cm3 s−1 (2σ errors) and the temperature dependence of the rate coefficient can be characterized in Arrhenius form by kCH3O2 + HO2(268 K < T < 344 K) = (5.1 ± 2.1) × 10−13 × exp((637 ± 121)/T) cm3 molecule−1 s−1. The rate coefficients obtained here are 14%–16% lower than the literature recommended values with an uncertainty which is reduced significantly compared to previous reports.

Role of monomolecular water and bimolecular water in IO + CH2O reaction.

A CCSD(T)//B3LYP method was employed to research the influence of monomolecular and bimolecular water molecules on the IO + CH2O reaction. H-abstraction and addition/elimination mechanisms have been located, and the H-abstraction mechanism occupied the whole reaction without water. The introduction of water complicates the reaction, but the final product remains unchanged. Water molecules influence each reaction pathway in six different pathways with monomolecular water and two different pathways with bimolecular water, respectively. The present calculations manifested that water has a positive influence on the IO + CH2O reaction with monomolecular water molecule, and plays negative catalytic influence on the IO + CH2O reaction with bimolecular water molecule. The effective rate constants are much lower than the IO + CH2O reaction without water.

Numerical study on the effects of reaction conditions on single-particle char combustion in O2/H2O atmospheres

The distributions of temperature, reaction rate, and component concentration in char are significant for the stable char-O2/H2O combustion. Based on the single-particle char combustion numerical model in O2/H2O atmospheres, the present work quantitatively studied the effects of reaction conditions on distributions of temperature, reaction rate, and component concentration in char under O2/H2O conditions. The simulation results show that the char surface temperature is always higher than the center temperature in the heating stage. The H2O and O2 concentrations have little effect on the char heating time and heating rate. The char center temperature gradually exceeds the surface temperature after the heating stage, and this gap narrows with the rise in H2O concentration and the decrease in O2 concentration. The C-O2 and C-H2O reaction rates first increase and then decrease along the char radius, and the ratios of the C-H2O reaction rate gradually reduce along the radius. At 1373 K with 5 % O2/20 % H2O, the ratios are below 20 %. The ratios increase significantly with the rise of temperature to 1673 K, especially in the char center, more than 70 %. The H2O and O2 concentrations in char are higher on the surface than in the center. However, the CO and H2 concentrations show the opposite characteristics, and the distribution of CO2 is highly uniform in char. The char-O2/H2O reaction gradually shifts to the diffusion controlled regime with the rise in temperature and O2 concentration, while it slowly turns to the chemical kinetic controlled regime with the increase in H2O concentration.

First Experimental Confirmation of the CH3O + H2CO → CH3OH + HCO Reaction: Expanding the CH3OH Formation Mechanism in Interstellar Ices

The successive addition of H atoms to CO in the solid phase has been hitherto regarded as the primary route to form methanol in dark molecular clouds. However, recent Monte Carlo simulations of interstellar ices alternatively suggested the radical-molecule H-atom abstraction reaction CH3O + H2CO → CH3OH + HCO, in addition to CH3O + H → CH3OH, as a very promising and possibly dominating (70%–90%) final step to form CH3OH in those environments. Here, we compare the contributions of these two steps leading to methanol by experimentally investigating hydrogenation reactions on H2CO and D2CO ices, which ensures comparable starting points between the two scenarios. The experiments are performed under ultrahigh vacuum conditions and astronomically relevant temperatures, with H:H2CO (or D2CO) flux ratios of 10:1 and 30:1. The radical-molecule route in the partially deuterated scenario, CHD2O + D2CO → CHD2OD + DCO, is significantly hampered by the isotope effect in the D-abstraction process, and can thus be used as an artifice to probe the efficiency of this step. We observe a significantly smaller yield of D2CO + H products in comparison to H2CO + H, implying that the CH3O-induced abstraction route must play an important role in the formation of methanol in interstellar ices. Reflection-absorption infrared spectroscopy and temperature-programmed desorption-quadrupole mass spectrometry analyses are used to quantify the species in the ice. Both analytical techniques indicate constant contributions of ∼80% for the abstraction route in the 10–16 K interval, which agrees well with the Monte Carlo calculations. Additional H2CO + D experiments confirm these conclusions.

Probing the Exit Channel of the OH + CH3OH → H2O + CH3O Reaction by Photodetachment of CH3O-(H2O).

Transition state dynamics of bimolecular reactions can be probed by photodetachment of a precursor anion when the Franck-Condon region of the corresponding neutral potential energy surface is near a saddle point. In this study, photodetachment of anions at m/z = 49 enabled investigation of the exit channel of the OH + CH3OH → H2O + CH3O reaction using photoelectron-photofragment coincidence spectroscopy. High-level coupled-cluster calculations of the stationary points on the anion surface show that the methoxide-water cluster CH3O-(H2O) is the stable minimum on the anion surface. Photodetachment at a 3.20 eV photon energy leads to long-lived H2O(CH3O) complexes and H2O + CH3O products consistent with both direct dissociative photodetachment and resonance mediated processes on the neutral surface. The partitioning of total kinetic energy in the system indicates that water stretch and bend excitation is induced in dissociative photodetachment and evidence for long-lived complexes consistent with vibrational Feshbach resonances is reported.

Numerical investigation on the heterogeneous pulsed dielectric barrier discharge plasma catalysis for CO2 hydrogenation at atmospheric pressure: Effects of Ni and Cu catalysts on the selectivity conversions to CH4 and CH3OH

AbstractThe simulation model of the pulsed dielectric barrier discharge plasma catalytic CO2 hydrogenation is established to numerically investigate the effects of Ni and Cu catalysts on the selectivity conversions to CH4 and CH3OH. Under plasma without catalyst, the electron impact CO2 and CO produce CO and C, and then stepwise hydrogenations of CO and C generate CH3OH and CH4. Under plasma with Ni catalyst, Langmuir–Hinshelwood (LH) reactions mainly form the CHx(s) and Eley–Rideal (ER) reaction CH3(s) + H → CH4 are the key paths of CH4 synthesis. Under plasma with Cu catalyst, the intermediate CH3O(s) is principally produced by the LH reaction between CH2O(s) and H(s), followed by the ER reaction CH2O(s) + H → CH3O(s). While CH3OH(s) is mainly produced by the ER reaction CH3O(s) + H → CH3OH(s), CH3O(s) + H(s) → CH3OH(s) + S is a rate‐limiting step owing to the higher reaction energy barrier.

Adsorption and catalysis of Bi-doped Fe2O3 on gas products of HMX decomposition: A DFT study

To clarify the role of Bi-doped Fe2O3(001) in the decomposition process of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX), the effect of Bi-Fe2O3(001) on the gas products of HMX(NO, NO2, N2O, H2O, CH2O) was emphatically investigated using density functional theory (DFT) calculation. The adsorption configuration, energy, electronic properties and possible reactions of gas products were considered. All of these gases are adsorbed on the Fe-top site of Bi-Fe2O3 surface in molecular form, resulting in the orbital hybridization and electron transfer. NO2 and CH2O interacting with Bi are of higher adsorption energy comparing with gas adsorbed on pure Fe2O3(001). Since the reaction of NO2 with CH2O and the dissociation of NO2 play an important role in the subsequent decomposition of HMX, the effects of Bi doping on these two reactions were investigated. TS search shows that the activation energy of these two reactions are all decreased on Bi-Fe2O3 surface, which may accelerate the consumption of NO2, indicating that Bi doping can promote the reaction of NO2 and CH2O, thus accelerating the subsequent decomposition of HMX.

Study on the reaction mechanism of CH2O + NO2 transformed by PbO/SnO in double-base propellants through theoretical calculation and experiment

The reaction of CH2O and NO2 plays an important role in the combustion of double-base propellants, the mechanism about the influence of PbO (SnO) on this reaction is still unclear. In this paper, we obtained the product PbCH2O2 (SnCH2O2) through DFT calculations. After wavefunction analysis (MBO, LMOs, ESP et al.), we not only deeply understood the properties of PbCH2O2 (SnCH2O2), but also realized that the introduction of heavy metals (Pb, Sn) will greatly increase the van der Waals interaction and electrostatic interaction. The calculations of reaction thermodynamics and reaction kinetics indicated that PbO (SnO) can obviously reduce the Gibbs free energy barrier and increase the reaction rate. The burning rate shown the positive correlation with the results of thermodynamics and kinetics. The analysis of the combustion residue showed that the elemental Pb (Sn) produced on the surface, which may be related to the further decomposition of PbCHO2 (SnCHO2) and also reveal a transformation cycle of PbO(SnO)-Pb(Sn). The RSFT-IR analysis of the double-base absorbent powder not only proved that the existence of PbO (SnO) could reduce the decomposition temperature of the absorbent, but also indicated that the existence of PbCH2O2 (SnCH2O2) and PbNO2 (SnNO2). Combining with the theoretical calculations and experiments, we established a reaction process about the cyclic catalysis of PbO (SnO) in double-base propellants. And more importantly, the effect of the metals with higher density and larger radius in double-base propellants deserves more attention.

Active site structure and methane oxidation reactivity of bimetallic Pd and Pt nanoparticles

Kinetic, oxygen uptake, microscopic, and spectroscopic studies shed light on the structural dynamics of PdPt bimetallic catalysts and their methane oxidation rates. Reductive treatments lead to Pd0Pt0 nanoparticles distributed in sizes and Pt:Pd ratios. Oxidative treatments, including treatments in CH4-O2 reaction mixture, lead the Pd, as the more oxophilic metal, to migrate onto the surfaces and undergo bulk oxidation, forming a thin PdO shell covering the underneath Pt-rich core. Residing on the PdO shell are Pd2+-O2− site pairs that are highly effective for C–H activation in methane—the CH4 turnover rates are the highest at 0.3 Pt:Pd ratio and the C–H activation barrier decreases from 64 to 37 kJ mol−1 as the Pt:Pd ratio increases from 0 to 1. H2O and SO2 impurities increase the effective barrier to 58 and 116 kJ mol−1, respectively, but such effects remain much smaller than on unpromoted PdO.

Printed sensor labels for colorimetric detection of ammonia, formaldehyde and hydrogen sulfide from the ambient air

We present a novel method to monitor the exposure to toxic gases in ambient air based on a visible color change of a colorimetric gas sensor, which can be evaluated by the camera of a smartphone, stationary reader or even naked eye. This sensor consists of a disposable paper tag or plastic card and a gas sensitive material, which has been deposited by a screen-printing process. The integration of the gas sensitive layer into the machine-readable pattern of a QR-like code that incorporates color references for color calibration; makes it suitable for quantitative as well as illumination and camera independent evaluation of the color change due to the reaction with the target gas. This work focusses on the development of printable pastes for the detection of ammonia (NH3), formaldehyde (CH2O) and hydrogen sulfide (H2S) for the application in a colorimetric sensor label. NH3 and CH2O are detected with commercially available pH sensitive color dyes. The alkaline gas NH3 is tracked by the reaction with a pH indicator directly, while CH2O is detected by an intermediate reaction of CH2O with a primary amine through nucleophilic addition. For the detection of H2S, an immobilized copper(II) complex of the azo dye 1-(2-pyridylazo)-2-naphtol (H-PAN) is synthesized. The color change of the printed sensors labels is characterized by the evaluation of RGB values taken with an in-situ readout station using a smartphone camera.

Experimental and Numerical Study of the Effect of CO2 Replacing Part of N2 present in Air on CH4 Premixed Flame Characteristics Using a Reduced Mechanism.

The effect of CO2, which replaces part of N2 present in air, on flame stability, laminar burning velocities (LBVs), and intermediate radicals (O OH) of CH4/O2/N2/CO2 premixed flames has been analyzed using detailed experiments and numerical studies. The numerical simulations were conducted using the PREMIX code with a detailed chemical reaction mechanism (GRI-Mech 3.0) and a reduced mechanism (39 species and 205 reactions) based on GRI-Mech 3.0 over a wide range of equivalence ratios (Φ = 0.7–1.3) and CO2 substitution ratios (0–30%). The reduced mechanism showed a good agreement with the other detailed mechanisms and experimental data. The experimental and numerical results showed that the substitution of CO2 diminishes the stability of the flame, and the flame blow-out speed is significantly reduced (the substitution ratio is 0–30%, and the corresponding flame blow-out velocity is 5.2–2.5 m/s). In addition, CO2 inhibits the LBV of the flame owing to the decrease of O and OH mole fractions. It not only accelerates the consumption of these two free radicals but also inhibits the generation of these two free radicals. Further analysis concluded that the substituted CO2 has the greatest influence on the LBV sensitivity coefficient of the HO2 + CH3 = OH + CH3O reaction.

Experimental and kinetic modeling study of methyl heptanoate low-temperature oxidation in a jet-stirred reactor

Methyl heptanoate (MHP) is a potential surrogate component for fatty acid methyl esters found in biodiesel. The carbon chain length of MHP is long enough to enable low temperature (low-T) reactivity and negative temperature coefficient oxidation behavior during the combustion experiments, similar to the real biodiesel fuels. This paper investigated the low-T oxidation of MHP at 780 Torr and equivalence ratios of 0.5, 1.0 and 1.5 in a jet-stirred reactor. Detailed speciation profiles of fuel, intermediates and products were obtained using synchrotron vacuum ultraviolet photoionization mass spectrometry. A comprehensive kinetic model with 779 species and 3594 reactions was developed and validated against the new experimental data. Model analysis indicated that the dominant reaction pathways for MHP consumption were H-abstraction reactions by radicals of OH, HO2 to produce MHP radicals under all experimental conditions. In this low-T oxidation region, O2 addition reactions were responsible for the consumption of MHP radicals. The formation pathways of unsaturated methyl esters were strongly related to the decomposition of cyclic ethers. Furthermore, the formations of CH3OOH and C2H5OOH were closely linked to the reactions of CH3O2 and C2H5O2 as well as the radicals of CH2O and HO2. This work provides detailed information relevant to low-T biodiesel oxidation chemistry and guidance for the application of biodiesel in internal combustion engines.

Explicit modeling of background HCHO formation in southern China

Abstract Formaldehyde (HCHO) is an abundant carbonyls and plays important roles in ozone formation and atmospheric oxidizing capacity. To better understand the formation mechanisms of HCHO and its effects on ozone formation, carbonyl compounds were measured at a regional background site of Hong Kong from 20 August to 22 December 2012. Among the total observed carbonyls, Formaldehyde (HCHO, 2.00 ± 1.04 ppbv) presents the most abundant concentration and plays the most important role in OH removal with LOH value of 0.47 s−1. To further dissect the secondary formation mechanism of HCHO at Hok Tsui, detailed modeling analyses were conducted by the OBM-AOCP model for two cases with different meteorological conditions. The result shows that HCHO production was dominated by the reactions of CH3O + O2, and RO + O2 (first-generation precursor of RO was Alkenes). The HCHO destruction pathways during two cases were governed by the reactions with OH and photolysis. The net generation rate of HCHO was controlled by meteorological conditions with alkenes (mainly ethylene (C2H4) and propylene (C3H6)) being the dominant parent hydrocarbons of HCHO. Overall, this study provides some new insights into the formation mechanisms of HCHO, especially their parent hydrocarbon species, underlines the important role of carbonyls in ozone pollution in Hok Tsui. Reducing the emissions of alkenes would be an effective way to mitigate photochemical pollution in the background atmosphere of China.

Measurements of Low Temperature Rate Coefficients for the Reaction of CH with CH2O and Application to Dark Cloud and AGB Stellar Wind Models

Abstract Rate coefficients have been measured for the reaction of CH radicals with formaldehyde, CH2O, over the temperature range of 31–133 K using a pulsed Laval nozzle apparatus combined with pulsed laser photolysis and laser-induced fluorescence spectroscopy. The rate coefficients are very large and display a distinct decrease with decreasing temperature below 70 K, although classical collision rate theory fails to reproduce this temperature dependence. The measured rate coefficients have been parameterized and used as input for astrochemical models for both dark cloud and Asymptotic Giant Branch stellar outflow scenarios. The models predict a distinct change (up to a factor of two) in the abundance of ketene, H2CCO, which is the major expected molecular product of the CH + CH2O reaction.

Mechanistic Insights into Methane Oxidation by Molecular Oxygen under Photoirradiation: Controlled Radical Chain Reactions

Abstract The selective oxidation of CH4 using O2 is one of the most attractive subjects as an elusive target reaction. Ohkubo and Hirose recently reported that chlorine dioxide radical (ClO2•), which is generated by mixing NaClO2 and HCl in an aqueous solution, acts as an efficient oxidant in the oxidation of CH4 to CH3OH and HCOOH under photoirradiation in the two-phase system of perfluorohexane and water (Angew. Chem., Int. Ed. 2018, 57, 2126). The reaction system gives CH3OH and HCOOH without further oxidation products. They proposed that methoxy radical (CH3O•) plays an important role as an intermediate in the oxidation of CH4. In the present work, we focus on the reactivity of CH3O• to CH4 in detail to propose a reasonable radical mechanism for the oxidation of CH4 using DFT calculations at the M06-2X/6-311+G** level of theory and UCCSD(T)/6-311+G** calculations. Our reaction analysis suggests that the reaction of CH3O• with CH4 and the disproportionation of CH3O• take place as CH4 + CH3O• → CH3• + CH3OH and 2CH3O• → CH3OH + HCHO, respectively. In contrast, the isomerization from CH3O• to CH2•(OH), suggested by Ohkubo and Hirose, is unlikely to occur under ambient conditions, due to the high activation barrier for this reaction. A better understanding of the well-controlled radical chain reactions is useful for reaction design of the hydroxylation of methane.

Initial-stage reaction of methane examined by optical measurements of weak flames in a micro flow reactor with a controlled temperature profile

To examine methane oxidation at intermediate temperatures (ca., 900–1200 K), chemiluminescence observation and laser-induced fluorescence (LIF) measurements for CH2O and OH were conducted for methane weak flames in a micro flow reactor with a controlled temperature profile (MFR) at atmospheric and elevated pressures. Locations of CH2O–LIF, chemiluminescence, and OH-LIF in MFR were arranged from the low temperature side at 1.0 and 5.0 bar. Spatial separation of methane oxidation was successfully demonstrated. One-dimensional computations with five detailed kinetic mechanisms were conducted. Computational profiles of CH2O molar concentration, heat release rate (HRR), and OH molar concentration normalized by their own peak values were compared with experimentally obtained intensity profiles of the CH2O–LIF, chemiluminescence, and OH-LIF. Computational results obtained with AramcoMech 1.3 showed better agreements with experimentally obtained results among the mechanisms employed. However, the flame position computed with AramcoMech 1.3 showed a slightly higher temperature region than the experimental flame position, indicating underprediction of methane reactivity. Sensitivity analysis identified a set of dominant reactions for weak flame positions. Rate constants of the identified reactions were modified within uncertainty to reproduce experimentally obtained weak flame positions. The modified mechanism also well predicted ignition delay times and flame speeds, and significant improvement of prediction was identified particularly for ignition delay times of lowest temperature and pressure investigated. Reaction path analysis highlighted the importance of intermediate-temperature oxidation chemistry for methane such as CH3→CH3O2→CH3O→CH2O reactions at higher pressures. Two-stage oxidation of methane was observed by chemiluminescence observation and numerical simulations at higher pressures (6.0–10.0 bar).

Quantum dynamical investigation of product state distributions of the F + CH3OH → HF + CH3O reaction via photodetachment of the F-(HOCH3) anion.

The photodetachment of the F-(HOCH3) anion, which sheds light on the post-transition-state dynamics of the F + CH3OH → HF + CH3O reaction, is investigated using a reduced-dimensional quantum wave packet method on ab initio based potential energy surfaces for both the neutral and anionic species. The detachment of an electron in the anion precursor produces both bound and resonance species in a hydrogen-bonded potential well in the product channel, in qualitative agreement with the photoelectron-photofragment coincidence (PPC) spectrum. The measured photoelectron-photofragment coincidence spectroscopy is reproduced by the quantum calculations. Our results indicated that the HF product is vibrationally excited, while the OCH3 product is internally cold, thus providing unambiguous assignments of the experimental spectrum.

Rapid Acceleration of Hydrogen Atom Abstraction Reactions of OH at Very Low Temperatures through Weakly Bound Complexes and Tunneling.

A generally accepted principle of chemical kinetics is that a reaction will be very slow at low temperatures if there is an activation barrier on the potential energy surface to form products. However, this Account shows that the reverse is true for gas-phase hydrogen abstraction reactions of the hydroxyl radical, OH, with organic molecules with which it can form a weakly bound (5-30 kJ mol-1) hydrogen-bonded complex. For hydrogen atom abstraction reactions of OH with volatile organic compounds (VOCs) containing alcohol, ether, carbonyl, and ester functional groups, the reaction accelerates rapidly at very low temperatures, with rate coefficients, k, that can be up to a 1000 times faster than those at room temperature, despite the barrier to products. The OH radical is a crucial intermediate in Earth's atmosphere, combustion processes, and the chemistry of the interstellar medium, where temperatures can reach as low as 10 K, so this behavior has very important implications for gas-phase chemistry in space. The key point is that at low temperatures the lifetime of the OH-VOC complex against re-dissociation back to reactants becomes much longer, and hence the probability of quantum mechanical tunneling under the reaction barrier to form products becomes much higher. These observations were made possible by using Laval nozzles to generate uniform supersonic flows at extremely low temperatures so that condensation of the reagents at reactor walls is avoided. In this Account, the use of laser flash-photolysis combined with laser-induced fluorescence spectroscopy within Laval flows is described to study the unusual kinetics of this type of reaction at temperatures down to 21 K and demonstrate the rapid upturn in the rate coefficient. For the reaction of OH with CH3OH, further evidence for the precomplex and tunneling mechanism comes from observation of the CH3O reaction product at very low temperatures, despite it being formed over the higher barrier to reaction. The experimental observations are supported by theoretical calculations using the MESMER master equation package to calculate k( T) and product yields as a function of temperature and which make use of potential energy surfaces determined using ab initio methods. The CH3O product is formed over a narrower barrier with a larger imaginary frequency and is calculated to be the sole product at very low temperatures. The kinetics of the OH reaction with CH3OH were measured to be independent of pressure, consistent with a tunneling mechanism rather than any collisional stabilization of the prereactive complex. In this Account, we collate available kinetic data and show that this newly discovered mechanism for H atom transfer reactions appears to be generally applicable for reactions of OH with organic molecules containing oxygenated functional groups, which have been observed in space by radio-astronomy. Rather than being ignored for a range of interstellar environments, these OH reactions are now being included in chemical networks in space and have been shown to significantly influence the abundance of OH, the organic molecules themselves, and reaction products and provide novel routes to forming even more complex functional groups, for example, precursors to prebiotic molecules.