Kinetic and Mechanistic Study of the Thermal Decomposition of Ethyl Nitrate

Thermal decomposition of ethyl nitrate (ENT; CH₃CH₂ONO₂) has been studied in a low‐pressure flow reactor combined with a quadrupole mass spectrometer. The rate constant of the nitrate decomposition was measured as a function of pressure (1–12.5 Torr of helium) and temperature in the range 464–673 K using two different approaches: from kinetics of ENT loss and those of the formation of the reaction product (CH₃ radical). The fit of the observed falloff curves with two‐parameter expression provided the following low‐ and high‐pressure limits for the rate constant of ENT decomposition: k ₀ = 1.0 × 10⁻⁴ exp(−16,400/T ) cm³ molecule⁻¹ s⁻¹ and k _∞ = 1.08 × 10¹⁶ exp(−19,860/T ) s⁻¹, respectively, which allow to reproduce (via above expression and with 20% uncertainty) all the experimental data obtained for k ₁ in the temperature and pressure range of the study. It was observed that the initial step of the thermal decomposition of ethyl nitrate is O–NO₂ bond cleavage leading to formation of NO₂ and CH₃CH₂O radical, which rapidly decomposes to form CH₃ and formaldehyde as final products. The yields of NO₂, CH₃, and formaldehyde upon decomposition of ethyl nitrate were measured to be near unity. In addition, the kinetic data were used to determine the O–NO₂ bond dissociation energy in ENT: 38.3 ± 2.0 kcal mol⁻¹.     

Bond length of perchlorate at different temperatures: X‐ray and neutron comparison

The averages (average deviations from the mean are given in square brackets) of uncorrected Cl—O bond distances in a perchlorate anion from an X‐ray diffraction analysis of (N‐{2‐[bis(pyridin‐2‐ylmethyl)amino]ethyl}pyridine‐2‐carboxamidato)(nitric oxide)manganese perchlorate acetonitrile disolvate, [Mn(C₂₀H₂₀N₅O)(NO)]ClO₄·2CH₃CN or [Mn(PaPy₃)(NO)]ClO₄·2CH₃CN, decrease from 1.447 [4] Å at 10 K to 1.428 [4] Å at 170 K. The 10 K value is close to the neutron value (1.441 [1] Å) at 18 K. Comparisons are made with a second X‐ray study at 30 K [1.444 (8) Å] and to libration‐corrected, density functional theory (DFT), and Cambridge Structural Database (CSD) values.     

Atmospheric chemistry of acetone: Kinetic study of the CH3C(O)CH2O2+NO/NO2 reactions and decomposition of CH3C(O)CH2O2NO2

Pulse radiolysis was used to study the kinetics of the reactions of CH₃C(O)CH₂O₂ radicals with NO and NO₂ at 295 K. By monitoring the rate of formation and decay of NO₂ using its absorption at 400 and 450 nm the rate constants k(CH₃C(O)CH₂O₂+NO)=(8±2)×10⁻¹² and k(CH₃C(O)CH₂O₂+NO₂)=(6.4±0.6)×10⁻¹² cm³ molecule⁻¹ s⁻¹ were determined. Long path length Fourier transform infrared spectrometers were used to investigate the IR spectrum and thermal stability of the peroxynitrate, CH₃C(O)CH₂O₂NO₂. A value of k₋₆≈3 s⁻¹ was determined for the rate of thermal decomposition of CH₃C(O)CH₂O₂NO₂ in 700 torr total pressure of O₂ diluent at 295 K. When combined with lower temperature studies (250–275 K) a decomposition rate of k₋₆=1.9×10¹⁶ exp (−10830/T) s⁻¹ is determined. Density functional theory was used to calculate the IR spectrum of CH₃C(O)CH₂O₂NO₂. Finally, the rate constants for reactions of the CH₃C(O)CH₂ radical with NO and NO₂ were determined to be k(CH₃C(O)CH₂+NO)=(2.6±0.3)×10⁻¹¹ and k(CH₃C(O)CH₂+NO₂)=(1.6±0.4)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The results are discussed in the context of the atmospheric chemistry of acetone and the long range atmospheric transport of NO_x. © John Wiley & Sons, Inc. Int J Chem Kinet: 30: 475–489, 1998     

Manganese(II) and cobalt(II) complexes of 1,4‐bis(diphenylphosphinoyl)butane

The title complexes, catena‐poly[[[diaquadiethanolmanganese(II)]‐μ‐1,4‐bis(diphenylphosphinoyl)butane‐κ²O:O′] dinitrate 1,4‐bis(diphenylphosphinoyl)butane solvate], {[Mn(C₂H₆O)₂(C₂₈H₂₈O₂P₂)(H₂O)₂](NO₃)₂·C₂₈H₂₈O₂P₂}_n, (I), and catena‐poly[[[diaquadiethanolcobalt(II)]‐μ‐1,4‐bis(diphenylphosphinoyl)butane‐κ²O:O′] dinitrate 1,4‐bis(diphenylphosphinoyl)butane solvate], {[Co(C₂H₆O)₂(C₂₈H₂₈O₂P₂)(H₂O)₂](NO₃)₂·C₂₈H₂₈O₂P₂}_n, (II), are isostructural and centrosymmetric, with the M^II ions at centres of inversion. The coordination geometry is octahedral, with each metal ion coordinated by two trans ethanol molecules, two trans water molecules and two bridging 1,4‐bis(diphenylphosphinoyl)butane ligands which link the coordination centres to form one‐dimensional polymeric chains. Parallel chains are linked by hydrogen bonds to uncoordinated 1,4‐bis(diphenylphosphinoyl)butane molecules, which are bisected by a centre of inversion. Further hydrogen bonds, weak C—H...O interactions to nitrate anions, and weak C—H...π interactions serve to stabilize the structure. This study reports a development of the coordination chemistry of bis(diphenylphosphinoyl)alkanes, with the first reported structures of complexes of the first‐row transition metals with 1,4‐bis(diphenylphosphinoyl)butane.     

Thermische Zerfallsreaktionen von Nitroverbindungen I: Dissoziation von Nitromethan

The thermal decomposition of CH₃NO₂ highly diluted in Ar has been studied in shock waves at 900 < T < 1500 K and 1.5 · 10^?5 < [Ar] < 3.5 · 10^?4 mol/cm³. Concentration profiles of CH₃NO₂ and NO₂ were recorded. The unimolecular reaction was found to be in its fall-off range. Limiting low pressure rate constants of k₀ = [Ar] · 10^17.1 exp(?42(kcal/mol)/RT) cm³/ mol sec in the range 900 < T < 1400 K and limiting high pressure rate constants of k_∞ = 10^16.25 exp (?(58.5 ± 0.5 kcal/mol)/RT) sec^?1 have been derived. A rate constant of 1.3 · 10¹³ cm³/mol sec was found for the first subsequent reaction CH₃+NO₂ → CH₃O+NO.     

Four 1D and 2D Cadmium(II) Complexes Based on Different Anions and Two Modified Bipyridyl Ligands: Syntheses,Structures, Thermogravimetric,and Fluorescent Properties

A series of cadmium(II) coordination polymers constructed from 1, 3‐bis(pyridine‐3‐carbonyl)imidazolidin‐2‐thioxo (3‐bpit) and 1, 3‐bis(pyridine‐4‐carbonyl)imidazolidin‐2‐thioxo (4‐bpit), namely,{[Cd(SCN)₂(3‐bpit)₂] · 2(CH₃OH)}_n ( 1 ), {[Cd(NO₃)₂(3‐bpit)₂] · 2(CH₃OH)}_n( 2 ), [CdI₂(4‐bpit)]_n ( 3 ), and [CdCl₂(4‐bpit)₄]_n ( 4 ) were prepared and characterized by single‐crystal X‐ray diffraction. Complexes 1 and 2 display different types of infinite 1D helical chain structures, both of which contain 24‐membered metallocyclic rings. Complex 3 is composed of 1D zigzag chains, which further form a 3D supramolecular architecture by weak C–H ··· S and S ··· I interactions. Complex 4 also features a 3D supramolecular network assembled from 2D rhombus‐shaped layer through intermolecular hydrogen bonding. These structures indicate that the conformation of the ligand and the diverse anions take important roles in the formation of different frameworks. Thermogravimetric and fluorescent properties over complexes are also discussed.     

Thermal Stability of n‐Acyl Peroxynitrates

Peroxynitrates (RO₂NO₂), in particular acyl peroxynitrates (R = R′C(O) with R′ = alkyl), are prominent constituents of polluted air. In this work, a systematic study on the thermal decomposition rate constants of the first five members of the series of homologous R′C(O)O₂NO₂ with R′ = CH₃ ( =PAN), C₂H₅, n‐C₃H₇, n‐C₄H₉, and n‐C₅H₁₁ is undertaken to verify the conclusions from previous laboratory data (Grosjean et al., Environ. Sci. Technol. 1994, 28, 1099–1105; Grosjean et al., Environ. Sci. Technol. 1996, 30, 1038–1047; Bossmeyer et al., Geophys. Res. Lett. 2006, 33, L18810) that the longer chain peroxynitrates may be considerably more stable than PAN. Experiments are performed in a temperature‐controlled, evacuable 200 L‐photoreactor made from quartz. n‐Acyl peroxynitrates are generated by stationary photolysis of mixtures of molecular bromine, O₂, NO₂, and the corresponding parent aldehydes, highly diluted in N₂. Thermal decomposition of R′C(O)O₂NO₂ is initiated by the addition of an excess of NO. First‐order decomposition rate constants k₁ of the reactions R′C(O)O₂NO₂ (+M) → R′C(O)O₂ + NO₂ (+M) are derived at 298 K and a total pressure of 1 bar from the measured loss rates of R′C(O)O₂NO₂, correcting for wall loss of R′C(O)O₂NO₂ and several percentages of reformation of R′C(O)O₂NO₂ by the reaction of R′C(O)O₂ radicals with NO₂. With increasing chain length of R′, k₁(298 K) slightly decreases from 4.4 × 10^?4 s^?1 (R′ = CH₃) to 3.7 × 10^?4 s^?1 (R′ = C₂H₅), leveling off at (3.4 ± 0.1) × 10^?4 s^?1 for R′ = n‐C₃H₇, n‐C₄H₉, and n‐C₅H₁₁. Temperature dependencies of k₁ were measured for CH₃C(O)O₂NO₂ and n‐C₅H₁₁C(O)O₂NO₂ in the temperature range 289–308 K, resulting in the same activation energy within the statistical error limits (2σ) of 0.9 and 1.5 kJ mol^?1, respectively. A few experiments on n‐C₆H₁₃C(O)O₂NO₂, n‐C₇H₁₅C(O)O₂NO₂, and n‐C₈H₁₇C(O)O₂NO₂ were also performed, but the results were considered to be unreliable due to strong wall loss of the peroxynitrate and possible complications caused by radical‐sinitiated side reactions.     

Computational study of the reaction of the methylsulfonyl radical,CH3S(O)2, with NO2

The mechanism of the reaction between the methylsulfonyl radical, CH₃S(O)₂, and NO₂ is examined using density functional theory and ab initio calculations. Two stable association intermediates, CH₃SNO₂ and CH₃S(O)ONO, may be formed through the attack of the nitrogen or the oxygen atom of NO₂ radical to the S atom. Interisomerization and decomposition of these intermediates are investigated using high level energy methods and specifically, CCSD(T), CBS‐QB3, and G3//B3LYP. The computational investigation indicates that the lowest energy reaction pathway leads to the products CH₃S(O)₃ + NO, through the decomposition of the most stable association adduct CH₃S(O)ONO. This result fully supports the relevant assumption of Ray et al. (Ray et al., J. Phys. Chem. 1996, 100, 8895], on which the experimental evaluation of the rate constant was based, namely that CH₃S(O)₃ + NO are the most probable products of the reaction CH₃S(O)₂ + NO₂. © 2014 Wiley Periodicals, Inc.     

Rate constants for the reaction of ground-state oxygen atoms with methanol from 297 to 544 K

The rate constant for the reaction of ground-state oxygen atoms with methanol has been determined between 297 and 544 K by a phase-shift technique using mercury photosensitized decomposition of N₂O to generate oxygen atoms. The relative oxygen atom concentration was monitored by the chemiluminescence from the reaction of oxygen atoms with nitric oxide. The results are accommodated by the Arrhenius expression k₁ = (9.79 ± 2.71) × 10¹² exp[(?2267 ± 111)/T]cm³/mol·s, where the indicated uncertainties are 95% confidence limits for 10 degrees of freedom. As an incidental part of this work, the third-body efficiency of CH₃OH relative to N₂O for the reaction O + NO + M → NO₂ + M (M = CH₃OH) was determined to be 3.1 at 298 K.     

Kinetics for the hydrogen‐abstraction of CH4 with NO2

The detailed mechanism of the NO₂+CH₄ reaction has been computationally investigated at the M06‐2X/MG3S, B3LYP/6‐311G(2d,d,p), and MP2/6‐311+G(2df,p) levels. The direct dynamics calculations were preformed using canonical transition state theory with tunneling correction and scaled generalized normal‐mode frequencies including anharmonic torsion. The calculated results indicate that the NO₂+CH₄ reaction proceeds by three distinct channels simultaneously, leading to the formation of trans‐HONO (1a), cis‐HONO (1b), and HNO₂ (1c), and each channel involves the formation of intermediate having lower energy than the final product. The anti‐Hammond behavior observed in channel 1a is well analyzed. Proper treatment of anharmonic torsions about the C···H···O (or N) axis in the transition structures greatly improves the accuracy of kinetics predictions. The activation energy for each channel increases substantially with temperature, but is not strictly a linear function of temperature. Therefore, the thermal rate constants are fitted to the four‐parameter expression recommended for this case over the wide temperature range 400–4000 K. © 2012 Wiley Periodicals, Inc.     

Ab initio and DFT Study of the Structural Properties and Thermochemistry of CH3S(O)2OONO2 Atmospheric Molecule and CH3S(O)2OO· Radical

The conformational properties of methanesulfonyl peroxynitrate, CH₃S(O)₂OONO₂ (MSPN), and its radical decomposition products CH₃S(O)₂OO· and CH₃S(O)₂O· were studied by ab initio and density functional methods. The dihedral angle around the S–O and the O–O single bond are calculated to be ?70.5° and ?97.8° (B3LYP/6‐311++G(3df,3pd)), respectively. The principal unimolecular dissociation pathways for MSPN were studied using complete basis set (CBS) methods. The reaction enthalpies for the channels CH₃S(O)₂OONO₂→ CH₃S(O)₂OO·+NO₂ and CH₃S(O)₂OONO₂→CH₃S(O)₂O·+NO₃ were computed to be 111.0 and 140.9 kJ/mol, respectively. The enthalpies of formation at 298 K for MSPN and CH₃S(O)₂OO radical were predicted to be ?358.2 and ?281.3 kJ/mol, respectively.     

Two‐dimensional square‐grid frameworks formed by self‐associating copper(II) complexes with 1‐(3‐pyridyl)‐ and 1‐(4‐pyridyl)‐substituted butane‐1,3‐diones

In bis­[1‐(3‐pyridyl)butane‐1,3‐dionato]copper(II) (the Cu atom occupies a centre of inversion), [Cu(C₉H₈NO₂)₂], (I), and bis­[1‐(4‐pyridyl)butane‐1,3‐dionato]copper(II) methanol solvate, [Cu(C₉H₈NO₂)₂]·CH₃OH, (II), the O,O′‐chelating diketonate ligands support square‐planar coordination of the metal ions [Cu—O = 1.948 (1)–1.965 (1) Å]. Weaker Cu⋯N inter­actions [2.405 (2)–2.499 (2) Å], at both axial sides, occur between symmetry‐related bis­(1‐pyridylbutane‐1,3‐dion­ato)copper(II) mol­ecules. This causes their self‐organization into two‐dimensional square‐grid frameworks, with uniform [6.48 Å for (I)] or alternating [4.72 and 6.66 Å for (II)] inter­layer separations. Guest methanol mol­ecules in (II) reside between the distal layers and form weak hydrogen bonds to coordinated O atoms [O⋯O = 3.018 (4) Å].     

Determination of the isomerization rate constant HOCH2CH2CH2CH(OO·)CH3 →HOC·HCH2CH2CH(OOH)CH3. Importance of intramolecular hydroperoxy isomerization in tropospheric chemistry

The rate constant of the title reaction is determined during thermal decomposition of di-n-pentyl peroxide C₅H₁₁O( )OC₅H₁₁ in oxygen over the temperature range 463–523 K. The pyrolysis of di-n-pentyl peroxide in O₂/N₂ mixtures is studied at atmospheric pressure in passivated quartz vessels. The reaction products are sampled through a micro-probe, collected on a liquid-nitrogen trap and solubilized in liquid acetonitrile. Analysis of the main compound, peroxide C₅H₁₀O₃, was carried out by GC/MS, GC/MS/MS [electron impact EI and NH₃ chemical ionization CI conditions]. After micro-preparative GC separation of this peroxide, the structure of two cyclic isomers (3S*,6S*)3α-hydroxy-6-methyl-1,2-dioxane and (3R*,6S*)3α-hydroxy-6-methyl-1,2-dioxane was determined from ¹H NMR spectra. The hydroperoxy-pentanal OHC( )(CH₂)₂( )CH(OOH)( )CH₃ is formed in the gas phase and is in equilibrium with these two cyclic epimers, which are predominant in the liquid phase at room temperature. This peroxide is produced by successive reactions of the n-pentoxy radical: a first one generates the CH₃C·H(CH₂)₃OH radical which reacts with O₂ to form CH₃CH(OO·)(CH₂)₃OH; this hydroxyperoxy radical isomerizes and forms the hydroperoxy HOC·H(CH₂)₂CH(OOH)CH₃ radical. This last species leads to the pentanal-hydroperoxide (also called oxo-hydroperoxide, or carbonyl-hydroperoxide, or hydroperoxypentanal), by the reaction HOC·H(CH₂)₂CH(OOH)CH₃+O₂→O()CH(CH₂)₂CH(OOH)CH₃+HO₂. The isomerization rate constant HOCH₂CH₂CH₂CH(OO·)CH₃→HOC·HCH₂CH₂CH(OOH)CH₃ (k₃) has been determined by comparison to the competing well-known reaction RO₂+NO→RO+NO₂ (k₇). By adding small amounts of NO (0–1.6×10¹⁵ molecules cm⁻³) to the di-n-pentyl peroxide/O₂/N₂ mixtures, the pentanal-hydroperoxide concentration was decreased, due to the consumption of RO₂ radicals by reaction (7). The pentanal-hydroperoxide concentration was measured vs. NO concentration at ten temperatures (463–523 K). The isomerization rate constant involving the H atoms of the CH₂( )OH group was deduced: or per H atom: The comparison of this rate constant to thermokinetics estimations leads to the conclusion that the strain energy barrier of a seven-member ring transition state is low and near that of a six-member ring. Intramolecular hydroperoxy isomerization reactions produce carbonyl-hydroperoxides which (through atmospheric decomposition) increase concentration of radicals and consequently increase atmospheric pollution, especially tropospheric ozone, during summer anticyclonic periods. Therefore, hydrocarbons used in summer should contain only short chains (<C₄) hydrocarbons or totally branched hydrocarbons, for which isomerization reactions are unlikely. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 875–887, 1998     

ZnII and CuII complexes generated from 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione

A new 1,3,4‐oxadiazole‐containing bispyridyl ligand, namely 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione (L), has been used to create the novel complexes tetranitratobis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}zinc(II), [Zn₂(NO₃)₄(C₁₄H₁₂N₄OS)₂], (I), and catena‐poly[[[dinitratocopper(II)]‐bis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}] nitrate acetonitrile sesquisolvate dichloromethane sesquisolvate], {[Cu(NO₃)(C₁₄H₁₂N₄OS)₂]NO₃·1.5CH₃CN·1.5CH₂Cl₂}_n, (II). Compound (I) presents a distorted rectangular centrosymmetric Zn₂L₂ ring (dimensions 9.56 × 7.06 Å), where each Zn^II centre lies in a {ZnN₂O₄} coordination environment. These binuclear zinc metallocycles are linked into a two‐dimensional network through nonclassical C—H...O hydrogen bonds. The resulting sheets lie parallel to the ac plane. Compound (II), which crystallizes as a nonmerohedral twin, is a coordination polymer with double chains of Cu^II centres linked by bridging L ligands, propagating parallel to the crystallographic a axis. The Cu^II centres adopt a distorted square‐pyramidal CuN₄O coordination environment with apical O atoms. The chains in (II) are interlinked via two kinds of π–π stacking interactions along [01]. In addition, the structure of (II) contains channels parallel to the crystallographic a direction. The guest components in these channels consist of dichloromethane and acetonitrile solvent molecules and uncoordinated nitrate anions.     

Two Oxime‐Based {LnIII3NiII3} Clusters with Triangular {Ln3(μ3‐Ο2)}7+ Core: Solvothermal Syntheses,Crystal Structures,and Magnetic Properties

Two isostructural heterometallic complexes, {[Dy₃Ni₃(H₂O)₃(mpko)₉(O₂)(NO₃)₃](ClO₄) · 3CH₃OH · 3CH₃CN} ( 1 ) and {[Gd₃Ni₃(H₂O)₃(mpko)₉(O₂)(NO₃)₃](NO₃) · 10.75CH₃OH} ( 2 ) [mpkoH = 1‐(pyrazin‐2‐yl)ethanone oxime], were solvothermally synthesized by varying lanthanide ions with different magnetic anisotropy. Structural analyses revealed that both complexes contain a peroxide anion‐aggregated triangular {Ln₃(μ₃‐Ο₂)}⁷⁺ core, which is surrounded by three Ni^II octahedra through threefold oxime linkages into a heterometallic hexanuclear cluster. Apparent antiferromagnetic interactions are observed between the adjacent spin carriers of 1 and 2 with the coupling constant J_{Ln ··· Ni} ≈ 12J_{Ln ··· Ln}. Additionally, 1 with highly anisotropic Dy^III site shows slow magnetization relaxation under zero dc field and 2 constructed from isotropic Gd^III ion displays significant cryogenic magnetocaloric effect with a maximum entropy change of 24.8 J · kg^–1 · K^–1 at 3.0 K and 70 kOe.     

On the Dynamic Interaction of n‐Butane with Imidazolium‐Based Ionic Liquids

The impact of a reactant from the gas phase on the surface of a liquid and its transfer through this gas/liquid interface are crucial for various concepts applying ionic liquids (ILs) in catalysis. We investigated the first step of the adsorption dynamics of n‐butane on a series of 1‐alkyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ILs ([C_nC₁Im][Tf₂N]; n=1, 2, 3, 8). Using a supersonic molecular beam in ultra‐high vacuum, the trapping of n‐butane on the frozen ILs was determined as a function of surface temperature, between 90 and 125 K. On the C₈‐ and C₃‐ILs, n‐butane adsorbs at 90 K with an initial trapping probability of ≈0.89. The adsorption energy increases with increasing length of the IL alkyl chain, whereas the ionic headgroups seem to interact only weakly with n‐butane. The absence of adsorption on the C₁‐ and C₂‐ILs is attributed to a too short residence time on the IL surface to form nuclei for condensation even at 90 K.     

Rate constant and products for the reaction of Cl atom with n‐butyraldehyde

The photooxidations of n‐butyraldehyde initiated by Cl atom were carried out at room temperature (298 ± 2K) and 1 atm pressure. The rate coefficient for the reactions of Cl atom with n‐butyraldehyde was determined as k = (2.04 ± 0.36) × 10^?10 cm³ molecule^?1 s^?1 by using relative rate techniques. The photooxidation products of n‐butyraldehyde reaction with Cl atom were also studied by using both gas chromatography‐mass spectrometry (GC‐MS) and gas chromatography techniques. C₂H₅CHO, CH₃CHO, CO and CO₂ were the major products observed. In the absence of NO, the observed yields of C₂H₅CHO, CH₃CHO, and CO were 60%, 3%, and 9%, respectively. However, when NO was introduced into the reaction chamber and the initial ratios of [NO]₀/[n‐butyraldehyde]₀ were between 1 and 8, the yield of C₂H₅CHO decreased to 33%, whereas that of CH₃CHO and CO rose up to 21% and 25%, respectively. On the basis of mechanism data deduced in this study and the fraction molar yields, the approximate branching ratios for Cl atom attack at ? C(O)H, α‐, β‐, and γ‐positions in n‐butyraldehyde could be derived as ?42%, <25%, 21%, and ?12%, respectively. © 2007 Wiley Periodicals, Inc. 39: 168–174, 2007     

Co‐MOFs Containing Flexible α,ω‐Alkane‐dicarboxylates and Bis(imidazole) Ligands: Synthesis,Structure, and Properties

Three structurally related flexible bis(imidazole) ligands reacted with Co(NO₃)₂ · 6H₂O and succinic acid (L₁) to yield three new metal‐organic frameworks {[Co(L₁)(L₂)] · (H₂O)}_n ( 1 ) [L₂ = 2‐bis(imidazol‐1‐yl)ethane], {[Co(L₁)(L₃)](H₂O)}_n ( 2 ) [L₃ = 1,4‐bis(imidazol‐1‐yl) butane], and {[Co(L₁)(L₄)] · (H₂O)}_n ( 3 ) [L₄ = 1,4‐bis(2‐methyl‐imidazol‐1‐yl)butane], respectively. These complexes were synthesized under solvothermal conditions and characterized by elemental analysis, IR spectroscopy, single‐crystal and powder X‐ray diffraction, as well as thermal analyses. Interestingly, the ligands in these complexes exhibit different conformations and further cause three different configurations. Complex 1 shows a three‐dimensional (3D) framework, which is connected by two‐dimensional (2D) layer structures through hydrogen bonds. Complex 2 is a diamond structure with threefold interpenetration. Complex 3 is a 3D framework linked by hydrogen bonds like complex 1 .     

Five solvates of a multicomponent pharmaceutical salt formed by berberine and diclofenac

A multicomponent pharmaceutical salt formed by the isoquinoline alkaloid berberine (5,6‐dihydro‐9,10‐dimethoxybenzo[g]‐1,3‐benzodioxolo[5,6‐a]quinolizinium, BBR) and the nonsteroidal anti‐inflammatory drug diclofenac {2‐[2‐(2,6‐dichloroanilino)phenyl]acetic acid, DIC} was discovered. Five solvates of the pharmaceutical salt form were obtained by solid‐form screening. These five multicomponent solvates are the dihydrate (BBR–DIC·2H₂O or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·2H₂O), the dichloromethane hemisolvate dihydrate (BBR–DIC·0.5CH₂Cl₂·2H₂O or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·0.5CH₂Cl₂·2H₂O), the ethanol monosolvate (BBR–DIC·C₂H₅OH or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·C₂H₅OH), the methanol monosolvate (BBR–DIC·CH₃OH or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·CH₃OH) and the methanol disolvate (BBR–DIC·2CH₃OH or C₂₀H₁₈NO₄⁺·C₁₄H₁₀Cl₂NO₂^?·2CH₃OH), and their crystal structures were determined. All five solvates of BBR–DIC (1:1 molar ratio) were crystallized from different organic solvents. Solvent molecules in a pharmaceutical salt are essential components for the formation of crystalline structures and stabilization of the crystal lattices. These solvates have strong intermolecular O…H hydrogen bonds between the DIC anions and solvent molecules. The intermolecular hydrogen‐bond interactions were visualized by two‐dimensional fingerprint plots. All the multicomponent solvates contained intramolecular N—H…O hydrogen bonds. Various π–π interactions dominate the packing structures of the solvates.     

The production of organic nitrates from atmospheric oxidation of ethers and glycol ethers

The production of organic nitrates from OH reaction (in the presence of NO) with methoxy propane, 1‐methoxy‐2‐propanol, ethoxy butane, and 2‐butoxyethanol was studied. The measured total organic nitrate yields were 1.8 (±0.4)%, 0.98 (±0.2)%, 7.7 (±2)%, and 9.6 (±1)%, respectively. The total organic nitrate yield for methoxypropane is 26% of that (7.0%) for n‐butane. The organic nitrate yield for ethoxy butane is 55% of that (14%) for n‐hexane. The peroxy radicals produced from OH reaction with the methylene groups α to the ether linkage have an organic nitrate branching ratio (k_3b/k₃) value ∼50% of those in analogous n‐alkanes. On the other hand, k_3b/k₃ values for peroxy radical functional groups not adjacent to the ether linkage (in γ and δ positions) are on average 1.7 times greater than for the analogous n‐alkyl peroxy radicals. The organic nitrate formation yield for 1‐methoxy‐2‐propanol is almost half that of methoxy propane, while for 2‐butoxyethanol it is 21% greater than that of butoxyethane. Our data lead us to the conclusion that the ether linkage imparts an inductive effect that decreases the value of k_3b/k₃ for peroxy radicals adjacent to it, yet has a stabilizing effect, from the additional vibrational modes for those peroxy radicals not adjacent to it, increasing their k_3b/k₃ values. The effect of both the  O and OH groups in these molecules and the importance of their position relative to the peroxy group are discussed in this paper. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 686–699, 2005