The oxidation of diethylhydroxylamine by nitrogen dioxide

Diethylhydroxylamine, (C₂H₅)₂NOH, was oxidized by NO₂ at 25°C in a long-path-length infrared gas cell. The measured products of the reaction were HONO and CH₃CHO. The reaction scheme which explains the reaction is was oxidized by NO₂, and the reaction was found to be very rapid with k₁ > 10^?16 cm³/s. The products of the reaction were verified by both infrared absorption (CH₃CHO, C₂H₅NO) and gas chromatography (CH₃CHO, NO).     

Beiträge zur Komplexchemie der Phosphine und Phosphinoxide,XXVIII. Übergangsmetall-aminoalkylphosphin-Komplexe Teil 2: Palladium- Und Platinkomplexe

On the Coordination Chemistry of Phosphines and Phosphine Oxides. XXVIII. Transition Metal Aminoalkylphosphine Complexes. Part II: Palladium and Platinum Complexes Aminoalkylphosphines – C₆H₅HP? CH₂ · CH₂? , (C₆H₅)₂P? CH₂ · CH₂ · CH₂? NH₂, (C₆H₅)₂P? CH₂ · CH₂ · CH₂? N?CHC₆H₅ – react with palladium and platinum salts to give coordination compounds of the type MX₂, MX₂()₂, and MX₂()₄ (M = Pd, Pt; X = Cl, BPh₄). The chelating activity of the ligands, structure and properties of the metal complexes are discussed.     

Polymerization of cyclic esters of phosphoric acid. VI. Poly(alkyl ethylene phosphates). Polymerization of 2-alkoxy-2-oxo-1,3,2-dioxaphospholans and structure of polymers

Five-membered cyclic esters of phosphoric acid of the general formula: ? CH₂CH(R)OP(O)-(OR′)O? polymerize readily to solid, soluble polymers of high molecular weight without any rearrangement known for various tri- and pentavalent organophosphorus monomers. ¹H-, ¹³C-, and ³¹P-NMR spectra of polymers confirmed their linear structure: where R is H, with R′ = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇; n-C₄H₉, CCl₃CH₂, or C₆H₅, or R is CH₂Cl and R′ is C₂H₅. The use of n-C₄H₉Li, (C₅H₅)₂Mg, or (i-C₄H₉)₃Al as initiators leads to polymers with M _n = 10⁴–10⁵.     

Photolysis of carbon tetrachloride in the presence of alkanes

The photolysis of carbon tetrachloride in the presence of a number of alkanes has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the alkane. The data have been used to determine Arrhenius parameters for hydrogen abstraction from the series of alkanes CH₄, C₂H₆, C₃H₈, and i-C₄H₁₀ by trichloromethyl radicals, The rate data obtained are used to explain why termination reactions involving alkyl radicals become less significant as the alkane becomes more complex.     

The potential energy surface for the [C2H2O]+˙ system: The ketene radical cation [CH2CO]+˙ and its isomers

Ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence electron correlation have been employed to examine the [C₂H₂O]^+˙ potential energy surface. Four [C₂H₂O]^+˙ isomers have been identified as potentially stable, observable ions. These are the experimentally well-known ketene radical cation, [CH₂?C?O]^+˙ (a), and the presently unknown ethynol radical cation, [CH₂?C? OH]^+˙ (b), the oxirene radical cation (c) and an ion resembling a complex of CO with [CH₂]^+˙, (d). The calculated energies of b, c and d relative to a are 189, 257 and 259 kJ mol^?1, respectively. Dissociation of ions a and d is found to occur without reverse activation energy.     

Amidrazones. VII. Formation of s-triazines by thermolysis of N1-benzyl-substituted amidrazone ylides

The preparation of ylides of the general structure is described. Thermolysis of 14a (R = CH₃, R' = H, Ar = C₆H₅) gave dimethylamine and 2,4-dimethyl-6-phenyl-s-triazine. Thermolysis of ylides 14b (R = C₆H₅; R' = CH₃, Ar = C₆H₅) and 14c (R = C₆H₅, R' = CH₃, Ar = p-tolyl) gave dimethylamine, ArCH = NCH₃ and 1-methyl-2-Ar-4,6-diphenyl-1,2-dihydro-s-triazines ( 19a,b ). Triazines 19a and 19b were also prepared by condensation of N-methylbenzamidine with benzaldehyde and p-tolualdehyde, respectively. Thermolysis of 14d (R = C₆H₅, R¹ = CH₂C₆H₅,Ar = C₆H₅) gave 1-benzyl-2,4,6-triphenyl-1,2-dihydro-s-triazine ( 19c ) and N-benzylidenebenzylamine. Mechanistic aspects of these reactions are discussed.     

Branching ratio of the C2H2 + O reaction at 290 K from kinetic modelling of relative methylene concentration versus time profiles in C2H2/O/H systems

In earlier work on the room temperature oxidation of C₂H₂ by O atoms, two distinct sources of methylene radicals have been identified: (i) direct, primary production via channel 1b of the C₂H₂ + O reaction, and (ii) delayed formation via the secondary reaction 3 involving the products HCCO and H of the other primary channel 1a: Presently, it was confirmed by a detailed sensitivity analysis that the precise shapes of the resulting total methylene concentration-versus-time profiles in C₂H₂/O systems depend strongly on the k_1a/k_1b branching ratio. Along that line, the important parameter k_1a/k_1b was determined from relative CH₂ concentration-versus-time profiles measured in a variety of C₂H₂/O/H systems using Discharge Flow-Molecular Beam sampling Mass Spectrometry techniques (DF-MBMS). The data analysis was carried out by deductive kinetic modelling; the method, as applied to profile shapes, is discussed at length. Via this novel, independent approach, the CH₂(³B₁) yield of the two-channel C₂H₂ + O reaction was determined to be k_1b/k₁ = 0.17 ± 0.08. The indicated 2σ error includes possible systematic errors due to uncertainties in the rate constants of other reactions that influence the shapes of the CH₂ profiles. The present result, which translates to an HCCO yield k_1a/k₁ = 0.83 ± 0.08, is in excellent agreement with other recent determinations. The above mechanism, with the subsequent reactions that it initiates, also reproduces the measured absolute [C₂H₂], [O], and [H] profiles with an average accuracy of 5%, thus validating the consistency of the C₂H₂/O/H reaction model put forward here. © 1994 John Wiley & Sons, Inc.     

Kinetics and mechanism of the reaction H + CH3ONO

The reaction of hydrogen atoms with methyl nitrite was studied in a fast-flow system using photoionization mass spectrometry and excess atomic hydrogen. The associated bimolecular rate coefficient can be expressed by in the temperature range of 223-398°K. NO, CH₃OH, CH₄, C₂H₆, CH₂O, and H₂O are the main products; OH and CH₃ radicals were detectable intermediates. The mechanism was deduced from the observed product yields using normal and deuterated reactants. The primary reaction steps were identified as followed by a rapid unimolecular decomposition of CH₂ONO into CH₂O and NO. Since the extent of reaction channel (1b) could not be determined independently, only extreme limits could be obtained for the individual contributions of the two channels of reaction (3) which follows the generation of CH₃O radicals: The most probable values, k_3a/k₃ = 0.31 ± 0.30 and k_3b/k₃ = 0.69 ± 0.30, support the previous results on this reaction, although the range of uncertainties is much greater here.     

High-temperature pyrolysis of acetaldehyde

High-temperature (>1000°K) pyrolysis of acetaldehyde (～1% in an atmosphere of pure nitrogen) was examined in a turbulent flow reactor which permits accurate determination of the spatial distribution of the stable species. Results show that the products in order of decreasing importance are CO, CH₄, H₂, C₂H₆, and C₂H₄. Rates of formation were consistent with the Rice–Herzfeld mechanism by including reactions to explain C₂H₄ formation and the possible presence of ketene. A steady-state treatment of the complete mechanism indicates that the overall reaction order decreases from \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{3}{2} $\end{document} to 1, which is supported by the new experimental data. Using earlier low-temperature results, the rate constant for the reaction CH₃CHO → CH₃ + CHO (1) was found as k₁=10^15.85±0.21 exp (?81,775±1000/RT) sec^?1. Also, data for the ratio of rate constants for reactions CH₃CHO + CH₃ → CH₄ + CH₃CO (4) and 2CH₃ → C₂H₆(6) were fitted to the empirical expression k₄/k₆^1/2=10^?13.89±0.03T^6.1 exp(?1720±70/RT) (cm³/mole·sec)^1/2 and causes for the curvature are discussed. The noncatalytic effect of oxygen on acetaldehyde pyrolysis at high temperature is explained.     

The use of transition-state theory to extrapolate rate coefficients for reactions of O atoms with alkanes

Conventional transition-state theory is used for extrapolating rate coefficients for reactions of O atoms with alkanes to temperatures above the range of experimental data. Expressions are developed for estimating structural properties of the activated complex necessary for calculating enthalpies and entropies of activation. Particular attention is given to the problem of the effect of the O atom adduct on the internal rotations in the activated complex. Differences between primary, secondary, and tertiary attack are discussed, and the validity of representing the activated complexes of all O + alkane reactions by a fixed set of vibrational frequencies and other internal modes is evaluated. Experimental data for reactions of O atoms with 15 different alkanes (CH₄, C₂H₆, C₃H₈, C₄H₁₀, C₅H₁₂, C₆H₁₄, C₇H₁₆, C₈H₁₈, i–C₄H₁₀, (CH₃)₄C, (CH₃)₂CHCH(CH₃)₂, (CH₃)₃CC(CH₃)₃, c–C₅H₁₀, c–C₆H₁₂, c–C₇H₁₄) are reviewed. The following approximate expressions for ΔS^?(298) and E(298), the entropy and energy of activation, respectively, are consistent with the experimental data and with the calculations: where n_C = number of carbon atoms in the alkane and n_H = the number of “equivalent” H atoms. Using the conventional transition state theory expression, k(298) = 10^15.06 exp(ΔS^?/R) exp(–E(298)/298R) L mol^?1s^?1, one then obtains: These expressions agree with experimental values within a factor approximately 2 for alkanes larger than C₃H₈.     

Rationalization of scrambling processes among [C2H3O]+ ions

Scrambling data for the three observed [C₂H₃O]⁺ isomers, namely [CH₃CO]⁺ (a), [CH₂COH]⁺ (b) and (c), are rationalized by using ab initio molecular orbital calculations. For ions a and c, processes leading to scrambling of the carbon atoms require substantially more energy than the threshold for decomposition to [CH₃]⁺ + CO. Accordingly, little or no carbon scrambling is predicted nor is any observed in the metastable dissociation of a and c. The observed carbon scrambling in b prior to metastable dissociation to [CH₃]⁺ + CO has previously been explained in terms of a mechanism involving the oxiranyl cation (c). However, this mechanism is shown to be unlikely because of the high energies involved. An alternative lower-energy pathway involving the intermediacy of protonated oxirene (h) is proposed. Such a mechanism is fully compatible with the experimental data.     

The pyrolysis of acetaldehyde in the presence of nitric oxide

The kinetics of the acetaldehyde pyrolysis have been studied at temperatures from 450° to 525°C, at an acetaldehyde pressure of 176 torr and at 0 to 40 torr of added nitric oxide. The following products were identified and their rates of formation measured: CH₄, H₂, CO, CO₂, C₂H₄, C₂H₆, H₂O, C₃H₆, C₂H₅CHO, CH₃COCH₃, CH₃COOCH?CH₂, N₂, N₂O, HCN, CH₃NCO, and C₂H₅NCO. Acetaldehyde vapor was found to react with nitric oxide slowly in the dark at room temperature, the products being H₂O, CH₃COOCH₃, CO, CO₂, N₂, NO₂, HCN, CH₃NO₂, and CH₃ONO₂. The rates of formation of N₂ and C₂H₅NCO depend on how long the CH₃CHO-NO mixture is kept at room temperature before pyrolysis; the rates of formation of the other products depend only slightly on the mixing period. The pyrolysis of “clean” CH₃CHO–NO mixtures (i.e., the results extrapolated to zero mixing time, which are independent of products formed in the cold reaction) are interpreted as follows: (1) There are two chain carriers, CH₃ and CH₂CHO, their concentrations being interdependent and influenced by NO in different ways: the CH₃ radical is both generated and removed by reactions directly involving NO, whereas CH₂CHO is generated only indirectly from CH₃ but is also removed by direct reaction with NO. (2) An important mode of initiation by NO is its addition to the carbonyl group with the formation of which is converted into ; this splits off OH with the formation of CH₃NCO or CH₃ + OCN. (3) Important modes of termination are The steady-state equations derived from the mechanism are shown to give a good fit to the experimental rate versus [NO] curves and, in particular, explain why there is enhancement of rate by NO at higher CH₃CHO pressures and, at lower CH₃CHO pressures, inhibition at low [NO] followed by enhancement at higher [NO]. The cold reaction is explained in terms of chain-propagating and chain-branching steps resulting from the addition of several NO molecules to CH₃CHO and the CH₃CO radical. In the “unclean” reaction it is found that the rates of N₂ and C₂N₅NCO formation are increased by CH₃NO₂, CH₃ONO, and CH₃ONO₂ formed during the cold reaction. A mechanism is proposed, involving the participation of α-nitrosoethyl nitrite, CH₃CH(NO)ONO. It is suggested that there are two modes of behavior in pyrolyses in the presence of NO: (1) In the paraffins, ethers, and ketones, the effects are attributed to the addition of NO to a radical with the formation of an oxime-like compound. (2) In the aldehydes and alkenes, where there is a hydrogen atom attached to a double-bonded carbon atom, the behavior is explained in terms of addition of NO to the double bond followed by the formation of an oxime-like species.     

The reaction of 3,4‐diamino‐1,2,5‐oxadiazoles with formaldehyde

The compounds 5,6‐dihydro‐4H‐imidazo[4,5‐c][1,2,5]oxadiazole ( 3a , R?H), 4,6,10,12‐tetramethyl‐5,6,11,12‐tetrahydro‐4H,10H‐bis(1,2,5)oxadiazolo[3,4‐d:3′,4′‐I][1,3,6,8]tetraazecine ( 4b , R?CH₃), N³,N³′‐methylenebis‐3,4‐diamino‐1,2,5‐oxadiazole ( 5a , R?H) and N³,N³′‐methylenebis(N,N′‐dimethyl‐3,4‐diamino‐1,2,5‐oxadiazolee) ( 5b , R?CH₃) were synthesized from the reaction of formaldehyde with 3,4‐diamino‐1,2,5‐oxadiazole and N,N′‐3,4‐dimethylamino‐1,2,5‐oxadiazole in an acetonitrile.     

Versuche zur Darstellung von zweifach silyliertem Nitramid

Experiments for the Preparation of Doubly Silylated Nitroamine Silylated derivatives of nitroamines can be obtained by treating nitryl compounds with silazanes, i. e. via formation of an N? N bond: The reaction product can be isolated in the case of R ? CH₃, R′? Si(CH₃)₃, whereas [(CH₃)₃Si]₂ NNO₂ is unstable and cannot be obtained at room temperature. Isomeric Bis(trimethylsilyl)-hyponitrite formed by reaction of silver hyponitrite with trimethylchlorosilane is similarly unstable. Cleavage of siloxanes by nitryl and nitrosyl compounds is discussed in connection with the above reaction.     

Preparation of new 2‐amino‐ and 2,3‐diamino‐pyridine trifluoroacetyl enamine derivatives and their application to the synthesis of trifluoromethyl‐containing 3H‐pyrido[2,3‐b][1,4] diazepinols

The synthesis of a novel series of the intermediates N²(N³)‐[1‐alkyl(aryl/heteroaryl)‐3‐oxo‐4,4,4‐trifluoroalk‐1‐en‐1‐yl]‐2‐aminopyridines [F₃CC(O)CH?CR¹(2? NH?C₅H₃N)] and 2,3‐diaminopyridines [F₃CC(O)CH?CR¹(2‐NH₂‐3‐NH? C₅H₃N)], where R¹ = H, Me, C₆H₅, 4‐FC₆H₄, 4‐CIC₆H₄, 4‐BrC₆H₄, 4‐CH₃C₆H₄, 4‐OCH₃C₆H₄, 4,4′‐biphenyl, 1‐naphthyl, 2‐thienyl, 2‐furyl, is reported. The corresponding series of 2‐aryl(heteroaryl)‐4‐trifluoromethyl‐3H‐pyrido[2,3‐b][1,4]diazepin‐4‐ols obtained from intramolecular cyclization reaction of the respective trifluoroacetyl enamines or from the direct cyclocondensation reaction of 4‐methoxy‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 2,3‐diaminopyridine, under mild conditions, is also reported.     

Structure and formation of gaseous [C4H5O]+ ions. IV—Ions derived from the cyclopropenium ion [C3H3]+

Characterization of [C₄H₅O]⁺ ions in the gas phase using their metastable ion and collisional activation spectra shows that the three isomeric ions HC?C? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}H? OCH₃, CH₃O? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?C?CH₂ and ? OCH₃ related to the two stable [C₃H₃]⁺ cations [HC?C? CH₂]⁺ and are stable for ≥ 10^?5s. In contrast to the formation of cyclopropenium ions, it is found that the methoxy cyclopropenium ion is not generated from acyclic precursor molecules. The small but significant intensity differences found in the collisional activation spectra of [C₃H₃]⁺ ions generated from HC?C? CH₂I and HC?C? CH₂Cl possibly indicate the presence of [C₃H₃]⁺ ions of different structures.     

Synthese und NMR-Spektren von λ5-Diphospheten Die Struktur des 2,4-Diphenyl-1,1,3,3-tetrakis(diethylamino)-1λ5,3λ5-diphosphets

Synthesis and NMR Spectra of λ⁵-Diphosphets. Structure of 2,4-Diphenyl-1,1,3,3-tetrakis (diethylamino)-1λ⁵, 3λ⁵-diphosphete Preparation, properties, and n.m.r. spectra of C₂H₅PF₂[N(C₂H₅)₂]₂, CH₂?PF[N(C₂H₅)₂]₂, and the diphosphetes {RC?P[N(C₂H₅)₂]₂}₂ (R) ? H ( 5a ), CH₃ [( 5b )] are described. The λ⁵-diphosphete {HC?P(NR₂)₂}₂ (R ? CH₃) reacts with BF₃ · O(C₂H₅)₂ to give which is transformed into by n-C₄H₉Li. The crystal and molecular structure of 2,4-diphenyl-1,3,3-tetrakis(diethylamino)-1λ⁵,3λ⁵-diphosphete 2 are reported and discussed.     

Determination of the composition and the stability constants of complexes of silver(I) with some sulphur containing pyridines a potentiometric investigation

A series of sulphide-containing pyridines of general formula ? (CH₂)_x? S? R where R = CH₃, C₂H₅, CH₂CH₂OH and x = 1, 2 has been prepared and studied potentiometrically in the presence of Ag⁺ in 0.5 M (K)NO₃ medium at 25°C. The complex formation is discussed in terms of the Taft σ*-parameters for the substituents. In acid region, where the complexes AgLH²⁺ and AgL₂H₂³⁺ were formed, coordination occurs through the thioether group. In neutral and alkaline medium their was evidence for the species AgL₂H²⁺, AgL⁺, AgL₂⁺, Ag₂L₂²⁺ and Ag₂L²⁺ in which Ag⁺? S and Ag⁺? bonds are involved. The five membered chelate rings for the AgL⁺ and AgL²⁺ species are found to be more stable than the six-membered ones.     

Polybenzimidazoles for High Temperature Fuel Cell Applications

Summary: Fuel cells were designed for high temperature operations. Poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI) was synthesized in a solution of P₂O₅, CH₃SO₃H, and CF₃SO₃H. The PBI was dissolved in a mixture of CF₃CO₂H and H₃PO₄ and the solution was used for the preparation of Pt catalyst slurry for membrane electrode assembly. The single cell showed a current density of 280 mA · cm⁻² at a cell voltage of 0.5 V with feeds of H₂ and O₂ at 160 °C and without external humidification.

     

Amino-phosphane. X. Einige Additionsreaktionen von N-Diphenylphosphinotetraphenyldiphosphin-imid

Diphenylphosphorous chloride and methyl iodide add readily to the N-bonded P(III)-atom of (C₆H₅)₂P? P(C₆H₅)₃?N? P(C₆H₅)₂ forming the salts [(C₆H₅)₂P? P(C₆H₅)₂ N P(C₆H₅)₂? P(C₆H₅)₂]Cl and [(C₆H₅)₂P? P(C₆H₅)₂ N P(C₆H₅)₂. CH₃]I, respectively. A similar behaviour is observed with sulfur: Under mild conditions (C₆H₅)₂P? P(C₆H₅)₂?N? P(C₆H₅)₂ = S is formed but forcing conditions are required to produce S = P(C₆H₅)₂? P(C₆H₅)₂?N? P(C₆H₅)₂?S. The monosulfide is also obtained by treating (C₆H₅)₂P(S)N[Si(CH₃)₃]₂ with diphenylphosphorous chloride, indicating the favoured formation of the phosphazene system as compared with the phosphazane system Confirmation of the structures comes from ³¹P nmr and IR data, and for the sulfides also from their degradation with bromine.