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Some paramagnetic species formed in the photoreactions of nitroalkanes with P-compounds have been characterized by ESR.The observed radicals are mostly nitroxides whose structures are consistent with the trapping of P-centred radicals by intermediate nitroso compounds.

The overall rate constant and an upper limit for the CH3ONO2 product channel for the CH3O2 + NO reaction have been measured using the turbulent flow technique with high-pressure chemical ionization mass spectrometry for the detection of reactants and products. At room temperature and 100 Torr pressure, the rate constant (and the two standard deviation error limit) was determined to be (7.8 +/- 2.2)E-12 cm3 molecule-1 s-1. The temperature dependence of the rate constant was investigated between 295 and 203 K at pressures of either 100 or 200 Torr, and the data was fit to the following Arrhenius expression: (9.2+6.0-3.9E-13) exp cm3 molecule-1 s-1. Although the room-temperature rate constant value agrees well with the current recommendation for atmospheric modeling, our values for the rate constant at the lowest temperatures accessed in this study (203 K) are about 50 percent higher than the same recommendation. No CH3-ONO2 product was detected from the CH3O2 + NO reaction (using direct CH3ONO2 detection methods for the first time), but an improved upper limit of 0.03 (at 295 K and 100 torr) for this branching channel was determined.

Well-defined 16-electron metal amido complexes bearing chiral Ts-diamine ligands readily react with nitromethane, acetone, or phenylacetylene to give new organometallic compounds in almost quantitative yields. For example, an Ir amido complex, Cp*Ir[(R,R)Tscydn], reacts with nitromethane at room temperature to give quantitatively a nitromethyl Ir complex, Cp*Ir(CH2NO2)[(R,R)-Tscydn], as a single diastereomer. The isolable organometallic compounds with chiral amine ligands are relevant to active catalysts for asymmetric C-C bond formation.

The γ-irradiation of solutions containing acetic acid, nitric acid and/or their salts produces nitromethane.

Gas-phase 1H NMR spectra of methyl nitrite are consistent with the following thermodynamic parameters for the syn anti conformational equilibrium: ΔHanti-syn, 998 (50) cal mol-1; ΔGanti-syn, 520 (5) cal mol-1 (at 205 K); and ΔSanti-syn 2.3(3) eu.These results agree well with values obtained from a statistical mechanical calculation.The large entropy difference between the conformers is due to a very low methyl top internal rotation barrier for the anti conformer.Neat liquid methyl nitrite and 1 percent solutions of methyl nitrite is carbon disulfide, acetone-d6, and n-pentane all produce temperature-dependent NMR spectra which are consistent with the following ranges of thermodynamic parameters: ΔHanti-syn, 803-866 cal mol-1; ΔGanti-syn, 440-460 cal mol-1 (at 205 K); ΔSanti-syn, 1.8-2.0 eu, demonstrating that in liquids the anti/syn partition function ratio is smaller and the equilibrium constant between the conformers is closer to 1.

Postsynthetic modification methods have emerged as indispensable tools for tuning the properties and reactivity of metal-organic frameworks (MOFs). In particular, postsynthetic X-type ligand exchange (PXLE) at metal building units has gained increasing attention as a means of immobilizing guest species, modulating the reactivity of framework metal ions, and introducing new functional groups. The reaction of a Zn-OH functionalized analogue of CFA-1 (1-OH, Zn(ZnOH)4(bibta)3, where bibta2- = 5,5′-bibenzotriazolate) with organic substrates containing mildly acidic E-H groups (E = C, O, N) results in the formation of Zn-E species and water as a byproduct. This Br?nsted acid-base PXLE reaction is compatible with substrates with pKa(DMSO) values as high as 30 and offers a rapid and convenient means of introducing new functional groups at Kuratwoski-type metal nodes. Gas adsorption and diffuse reflectance infrared Fourier transform spectroscopy experiments reveal that the anilide-exchanged MOFs 1-NHPh0.9 and 1-NHPh2.5 exhibit enhanced low-pressure CO2 adsorption compared to 1-OH as a result of a Zn-NHPh + CO2 ? Zn-O2CNHPh chemisorption mechanism. The MFU-4l analogue 2-NHPh ([Zn5(OH)2.1(NHPh)1.9(btdd)3], where btdd2- = bis(1,2,3-triazolo)dibenzodioxin), shows a similar improvement in CO2 adsorption in comparison to the parent MOF containing only Zn-OH groups.

Methyl 2-nitroacetate and methyl acetoacetate have in common the presence of an electron-withdrawing substituent geminal to the methyl ester function but the well-known ease of thermal transesterification of methyl acetoacetate has not been found in methyl 2-nitroacetate. The latter gives uncatalysed thermal transesterification only in low yield and at a temperature higher than that of methyl acetoacetate. Comparative experiments provided further insight into the reactions; protic and Lewis acid catalysts promoted the smooth exchange of the alkanoyl groups, observing first the transesterification of methyl 2-nitroacetate with ethanol, already proved difficult to proceed. Dibutyltin(IV)oxide (DBTO) catalyst offered the spur to set up a convenient synthetic methodology from methyl 2-nitroacetate, encompassing higher molecular weight and functionalised alcohols: aliphatic, unsaturated and oxidation sensitive species were suited to react, delivering the corresponding 2-nitroacetate esters in good yields in most cases.

The invention relates to a preparation method of nitromethane, and relates to the field of organic synthesis. The preparation method comprises the following step of mixing dimethyl sulfate, nitrite, alkali and poly(4-vinylpyridine) to react. The preparation method has the advantages that by adding the poly(4-vinylpyridine), the amount of harmful gas in the production process is reduced, and the yield rate and purity of the product are greatly improved; the poly(4-vinylpyridine) is easy to separate, and the poly(4-vinylpyridine) is suitable for the recycling of byproduct (sulfate); the conditions are mild, the operation is simple, and the production method is suitable for industrialized large-scale production. The application of the poly(4-vinylpyridine) is characterized in that the poly(4-vinylpyridine) is applied into the synthesis reaction of the nitromethane, the yield rate and purity of the nitromethane are improved, and the influence to the recycling of the byproduct is avoided.

The utility model provides a for continuous production of nitromethane in the reactor, which comprises a series of n reaction zone, wherein the reaction region comprises a: housing, is arranged in the casing of the mixing chamber and the mixing chamber is connected to the reaction tube, the shell is provided with a mixing chamber connected to the dimethyl sulfate sodium nitrite inlet and inlet, with said reaction tube connected to the outlet of the reaction product, and heat transfer medium inlet and outlet; the reaction zone b to reaction zone n the reaction areas of the respective includes: shell, is arranged in the casing of the mixing chamber and the mixing chamber is connected to the reaction tube, the shell is provided with a connected on the mixing chamber of the reaction product of a reaction zone inlet and dimethyl sulfate inlet, with said reaction tube connected to the outlet of the reaction product, and heat transfer medium inlet and outlet; in addition to the last reaction zone other than the reaction zone of the reaction product outlet and the next reaction zone of the product inlet connected by pipelines.

(D3-)Methanol-nitrogen monoxide (CH3OH/CD3OH-NO) ices were exposed to ionizing radiation to facilitate the eventual determination of the CH3NO2 potential energy surface (PES) in the condensed phase. R

The invention belongs to the field of organic chemical industries, and provides a green synthesis method for preparing nitroalkanes by oxime oxidation. At the temperature of 55 to 120 DEG C and under the pressure of 0 to 1.0 MPa, oxime, a solvent and hydrogen peroxide are reacted for 20 to 200min in the presence of certain amounts of nanoporous skeleton metal hybrid catalysts and cocatalysts, a reaction liquid is subjected to membrane separation, the catalysts can be repeatedly used for more than 7 times, and distilled to obtain nitroalkane products, the purity of the products is not less than 99%, and the yield of the products is not less than 95%. Furthermore, the green synthesis method for preparing nitroalkanes by the oxime oxidation disclosed by the invention is a green synthesis method of nitroalkanes, and suitable for large-scale industrialized production.

Electroreduction of the Henry reaction product - i.e. 1-phenyl-2- nitroethanol (PNE) - in 0.1 M Bu4NClO4 solution in Me-CN has been investigated by a set of experimental (cyclic voltammetry, chronoamperometry, and controlled potential electrolysis) and theoretical (digital simulation and quantum chemical calculations) methods. The results obtained show that cathodically generated radical anion of PNE undergoes C-C bond cleavage reaction resulting in the formation of the free radical of benzyl alcohol and nitromethane anion. The proton transfer between these species affords nitromethane and benzaldehyde radical anion. Electron transfer from the last to PNE initiates the cyclic process of the PNE degradation.

A di-bromo substituted nitrovinylfuran with reported broad-spectrum antibacterial activity was found to be a potent inhibitor of MurA, a key enzyme in peptidoglycan biosynthesis. Further characterization of the compound was carried out to assess its reactivity towards thiol nucleophiles, its stability and degradation under aqueous conditions, inhibitory potential at other enzymes, and antibacterial and cytotoxic activity. Our results indicate that the nitrovinylfuran derivative is reactive towards cysteine residues in proteins, as demonstrated by the irreversible inhibition of MurA and bacterial methionine aminopeptidase. Experiments with proteins and model thiols indicate that the compound forms covalent adducts with SH groups and induces intermolecular disulfide bonds, with the intermediate formation of a monobromide derivative. The parent molecule as well as most of its breakdown products are potent antibiotics with MIC values below 4 μg/mL and are active against multiresistant strains such as methicillin-resistant Staphylococcus aureus (MRSA). Further development of the bromonitrovinyl scaffold towards antibiotics with clinical relevance, however, requires optimization of the antibiotic-cytotoxic selectivity profile.

Provided is a process for making nitrated hydrocarbons by reacting aqueous nitric acid with a hydrocarbon feedstock and a carboxylic acid under specific reaction conditions.

Despite the high nucleophilicity of sulfur atoms, thiacalixarenes have been alkylated only on oxygen atoms thus far. Using strong alkylating agents (triflates, trialkyloxonium salts), the substitution of the sulfur bridges has been successfully accomplished. The corresponding sulfonium salts of thiacalix[4]arene are formed regio- and stereoselectively as a completely new type of substitution pattern in thiacalixarene chemistry. These compounds possess interesting conformational behavior and could be used as unusual alkylating agents with uncommon selectivity.

Disclosed are a process and an apparatus for synthesizing nitroalkanes by reaction of a hydrocarbon feedstock with aqueous nitric acid. Energy and capital costs may be reduced by recycling a majority of the aqueous phase back to the reactor.

Disclosed are a process and an apparatus for synthesizing nitroalkanes by reaction of a hydrocarbon feedstock with aqueous nitric acid. By using an isothermal reactor with multiple input ports for aqueous nitric acid, a hydrocarbon feedstock may be sequentially exposed to a plurality of flows of aqueous nitric acid as it flows through the reactor.

The asymmetric Henry reaction catalyzed by hydroxynitrile lyase from Hevea brasiliensis is an example of enzymatic catalytic promiscuity. It could be an attractive method to produce optically active β-nitroalcohols, but unfortunately the enzyme has very low activity in this unnatural reaction. To get an insight into the reaction mechanism, the enzyme kinetics of this promiscuous biotransformation were studied using the cleavage and synthesis of 2-nitro-1-phenylethanol as a model system. The results indicate that the kinetic behavior of the enzyme in the Henry reaction fits the classical Rapid Equilibrium Random Bi Uni/Uni Bi mechanistic model with independent substrate binding. The measured kinetic parameters imply that the bottleneck for this biotransformation is the very low turnover number of the enzyme, not the binding of the substrates.

In non-competitive solvents, the tris(3-ureidobenzyl)amines 1a-c form dimeric assemblies in which guests such as CH3CN, CH 3NO2, CH2Cl3, CH3I, CH2BrCl, CH2Br2, CHCl3 and C 6H6 can be encapsulated. Variable temperature 1 and 1H,1H-ROESY NMR spectroscopy, as well as pulsed-gradient spin-echo (PGSE) diffusion measurements were used to in-ivestigate the encapsulation within 1a·1a (1a: tris{3-[N′-(4- butylphenyl)-ureido]benzyl}amine). Kinetic parameters for the encapsulation of CH3NO2, CH2Cl2 and CH3I, both in CDCl3 and in [D8]toluene have been obtained by using magnetisation transfer methods. These data are discussed together with the thermodynamic parameters. The affinity between guest and capsule seems to be dictated mainly by the electronic, size and shape complementarity between cavity and guest. A gating mechanism for guest exchange is proposed.

(Chemical Equation Presented) Lost control: The rationalization of the ambident reactivity of NO2- by the change between charge control to orbital control has to be revised. SN1-type reactions of carbocations with NO2- give kinetically controlled product mixtures only when these reactions proceed without activation energy (diffusion control). Activation-controlled SN1 alkylations are reversible and lead to the thermodynamically more stable nitro compounds.

The kinetics of the gas-phase elimination of several 2-substituted primary, secondary and tertiary hydroxy groups in nitroalkanes were determined in a static reaction system over the temperature range 220-400°C and pressure range of 29-235 Torr. The reactions, in seasoned vessels, are homogeneous and unimolecular and obey a first-order rate law. The presence of secondary and tertiary hydroxy substituent at the 2-position of the nitro group in nitroalkanes leads to a retro-aldol type of decomposition. The mechanism may be rationalized in terms of a six-membered cyclic transition state to give the corresponding aldehyde or ketone and the nitroalkane, respectively. However, some of the primary 2-hydroxy groups in nitroalkanes undergo a dehydration process with very limited isomerization to the corresponding alkyl nitrate. The mechanism of dehydration is believed to proceed through a six-membered rather than the already reported four-membered cyclic transition state to give the nitroalkene and water. In the case of the primary hydroxy substituent in 2-methyl-2-nitro-1-pentanol, the products of elimination are HNO2 gas and 3-hydroxy-2-methyl-1-propene. This reaction is rationalized in terms of a four-membered cyclic transition state type of mechanism. The kinetic and thermodynamic parameters of the hydroxynitroalkane substrates are presented and discussed. Copyright 2004 John Wiley & Sons, Ltd.

The effect of the acidity of CH groups within the guests on the binding ability of the aromatic cavity of rigid cone conformers of p-tert-butylcalix[4]arene toward guests containing acid CH3 and CH2 groups have been investigated in a

The partial oxidation of methane in the gas phase reaction of CH4-O2- NO2 was enhanced with the addition of a small amount of methanol; the selectivity of methanol at the same level of CH4 conversion was enhanced in the presence of methanol which showed this effect exclusively in the presence of NO2.

The selective oxidation of methane with oxygen to C1 oxygenates (methanol and formaldehyde) is an important process. However, the precise reaction mechanism in a gaseous chain reaction has not been clarified. Methane activation and the selectivity of C1 oxygenates (CH3OH, CH2O) in a gaseous selective oxidation of CH4O2-NO2 have been examined under atmospheric pressure with both theoretical and experimental approaches. Theoretically calculated transition barrier of hydrogen abstraction from CH4 of the reaction CH4 + NO2 → CH3 + HNO2 was lower than that of the reaction with O2, i.e., CH4 + O2 → CH3 + O2H. This decrease of the transition barrier was experimentally verified by the linear enhancement of CH4 conversion with NO2 concentration in CH4-O2-NO2. The experimental varied results of selectivity of C1 oxygenates on various reaction conditions (NO2 concentration, CH4O2 ratio, space velocity) showed the appropriateness of the consideration on the selectivity with the calculated values of transition barriers and rate constants of the selected reaction routes from CH3O to CH3OH and CH2O. After considering the transition barriers and rate constants of each elemental reaction route, we attained ca. 7% yield of C1 oxygenates.

The title reactions were investigated using pulsed laser photolysis combined with pulsed laser induced fluorescence detection of CH3O to determine the rate coefficients for CH3+NO2→products (3) and CH3O+NO2→products (5) as a function of temperature and pressure, and to estimate the yield of CH3 (and thus the yield of CH3C(O)OH) from the reaction of OH with CH3C(O)CH3 (2) at two different temperatures. Reaction 3 has both bimolecular and termolecular components: a simplified falloff parametrization with Fcent = 0.6 gives k3b0 = (3.2±1.3)×10-28(T/297)-0.3 cm6 s-1 and k3b∞ = (4.3±0.4)×10-11(T/297)-1.2 cm3 s-1 with CH3NO2 the likely product. The rate constant for the bimolecular reaction pathway to form CH3O+NO (3a) was found to be 1.9×10-11 cm-3 s-1. The low- and high-pressure limiting rate coefficients for reaction between CH3O and NO2 to form CH3ONO2 (5b) were derived as k5b0 = (5.3±0.3)×10-29(T/297)-4.4 cm6 s-1 and k5b∞ = (1.9±0.05)×10-11(T/297)-1.9 cm3 s-1, respectively. Although the final result is associated with some experimental uncertainty, we find that CH3 is formed in the reaction between OH and CH3C(O)CH3 at ≈50% yield at room temperature and 30% at 233 K.

Thermal decomposition of dinitramide onium salts proceeds via the dissociative mechanism when pKa of the base is lower than 5.0 and via the monomolecular decay of the anion at pKa > 7.0. On going from the melt to the solid state, the reaction mechanism does not change, and the rate decreases by 1-2 orders of magnitude. No anomalous effects inherent in dinitramide metal salts in the solid phase are observed during decomposition of onium salts.

A new series of calix[4]arenes, diametrically bridged at the upper rim with pyridino systems, has been synthesized. The shape, rigidity, and chemical structure of the bridge influence the host-guest complexation properties of these systems in solution toward several neutral molecules having acidic C-H bonds. Additionally, selective complexation of methylammonium tosylate in comparison with other ammonium salts has been observed and the strength of this complexation enhanced by electron-donor ability of the p-substituent on the pyridine moiety of the calixarene host. X-ray crystal structures of endo complexes of host 5 with malononitrile and nitromethane have been resolved, verifying specific C-H bonding with the hard oxygen and nitrogen atoms of the bridge and the soft aromatic ring of the calixarene.

Rates of reversible carbon deprotonation of 2-nitroethanol (2) and 2-nitro-1,3-propanediol (3) by hydroxide ion, water, amines, and carboxylate ions and pKa values for the ionization at carbon (pKaCH) and oxygen (pKaOH) and ionization of the aci-forms (pKaNOH) were determined in aqueous solution at 25 °C. The pKaCH values for 2 and 3 are 8.60 and 7.68, respectively, as compared to 10.22 for CH3NO2. The acidifying effect of the CH2OH groups is attributed to a combination of inductive electron withdrawal and hyperconjugative stabilization of the respective nitronate ions, possibly coupled with intramolecular hydrogen bonding stabilization of this ion. The higher acidity of 2-nitroethanol compared to nitromethane is reflected in higher rates of proton transfer from 2-nitroethanol, implying a "normal" Br?nsted α between 0 and 1. This contrasts with the negative α value based on the reaction of OH- with nitromethane, nitroethane, and 2-nitropropane (Kresge, A. J. Can. J. Chem. 1974, 52, 1897). Reasons why a normal α value is observed in the current system are discussed.

The addition of NO2 to the gas-phase reaction of CH4 with O2 conducted under normal pressures at temperatures of 400-460 deg C enhances the partial oxidation of methane with improved selectivities to organic products.

It was shown that pure low-molecular nitroparaffins can be synthesized by the reaction between alkyl sodium sulfates and nitrite ion in ionic melts.The yield of the product is temperature controlled.Because of the ambident nature of nitrite ion, the main side product is alkyl nitrite, subsequent decomposition of which results in formation of a series of organic oxygen-containing compounds.The formal kinetics of the alkylation of nitrite ion by alkyl sodium sulfates was found to be described by the first-order equation.

The kinetics of retroaldol reaction of β-nitrostyrene and β-methyl-β-nitrostyrene and their para-substituted derivatives have been studied spectrophotometrically in 1:1 methanol-water (v/v) in the presence of sodium hydroxide.The order is unity in and fractional in ->.In the reaction of β-methyl-β-nitrostyrene the order in and -> is unity each.On the basis of the kinetic data, a stepwise reaction mechanism has been proposed which involves nucleophilic attack of OH- on the α-carbon and subsequent cleavage of Cα - Cβ bond.The rate of β-methyl-β-nitrostyrene is less than that of β-nitrostyrene.Electron-withdrawing substituents retard it.Satisfactory Hammett correlations have been observed in both reaction series.

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The kinetics of the reactions of CH3O and CD3O with NO have been studiedusing a discharge flow reactor.CH3O and CD3O were detected using laser-excited fluorescence (LEF) near 300 nm.Total rate coefficients for the reaction of CH3O with NO were measured as a function of temperature (220-473 K) and presure (0.75-5.0 Torr) of He or Ar.Total rate coefficients for the CD3O + NO reaction were measured at ca. 294 K over the pressure range 0.75-5.0 Torr He.Using molecular-beam mass spectrometry, the CH3ONO zield of the CH3O + NO reaction was measured at 297 K (0.5 and 1.0 percentTorr) and 223 K (1.0 Torr), showing that disproportionation to H2CO + HNO is the major channel at low pressures.These results were combined to obtain the following expressions for the disproportionation and low-pressure recombination rate coefficients.For the CH3O + NO reaction, kDISP=(1.3 +/- 0,4) x 10-12 exp cm3s-1, kolll=(1.8 +/- 1.3) x 10-29 (Τ/300)-(3.2+/-0.5) cm6 s-1.For the CD3O + NO reaction at 294 +/- 2 K, kDISP =(3.0 +/- 0.4) x 10-12 cm3 s-1, and kolll = (2.5 +/- 0.4) x 10-29 cm6 s-1.While the uncertainty associated with the measured rate coefficients is ca. +/- l5percent, the product channel-specific rate coefficients obtained from these expressions are less certain, ca. +/- 50percent.Using MBMS, the CH3NO2 yield of the CH3 + NO2 reaction was measured at 297 K )0.5 and 1.0 Torr) and 223 K (1.0 Torr).Combined with the previously reported rate coefficient, these results indicate a low-pressure, third-order recombination rate coefficient of (6 +/- 2) x 10 -29cm 6 s-1 in He at 297 K.

A scale of equilibrium cryptate acidity in tetrahydrofuran is constructed.Its distinguishing feature is the constancy of the contribution from ionic association.A method is proposed for determination of the constants for the association of the ions into ion pairs in dimethyl sulfoxide.

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Rate constants of ionization of phenylnitromethane in seven amine buffers and six carboxylate buffers and of nitromethane in five amine buffers were determined in 90percent Me2SO-10percent water.Similar experiments with a smaller selection of buffers were performed in water, 50percent Me2SO-50percent water, and 70percent Me2SO-30percent water.Buffer plots with amine buffers in 70percent and 90percent Me2SO, but not with carboxylic acid buffers, showed downward curvature, which was attributed to a hydrogen-bonded association complex between the nitronate ion and the protonated amine.Asocciation equilibrium constants for these complexes were determined, and τ values for hydrogen bond ing were calculated on the basis of the Hine equation.These τ values ranging from 0.024 to 0.039 are much higher then those for the association between protonated amines and phenoxide ions in water (τ = 0.013, Stahl and Jencks, J.Am.Chem.Soc. 1986, 108, 4196), presumably because of reduced hydrogen-bonding stabilization of the nitronate ions by the solvent.Absence of downward curvature in the buffer plots with carboxylic acids is believed to be a consequence of somewhat lower association constans and, more importantly, of competing nitronic acid formation at the low pH values required to study the carboxylic acids.The possibility that the association complex might represent Bordwell's intermediate in the deprotonation of nitroalkanes (BH+...H(R)NO2) is discussed and rejected.The intrinsic rate constants for proton transfer (k0 = k1 B/q = k-1 BH/p at ΔpK + log p/q = 0) increase strongly with increasing Me2SO content of the solvent, but more so when the ionizing base is a carboxylate ion than when it is an amine.This increase is mainly due to a transition state in which solvation of the developing nitronate ion lags behind proton transfer.When the ionizing base is a carboxylate ion, early desolvation of the base adds to the solvent effect on k0.The Broensted β values show the familiar increase with increasing Me2SO content of the solvent, irrespective of buffer type.

The acid dissociation energies of several key biological hydrogen donors are found to fall into a narrow range, ΔHoacid=352-355 kcal/mol.The strong acidities of these donor groups enhance the hydrogen bond strengths involved in the protein α-helix, imidazole enzyme centers and DNA.Specifically, the peptide link is modeled by the dipeptide analogue CH3CO-Ala-OCH3.Its acidity is strengthened, i.e. ΔHoacid is decreased by 8 kcal/mol compared with other amides, due to electrostatic stabilization by the second carbonyl in the peptide -CON-CH(CH3)CO- grouping.The acidity of imidazole is also strengthened by 8 kcal/mol compared with that of the parent molecule, pyrrole, primarily due to resonance stabilization of the ion.Hydrogen donor NH2 groups of adenine and cytosine are modeled by 4-aminopyrimidine, and the acidity of this amine group is strengthened by ring aza substitution.An intrinsic acidity optimized for hydrogen bonding strength therefore emerges as a common property of the diverse hydrogen donors in the protein α-helix, enzymes and DNA.This property may therefore be in part responsible for the natural selection of these molecules as principal biological hydrogen donors.

Desilylative nitration of methyl- and ethylsilanes with nitronium tetrafluoroborate in sulfolane solution gives nitromethane and nitroethane, respectively.Higher alkylsilanes are also nitrated, but the reactions are followed by HNO2 elimination.The method represents the first successful nitrodesilylations at saturated carbon.Allylsilanes react cleanaly with NO2BF4 in methylene chloride solution to give nitropropanes in good to excellent yield.These reactions, however, involve initial attack by NO2+ on the allylic ?-system followed by fluoride-induced trimethylsilyl elimination and not direct desilylative nitration at saturated carbon. 1-(Trimethylsilyl)but-2-ene gives exclusive secondary 3-nitrobut-1-ene and not the primary direct nitrodesilylation product 1-nitrobut-2-ene.

The reactions of the three activated dibenzfulvene derivatives 9-dicyanomethylene, 9-dinitromethylene-, and 9-nitromethylene-fluorene (FDCN, FDN, and FN respectively) with NaOH in water containing 1percent dioxane were followed at 25 deg C.The reactions were found to be zero-order in the substrate and zero-order within a run in the hydroxyde.Overall, the reaction was first-order in the hydroxide.Under these conditions zero-order kinetics are also obtained for the reaction of CN- with FDCN. 'Normal' first-order kinetics were obtained under these conditions for the reaction of OH- with 1,1,diphenyl-2,2-dinitroethylene as well as for FDN when the dioxane concentration was increased to 25percent (v/v).It is suggested that owing to their planar structure these substrates undergo efficient stacking in the solution with only a small fraction left as a free rective monomer and the aggregate maintains a constant monomer concentration in the solution.A Tyndall effect of the aggregated particles could not be observed with the nacked eye.The particles also pass through a Whatman No. 1 filter paper.However, other observation such as solvent and temperature effects on the absorbance in the u.v. range strongly support the suggested explanation.

The dehydration of nitraraine leads to the formation of 1-(2',6'-dimethylbenzyl)-β-carboline, together with other products.Several isomeric 1-(dimethylbenzyl)-β-carbolines have been synthesized for comparison.The products of acylation, hydrogenation, and oxidation of the alkaloid nitraraine have been studied.The results obtained have shown its structure as (+/-)-16-hydroxymethylyohimb-16-ene.

In the AgNO3-NaNO3-NaNO2-H2O system alkyl iodides RI are converted into nitroalkanes and alcohols.The formation of alcohols with a rearranged structure was used as a test for the M+-SN1 mechanism of hydrolysis, and the increase in the accumulation rate of RNO2 with increase in the concentration of NO2- and silver complexes was used as a test for the M+-SN2 mechanism of substitution of iodide by a nitrite ion.It was established that the rate constants vary in the order CH3I +-SN1 paths and CH3I (CH3)2CHCH2I >> (CH3)3CCH2I for the M+-SN2 paths.

Equilibria of addition of water, methanol, methanethiol, ammonia, methylamine, nitromethane, and ethylene glycol to acetaldehyde have been compared in water and in chloroform, and the partition coefficients of reactants and products between the two solvents have been estimated by direct and indirect methods.Single additions of oxygen nucleophiles were found to proceed equally favorably in either solvent, whereas single additions of sulfur, nitrogen, and carbon nucleophiles proceeded much further toward completion in water than in chloroform.Equilibria of acetal formation, involving methanol or ethylene glycol, were somewhat more favorable in chloroform than in water.Reexamination of the vapor pressures of ethylene glycol and related compounds over water indicated that their hydrophilic character was greater than had been supposed.

Using negative ion photoelectron spectroscopy we have measured the electron affinities (EA) of CCO and HCCO.We find EA(CCO) = 1.848 +/- 0.027 eV and EA(HCCO) = 2.350 +/- 0.020 eV.In separate experiments with a flowing afterglow device, we have determined the gas-phase acidity of ketene and report it as ΔH0acid(CH2CO) = 365 +/- 2 kcal/mol.These data afford the ketene bond dissociation energy, DH0298(H-CHCO) = 105.9 +/- 2.1 kcal/mol, and the heats of formation: ΔHf0298(HCCO) = 42.4 +/- 2.1 kcal/mol and ΔHf0298(HCCO-) = -13.3 +/- 2.1 kcal/mol.

Spin-trapping e.s.r. experiments employing both MeNO2 (in conjunction with generation of .OH from the TiIII-H2O2 couple in a flow system) and ButNO ( in conjunction with the photolytic decomposition of H2O2) confirm that the reaction of .OH with methionine, S-methylcysteine, and some related compounds effects oxidative decarboxylation.It is proposed that the reaction proceeds via the sequential formation of an hydroxyl adduct at sulphur, a sulphur-centred radical-cation, and a (cyclic) sulphuranyl radical in which the carboxylate function becomes bonded to sulphur.

The reaction products of unsymmetrical dimethyl hydrazine (UDMH) with nitric acid, under ignition and near ignition conditions have been examined through methods of intrumental analysis.Spectroscopic methods which include uv, ir, nmr and mass spectra have been used for the liquid products and gas chromatography for the gaseous and the liquid products.A mechanism for the reaction is proposed on the basis of the known chemistry of UDMH and HNO3 as well as reactions and intermediates that are known and on analogous reactions of similar reagents.

Ralative two-ligand dissociation enthalpies, δD(Cu+-2L), for Cu+ with 43 organic molecules are determined.A pulsed-laser volatilization/ionization sourse is used to generate Cu+ which reacts with EtCl and/or other molecules to give Cu(ligand)2+ species.Equilibrium constants are measured for the ligand-exchange reactions which occur when pairs of ligand molecules are present.Free energies for two-ligand exchange are obtained from the equilibrium constant for the reaction Cu(A)2+ + 2B ->/+ + 2A.The free-energiy differences are added to give a scale of relative free energies for ligand exchange.These are converted to enthalpies to give δD(Cu+-2L) scale with the assumption that enthropy changes are small and can be neglected except for symmetry corrections which are made in appropriate cases.Dependence of δD(Cu+-2L) on functional group and substituent effects is analyzed.These results for Cu+ are compared to available results for other reference acids: H+, Al+, Mn+, Li+, and CpNi+.These comparisons show that Cu+ is a softer acid than the other reference acids.This is apparent from the relative preference of Cu+ for mercaptans and HCN compared to alcohols and other oxygen bases.

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Investigation of the formation of complex reaction products in the gas-phase system O3/NO2/(Z)-2-butene by combination of linear reactors with IR. matrix and microwave Stark spectroscopy is reported.Besides the polyatomic products observed earlier in the gas-phase ozonolysis of (Z)-2-butene, the following products were identified: N2O5, HNO3, HNO4, CH3NO2, CH3ONO, CH3COONO2 and CH3COO2NO2 (peroxyacetyl nitrate PAN).Matrix IR spectra of N2O5, HNO3, CH3COONO, CH3COONO2 required for reference purposes are presented.It is shown that PAN-formation occurs already in the absence of light.A reaction scheme is proposed for explanation of the observed complex NOx-containing products, which assumes methyldioxirane as a central intermediate.Particular reaction steps of the scheme will be discussed, including thermochemical estimates of reaction enthalpies.

Studied by static method the reaction is followed by measuring the derivative of the pressure variations as a function of time and by analysis of methanol, ethanol, acetone, nitromethane, 2,3 epoxy butane, 1,2 epoxy butane, butanone, 2-butanol and carbon oxide and dioxide by gas-chromatography.The methylamines are analysed by colorimetry through pH measurements.The analyses are mainly performed in the slow branched-chains reaction zone and followed as a function of the butane concentration and for increasing amounts of each of the three additives.A relevant explanation of the nitromethane formation in presence of methylamines enable us to enlighten some interesting features of the reaction mechanism.