Decomposition Of Diazomethane Research Articles

Catalytic cyclopropanation of spiro[2.4]hepta-4,6-diene with diazomethane

Catalytic cyclopropanation of spiro[2.4]hepta-4,6-diene with diazomethane in the presence of copper or palladium compounds results in mono- and dicyclopropanation products, namely, spiro[bicyclo[3.1.0]hex-3-ene-2,1′-cyclopropane] and spiro[cyclopropane-1,5′-tricyclo[4.1.0.02,4]heptane], with different efficiency. The use of Pd compounds as catalysts allows the cyclopropanation to be performed under conditions of simultaneous generation and decomposition of diazomethane.

Silicon carbide nanotubes (SiCNTs) serving for catalytic decomposition of toxic diazomethane (DAZM) gas: a DFT study

ABSTRACTIn the present study, the adsorption and decomposition of diazomethane (DAZM) on the surface of (6,0) zigzag silicon carbide nanotube (SiCNT) are investigated using density functional theory calculations. The geometry structures of the three stable configurations, adsorption energies and electronic properties of DAZM adsorption on the surface of SiCNT are investigated. It was found that the DAZM molecule is decomposed over the surface of (6,0) SiCNT with activation energy (Eact) of 0.523 eV. The curvature effect on the adsorption energies of the DAZM molecule is also considered by studying (5,0) and (7,0) SiCNTs. The results display that DAZM adsorption over smaller diameter of SiCNT is thermodynamically more favourable than larger one.

Excitation of chemiluminescence in the reaction of benzophenone-O-oxide with diphenyldiazomethane. Quantum-induced decomposition of diphenyldiazomethane

The excitation yield (⌽+) of triplet benzophenone in the chemiluminescence reaction of thermal decomposition of diphenyldiazomethane (Ph2CN2) was measured. Triplet benzophenone was produced by the reaction of benzophenone-O-oxide with Ph2CN2 in a MeCN solution. The ⌽+ value is equal to 0.05 and temperature-independent. Analysis of the dependences of the observed rate constant of chemiluminescence decay on the concentration of Ph2CN2 both in the presence and absence of a luminescence activator suggests the quantum-induced decomposition of diazomethane in the reaction with triplet benzophenone. The rate constant of the reaction of triplet benzophenone with Ph2CN2 was estimated.

ChemInform Abstract: Cyclopropanation of Allenes by Diazomethane in the Presence of Palladium(II) Compounds.

AbstractThe cyclopropanation of the unsymmetrically substituted allenes (Ia), (Ib) and (V) is accomplished by the decomposition of diazomethane (II) in the presence of Pd(II) compounds to yield the methylenecyclopropanes (IIIa), (IIIb) or (VI), which result by cyclopropanation of the less substituted carbon‐carbon double bond of the starting allenes.

Reaction of carbenoid species diazomethane decomposition over zeolite ZSM-5

Decomposition of diazomethane over zeolite ZSM-5 gives ethene and propane as the major products; this supports the existence of carbenoid intermediates proposed in methanol conversion into ethene and higher hydrocarbons over this catalyst.

Problems incurred in stabilizing polymers against oxidative degradation. Model studies on active functional groups in the polymer substrate and new inhibitors

An investigation was made into the formation of functional groups that occur in unstabilized polyethylene during oxidation under the conditions of the induction test. Model substances were synthesized in which the nature and amount of functional groups, e.g. peroxide, carbonyl, hydroxyl, vinyl, etc., differed. The behaviour of these specimens was studied under the conditions of the oxidation test. The relationship of the induction time to the type of functional group allowed a sequence of reactivity to be drawn up. i.e. •—OOH > CO > —CH2CH CH2 > O—CH==C112 > —C=C-->—C---H > 01011 > CH—OR Here the damaging effect of the peroxide group on the alkyl ether group decreases from left to right. Comparison was made with a specimen stabilized with substituted phenols and a polymethylene produced by the decomposition of diazomethane. The second part of the paper presents substances of the following structures containing S-: e CH2:CHS—CH2CH2R CII2CH -S--CH2—CH20H X R H0--CH2---C112--S—CH2-—CH2-—S—CH2-—CH2—OH The functional groups of these compounds compensate the injurious effect of the groups in the substrate, with the result that the compounds act as inhibitors. For example, the thioether bridges are converted to SO and ) SO2 derivatives. The sulphurous substances that also contain a vinyl double bond allow capture by disproportionation and addition reactions. Although much work has been devoted to it, the problem of stabilizing polymers against oxidative degradation is still widely discussed. It retains its importance for the following reasons. (1) Increasing demands are being imposed by plastics processors and end users. (2) There are no technically 253 HERBERT NAARMANN perfect products available, i.e. most products display some defects, have fluctuations in their molar weights and morphology, and contain some impurities. Improvements in manufacturing processes and changes in the specifications for the raw materials may appear to be insignificant microscopically but, when regarded in detail, are often the reason for troublesome secondary effects. The need for developing even more effective inhibitors has not lost its urgency. Because of this, oxidative reactions in polymers assume great practical importance. Much work has been carried out in this field, it is assumed that the first stage of oxidation is the formation of radicals and of hydroperoxides, which have been detected in all polyolefin oxidation processes. We have tried to establish a relationship between oxidative degradation and the chemical structure of products with a defined amount of functional groups in the light of the many hypotheses that have been put forward and the analytical data available. Polyethylene was taken as a model.

A spectroscopic study of the photodecomposition of diazomethane.

Abstract— The decomposition of diazomethane by photolytic means has been studied both in inert gas matrices near 4°K and in the gas phase near 295°K. The direct detection of the diazomethyl radical, HCNN and DCNN, and evidence for the participation of methanal azine, H2C=‐N=CH2, by vibrational spectroscopy proved that both species play a significant role in the decomposition schemes under the conditions of investigation. The present results make possible the reinterpretation of the data from earlier published experiments to conform to these schemes. The isomerisation of diazomethane is also discussed, and evidence is presented for the production of both diazirine and isodiazomethane under certain photolytic conditions, the former by an intramolecular process and the latter by the recombination of the diazomethyl radical with a hydrogen atom. The vibronic absorption spectra of gaseous diazomethane at 295°K are presented, and deductions concerning photochemical processes are drawn.

SINGLET METHYLENE FROM THERMAL DECOMPOSITION OF DIAZOMETHANE. UNIMOLECULAR REACTIONS OF CHEMICALLY ACTIVATED CYCLOPROPANE AND DIMETHYLCYCLOPROPANE MOLECULES

The thermal decomposition of diazomethane (DM) into singlet methylene radicals and nitrogen has been studied from 225° to 450° in 10:1 olefin–diazomethane mixtures. At 2.5 cm pressure, k = 1.2 × 1012 exp (−34,000/RT) sec−1. The methylene radicals have similar reactivity to methylene generated from photolytic decomposition of DM, as judged by the follow-up reactions with ethylene and cis-butene-2. The structural isomerization reactions of energized cyclopropane and the structural and geometric isomerization of 1,2-dimethyl-cyclopropane (DMC), formed from the addition of the thermally generated methylene to the olefins, were measured from 250° to 450° over a wide range of pressures. For comparison, cyclopropane formed from photolysis at 4358 Å and 25° of DM and ethylene was studied. As judged from comparison of the experimental isomerization rate constants, the energy of the cyclopropanes formed at 350° in the thermal DM system is about the same as for cyclopropanes formed by photolysis at 4358 Å of DM at 25°. The experimental rate constants obtained on the assumption of strong collisions are compared with calculated rate constants which are based on quantum statistical models for kE which fit literature data on conventional thermal isomerization of cyclopropane and DMC. From this comparison, the average energies of the formed molecules in the thermal systems are estimated to be between 107 and 115 kcal/mole, depending upon the temperature. Photolysis at 25° of the ketene–ethylene system (3200 Å) and of DM–ethylene system (4358 Å) give cyclopropane characterized as being at 103 and 111 kcal/mole respectively. These energies deduced from kinetic data are compared with available thermochemical quantities; the existing value of ΔHf0(CH2N2) is questioned. Further support for fast intramolecular relaxation of vibrational energy in DMC, relative to the relaxation process for reaction, is noted. Comparison of data in the literature on the ketene and DM photolytic systems strongly suggests that a larger fraction of the excess light energy resides with methylene from ketene (0.65–0.8) than with methylene from DM (0.3–0.5). Various approximations for the calculation of kE are examined and are compared with accurate quantum statistical evaluation.

Reactions of diazoalkanes upon metallic surfaces: Polymer formation and a stereoregulating action of gold

AbstractEarlier investigations are reported on the decomposition of diazomethane in ethereal solution, in the presence of gold chloride as a catalyst: these have shown that the catalytic activity in obtaining polymethylene from the diazo compound is due to gold metal.The catalytic action of gold under similar conditions upon diazoethane has brought to the formation of crystalline polyethylidene, obtained by the authors for the first time. The gold surface, then, in the present case, exhibits a stereoregulating activity in the reaction.These results led the authors to investigate more thoroughly the polymerizing action of different metal surfaces, prepared as evaporated films, on the first terms of the diazoalkane series.The main results are reported as obtained by following the reaction with the help of chromatographic analyses of the gases, liberated aside of nitrogen. The present remarks have been made:The following metals, in decreasing order of yield, give amorphous polymers: Cu, Ti, Fe, Mg, W, Ni, Mn, V, Ta, Pt, Co, Zn, Cd, Au, Cr, Al, whilst Mo, Pd, Rh, Zr, Ag, give practically no polymer, although causing the decomposition of the diazo compound. These experiments are related to diazoethane in ethereal solution.It is confirmed that gold only, among the metals tried up to the present, shows a stereospecific action in the formation of polymer from diazoethane.The chromatographic analysis of the gases developed from the decomposition of diazoethane on the following metals: Pd, Ag, Mo, Cu, Au, show that, the surfaces catalyzing polymer formation give out chiefly the butenes‐2, with small quantities of ethylene, whilst the metals not forming polymer develop chiefly ethylene together with small quantities of ethane.For the first time, still by the action of gold metal surfaces, apparently crystalline polymers from diazopropane and diazobutane have been obtained, showing that the stereospecific action of gold, looks not to be limited to the only case of diazoethane, but to be valid also for the higher terms of the series with formation of apparently stereoregular polymers of the type CHRCHRCHR, where R is a chemical group.The crystalline structure of polyethylidene is discussed.The following infrared spectra are reported: (a) of gaseous diazoethane (whose structure is discussed); (b) of amorphous polybutylidene; (c) of the crystalline polymers obtained from the corresponding diazoalkanes, namely polyethyl‐, polypropyl‐, polybutylidene. Some simple schemes for the reaction paths, drawn from the present experimental data, are suggested.

Molecular weight‐intrinsic viscosity relationship and molecular weight distribution of low pressure polyethylenes

AbstractMolecular weights of low pressure polyethylene fractions were measured by an ebulliometric method and an osmotic pressure method. The results can be correlated by an equation, [η] = 5.10 × 10−4 M0.725, with the intrinsic viscosity measured at 130°C. in Tetralin, for a molecular weight greater than 3750. All three types of polymer fractions, Ziegler‐type low pressure polyethylene, Phillips low pressure polyethylene, and polymethylene from the decomposition of diazomethane, conform to the above correlation. The molecular weight distributions of two samples of Ziegler type polyethylene and one sample of Phillips' Marlex 50 were determined. All three distributions were found to be very broad and contained large amounts of low molecular weight materials.

CONTRIBUTION TO THE SYNTHESIS OF ORGANIC DEUTERIUM COMPOUNDS: I. DEUTEROPOLYMETHYLENE

An improved method of preparing polymethylene, (CH2)n, by the decomposition of diazomethane is described. A new polymer, polyethylidene, (CH3∙CH)n, has been obtained from diazoethane by the same reaction. Diazomethane-d2 is reported for the first time. A new deuterated polymer, (CD2)n, obtained by the decomposition of diazomethane-d2 has been synthesized.