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81.
The mass spectra of the three isomeric trimethylanilinium oxides and their methyl-d3 analogues show that the m- and p- isomers undergo intermolecular trans-O-alkylation before evaporation. In the o-isomer, only 10% transalkylated product is observed and there is strong evidence that most of this isomer evaporates without undergoing structural changes. By indirect introduction, however, the o-isomer showed only transalkylated product. The most important fragmentation patterns on electron-impact are α-cleavage on the N-methyl carbon or expulsion of the O-substituent with formation of a quinoid structure. The latter dominates for the o- and p-methyl ethers while the former is the most important pathway for the m-isomer and for the corresponding phenols. Lower fragments are of modest intensity. 相似文献
82.
Stanoeva T Neshchadin D Gescheidt G Ludvik J Lajoie B Batchelor SN 《The journal of physical chemistry. A》2005,109(49):11103-11109
The degradation of dyes is frequently initiated by one-electron oxidation or reduction; however, relatively little is known about the initially formed radicals. Acid Green 25 (AG25), Crystal Violet (CVI), Methylene Blue (MB), and Acid Orange 7 (AO7), representing paradigms of four types of commercial organic dyes, were therefore investigated in terms of their redox behavior. Their redox potentials in MeCN and buffered aqueous solutions were determined by cyclic voltammetry. The structures of the one-electron reduced and oxidized dyes were established by EPR spectroscopy and by theoretical calculations on the density functional level of theory. 相似文献
83.
84.
Zusammenfassung Acenaphthylen wurde durch Anpolymerisation und zweifache Hochvakuumsublimation gereinigt. Die Reinigungsmethode wird ausführlich beschrieben.Bei verschiedenen Temperaturen wurde mit einer dilatometrischen Methode die thermische Bruttogeschwindigkeit gemessen. Zwischen 95 und 105 °C giltk
br=7,08·1010 exp (– 30,9 kcal/RT).Die beträchtliche Aktivierungsenergie der Bruttoreaktion ist sowohl auf eine große Aktivierungsenergie der thermischen Startreaktion als auch auf eine relativ hohe Wachstumsaktivierungsenergie zurückzuführen.Das Polymerisationsverhalten von Acenaphthylen kann vermutlich aufgrund seiner sterischen Eigenschaften erklärt werden.
Summary Acenaphthylene was purified by partial polymerisation, followed by double stage high vacuum sublimation. The method of purification is described in detail.The thermal overall rate was measured at different temperatures by a dilatometric method. Between 95 and 105 °C the following relation holds:k th=7,08 · 1010 exp (– 30,9 kcal/RT).The considerable energy of activation of the overall reaction depends on a relatively high energy of activation of both the thermal initiation and the propagation reaction.It is supposed, that the polymerisation behaviour of acenaphthylene depends mainly on its steric properties.相似文献
85.
Pericet-Camara R Papastavrou G Borkovec M 《Langmuir : the ACS journal of surfaces and colloids》2004,20(8):3264-3270
The adsorption behavior of poly(amidoamine) dendrimers to mica surfaces was investigated as a function of ionic strength and pH. The conformation and lateral distribution of the adsorbed dendrimers of generations G8 and G10 were obtained ex situ by tapping mode atomic force microscopy (AFM). The deposition kinetics of the dendrimers was found to follow a diffusion-limited process. Fractional surface coverage and pair correlation functions of the adsorbed dendrimers were obtained from the AFM images. The data are interpreted in terms of the random sequential adsorption (RSA) model, where electrostatic repulsion due to overlapping double layers is considered. Although the general trends typical for an RSA-determined process are well-reproduced, quantitative agreement is lacking at low ionic strengths. 相似文献
86.
The rhodium(I) complexes trans‐[Rh(diphos)(CO)Cl] 7 (diphos=pbpb), 8 (diphos=nbpb), and 9 (diphos=cbpb) were synthesized (Scheme 4) and used as catalysts for the carbonylation of MeOH to AcOH (Scheme 1). The trans coordination imposed by the rigid C‐spacer framework of the diphos ligands pbpb, nbpb, and cbpb, demonstrated by 31P‐NMR and IR spectroscopy of 7 – 9 and unambiguously confirmed by single‐crystal X‐ray structure analysis of 7 , improved the thermal stability of the rhodium(I) system under carbonylation conditions and, hence, the catalytic performance of the complexes. For the catalytic carbonylation of MeOH, the active catalyst could be prepared in situ from the mixture of [Rh(CO)2Cl]2 and the corresponding diphos ligand pbpb, nbpb, or cbpb, giving the same results as carbonylation in the presence of the isolated complexes 7, 8 or 9 (see Table). The highest activity was observed for complex 7 (or the mixture [Rh(CO)2Cl]2/pbpb, the catalytic turnover number (TON) being 950 after 15 min (170°, 22 bar). 相似文献
87.
Frank W. Vergeer Taasje Mahabiersing Enrique Lozano Diz Georg Süss-Fink František Hartl 《Journal of Cluster Science》2004,15(1):47-59
Electrochemical and photochemical properties of the tetrahedral cluster [Ru3Ir(
3-H)(CO)13] were studied in order to prove whether the previously established thermal conversion of this cluster into the hydrogenated derivative [Ru3Ir(-H)3(CO)12] also occurs by means of redox or photochemical activation. Two-electron reduction of [Ru3Ir(
3-H)(CO)13] results in the loss of CO and concomitant formation of the dianion [Ru3Ir(
3-H)(CO)12]2–. The latter reduction product is stable in CH2Cl2 at low temperatures but becomes partly protonated above 283K into the anion [Ru3Ir(-H)2(CO)12]– by traces of water. The dianion [Ru3Ir(
3-H)(CO)12]2– is also the product of the electrochemical reduction of [Ru3Ir(-H)3(CO)12] accompanied by the loss of H2. Stepwise deprotonation of [Ru3Ir(-H)3(CO)12] with Et4NOH yields [Ru3Ir(-H)2(CO)12]– and [Ru3Ir(
3-H)(CO)12]2–. Reverse protonation of the anionic clusters can be achieved, e.g., with trifluoromethylsulfonic acid. Thus, the electrochemical conversion of [Ru3Ir(
3-H)(CO)13] into [Ru3Ir(-H)3(CO)12] is feasible, demanding separate two-electron reduction and protonation steps. Irradiation into the visible absorption band of [Ru3Ir(
3-H)(CO)13] in hexane does not induce any significant photochemical conversion. Irradiation of this cluster in the presence of CO with
irr>340nm, however, triggers its efficient photofragmentation into reactive unsaturated ruthenium and iridium carbonyl fragments. These fragments are either stabilised by dissolved CO or undergo reclusterification to give homonuclear clusters. Most importantly, in H2-saturated hexane, [Ru3Ir(
3-H)(CO)13] converts selectively into the [Ru3Ir(-H)3(CO)12] photoproduct. This conversion is particularly efficient at
irr
>340nm. 相似文献
88.
Werner Georg Nowak 《manuscripta mathematica》1982,39(2-3):277-285
Let G (R) denote the number of lattice points (,) **Z2 in the domain B(R) bounded by the lemniscate (x2+y2)2=2R2 (x2–y2) and put P(R)=G(R)-R2(R2 being the area of B(R)). The purpose of this paper is to determine the order of magnitude of P(R) for large R by proving the asymptotic relation (3). An analogous result is given for the eight curve x4=R2 (x2–y2). 相似文献
89.
Bismuth Monoiodide, a Compound with Bi(O) and Bi(II) Bismuth monoiodide was synthesized in closed tubes from the elements as well as from Bi and HgI2 as a black coloured crystalline compound. With increasing temperature BiI passes two transitions. α-BiI is stable below 370 K and changes to β-BiI by a martensitic transition. γ-BiI is the stable modification above 564 K and decomposes at 585 K peritectically to BiI3 and a lower iodide. All three modification crystallize in the monoclinic space group C2/m. The structures (single crystal studies) of α-BiI and β-BiI are characterized by onedimensional infinite chains [Bi4I4] with covalent bonds but only weak interactions in between. The [Bi4I4]-chains are built up by two completely different Bi atoms. Bi(A) is only bonded to three Bi whereas Bi(B) has bonds to one Bi and four I. The average bond lengths are Bi? Bi = 304.5 pm and Bi? I = 313.7 pm respectively. The configuration of the Bi(A) atoms is typical for BiO and that one of the Bi(B) atoms is characteristic for Bi2+ with the electron configuration s2p1. Therefore, α-BiI and β-BiI are mixed valence compounds [BiOBi2+I4]. The structures are variants of the simple cubic polonium type of structure and differ in the stacking of connected units. The structures and their transitions, the possible configurations for monohalides BiX on principle as well as the energy balances of the disproportionation of Bi+ are discussed together in detail. 相似文献
90.
[reaction: see text] The combination of diethyl phosphite and DMAP as ligands for nickel in an 8:1 THF-N-ethylpyrrolidinone (NEP) mixture allows a very efficient cross-coupling reaction to be performed between various functionalized arylzinc halides and aryl bromides, triflates and activated chlorides. The reaction proceeds at 25 degrees C within 1-48 h and requires only 0.05 mol % of the nickel catalyst. 相似文献