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1.
Julio Casado J. Ramón Leis Manuel Mosquera L. Carlos Paz M. Elena Peña 《Monatshefte für Chemie / Chemical Monthly》1984,115(2):155-163
Acetic acid/acetate ion buffer acts catalytically upon the nitrosation of amines under conditions in which the only nitrosating agents are N2O3 and NOBr, but inhibits nitrosation by H2NO
2
+
. The kinetic characteristics of these phenomena have been analysed quantitatively and compared with similar effects caused by the solventsTHF, DMSO and dioxane. The experimental results show that this behaviour is an effect of the medium.
Kinetische Untersuchungen zur Bildung von N-Nitroso-Verbindungen, 8. Mitt.: Nachweis eines Medium-Effekts von Essigsäure/Acetat-Puffer auf die Geschwindigkeitskonstante der Nitrosierung
Zusammenfassung Essigsäure/Acetat-Puffer wirkt bei der Nitrosierung von Aminen katalytisch, unter Bedingungen, wo die alleinigen nitrosierenden Agentien N2O3 und NOBr sind; andererseits wird die Nitrosierung durch H2NO 2 + unterbunden. Die kinetischen Charakteristika dieses Phänomens wurden quantitativ analysiert und mit ähnlichen Effekten der LösungsmittelTHF, DMSO und Dioxan verglichen. Die experimentellen Ergebnisse zeigen, daß dieses Verhalten auf einen Mediumeffekt zurückzuführen ist.相似文献
2.
Julio Casado Albino Castro Manuel Mosquera M. Flor Rodríguez Prieto José Vázquez Tato 《Monatshefte für Chemie / Chemical Monthly》1984,115(6-7):669-682
A study of the nitrosation of N-methylaniline and piperazine by nitrous acid in acetate buffer supports a mechanism covering both reactions, whose effective pathway depends on the relationship between the concentrations of nitrite ion, acetate ion, and nitrosatable substrate. In the case of N-methylaniline the only nitrosating agent is nitrosyl acetate, whereas in the nitrosation of piperazine the nitrous acidium ion and dinitrogen trioxide are also involved.The results obtained seem to show that nitrosation by nitrosyl acetate is diffusion controlled. On this assumption, the equilibrium constant of the reactionAcOH + HNO2 AcONO + H2O has been estimated from kinetic measurements as approximately 1.4 · 10–8
M
–1. This means that the concentration of nitrosyl acetate in the medium must be extremely small, which explains the virtual impossibility of detecting it in aqueous solution except by kinetic methods.
Kinetische Untersuchungen zur Bildung von N-Nitroso-Verbindungen, 9. Mitt.: Nitrosylacetat als Nitrosierungsreagens
Zusammenfassung Die Untersuchung der Nitrosierung von N-Methylanilin und Piperazin mit Salpetriger Säure in Acetat-Puffer unterstützt einen für beide Fälle geltenden Mechanismus, dessen effektiver Ablauf von den Konzentrationsverhältnissen des Nitritions, des Acetations und der nitrosierbaren Substanz abhängt. Im Fall des N-Methylanilins ist das einzige Nitrosierungsagens Nitrosylacetat, während bei der Nitrosierung von Piperazin das Nitrit-Acidium-Ion und Distickstofftrioxid ebenfalls beteiligt sind.Die erhaltenen Resultate scheinen zu zeigen, daß die Nitrosierung durch Nitrosylacetat diffusionskontrolliert ist. Unter dieser Annahme kann die Gleichgewichtskonstante der ReaktionAcOH + HNO2 AcONO + H2O aus kinetischen Messungen zu etwa 1,4 · 10–8 M –1 abgeschätzt werden. Das bedeutet, daß die Konzentration von Nitrosylacetat im Medium extrem gering sein muß; das erklärt die praktische Undetektierbarkeit dieser Spezies in wäßriger Lösung, ausgenommen mit kinetischen Methoden.相似文献
3.
4.
A. K. Jain B. B. Sahoo N. Atray V. Jain P. Singh 《Reaction Kinetics and Catalysis Letters》1998,63(1):171-178
Pyrrolidinolysis and piperidinolysis ofO-aryl oximes show third order dependence on amine with no uncatalytic route. The effect of temperature on separate routes
and overall rate is reported and explained. 相似文献
5.
Stanisław Zieliński Lechosław Lomozik Anna Wojciechowska 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1245-1252
The formation of the lanthanide (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) complexes with proline and hydroxyproline has been investigated by potentiometric methods as well as by a turbidimetric one which has provided some additional conclusions. It has been found that 11 and a slight amount of 21 complexes are formed. The deviation from the typical course of the formation function is discussed. It is suggested that the perturbations of complex formation in the systems are caused by hydrolysis. The stability constants of the complexes are reported.
Potentiometrische Untersuchungen an Lanthanid-Komplexen von Prolin und Hydroxyprolin
Zusammenfassung Die Bildung von Lanthanid-Komplexen (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) mit Prolin und Hydroxyprolin wurde potentiometrisch und mit Hilfe von Trübungsmessungen untersucht. Es wurde festgestellt, daß sich Komplexe der Zusammensetzung 11 und in kleiner Menge auch 21 bilden. Die Abweichung von typischem Verlauf der Bildungskurven wurde untersucht. Es wurde dabei festgestellt, daß für die Störungen in der Komplexbildung die Hydrolyse verantwortlich ist. Die Stabilitätskonstanten wurden bestimmt.相似文献
6.
Krasnov V. P. Levit G. L. Korolyova M. A. Bukrina I. M. Sadretdinova L. Sh. Andreeva I. N. Charushin V. N. Chupakhin O. N. 《Russian Chemical Bulletin》2004,53(6):1253-1256
The influence of the reaction conditions (solvent, base) on the diastereoselectivity of acylation of (±)-3-methyl-2,3-dihydro-4H-1,4-benzoxazine with (S)-naproxen and N-tosyl-(S)-proline chlorides was studied. The highest diastereoselectivity was observed for the reaction carried out in benzene in the presence of aliphatic tertiary amines. 相似文献
7.
The reactions of chloranil (Cl4Q) and bromanil (Br4Q) with aliphatic amines in a DMF : H2O (5 : 1, vol/vol) mixture were studied. The radical anions of 2,5-didimethylamino-3,6-chloro-p-benzoquinone and 2,5-didimethylamino-3,6-bromo-p-benzoquinone were identified by ESR spectra. The reaction rate constant of the replacement of two chlorine atoms by the amino groups in the radical anion of Cl4Q at 288 K was estimated. 相似文献
8.
M. P. Shurygina S. A. Chesnokov M. A. Lopatin V. K. Cherkasov G. A. Abakumov 《Russian Chemical Bulletin》2004,53(11):2485-2489
A study of the kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of hydrogen donors (para-substituted N,N-dimethylanilines and polymethylbenzenes) showed that plots of the quantum yield of photoreduction (H) and apparent reaction rate constant (k
H) vs. oxidation potential of hydrogen donors are extreme. In the presence of amines, k
H and H increase, as a whole, whereas they decrease in the presence of polymethylbenzenes. In coordinates H-G
e (G
e is the change in the free energy of electron transfer) for pairs quinone-H donor, H increases with G
e approaching to zero. For the amine series, this effect is mainly in the exothermic region of G
e (G
e < 0). For the series of polymethylbenzenes, this increase is observed in the endothermic region (G
e > 0).__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2381–2385, November, 2004. 相似文献
9.
Adam Bartecki Bożena Bachmatiuk Maria Cieślak-Golonka Roman Gancarz 《Monatshefte für Chemie / Chemical Monthly》1980,111(4):851-861
The studies on reaction of newly obtained aminophosphonic acid diethyl ester derivatives of fluorene with Cr2O7
2–, CrO4
2–, CrO3Cl– and CrO3 have been investigated using electronic, infrared,Raman and NMR spectral methods. It has been found that the resulting compounds are of the type (AH)2Cr2O7, whereA stands for the organic part of the molecule. The organic cation and solvent effects on the electronic states of pseudotetrahedrally arranged Cr(VI) anions are discussed.
Spektroskopische Untersuchungen über Reaktionen von Chrom(VI)-Verbindungen mit Aminophosphonsäure-Estern
Zusammenfassung Es wurden Elektronen-, Ultrarot-,Raman- und NMR-spektroskopische Untersuchungen beschrieben, die an neuen Verbindungen durchgeführt wurden, welche als Reaktionsprodukte von Cr2O7 2–, CrO4 2–, CrO3Cl– und CrO3 mit Aminophosphonsäurediethylesterderivaten von Fluorene synthetisiert worden waren. Es wurde festgestellt, daß diese Verbindungen mit einer allgemeinen Formel (AH)2Cr2O7 beschrieben können werden, in derA den organischen Teil der Verbindungen bedeutet. Der Einfluß des organischen Kations wie auch der von Lösungsmitteln auf die Elektronenzustände des pseudotetraedrischen Cr(VI)-Anions wurde gleichfalls untersucht.相似文献
10.
A. D. Kirilin A. A. Dokuchaev I. N. Menchaikina E. V. Semenova N. B. Sokova E. A. Chernyshev 《Russian Chemical Bulletin》1996,45(9):2192-2195
The reaction of hydrosilanes with carbon dioxide and secondary amines or silylamines was studied for the first time. The dependence of the composition and the structure of the products obtained on the nature of the reagents and on the reaction conditions was found. The hydrosilane-carbon dioxide system, unknown previously, can be used as anN-siloxycarbonylating reagent in the synthesis ofO-silylurethanes. A scheme for the formation ofO-silylurethanes was proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2309–2312, September, 1996. 相似文献
11.
Casado Julio Castro Albino Leis J. Ramón López Quintela M. Arturo Mosquera Manuel 《Monatshefte für Chemie / Chemical Monthly》1983,114(6-7):639-646
Monatshefte für Chemie - Chemical Monthly - Using a differential spectrophotometric technique in water at 25°C measurements were made of the reaction rate in the nitrosation of a number... 相似文献
12.
J. Zsakó J. Horák Cs. Várhelyi A. Benkő 《Monatshefte für Chemie / Chemical Monthly》1981,112(8-9):945-957
The thermal deamination of [Co(diox·H)2(amine)2]X type complexes were studied in dynamic temperature conditions (diox·H2 stands for 1,2-cycloheptanedione dioxime (heptoxime, heptox·H2) and 1,2-cyclo-octanedione dioxime (octoxime, octox·H2), amine for aniline and pyridine,X for Br, I and NCS). Kinetic parametersn, E and logZ have been derived for some derivatives by means of two computerized integral methods. The influence of the sample weight, heating rate and chemical constitution upon the kinetic parameters, as well as the kinetic compensation effect are discussed.
Thermische Desaminierung einiger Komplexe des Typs [Co(Diox·H) 2 (Amin2]X. Über -Dioximinkomplexe der Übergangsmetalle, LXIV.
Zusammenfassung Die thermische Desaminierung einiger Komplexe des Typs [Co (Diox·H)2(Amin)2]X wurde bei dynamischen Temperaturbedingungen untersucht [Diox·H2 bedeutet 1,2-Cycloheptandiondioxim, (Heptoxim, Heptox·H2) und 1,2-Cyclooctandiondioxim (Octoxim, Octox·H2), Amin bedeutet Anilin und Pyridin,X bedeutet Br, I, bzw. NCS]. Die kinetische Parametern, E und logZ wurden mit Hilfe von zwei computergeeigneten Integralmethoden bestimmt. Der Einfluß des Gewichtes der Proben, der Heizungsgeschwindigkeit und der chemischen Zusammensetzung auf die kinetischen Parameter, bzw. der kinetische Kompensationseffekt werden diskutiert.相似文献
13.
Ab initio calculations on the ground and two excited triplet states (3B1g and 3B1u) of p-benzoquinone are described. The geometries of the three states were fully optimised at the SCF level using the 3-21G basis set. For the excited states, both D2h
and C2v
geometries were investigated. Comparison was made between UHF and ROHF levels of theory. 相似文献
14.
N,N-dimethyl-3-oxa-glutaramic acid was purified and characterized by 1H-NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The thermal decomposition of the title compound
was studied by means of thermogravimetry differential thermogravimetry (TG-DTG) and FT-IR. The kinetic parameters of its second-stage
decomposition reaction were calculated and the decomposition mechanism was discussed. The kinetic model function in a differential
form, apparent activation energy and pre-exponential constant of the reaction are 3/2 [(1−α)1/3−1]−1, 203.75 kJ·mol−1 and 1017.95s−1, respectively. The values of ΔS
≠, ΔH
≠ and ΔG
≠ of the reaction are 94.28 J·mol−1·K−1, 203.75 kJ·mol−1 and 155.75 kJ·mol−1, respectively.
Supported by the National Natural Science Foundation of China (Grant No. 20106009) 相似文献
15.
Cody Timmons Dianjun Chen C. Elizabeth Barney Sameer Kirtane Guigen Li 《Tetrahedron》2004,60(52):12095-12099
A new nitrogen source combination was found for the regio- and stereoselective diamination of α,β-unsaturated ketones. This combination employs the readily available and inexpensive combination of NCS and 2-NsNH2 as the electrophilic nitrogen source, and acetonitrile as the nucleophilic nitrogen source, respectively. The reaction is easily performed by mixing olefin, 2-NsNH2, NCS and 4 Å molecular sieves in freshly distilled acetonitrile at room temperature. The reaction is chemoselective without the formation of any haloamine side products. A new aziridinium ion formed from enones and 2-NsNHCl is suggested to exist and to react with nitrile via a [2+3] cycloaddition mechanism, which is responsible for the excellent regio-, stereoselectivity of the resulting diamination products. 相似文献
16.
17.
Paul R. Davies Frederick Kurzer Alan R. Morgan 《Monatshefte für Chemie / Chemical Monthly》1980,111(5):1097-1109
Hydrolysis and acetolysis of 8-bromo-1-hydroxydi-isophor-2(7)-en-3-one yields both epimeric forms of the corresponding 4-hydroxy and 4-acetoxy-compounds, probably by a mechanism involving a bimolecular (SN2) displacement. The action of excess of hydrazine on the same reactant occurs with evolution of ammonia, to produce good yields of 4-hydrazono-1-hydroxydi-isophor-2(7)-en-3-one. This is convertible into N- and O-acyl derivatives, but its 3-oxo-group fails to raact with the usual ketonic reagents. Instead, its 4-hydrazono-group is displaced by substituted hydrazines and semicarbazides in an exchange process (transhydrazination).Part 5:A. A. Allen, F. Kurzer, andA. R. Morgan, J. C. S. Perkin I1980, 733. 相似文献
18.
J. Casado A. Castro M. A. Löpez Quintela 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1221-1238
The mechanism of formation ofN-nitroso compounds, which are considered as potential chemical carcinogens was studied. The kinetics of nitrosation of piperazine (PIP) in aqueous solution of perchloric acid have been investigated using a differential spectrophotometric technique. Based on our experimental results, the following rate law, in thepH-range 0.85 4.36, is proposed: $$v_0 = \left[ {nitrite} \right]_0 2 \left[ {PIP} \right]_0 /\left( {1 + f/\left[ {H^ + } \right]} \right)^2 \left( {g \left[ {PIP} \right]_0 + h + j\left[ {H^ \div } \right]} \right)$$ where [nitrite]0 and [PIP]0 represent initial stoichiometric concentrations. At 298.2K and μ=1.0M,f=(1.17±0.11) 10?3 M,g=(3.5±0.7) 10?2 M s,h=2.6×10?6 M 2 s andj=(0.95±0.04)M s. When the acidity is increased ([HClO4]≥1M), a new kinetic term comes into play: $$v_0 ' = p\left[ {nitrite} \right]_0 \left[ {PIP} \right]_0 $$ At 298.2 K and μ=3.0M,p=(1.9±0.2) 10?3 M ?1 s?1. A general mechanism for the nitrosation of anyN-nitrosable substrate in aqueous perchloric solution in which the only nitrosating agents are N2O3 and H2NO2 +/NO+ is proposed. Also, the various particularities of this mechanism, according to thepK of theN-nitrosable substrate, are discussed. 相似文献
19.
A. S. Khamidullina I. V. Vakulin R. F. Talipov I. S. Shepelevich 《Journal of Structural Chemistry》2005,46(6):985-990
The mechanism of complexation of the protonated lincomycin molecule with para-substituted nitrobenzenes in the gas phase is analyzed by quantum chemical methods. The regioselectivity of lincomycin protonation is treated in a B3LYP/6-31G(d′, p) approximation; the geometrical structure and conformation of the molecule are analyzed. The lincomycin molecule is protonated at the nitrogen atom of the pyrrolidine cycle. In stable conformers, a pseudovoid is formed and stabilized by intramolecular hydrogen bonding. The cross section of the pseudovoid (1.77–2.62 Å) is too small for the protonated lincomycin molecule to participate in host guest complexation with organic compounds. According to B3LYP/6-31G(d′, p) calculations, complexation of the protonated lincomycin molecule with nitrobenzenes occurs through hydrogen bonding. 相似文献
20.
The dipole moments of a number of substituted benzaldehydes are measured in benzene solution. The angle which the dipole axis
of the CHO group makes with the axis of rotation of the group is determined. The observed moments of the ortho-substituted
benzaldehydes are compared with the moments calculated for free rotation as well as fors-trans ands-cis orientations of the -CHO group.o-Fluorobenzaldehyde exists mostly in thes-trans conformation.o-Chloro-,o-bromo-ando-nitro-benzaldehydcs also exist in thes-trans conformation; their observed dipole moments are even lower than the values calculated fors-trans forms, indicating mutual induction of the ortho substituents. Though 2,5-dichlorobenzaldehyde is expected to have the same
dipole moment as benzaldehyde, the observed moment is significantly lower due to mutual induction of the ortho substituents.
2,5-Dimethylbcnzaldehyde has, however, almost the same moment as benzaldehyde. The dipole moment ofo-methoxybcnzaldchyde is considerably higher than the values calculated for boths-cis ands-trans conformations. An explanation is given for this.o-Hydroxybenzaldehyde exists exclusively in thes-cis form due to internal H-bonding. 相似文献