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1.
T. K. Gar O. A. Dombrova D. A. Ivashchenko V. F. Mironov 《Russian Chemical Bulletin》1993,42(10):1717-1723
The formation of trichlorogermyl-substituted amides, lactams, and imides occurs when 2Et2O·HGeCl3 is condensed with compounds possessing the -NCH2Cl fragment and equally well when HGeCl3 interacts with compounds containing -NCH2OH and-NCH2OSiMe3 groups. In some cases, the use of the latter is more advantageous from the preparative point of view. In compounds thus obtained,
the germanium is five-coordinate due to the coordination
.
Deceased August 13, 1993.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1793–1799, October, 1993. 相似文献
2.
The geometries and bonding characteristics of the complexes of the first-row transition-metal ions with CH, CH2 and CH3 were investigated byab initio molecular orbital theory. MCH+ and MCH2
+ are linear and coplanar, respectively. Both of them are with obvious treble or double bond characteristics, but these multiple
bonds are mostly “imperfect”. The calculated bond dissociation energies of
, and
are mostly close to the experimental values, and appear in similar periodic trends from Sc to Zn.
Project supported by the National Natural Science Foundation of China (Grant No. 29170070). 相似文献
3.
Summary There is no apparent paucity of examples illustrative of the structural changes observed during the gas chromatography of
diverse carbamates and thiocarbamates. In many cases the resultat thermal degradation products observed are analogous in some
measure to the three possible modes of decomposition reported in nonchromatographic thermal studies for N-phenyl carbamates
[4, 35, 36], e.g.,
Dyer andWright [35] have shown that when R is a primary or secondary alkyl group, all three modes of decomposition can occur when the reaction
is carried out in the absence of solvents. If the amine and isocyanate products are allowed to remain in the formation mixture,
diphenyl urea is also formed, viz.,
As has been shown, the thermal and hydrolytic stabilities of carbamates exhibit a marked dependence upon the degree and type
of N-substitution. Disubstituted carbamates are quite resistant to thermal decomposition (as well as hydrolysis). Monosubstituted
carbamates readily undergo thermal decomposition at elevated temperatures to yield primarily the respective isocyanate while
unsubstituted carbamates have been reported to decompose to allophanates, cyanuric acid, and alcohol [37]. The thermal decomposition
of unsubstituted carbamates is accelerated appreciably in the presence of eventrace amounts of metal salts, giving rise to the formation of cyamelide. The degradative scheme for the diol dicarbamates (as typified
by the medicinal carbamates, meprobamate and soma) is more difficult to interpret.Paquin [38] reported that the pyrolysis of the dicarbamate of 1,3-butylene glycol (I), yielded an oxazolidone (II) and a cyclic
urea (III) as follows:
The further degradation of compounds II and III under pyrolytic conditions remains a distinct possibility.
Strukturumwandlungen w?hrend der Gas-Chromatographie von Carbamaten
Zusammenfassung Es besteht offenbar kein Mangel an Beispielen für Strukturumwandlungen w?hrend der Gas-Chromatographie verschiedener Carbamate und Thiocarbamate. In vielen F?llen entsprechen die beobachteten resultierenden thermischen Abbauprodukte in gewissem Ma?e den drei m?glichen Abbauformen, über die in nichtchromatographischen thermischen Untersuchungen von N-Phenylcarbamaten berichtet wird [4, 35, 36], z.B. Dyer Wright [35] haben gezeigt, da?, wenn R eine prim?re oder sekund?re Alkylgruppe ist, alle drei Abbauformen vorkommen k?nnen, wenn die Reaktion in Abwesenheit von L?sungsmitteln stattfindet. Wenn die Amin- und Isocyanat-Produkte in der Mischung belassen werden, bildet sich auch Diphenylharnstoff, n?mlich: Wie gezeigt wurde, besitzt die thermische und hydrolytische Stabilit?t von Carbamaten eine starke Abh?ngigkeit von Grad und Art der N-Substitution. Disubstituierte Carbamate sind ziemlich resistent gegen therm?sche Zersetzung (wie auch gegen Hydrolyse). Monosubstitutierte Carbamate lassen sich bei h?heren Temperaturen leicht thermisch zersetzen, wobei haupts?chlich das entsprechende Isocyanat entsteht, w?hrend sich unsubstituierte Carbamate nach [37] in Allophanate, Cyanurs?ure und Alkohol zersetzen. Der thermische Abbau unsubstituierter Carbamate wird durch Anwesenheit selbst geringer Spuren von Metallsalzen nennenswert beschleunigt, wobei Cyamelid entsteht. Das Abbauschema für die Diol-Dicarbamate (typische Beispiele: medizinische Carbamate, Meprobamat und Soma) ist schwieriger zu interpretieren.Paquin [38] berichtet, da? bei der Pyrolyse des Dicarbamats von 1,3-Butylenglycol (I) ein Oxazolidon (II) und ein cyclischer Harnstoff (III) in der folgenden Weise entstanden: Der weitere Abbau der Verbindungen II und III unter Pyrolysebedingungen ist nicht auszuschlie?en.
Transformations de structure pendant la chromatographie en phase gazeuse de carbamates
Sommaire On ne manque pas d'exemples qui illustrent les transformations de structure observées pendant la chromatographie en phase gazeuse de divers carbamates et thiocarbamates. Souvent les produits de dégradation thermiques obtenus sont analogues, dans une certaine mesure, a ceux formés par décomposition thermique selon un des schémas probable signalé ci-après, procédés qui furent decrits pour des carbamates N-phényliques [4, 35, 36] dans des études de stabilité thermique non-chromatographiques, par exemple: Dyer etWright [35] ont démontré, si R est un groupe alkyle primaire ou secondaire, les trois modes de décomposition peuvent avoir lieu si la réaction se produit en l'absence de solvants. Si les amines et les isocyanates sont laissés dans le mélange, il y a aussi formation de diphénylurée, c'est-à-dire Il a été montré que la stabilité thermique et hydrolytique de carbamates dépend fortement du degré et type de la N-substitution. Des carbamates disubstitués sont assez résistants à la décomposition thermique (ainsi qu'à l'hydrolyse). Les carbamates monosubstitutés sont facilement sujets à la décomposition thermique à des températures élevées, produisant surtout l'isocyanate correspondant, tandis que, selon la littérature, des carbamates non-substitués sont décomposés en formant des allophanates, acide cyanurique, et alcool [37]. La décomposition thermique de carbamates non-substitués est accélérée sensiblement par la présence de sels métalliques, même à l'état de trace, provoquant la formation de cyamélide. Le schéma de dégradation des diol-dicarbamates (exemples typiques: carbamates médicinaux, méprobamate, soma) est plus difficile à interpréter.Paquin [38] a trouvé que la pyrolyse du dicarbamate de 1,3-butylène glycol (I) produit un oxazolidone (II) et une urée cyclique (III) d'après le schéma suivant: La dégradation ultérieure des composés II et III sous des conditions pyrolytiques n'est pas à exclure.相似文献
4.
A. A. Kamyshova A. Z. Kreindlin M. I. Rybinskaya P. V. Petrovskii 《Russian Chemical Bulletin》1999,48(3):581-585
Decamethylmetallocenes Cp*
2M (M=Ru, Os) in the presence, of acids (CF3CO2H, CF3SO3H) give thepprotonation products [Cp*
2MH]+An−. Broad-band UV photolysis of their solutions results in the formation of the salts of onium cations
. A preparative procedure for the synthesis of these salts has been developed. Hydrolysis of the salts gives the carbinol
Cp*MC5Me4CH2OH.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 587–591. March, 1999. 相似文献
5.
Infrared spectra and normal vibrations of ions of the type
and
, with X and Y as S, O and N have been compared and discussed. 相似文献
6.
I. V. Borisova N. N. Zemlyanskii A. K. Shestakova V. N. Khrustalev Yu. A. Ustynyuk E. A. Chernyshev 《Russian Chemical Bulletin》2000,49(5):933-941
The [Ph3P+−CMe2−SiMe2−SEt]Br− salt was prepared by the reaction of betaine Ph3P+−CMe2SiMeR−S− (1a: R=Me) with EtBr. Acetylation of betaine1a or Et3P+−CHMeSiMe2−S− (2a) afforded 2,2,6-trimethyl-1,3-dioxa-2-silacyclohex-5-ene-4-thione 相似文献
7.
S. V. Burov O. A. Kaurov V. F. Martynov M. P. Smirnova 《Chemistry of Natural Compounds》1980,16(5):518-524
In order to study the influence of substituents of the aromatic ring of D-phenyl-alanine on the inhibiting capacity of luliberian
analogs, we have synthesized two new analogs:
and
luliberin. The synthesis was performed by the fragmentary condensation method using 2+(3+5) and 2+(5+3) schemes. A new and
convenient method of obtaining the amide of the C-terminal tetrapeptide of the luliberin sequence has been developed. In the
condensation of the fragments, both the azide and the carbodimide method of synthesis with the addition of l-hydroxybenzotriazole
were used. The guanidino group of arginine was protected by nitration, while the hydroxy groups of serine and of tyrosine
were not protected. The complete elimination of the protective groups from the decapeptides was performed by catalytic hydrogenation
over Pd on carbon and by anhydrous HF with the addition of anisole at 0°C. The protected octa- and decapeptides were purified
by gel filtration on Sephadex LH-20 in ethanol or by preparative thin-layer chromatography on silica gel plates. The final
peptides were purified by ion-ex-exchange chromatography on Sephadex CM-25.
A. A. Zhdanov Leningrad State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 706–714, September–October,
1980. 相似文献
8.
J. A. K. Tareen A. R. Fazeli B. Basavalingu G. T. Bhandige 《Journal of Thermal Analysis and Calorimetry》1995,44(4):937-954
Decarbonation curve for the synthetic dolomite analogues; (Cd-dolomites) were determined for CdMg(CO3)2, CdMn(CO3)2 and CdZn(CO3)2 under CO2 pressure of up to 2.5 kbar. All the three double carbonates were completely disordered at the decomposition temperatures and hence the thermodynamic data (Standard enthalpy; ΔH f o, Standard free energy; ΔG f o) retrieved from the univariant decarbonation curve corresponds to the disordered phases. They are: The mixing enthalpies and free energies for the formation of the disordered 1∶1 solid solution phases are: The thermodynamic data (ΔH f o, ΔG f o and ΔH r o, ΔG r o) showed a positive correlation with the decomposition temperatures. The mixing energies of the disordered double carbonates also show a direct correlation with the cationic size differences. 相似文献
9.
Zhengbin Zhang Liansheng Liu Hongbin Zhao Youjun Fu Fengyun Cheng Weihong Zhao 《中国科学B辑(英文版)》1997,40(4):353-364
A new method for the study of ternary surface complexes at liquid-solid interface, theE(%) -pH curve method, was proposed. Four types ofE(%)-pH curves, namely, phenomenon of left-right shifts of S-shaped curve, V-shaped curve, monodirection shift curve and X-shaped
curve, were discovered. Correspondingly, apart from type (I) ternary surface complex
and type (II) ternary surface complex
, a new type of ternary surface complex
was discovered.
Project supported by the National Natural Science Foundation of China and the Fund of Doctoral Degree’s Spot. 相似文献
10.
Résumé Les auteurs ont étudié le comportement chromatographique sur plusieurs phases stationnaires polaires et non polaires de composés cyclopropaniques stéréoisomêres: où R=H ou CH3 et X=CH, COOCH3 ou CH2OH. Les résultats sont interprétés en fonction de la configuration de X par rapport à , de la nature électronique de X et de l'orientation du phényle par rapport au plan du cyclopropane.
Relationship between chemical structure and retention. VII. Cyclopropane compounds
Summary The chromatographic behaviour, on several polar and non polar phases, of stereoisomeric cyclopropanes has been studied R=H or CH3 and X=CN, COOCH3, CH2OH. The results are interpreted in terms of the X versus configuration, the electronic nature of X and the orientation of the phenyl ring in relation to plane of the cyclopropane ring.相似文献
11.
New hybrid organic-inorganic alumina gels have been prepared by reacting aluminum sec-butoxide and propane-1,2-diol, in CCl4 as solvent. This reaction occurred without water addition and without the use of any catalyst, leading to the formation of
transparent and monolithic gels. IR,27Al and13CNMR show that an interchange reaction between OBu
s
alkoxide groups and
diol groups occurred, leading to the hybrid gels.
Samples heat treated at different temperatures under argon are weakly porous and have a small specific surface area. XRD indicates
the presence of pure α-alumina at 1450°C. 相似文献
12.
Solutions of benzidine and diphenylamine in benzene produce cation radicals on the surface of zeolite, -alumina and V2O5 doped alumina and zeolite. The sequence of the electron acceptor site strength on the surface is as follows: 相似文献
13.
Xie Yi Hu Rongzu Zhang Tonglai Li Fuping 《Journal of Thermal Analysis and Calorimetry》1993,39(1):41-51
Three new rare-earth metal (Pr, Nd and Sm) salt hydrates of 3-nitro-1,2,4-triazol-5-one (NTO) were prepared and characterized. The thermal behaviour of the three salt hydrates, M(NTO)3·nH2O (M=Pr and Nd,n=9;M=Sm,n=8) were studied by means of TG and DSC under conditions of linear temperature increase. The thermal decomposition intermediates were determined by means of IR, MS and X-ray diffraction spectrometry. The thermal decomposition mechanisms of these hydrates were proposed as follows:
We express our thanks to Professor Zhu Chunhua, Associate Professor Fu Xiayun, and Lecturers Fan Tao and Liang Yanjun for their help in this work. 相似文献
14.
Isabel Castro Juan Faus Miguel Julve Michèle Philoche-Levisalles 《Transition Metal Chemistry》1992,17(3):263-269
Two complexes of formula [Cu(terpy)(H2O)](CF3SO3)2 (1) and [Cu(terpy)(OH)]BPh4 (2) (terpy=2,2′∶6′,2″-terpyridine and BPh4=tetraphenylborate anion) have been synthesized and characterized by spectroscopic techniques. The x-ray crystal structure
of (1) has been determined by x-ray diffraction. The structure is made up of [Cu(terpy)(H2O)]2+ mononuclear cations plus semi-coordinated CF3SO3
− anions. The coordination geometry around the copper atom is approximately elongated tetragonal octahedral. The oxygen atom
of water and the three nitrogen atoms of terpy occupy the equatorial sites whereas the apical ones are filled by trifluoromethanesulphonate
oxygen atoms. The formation of hydroxo complexes of [Cu(terpy)(H2O)]2+ has been investigated by potentiometry in aqueous solutions and the constants of the Equilibria (1) and (2)
相似文献
15.
Ling-Ju Chang Manohar V. Kulkarni Chung-Ming Sun 《Central European Journal of Chemistry》2005,3(2):288-294
Liquid phase combinatorial synthesis using a soluble polyethylene glycol (PEG) polymer support and commercially available
3-nitro-4-fluoro benzoic acid is carried out in order to create a molecular library of trisubstituted benzimidazoles. The
PEG-ester conjugate of 3-nitro-4-fluoro benzoic acid is subjected to ipso-fluoro displacement by various primary amines. The nitro group is reduced under neutral conditions using excess zinc and
ammonium chloride, producing the polymer-boundo-phenylene diamines. Reaction of the diamines with different aldehydes results in cyclisation to benzimidazoles. The polymer
support is cleaved releasing the desired products in high yields and purity. All reactions are performed at room temperature.
相似文献
16.
1-Chloro-1-aryl-2,2,2-trifluoroethylheterocumulenes (isocyanates and carbodiimides) undergo regioselective cyclization with diphenylguanidine to give 2-aryl-2-trifluoromethyl-4-oxo-6-imino- and 2-aryl-2-trifluoromethyl-4,6-diiminoperhydro-1,3,5-triazines. An IR study of the 4-oxo-1,3,5-triazine derivatives showed a tendency for the formation of intermolecular aggregates or intramolecular hydrogen bonding, while a similar study of the 4-imino-1,3,5-triazine derivatives revealed that these compounds tend to undergo prototropic isomerization in the moiety.Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 252660 Kiev, Ukraine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 706–710, May, 1997. 相似文献
17.
The polamgraphic behavior and catalytic wave mechanism of medroprogestemne acetate (MPA) were studied in both aqueous and
DMF media. In 0.2 mol/L acetic acid-sodium acetate (pH 5.0) buffer solution, the
bond of MPA first undergoes le, lH+ reduction to form protonated free radical HMPA, the further reduction of HMPA in le,1H+ process is simultaneous with the dimerization reaction between HMPA and neutral molecular MPA. In DMF media containing 0.1
mol/L tetrabutylammonium tetrafluoborate (TBA.BF4), the
bond of MPA shows two le, 1H+reduction waves, which are ascribed to the reduction of MPA and free radical MPA.-, respectively. Here, no dimerization reaction occurs. These processes produce the reduction wave of MPA. In the presence
of oxidant KIO3,a polamgraphic catalytic wave of MPA is observable due to a chemical reaction between HMPA. or MPA.- and KIO3 as well as its intermediate species to regenerate MPA. The catalytic wave, which is caused by the reduction of organic compound
itself and the chemical reaction between oxidant and organic intermediate free radical to regenerate original organic compound,
is a new-type wave of organic compound. Under optimum experimental conditions, the sensitivity of MPA catalytic wave in the
presence of KIO3 is an order of magnitude higher than that of its reduction wave. The catalytic wave can be used for analytical purpose. The
calculated rate constant of catalytic reaction is 1.7 × 103 mol·L-1·s-1.
Project supported by the National Natural Science Foundation of China (Grant No. 29875017). 相似文献
18.
It is proposed that in the long wavelength (λ ≥ 290 nm) photolysis of CS2 vapor the observed CS and S2 are produced in the reaction sequence:
相似文献
19.
J. Kuruc 《Journal of Radioanalytical and Nuclear Chemistry》1991,154(1):61-72
EPR spectra of paramagnetic centers originating from X-ray-irradiation of aluminium hydroxide at room temperature have been measured. The EPR spectrum represents a superposition of EPR spectra of ionic centers O–, holes of type and trapped electrons. Radiation chemical yield of paramagnetic centers observed at room temperature (293 K) is G(spins.)=4.4±0.6) spins per 100 eV absorbed energy. The decay of paramagnetic centers in irradiated Al(OH)3 was oberved at 293 K. The rate constant of the paramagnetic centers decay in irradiated Al(OH)3 is K2=(0.0980±0.0019) kg·mol–1·min–1 and their half-life is 9.43±0.18 days.Dedicated to the memory of the late Genrikh Markovis Kolyiari. 相似文献
20.
Maria M. Milanova Dimitar S. Todorovsky Christo C. Balarew Natalia L. Minkova Katya I. Ivanova 《Central European Journal of Chemistry》2007,5(1):13-19
The cocrystallization of Ce2(SO4)3 and La2(SO4)3 is studied in aqueous and H2SO4 (150 g/dm3) solutions at 25 °C and 64 °C. The effect of the formation of inner sphere sulfate complexes of the type LnSO
4
+
in determining the composition of the equilibrium phases is revealed.
相似文献