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991.
Microwave spectra of CH2FCONH2, CH2FCOND(1)H(2), CH2FCONH-(1)D(2), and CH2FCOND2 are reported. The stable form of the molecule is shown to possess a planar FCCONH2 skeleton, with two out-of-plane hydrogens. The C-F and CO bonds are trans to one another and a weak intramolecular hydrogen bond is formed between the fluorine atom and the nearest amide group hydrogen atom stabilizing the identified rotamer. Other conformations are not present in concentrations exceeding 10% of the total. Nine vibrationally excited states were assigned. Six of these were attributed to the C-C torsional mode and one to the lowest in-plane bending mode. The first excited state of -NHz out-of-plane deformation mode was tentatively assigned. Relative intensity measurements yielded 114±14 cm?1 for C-C torsional mode and 239±20 cm?1 for the in-plane bending mode. The dipole moment was determined asμa = 1.27±0.01 D, μb = 1.67±0.02 D, and μtot = 2.10±0.02 D, while the 14N quadrupole coupling constants were found to be χaa = 1.6±0.2 MHz, χbb = 1.6±0.2 MHz and χcc = ?3.2±0.3 MHz. 相似文献
992.
Electron impact induced water elimination from the metastable molecular ions of N-acetyl- and N-benzoyl-4a-hydroxydecahydroquinoline mainly follows a formal [1,2] elimination. The initiating and ratedetermining step in the reaction is the hydrogen rearrangement from C-8a onto the carbonyl group. The transferred hydrogen is subsequently lost, together with the hydroxyl group. The almost complete absence of H2O loss from both diastereomers of N-methyl-4a-hydroxy-2-oxodecahydroquinoline confirms that the reaction can only proceed when the carbonyl group is able to function as ‘hydrogen carrier’ by occupying positions in the vicinity of both a hydrogen and the hydroxyl function. 相似文献
993.
Two cyclotriphosphazene rings can be covalently linked via ring N-centres by a 2-butene-1,4-diyl unit and vice versa a cyclotriphosphazene molecule is able to bridge two cinnamyl groups via two ring N-centres yielding in either case dicationic assemblies which offers a route to novel polycations. 相似文献
994.
Microwave spectra of CHO-COOH and CHO-COOD are reported. The molecule has a planar equilibrium conformation with the two carbonyl groups trans to each other. A weak five-member intramolecular hydrogen bond is formed between the hydroxyl proton of the carboxyl group and the oxygen atom of the carbonyl group thus stabilizing the trans planar form. Other conformations having a statistical weight of 1 (cis and trans) are at least 1.3 kcal mol?1 less stable, and rotamers with a statistical weight of 2 (e.g., gauche and skew) have at least 1.7 kcal mol?1 higher energy. Four vibrationally excited states of CHO-COOH have been analyzed and relative intensity measurements yielded 167 ± 12 cm?1 for the C-C torsional mode and 288 ± 26 cm?1 for the lowest in-plane bending mode. The dipole moment was determined to be μa = 1.85 ± 0.03 D, μb = 0.20 ± 0.10 D, and μtot = 1.86 ± 0.04 D. A seven-parameter centrifugal distortion analysis has been carried out for the ground vibrational state of CHO-COOD and for the ground and three vibrationally excited states of CHO-COOH. 相似文献
995.
Chatgilialoglu C Duca M Ferreri C Guerra M Ioele M Mulazzani QG Strittmatter H Giese B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(5):1249-1255
The reaction of hydrated electrons (e(-)(aq) with 8-bromoadenosine 7 has been investigated by radiolytic methods coupled with product studies. Pulse radiolysis revealed that one-electron reductive cleavage of the C-Br bond gives the C8 radical 8 followed by a fast radical translocation to the sugar moiety. The reaction is partitioned between C5' and C2' positions in a 60:40 ratio leading to 5'-adenosinyl radical 9 and 2'-adenosinyl radical 11. This radical translocation from C8 to different sites of the sugar moiety has also been addressed computationally by means of DFT B3LYP calculations. In addition, ketone 21 was prepared and photolyzed providing an independent generation of C2' radical 11. Both C5' and C2' radicals undergo unimolecular reactions. Radical 9 attacks adenine with a rate constant of 1.0 x 10(4) s(-1) and gives the aromatic aminyl radical 10, whereas C2' radical 11 liberates adenine with a rate constant of 1.1 x 10(5) s(-1). 相似文献
996.
The amphiprotic cyclophosphazene [CH3O(CH2)3NH]6P3N3 (1) incorporates lithium chloride via successive protonation with HCl and deprotonation with Bu(n)Li (or vice versa) to generate the coordination polymer 1.2LiCl, a molecular model compound for lithium ion containing solid polymer electrolytes. 相似文献
997.
Leray and Schauder [8] have defined a topological degree for mappings in Banach spaces of the form I-f, where f is compact. A product formula for this degree, i.e. a formula for the degree of the composed map (I-f)(I-g), has been given by Nagumo [10]. In recent years, this degree has been extended to mappings I-f, where f is a strict -contraction or -condensing with respect to a rather general measure of noncompactness . It has been shown that all the properties of the Leray-Schauder degree are still valid (see [11] and [12]), while the validity of the product formula remained an open question. Nussbaum [11] has announced this formula for the special case of 1 -spaces and mappings f that are strict - and ß-contractions, simultaneously. Fenske [5] has shown that this formula holds in every Banach space provided f is a differentiable strict -contraction. In this note we shall establish this formula for an arbitrary Banach space and an arbitrary strict -contraction. 相似文献
998.
Siegfried Steiner 《manuscripta mathematica》1977,20(3):277-300
Let E be a n-dimensional euclidean vector space. The subset V
k
n
={x ... x | x E} of kE is called a Veronesemanifold. The scalar product of E induces a euclidean structure on kE. Passing to the corresponding projective space
, one may consider
as a riemannian submanifold of the space form
. In this paper we study properties of the pair
of riemannian manifolds. 相似文献
999.
From equilibration experiments with ferrocenyl cyclohexanes substituted at position 4, an average conformational free enthalpy of 2.9±0.1 kcal/mole was established for the ferrocenyl group. The spatial requirement of ferrocenyl at the equilibrium equatorial ? axial is approximately equivalent to that of the phenyl residue (3.0±0.1 kcal/mole). 相似文献
1000.
Bickley JF Copsey MC Jeffery JC Leedham AP Russell CA Stalke D Steiner A Stey T Zacchini S 《Dalton transactions (Cambridge, England : 2003)》2004,(7):989-995
The tetraanilino phosphonium cation, [P(N(H)Ph)4]+, 1+, is sequentially deprotonated by Bu(n)Li in thf. The deprotonation reaction of the chloride derivative, Cl, was monitored by (31)P NMR, which revealed the successive formation of the neutral [P(N(H)Ph)3(NPh)], 2, the monoanionic [P(N(H)Ph)2(NPh)2]-, 3-, the dianionic [P(N(H)Ph)(NPh)3]2-, 4(2-), and finally the trianionic species [P(NPh)(4)](3-), (3-). Considering the isoelectronic relationship of oxo, =O, and imino groups, =NR, as well as hydroxy, -OH, and amino groups, -N(H)R, the neutral complex corresponds to phosphoric acid, H3PO4, whereas the anions 3-, 4(2-) and 5(3-) are analogues of dihydrogen phosphate, H2PO4-, monohydrogenphosphate, HPO4(2-), and orthophosphate ions, PO4(3-), respectively. Solid state structures were obtained of 1Cl, 2LiCl(thf)(2), 3Li(thf)(3.5), 3Li(2)Cl(thf)(4.25), 3Li(2)Cl(thf)(6) and 5Li(4)Cl(thf)(4). All systems provide two separate N-P-N chelation sites at opposite ligand faces, either consisting of the di(amino) arrangement P(NH)(2), acting as a double H-bond donor, the di(imino) arrangement PN(2), donating two electron pairs, or the mixed amino imino arrangement P(N)(NH), which supplies both electron pair and H-donor site. Interesting in this aspect is the mixed amino imino derivative 3- which has the ability to chelate a Lewis acid, such as a metal ion, at one face and a Lewis base, such as an anionic or neutral donor at the opposite ligand face. The formation of 1-D aggregates and the entrapment of lithium chloride are key characteristics of the supramolecular structures of the discussed complexes. 相似文献