Excitation profiles in resonance Raman scattering: Comparison between the displaced oscillator model and the reflection approximation

We study the resonance Raman scattering tensor with a model based on a displaced harmonic oscillator. It is shown that when the lines of the absorption spectrum are broadened, the Raman excitation profiles are determined by the formulas of the reflection approximation.     

Transposition des Cycles Satures en Spectrometrie de Masse IV—Dioxolanes Derives de Cetones a Cycle Moyen et Grand

The fragmetation mechanism of cyclanone ethylene acetals in the medium ring and macrocyclic series has been re-investigated. The fragmentation pattern can be explained entirely on the basis of a new rearrangement, involving a ring contraction and hydrogen migrations, which have been checked by using deuterated compounds.     

Obtention d'hétérocycles par action de binucléophiles diazotés sur des chalcones: Influence du substituant en position 2

Reactivity of 2-susbituted chalcones against diaza binucleophiles (hydrazines, thiourea, guanidine) has been studied. Various heterocycles (pyrazoles, pyrazolines, pyrimidines) or substituted hydrazines were obtained. A general interpretation is given according to the substituent of the enone system, R, the nature of binucleophile and the medium.     

On Krull's Separation Lemma

We show that Krull's Separation Lemma for arbitrary rings and a certain lattice-theoretical generalization of it are equivalent to the classical Prime Ideal Theorem for Boolean algebras. As an application, we derive the intersection theorem for Baer radicals from choice principles weaker than the Axiom of Choice. A central tool for our considerations are Scott-openm-filters in quantales.     

1H NMR utilization of through-space effects. II—conformation of dienic ketones

The configurational and conformational assignments of the carbonyl group in the Z- and E-1-(3-substituted-5,5-dimethyl-2-cyclohexen-1-ylidene)-2-butanones are carried out using only the through-space effects of the carbonyl group. It is demonstrated that, regardless of the Z- or E-configuration or the nature of the substituent in position 3, the conformation of the carbonyl group is always s-cis.     

The Riemann solution in the one-dimensional inverse problem

It is shown that the introduction of the Riemann method in potential scattering is a natural device. Thereafter, the one-dimensional Schrödinger equation is considered using the Riemann method. An estimate is found for the associated translation kernel. This estimate reduces to Marchenko's when the domain of the variables is restricted to the positive quadrant of the (x, y) plane. The possibility of a Fourier transform of the Schrödinger equation solution is studied via Riemann's method. Extension of the investigations to the case where a dependence on threshold energies appears in the Schrödinger equation is discussed.     

Regioselectivity of S-silylketene S,N acetals and titanium - (ate) - enethiolates addition to unsaturated ketones

(Z) S-Silylketene S,N acetals react with α-enones to afford exclusive 1-2 addition. Titanium enethiolates and titanium - ate - complexe enethiolates undergo 1-2, 1-4 addition.     

Groups with strongly self-centralizing 3-centralizers

LetG be a finite group with a subgroupM which is the centralizer inG of each of its nonidentity elements and let 3 divide the order ofM. Such groups are classified under the assumption that eitherq=[N _G (M):M]=2^s;s≧0 ands ≠ 3 orq<8. This paper was written while the author was visiting the Department of Mathematics, University of Illinois, Urbana, Illinois 61801.     

Selenium-77 nuclear magnetic resonance in mono- and disubstituted benzo[b]selenophenes

The ⁷⁷Se chemical shifts of 79 mono- or disubstituted benzo[b]selenophenes are reported. The results in the 2- and 3-substituted derivatives closely parallel those previously obtained in the corresponding selenophenes. The measured parameters also correlate well with those measured in benzo[b]tellurophenes. The ¹²⁵Te and ⁷⁷Se chalcogen nuclei appear to be much more sensitive to substituent effects than the more classical nuclei. The effects of Cr(acac)₃, Eu(dpm)₃ and concentration on the ⁷⁷Se NMR spectra are briefly discussed.