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A new sesquiterpene was isolated from extracts of Sumatra benzoin gum. Its structure was elucidated by means of mass spectrometry and two-dimensional NMR. This new compound presented an acenaphthylene-type skeleton unpreviously described among the family of sesquiterpene hydrocarbons.

A new approach for 13C chemical shift prediction using 3D descriptors is described. The stereochemical environment of each carbon atom of a data set of steroids with assigned chemical shifts was encoded and atoms of similar environment were grouped into clusters. Management of errors and optimization of the methods' parameters in order to obtain the best results in chemical shift predictions were handled by special routines. The predicted chemical shifts of unknown compounds were matched against the values observed on the experimental spectra to calculate a degree of support index. It is shown that this index can be used to reject bad structures proposed by structure generators in the task of structure elucidation.

In a series of 4-substituted camphors, in which the substituent, X, varies from ethyl through hydrogen to nitro, we have shown that the enthalpies of complexation, with BF3 in dichloromethane, which cover a range of 14.5 kJ mol–1 correlate well with r > 0.99 with polar substituent constants with the sensitivity ρ*ca. 8.IR spectroscopy of the free ketones and the more polar BF3 complexes indicates that the latter are ca. 1.44 times more sensitive to substituent variation.Complexation occurs at both sites when X = OAc and only at the ketone when X = CO2Me.We rationalise the smaller sensitivity of the protons to substituent-induced 1H shift displacement when in the E-complexed form to the electron-attracting effect of complexation that leads to diminished electronic screening. The 4JH3exo–H5exo coupling is diminished by complexation which enhances hyperconjugation between the C(3)–Hσ and the carbonyl p orbitals to the detriment of back lobe C(3)–H3exo–C(5)–H5exoσ–σ overlap. A number of chemical shift and coupling correlations are reported.

Various procedures were attempted in order to prepare α,β,γ,δ-unsaturated nitriles via the Wittig-Horner reaction of β-substituted cyclohex-2-en-1-ones with diethyl cyanomethyl phosphonate. Among them, the one using NaH as base in refluxing THF gives only the products resulting from carbonyl attack, in good yields. The stereochemistry of the reaction is discussed.

The principal spectroscopic properties of the four dihydrocarveol diastereoisomers are reinvestigated. The interpretation of their 1H-NMR spectra allows unambiguous differentiation of the diastereoisomers and the determination of their conformations. ‘Negative ion chemical ionization-Collision-induced dissociation’ experiments have been performed on the quasimolecular ions [M - H]− using a FT-ICR spectrometer. The daughter ion spectra of the alkoxide negative ions [M - H]− of the four isomers show substantial differences which can be used for a diastereoisomeric differentiation and the confirmation of the conformations. The gas phase FT-IR spectra are recorded. The MS and IR results can be used for essential oil analysis using GC–MS and/or GC-FTIR techniques.

The ring opening of 3-aza 1,8,8-trimethyl tricyclo [5.2.1.02,4]octane isomers by HF-pyridine has been studied. A series of γ-fluoroamines and non fluorinated amines, isomers of the starting aziridines, was obtained. No β-fluoroamines were isolated. The structures of diastereoisomeric amines, established by 1H and 19F NMR, show product structure dependence upon the exo-endo aziridine configuration. A comparison between aziridine reactivity and oxirane one is done.

Electron impact ionization−collision-induced dissociation (EI−CID) and negative ion chemical ionization−collision-induced dissociation (NICI−CID) experiments have been performed on the molecular and quasi-molecular ions (M +. or [M − H] − ) of series of terpenoid alcohols, using a Fourier transform ion cyclotron resonance spectrometer. These terpenes belong to the p-menthane family and bear a hydroxyl group in various positions relative to the isopropyl or isopropenyl substituent (positional or stereochemical isomers). In the case of positional isomers, different CID spectra were always obtained. Within a given diastereoisomeric series, stereochemical differences were also observed in both NICI−CID and EI−CID experiments

Teaching chemistry students to deduce chemical structures from the results of spectroscopic methods suffers severe practical problems. Often the theoretical basis of the method lies beyond the student's comprehension. Although theoretical models allow the prediction of spectra of simple compounds from their structures, the models have limited utility for the inverse operation of determining structures from spectra. This later operation is primarily empirical and does not lend itself to a systematic teaching approach. The ability to elucidate chemical structures is built largely on implicit heuristics and informal experience accumulated by solving numerous examples.

A set of 100 exercises in organic structure determination from NMR, IR, and mass spectra are offered for online use.

In a series of 4-substituted camphors, in which the substituent, X, varies from ethyl through hydrogen to nitro, we have shown that the enthalpies of complexation, with BF3 in dichloromethane, which cover a range of 14.5 kJ mol–1 correlate well with r > 0.99 with polar substituent constants with the sensitivity ρ*ca. 8.IR spectroscopy of the free ketones and the more polar BF3 complexes indicates that the latter are ca. 1.44 times more sensitive to substituent variation.Complexation occurs at both sites when X = OAc and only at the ketone when X = CO2Me.We rationalise the smaller sensitivity of the protons to substituent-induced 1H shift displacement when in the E-complexed form to the electron-attracting effect of complexation that leads to diminished electronic screening. The 4JH3exo–H5exo coupling is diminished by complexation which enhances hyperconjugation between the C(3)–Hσ and the carbonyl p orbitals to the detriment of back lobe C(3)–H3exo–C(5)–H5exoσ–σ overlap. A number of chemical shift and coupling correlations are reported.

The configurational assignment of Z and E nitrogen derivatives () of 3,5,5-trimethyl-2-cyclohexen-1-one was made taking into consideration the through-space effects on oxime, O-methyloxime, dimethylhydrazone, tert-butylimine, N,N,N -trimethylhydrazonium iodide and oxime hydrochloride derivatives. The relationship between the magnitude of the chemical shifts of the α-protons and the dihedral angle formed by the α-CH bond and the CNOH plane was interpreted in terms of the geometrical dependence of the electric field effect. For the different Y substituents, the change in chemical shift between the Z and the E configuration of the proton near the functional group was mainly dependent on the electric field effect.

L'etude des couplages magnetiques a longue distance releves dans les spectres RMN du proton a 60 MHz d'aziridines du type aza-7 bicyclo[4.1.0]heptane, permet de preciser la conformation de ces composes et de demontrer sans ambiguite l'existence de structures bloquees pour certains isomeres. The study of long range coupling constants in the 1H NMR spectra (60 MHz) of aziridines with a 7-azabicyclo[4.1.0]heptane skeleton allows the determination of the conformation of these compounds and shows that some isomers have a rigid structure.

The ring opening of three isomeric α,β-ethylenic aziridines by HF-pyridine has been studied. The reaction proceeds, depending on temperature, solvent or structure, either to expected 2-fluoro amines and 4-fluoro allylic amines or to elimination products. A type of Wagner-Meerwein rearrangement was observed and benzene as solvent gave a type of Friedel-Crafts reaction. The steric constraints may explain the differences in the yields of cis and trans addition products. Also, the rigid structures allow the detection of vicinal couplings and the study of configuration and conformation.

Dynamic conformational analysis of the cleavage of methyl-substituted 7-aza bicyclo [4.1.0] heptanes by Olah's reagent (30 wt % of pyridine in hydrogen fluoride), using the torsion angle notation, allows structural and conformational prediction of the 2-fluoro cyclohexylamine products. Consequently, a mechanism for the cleavage is proposed.

The changes in chemical shift induced by isomerization for all the ring protons of the Z- and E-5,5-dimethyl-2-cyclohexenylidene acetonitriles depend only on the through-space effects of the cyano group. The configurational assignments were made taking into consideration the anisotropic and electric field effects, either separately or together. In the first case, the total effects are ΔXCNT=−14.7×10−6cm3 mol−1 and bμCNT=14.7×10−30 cm3, respectively. The second approach allows the estimation of the values ΔXCN=−4.9 × 10−6 cm3 mol−1 and bμCN=9.8 × 10−3 cm3, reflecting the combined contributions of magnetic anisotropy and electric field to the total effect.

L'analyse des spectres RMN 1H d'une serie d'acetoxy-1 ou 3 chloro-6 cyano-6 bicyclo[2.2.2]octenes-2 et de chloro-6 cyano-6 bicyclo[2.2.2]octanones-3 permet de determiner l'anisotropie magnetique d'un groupment chloro-nitrile gemine a l'aide de la relation de McConnell. Les resultats obtenus rendent possible l'attribution de la position endo ou exo des substituants CN et Cl par rapport a la double liaison ou au carbonyle pour ces composes et confirment les conclusions de la litterature relatives aux chloro-5 cyano-5 bicyclo[2.2.2]octenes-2. 1H n.m.r. spectra in a series of 1- or 3-acetoxy-6-chloro-6-cyanobicyclo[2.2.2]oct-2-enes and 6-chloro-6-cyanobicyclo[2.2.2]octan-3-ones have been analysed. The anisotropic contribution of the geminal substituents CI and CN is discussed and evaluated using McConnell's equation. The results obtained allow us to assign the endo or exo position of these substituents for these compounds and confirm the conclusions in the literature.

The reduction of several cyclohexenone oximes using lithium aluminum hydride and sodium dihydrobis-(2-methoxyethoxy)aluminate yields saturated and unsaturated aziridines with a 7-azabicyclo[4.1.0]heptane skeleton and cyclohex-2-ene amines. The use of oximes of E and/or Z configuration demonstrates the regioselectivity of the reduction and allows us to propose reaction schemes explaining the formation of the different types of products.

Cis and trans epimino cyclohexanes containing no groups exerting any marked polar or conjugative effects produce, with HF-pyridine, 2-fluoro amines. The structures of the diastereoisomeric amines established by 1 H and 19 F NMR show that Furst and Plattner rule applies to the stereochemical course of HF-pyridine ring opening of those aziridines. In every case, the opening involves F trans addition to NH 2 .

Nous avons effectue les spectres de masse de phenoxazines et d'azaphenoxazines substituees. Ces composes sont caracterises par la presence d' un hydrogene sur l'azote heterocyclique et la position de substituants NO2 et Cl sur les cycles aromatiques. A l'aide de mecanismes classiques, nous avons rationalise les processus de fragmentation et explique les pics principaux de ces specters. La presence de substituants Cl et NO2 perturbent totalement la fragmentation observee dans le cas de la molecule de phenoxazine. Ils favorisent la localisation de la charge suivant leur position sur le cycle, soit sur l'azote, soit sur l'oxygene heterocycliques. Quant au gropement NO2 par isomerisation (forme nitroso), il donne lieu ea une fragmentation specifique. Mass spectra of substituted phenoxazines and azaphenoxazines have been determined and are discussed here. These compounds are characterised by hydrogen on the heterocyclic nitrogen and aromatic rings with nitro groups and chlorine as substituents. The fragmentation patterns are explained by known mechanisms. An interpretation of almost all the peaks is offered. The presence of the substituents causes a complete change in the fragmentation patterns compared with the unsubstituted phenoxazine. This is due to changes in charge localisation, caused by the substituents. Isomerisation of the nitro group to the nitroso group gives rise to a particular fragmentation route.

Preliminary results obtained with a home-made Fourier transform ion cyclotron resonance mass spectrometer on the sequential clustering reactions of silane using yttrium cation activation are reported. [YSinH2n]+ and [YSinH2n − 2]+ ions are formed. So far, we have observed these ions up to n = 7, and a sequential clustering mechanism is proposed. The ion structures are characterized by collision-induced dissociation, and kinetic measurements to determine the formation and decay rates of each ion are performed.