Magnetic Resonance in Chemistry

doi: 10.1002/mrc.1270080501pmid: N/A

doi: 10.1002/mrc.1270080516pmid: N/A

Chukovskaya, E. C.; Dostovalova, V. I.; Vasil'eva, T. T.; Freidlina, R. Kh.

doi: 10.1002/mrc.1270080502pmid: N/A

13C n.m.r. spectra have been measured for thirty‐two polychloroalkenes including (i) monosubstituted compounds CH2CHCClnH2−nX, where X stands for H, Cl, alkyl, and trisubstituted alkenes CCl2CHAlk, none of which form geometric isomers; (ii) disubstituted compounds RCHCHR′; (iii) and (iv) trisubstituted compounds of the types RCClCHR′ and CHClCClR, respectively. Compounds (ii) to (iv) represent either individual isomers or mixtures of the Z and E forms. In the case of compounds (ii) and (iii), the ordering of chemical shifts is δE > δZ for the sp2‐carbon atoms and δE < δz for the adjacent tetrahedral ones. On the contrary, the signals of the sp2‐carbon atoms of compounds (iv) obey the rule δE < δz. The effect of vinyl and allyl groups as substituents on the 13C chemical shifts of chlorine‐containing groups is discussed. The dependence of the sp2‐carbon spin–spin coupling constants J(13C1H) on the number of chlorinated substituents in the molecule is also considered.

Piccinni‐Leopardi, C.; Fabre, O.; Reisse, J.

doi: 10.1002/mrc.1270080503pmid: N/A

From ΔGTc≠ values obtained by 1H and 13C dynamic nuclear magnetic resonance studies of the same dynamic process, it is possible to estimate ΔH≠ and ΔS≠. Nevertheless, the accuracy of the temperature measurement is a factor which limits the applicability of this method. A very simple procedure for calibrating the usual temperature sensors is described, which can be applied to all types of n.m.r. probes. By the use of this procedure it is possible to measure coalescence temperatures in 1H and 13C n.m.r. with such an accuracy that ΔS≠ can be effectively determined from the difference between ΔGTc≠ values.

Staško, A.; Tkáč, A.; Laurinc, V.; Malík, L.

doi: 10.1002/mrc.1270080504pmid: N/A

The anion radical of acetylacetonate is formed by the reaction of nickel (II) acetylacetonate with Grignard reagents. From the two coupling constants found in the e.s.r. spectrum, the one of 2·6 G was assigned to the methine proton and the one of 12·5 G to the six equivalent methyl protons of acetylacetonate. The calculations of spin densities for the anion radical of acetylacetonate by the INDO method are in relatively good agreement with experiment.

Matthews, R. S.

doi: 10.1002/mrc.1270080505pmid: N/A

The signs and magnitudes of every fluorine–fluorine coupling constant in perfluoroquinoline (1), 2,4‐dichloropentafluoroquinoline (2) and 2‐bromohexafluoroquinoline (3) have been determined by 19F n.m.r. These provide an unambiguous assignment of the spectrum of the first compound and its derivatives. Inter‐ring fluorine–fluorine coupling constants were found to be positive over an odd number of bonds and negative over an even number of bonds, similar to that observed in proton–proton coupling constants in multicyclic systems.

Hiller, A.; Kleinpeter, E.; Schulze, K.

doi: 10.1002/mrc.1270080506pmid: N/A

Die 1H‐NMR‐Spektren einer Reihe aliphatisch und phenylsubstituierter Alkendiine werden vorgestellt und, unter Berücksichtigung einiger literaturbekannter Verbindungen, chemische Verschiebungen und Kopplungskonstanten diskutiert.

Clark, P. D.; Ewing, D. F.; Scrowston, R. M.

doi: 10.1002/mrc.1270080507pmid: N/A

All carbon resonances in the title compounds have been unequivocably assigned. Steric effects in the peri substituted compounds have been compared with analogous effects in naphthalene and benzo[b]furan. The observed effects are not explained by current theory. Unusual deshielding steric shifts are observed at some carbons. Methyl substituent effects are not additive at any position in the sterically crowded 2,3‐disubstituted compounds.

Crabb, Trevor A.; Mitchell, Jacqueline S.

doi: 10.1002/mrc.1270080508pmid: N/A

cis(4‐H,11b‐H)‐4‐Aryl‐1,6,7,11b‐tetrahydro‐2H,4H‐[1,3]oxazino [4,3‐a]isoquinoline and the related thiazino compound preferentially adopt in solution the O (or S) inside cis‐conformation in contrast to cis(1‐H,4a‐H)‐1‐arylperhydropyrido[1,2‐c][1,3]oxazine which adopts the trans fused conformation. 1‐(β‐Hydroxy‐ethyl)‐1,2,3,4‐tetrahydro‐β‐carboline condenses with benzaldehyde to give the 1,3‐oxazine derivative rather than the dimeric structure reported in the literature.

Kleinpeter, E.; Kühn, H.; Mühlstädt, M.

doi: 10.1002/mrc.1270080509pmid: N/A

Die Bestimmung der Stereochemie einer Reihe exo/endo‐isomerer 9.10‐Dihydro‐ bzw. Tetrahydrodicyclopentadien‐9.10‐diole (exo/exo bzw. endo/endo) unter Verwendung von Eu(fod)3 zur Auftrennung ihrer 1H‐NMR‐Spektren wird beschrieben. Die für halbmolares Verhältnis Eu(fod)3/Diol bestimmten Verschiebungswerte ΔEu gestatten dabei eine eindeutige stereochemische Zuordnung der Verbindungen. Die ΔEu‐Werte werden mit dem Abstand Hi…O‐Atom (Ri) korreliert.