Chemische Verschiebungen in der kernmagnetischen Resonanz von ¹⁷O in organischen Verbindungen

Abstract

Solutions with pentavalent vanadium contain between pH 3 and 5,5 only decavanadate ions in the forms of H2V1,0zs4-, HV100285-, and V,00286-. The cristallized sodiumas well as the potassium decavanadates containing the ions V,,OZS6-and HVloOzs5-are highly soluble salts. The double salts {K,NaV,oO,,,lOH,O} and {K,NaHV,0028,10H20} on the other hand are so sparingly soluble that they can be used for the quantitative precipitation of sodium. Even from solutions with a ratio K : Na = 10000: 1 the precipitates obtained have an exact stoichiometric composition. 865 Zurich, Laboratorium fur Anorganische Chemie der Eidg. Technischen Hochschule -99. Chemische Verschiebungen in der kernmagnetischen Resonanz von 1 7 0 in organischen Verbindungen1)2) von H. A. Christ3), P. Diehls), HR. Schneider4) und H. Dahn4) (7.111. 61) Von den drei stabilen Sauerstoff-Isotopen besitzt nur I7O ein magnetisches Moment. Da dieses Isotop eine naturliche Haufigkeit von nur 0,037% hat, sind die Kernresonanzlinien ohne kiinstlichen Anreicherung ausserst schwach. Sie konnen nur beobachtet werden, wenn die Probe geniigend Sauerstoff enthalt, d. h. vor allem in kleinen Molekeln, und auch dann nur mit besonders rauscharmen Spektrometern. Daher kommt es, dass trotz der Wichtigkeit von Sauerstoff fur die Chemie bisher wenig uber die 170-Kernresonanz (NMR) in der organischen Chemie bekannt geworden ist. ALDER & Yu 5, wiesen als erste die Kernresonanz von 1 7 0 nach und fanden eine chemische Verschiebung zwischen Wasser und Essigsaure. WEAVER, TOLBERT & LA FORCE^) massen 1955 die chemischen Verschiebungen von 10 organischen und 5 anorganischen Verbindungen ; 1959 erweiterten DHARMATTI, SUNDARA RAO & Vr JAYARAGHAVAN 7) diese Liste urn 10 weitere organische Stoffe. Neuerdings sind ausserdem Arbeiten uber Verschiebungen der Resonanzlinien von Hydratwasser in anorganischen Salzen erschienen *) ; dabei wurde erstmals angereichertes H2'O verwendet .

17O‐NMR Spectra of Mesoionic Compounds: The polarized carbonyl group

“…This assignment is, however, in contradiction with the general experience [7] that =O resonates at lower field than -0-. In view of the importance for the interpretation of the bonding state in mesoionic compounds, a strict attribution of the signals appears necessary.…”

“…-Furoxans. A further group of mesoionic compounds are the furoxans (furazan oxides), in which the exocyclic 0-atom is bound to N instead of C; compounds 6 and 7, measured earlier [7] [24], show 6, at 475, 350 and 490, 380 ppm, respectively.…”

“…We have shown earlier [7] that the chemical-shift values of "0-NMR give a good indication of the electron density around 0-atoms, distinguishing clearly between doubly 1A 1B 1c 1D…”

Relationship between oxygen-17 nuclear magnetic resonance chemical shifts and Π-bonding to oxygen in the dichromate ion

“…These data for oxygen bonded to a transition metal atom are particularly appropriate for assessing the effects of a-bonding because the paramagnetic shifts observed are 2-3 times larger than those observed for oxygen a-bonded to a non-transition element such as carbon ( 2 ) . In order to relate chemical shifts to a-bond character, an index of this latter parameter is required.…”

17O NMR chemical shifts: a simple and useful rule for substituent additivity on oxygen atoms with a coordination number of two

“…1 The replacement of a hydrogen by a methyl group at various positions in organic compounds containing an oxygen atom induces 17 O chemical shift perturbations 2 -5 which have been interpreted in terms of the substituent chemical shifts (SCS), a concept 6 widely used in 13 C NMR. Despite the abundance of 17 O NMR data for aliphatic compounds such as ethers, 1,3,7,8 alcohols, 1,2,7,8 alkyl vinyl ethers, 1,9 alkyl phenyl ethers, 1,9 acetals 1,8 and esters 1,8,10 in the literature, little work has been devoted to the systematic determination of substituent oxygen chemical shifts in organic compounds. 4,11 -13 The use of empirical relationships in NMR is extremely useful for the structural determination of unknown compounds and their conformational analysis.…”