The 'H-NMR spectra of symmetric compounds with two phosphorus atoms of the type R-X-P-Y-P-X-R, R = CH,, C,H,, X = -, 0, NCH,, NCH,-, Y = NCH,, have been determined. After elimination of eventual couplings within the alkyl protons these spectra always show triplets in the case of trivalent phosphorus and doublets in the case of pentavalent phosphorus atoms. Since this paper establishes an unequal coupling between the alkyl protons and the two phosphorus nuclei, it is concluded that these compounds show a degenerate, however deceivingly simple, coupling:The spectra of symmetric diorgano diphosphines can be interpreted via the same mechanism. Calculations to substantiate these findings are reported.Zusammenfassung-Es wurden lH-NMR Spektren symmetrisch aufgebauter, zwei Phosphorkerne enthaltender Verbindungen vom Typ R-X-P-Y-P-X-R, R = CH,, C,H,, X = -, 0, NCH,, NCH,-, Y = NCH,, gemessen. Die Spektren der Protonen aus den Resten R ergaben (nach Elimination etwaiger Kopplungen zwischen den R-Protonen) im Falle dreiwertigen Phosphors stets Triplett-Signale, im Falle fiinfwertigen Phosphors Dublett-Signale. Da gleiche Kopplungen von R zu beiden Phosphorkernen ausgeschlossen werden konnten, murj eine entartete, tauschend einfache Kopplung vorliegen, die in der vorliegenden Arbeit gekllrt wird : J(P, P) > J(P, R) + Triplett, J(P, P) < J(P, R) -+ Dublett. Auch in den bisher vermessenen symmetrischen Diorgano-diphosphinen diirfte dieses Kopplungssystem vorliegen. Die Berechnungen dieses Systems werden mitgeteilt. IN MEHREREN VeroiTentlich~ngen~~~~~*~ wurde das Auftreten von JH Triplettresonanzsignalen fur an Phosphor gebundene Methylgruppen in Diphosphinen berichtet. Als Erklarung der Triplettstruktur der Signale wurde meist eine gleiche Kopplung der Methylprotonen zum benachbarten und enfernten Phosphorkern postuliert. Da ein Teil der in der vorliegenden Arbeit untersuchten Verbindungen vom Typ R-PNP-R ebenfalls Triplettstruktur fiir die R-Protonen ergab, erschien uns die obige Erklarung als generelle Erklarung der bei symmetrisch aufgebauten, zwei Phosphorkerne enthaltenden Verbindungen beobachteten lH-Triplett-Resonanzsignale als fragwiirdig. Dies war der Ausgangspunkt fur die nachstehende Untersuchung.485
A new effect was observed: The overall field ion current generated by thin wires or tips changes with the average work function of the metal if different organic substances are adsorbed.The shift of the tunneling probability versus voltage curve with change of work function and of ionization potential for molecules such as heptane, and heptene is calculated. This is compared with the shift of the experimental current-voltage curves with change of work function and ionization potential when supplying different organic compounds into the field ionization chamber and after addition of small amounts of another organic substance to the substance under discussion.Physically adsorbed substances on platinum, like n-paraffins, are always shifting these curves to higher voltages. This corresponds to a lowering of the average work function. The shift is more pronounced with alcohols on platinum because of the large work function (hange due to the polar groups. The higher aliphatic alcohols -starting with pentanol -are forming two dimensional condensed phases as postulated by KEMBALL. This was proven by detection of stepwise increase of dimeric ions in the FI mass spectra of pentanol as compared with the lower alcohols. The hydrocarbon chains of the alcohol molecules are ordered perpendicular to the metal surface in these phases.Benzene, ethylene and acetylene additives are shifting the FI-curves of paraffins to lower voltages, thus indicating a chemisorption process of these unsaturated compounds increasing the average work function of the platinum surface.
The dependence of neutral particle supply to the emission centres of a field ion emitter on adsorption and surface diffusion is investigated. An equation is derived relating the field ion current to the adsorption energy of organic adsorbates. It follows from this equation that the ion current increases with increasing adsorption energy. This was confirmed experimentally by a set of seven heptane isomers where the ion current increases with increasing boiling points. The ion intensities of a series of n-paraffins as a function of molecular weights are also discussed.
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