The proton exchange reaction between indene and the indenyl anion

Vos, H. W.; Bakker, Y. W.; Velthorst, N.H.; MacLean, C.

doi:10.1002/mrc.1270061104

Cited by 5 publications

(1 citation statement)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is well-known that the various types of ion pairs can also be distinguished by their reactivities in chemical reactions (1 & 3). We have observed such a difference for the symmetrical proton exchange reaction between indene and indenyl (23).…”

Section: Proton Exchange Reaction Between Indene and Indenylmentioning

confidence: 70%

Optical and NMR Investigations on Alkali Ion Pairs of Carbanions and Nitranions

Velthorst

1979

Ions and Ion Pairs and Their Role in Chemical Reactions

View full text Add to dashboard Cite

-The ion pair formation of some cyclic conjugated carbanions and nitranions has been studied by absorption and fluorescence spectroscopy. From the spectra, recorded as a function of temperature, solvent and counter ion it becomes clear that the absorption spectra of contact ion pairs are always shifted to high energy with respect to the spectra of solvent separated ion pairs, but in the fluorescence spectra shifts in both directions have been found. The observed phenomena can be explained satisfactorily by theoretical 71-electron charge distributions in the ground and first excited states. Also with 'H and '3C NMR spectroscopy valuable information concerning the ion pairing has been obtained. An apparent discrepancy between the structure of the contact ion pair of the carbanion indenyl inferred from calculations and from 'H NMR is resolved by a theoretical examination of the effects of the cationic field on the proton chemical shifts. The '3C NMR data support the interpretation of the temperature dependence of the 'H chemical shifts in terms of a "direct" and an "indirect" effect of the cation. In order to explain the 'H chemical shifts of some anions with 16 r-electrons the occurrence of paramagnetic ring currents has to be postulated. 7Li NMR data give evidence for the structure of the contact ion pairs, a-or r-complex. The influence of ion pair formation on the reaction rate of the symmetrical proton exchange reaction between a carbanion and its parent molecule has been studied from the exchange line broadening for the system indene/indenyl in various solvents.

show abstract

Section: Proton Exchange Reaction Between Indene and Indenylmentioning

confidence: 70%

Optical and NMR Investigations on Alkali Ion Pairs of Carbanions and Nitranions

Velthorst

1979

Ions and Ion Pairs and Their Role in Chemical Reactions

View full text Add to dashboard Cite

show abstract

The alkali cation effect on the ¹H NMR chemical shifts of the indenyl carbanion

Gooijer¹,

Velthorst²

1979

Org. Magn. Reson.

Self Cite

View full text Add to dashboard Cite

The complex character of the temperature dependence of the 'H N M R chemical shifts of indenyl-lithium and -sodium in dimethoxyethane is explained. It is shown that the cation causes a polarisation of the C-H bonds and thus inflnenees the proton shifts of the anion, both directly by i t s electric field along the bonds (the direct effect) and induectly via its effect on tEe Ir-electron distribution (the indirect effect). The indirect effect is inferred from uC NMR chemical shift data. By subtracting the temperature dependent contribution of the indirect effect from the experimental 'H data, the direct effect is visualised. It appears that information on ion pairs obtained by 'H and "C NMR on the one hand and optical spectroscopy on the other hand is complementary. Apparently, aggregation of ion pairs does not seriously affect the chemical shift data.

show abstract