The Specific Conductance and NMR Spectra of Fused Pyridinium Salts

Abstract

The specific conductance of p y r i d i n i u m HCI, N -m e t h y l p y r i d i n i u m chloride, N -m e t h y l p y r i d i n i u m bromide, 4-methylpyridinium bromide, and p y r i d i n i u m bromide, was measured as a function of temperature. The NMR spectra of the first three fused salts were also measured over the same temperature ranges. Correlations between conductance data and spectral data were found to exist.The experimental results indicate that the "friction" between the chloride and pyridinium ion is greater than between the bromide and the p y r i d i n i u m ion. The positive charge of the pyridinium ion seems to be localized on the nitrogen. In the pyridinium HC1 system the labile proton is probably contributing to the conductivity.

Magnetic resonance spectroscopy in ionic liquids

“…The triflate anion was found to form a transient a-glycosyl triflate, which directed the attack of the acceptor to the b-face. The intermediate was detected by 1 H and 19 F experiments. In a control experiment with [emim]PF 6 , the opposite product configuration was found, since the hexafluorophosphate anion is not able to react in a similar fashion.…”

“…The latter product was unambiguously assigned by replacement of methanol with methanol-d or ethanol leading to the observation of 2 D coupling splittings or ethyl carbonate signals, respectively. 19 F spectra showed decomposition as well. Apart from the fluoride anion resonance and a second, broad resonance attributed to hydrated fluoride, methyl fluoride was detected and suggested to be a product of dehydration of methanol with HF.…”

“…Newman et al were probably the first (in 1972) to obtain well-resolved 1 H NMR spectra of fused salts similar to ionic liquids: pyridinium hydrochloride, [mpy]Br, and [mpy]Cl [19]. The authors investigated the temperature dependence of the chemical shifts and found only a weak effect of the [mpy] methyl group 1 H shift on the type of anion.…”

“…A combined heteronuclear 1 H, 19 F-HOESY and 1 H and 19 F DOSY study has been published by Pregosin et al [82] for [bmim]BF 4 and [bmim]Tf 2 N (Fig. 18).…”

The electrochemical reaction of methyl pyridinium chloride in acetonitrile

“…A constant current ranging from 4 to 16mA/cm 2 was applied. [7] The electrolysis using MPC1 as the reactant which was chemical prepared by reacting methyl chloride with pyridine. 74.3 g of pyridine was placed in a sealed container and then methyl chloride gas was passed through at room temperature.…”