High-temperature NMR studies

In a pioneering high-temperature NMR study, Stebbins et al. (1992) reported Al chemical shifts for four compositions of the NaF-AlF3-Al203 system that were systematically much higher in liquid than in the solid phases. They emphasized the dramatic effect of composition and temperature on the liquid structure and proposed an evolution of aluminum environment toward a higher fraction of a 4-fold coordinated environment of aluminum. 

R 84 O.B. Lapina, V.V. Terskikh, B.S. Bal Zhinimaev, K.M. Eriksen and R. Fehrmann, High-Temperature NMR Studies of Ionic-Liquid Catalysts , p. 85... 

Nuta, L, Veron, E., Matzen, G. and Bessada, C. (2011) High temperature NMR study of aluminum metal influence on speciation in molten NaF-AlFj fluorides. Inorg. Chem., 50(8), 3304-3312. 

Low-temperature NMR studies of the reaction of 2-methoxycyclohexanone with SnCU in the presence of a base confirm the formation of a chelated tin enolate (Equation (84)). A synthetic application, a high stereoselective synthesis of sanfetrinem, has been described.239... 

Isomerization of cryptand-containing spirobenzopyran 63 (Scheme 3) to the open-colored merocyanine 63 in the presence of Srl2 has been studied by H NMR spectroscopy at 500 MHz. In several deuterated solvents (e.g. CDC13, CD3CN, DMSO-d6) the H NMR signals of 63 were considerably broadened at room temperature. High-temperature NMR (85 °C) in DMSO-d6 succeeded in resolv-... 

The general problem of solution homogeneity represents a major area of concern in high-resolution solution NMR studies of complex hydrocarbon mixtures encountered in coal products. Although alternate NMR approaches could be used or developed (e.g., solid-state NMR, high-temperature NMR, ideal NMR solvents, etc.), the quantitative NMR approach used in the present study can distinguish this problem when complementary elemental combustion data is available. 

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