High pressure NMR of liquids

In the following, we will present a selected choice of high-pressure cells developed for high-resolution NMR. We have divided the applications of high-pressure NMR into three sections. First, we will describe high pressure equipment used to study liquids under hydrostatic pressure up to 1000 MPa then, we present some special approaches used to study supercritical fluids which, besides moderate pressure, often need high temperatures. Finally, we discuss NMR cells to study solutions under gas pressure, a situation which is quite common in catalysis. 

---

Miscellaneous high-pressure NMR studies of inorganic systems High-pressure NMR studies using sapphire tubes Various high-pressure studies of polymers and complex liquids High-pressure studies of liquids confined to porous media High-pressure NMR studies of solids... 

This type of high pressure NMR flow cell is specially convenient for mechanistic studies in gas-liquid reactions [61-69]. 

J. Jonas, High Pressure NMR Studies of the Dynamics in Liquids and Complex Systems, Ed. J. Jonas, Springer Verlag, Berlin, 1991, Vol. 24, pp. 85-128. 

Yonker, C. R. and Linehan, J. C., A high-pressure NMR investigation of reaction chemistries in a simple salt hydrate,. Supercrit. Fluids, 29, 257 2004. Mehnert, C. R, Supported ionic liquid catalysis, Chem. Eur. ]., 11,50,2005. Giernoth, R. and Bankmann, D., Transition-metal free synthesis of perdeuter-ated imidazolium ionic liquidsby alkylation and H/D exchange, Eur. J. Org. Chem., 2008 (in print). DOT 10.1002/ejoc.200700784. 

Jonas J, Adamy ST, Grandinetti PJ, Masuda Y, Morris SJ, Campbell DM, Li Y. High pressure NMR study of transport and relaxation in complex liquids of 2-ethylhexyl cyclohexanecarboxylate and 2-ethylhexyl benzoate. J Phys Chem 1990 94 1157. 

The first high-pressure NMR studies were performed by Benedek and Purcell in the mid nineteen-fifties. They discovered that the beryllium-copper alloy Berylco-25 is nonmagnetic and that it is very suitable for high-pressure equipment for magnetic studies. Their pressurizable NMR probe (see Fig. 4.19) was similar to designs used today, and it was used at pressures up to 1 GPa (10000 atm) to study the variation with viscosity of proton relaxation times and self-diffusion eonstants in a series of liquids. Since then a variety of systems for variable-pressure experiments have been developed. Three basic approaches have been used ... 

Fig. 5.1 Samples of high-pressure-NMR capillary cells (a) the standard Yamada-type capillary, shown within an autoclave (b) thin cell for supercooling liquids (c) a modified cell for use with liquids which wouid be gaseous at ambient conditions.

Sapphire tubes introduced by Roe [17] paved toe way for more routine applications of high-pressure NMR involving gas-liquid interphases. Systems similar to the original one have been extensively used for numerous applications [2,18-20,72,73]. For applications with supercritical media such as CO2, CHF3, and CF3CI, a modified cell equipped with a pressure sensor and a 10-mm sapphire tube has recently been described (Figure 3.2-27) [74]. 

---