A high-pressure probe for high-resolution nuclear magnetic resonance

Volume profile of the degenerate equilibration of a nonclassical 7-norbornadienyl cation

“…Since the rate of this equilibration can conveniently be determined by means of the temperature dependence of the methoxy proton magnetic resonance line shapes, use was made of our recently developed apparatus for measuring NMR spectra of solutions under pressure. 4 The volume of activation for the reaction was found to be +8 cm3/mol, in good, if qualitative, agreement with the result expected on the grounds that charge dispersal leads to diminished solvent-ion interactions (Drude-Nernst or Born formal-isms5) and hence to expansion. We concluded that this finding supports the validity of the use of activation volumes as a criterion for carbon participation in solvolysis,6 at least in those cases in which the positive charge is equally distributed among at least two centers in the incipient cation.…”

Lithiation of N,N-dimethylmethallylamine

“…2-[3-(Dimethy lamino)-2-methylenepropyl]-1,7,7-trimethylbicyclo[2.2.1 ]heptan-2-ol (4). The allylic anion (25 mmol) prepared as described above was cooled to -70 °C and a solution of 1.9 g (12.5 mmol) of dZ-camphor in 5.0 mL of dry THF was added in one portion by syringe.…”

“…Ethyl (-)-(S)-2-(Mesyloxy)propanoate (4). Redistilled ethyl (+)-(S)-lactate (3; 82.0 g, 0.695 mol) was combined with triethylamine (111.0 mL, 0.798 mol) in 1 L of toluene in a 2-L round-bottomed flask equipped with a magnetic stirrer.…”

In Situ pH Probing of Hydrothermal Solutions by NMR

“…Second, a development of NMR tubes and probes suitable for NMR experiments at high temperature or high pressure or in corrosive media has recently occurred. − Several designs have been published for solution NMR at high pressures and temperatures. Merbach et al distinguished two groups of designs: on one hand, specific strong NMR tubes located in conventional probes 13-19 and, on the other hand, high-pressure NMR probes where the radio frequency coil, NMR sample, and pressurizing fluid are contained in a strong vessel. − Temperatures and pressures involved in the synthesis of inorganic materials do not usually require the use of high-pressure probes but just the availability of strong vessels withstanding autogenous pressures for samples heated to 200 °C, using commercial probes. Because of harsh chemical conditions encountered in the experiments (extreme pH values, fluoride ions), the vessels we use are protected by sealed inert Teflon (Dupont de Nemours) inserts .…”