Trapp mixture

SCHEME 85. (Trapp mixture is a mixture of THE, ether and pentane which freezes at <110°C)... 

Solvent plays an important role in these reactions. A highly basic solvent, usually THF, is used to provide stabilization of the lithium halocarbenoid, due to coordination which disrupts the internal Li-Br interaction which would otherwise lead to a-elimination (equation 20). The extreme low temperature of many of the reactions requires special solvent systems, commonly a mixture of THF, diethyl ether, and petroleum ether or pentane in a ratio of 4 1 1 (Trapp mixture). Solvent has also been noted to alter the mechanistic course of the reaction for example, reaction of ketones with lithiobromomethane in hexane was observed to give rise to alkenes rather than epoxides. ... 

Hoffmann has shown that diastereoselective bromine-lithium exchange may be achieved even in acyclic systems.118 Treatment of 138 with BuLi in the Trapp solvent mixture at -120 °C in the presence of acetone generates the epoxides 139 and 140 in a 94 6 ratio of diastereoisomers.119 120 The selectivity was found to depend on the organolithium used for the bromine-lithium exchange, and it must therefore be under kinetic control. 

Figure 1. Boiling-point diagram for the binary system -octane and n-dodecane at P = 20 kPa. Open and filled symbols are used for the TraPPE and SKS force fields, respectively. The dashed line represents the experimental data. The calculated boiling points for the pure substances are shown as circles. Simulation results for binary mixtures are depicted as diamonds, upward-pointing triangles, squares, and downward-pointing triangles for simulations containing total mole fractions of -octane of 0.1,0.25,0.5, and 0.75, respectively.

Tosylmethyl isocyanide, 493-494 Transesterification, 81-82 Transfer RNA, 198 Translactonization, 488-489 Transmetalation, 86-87 Trapp s mixture, 175 Tri-f-bulylphenol, 494... 

Maerzke, K. A., N. E. Schultz, R. B. Ross, and J. 1. Siepmann. 2009. TraPPE-UA force field for acrylates and Monte Carlo simulations for their mixtures with alkanes and alcohols. Journal of Physical Chemistry B. 113, 6415. 

There have been two approaches to modeling the effect of pressure on the viscosity of mixtures. Either the effect of pressure is implicitly included in the model (for example, as in the case of Cao et al. or in the TRAPP method, in which the effect of pressure on density directly affects the viscosity), or viscosities are first calculated at low pressure (from saturation to a few atmospheres) and then corrected... 

The Meisenheimer rearrangement can compete with the formation of highly strained alkenes. The pyrolysis of the homoadamantylamine oxide (34 equation IS) gave a mixture of products, including hydro-caibons believed to have been formed by dimerization of 3-homoadamantene (36), which was trapp by 1,3-diphenylisobenzofuran, and die Meisenheimer product (35). ... 

A series of authors has defined the solvent relative strength for polar adsorbents in the form of eluotropic series, grouping them in order of their chromatographic elution strength, with both pure solvents and mixtures of solvents included. The most familiar of these is, of course, the one set up by Trappe, and variations of this have been published from time to time. Trappe gave the... 

Since monoterpenes are volatile, large amounts can only be accumulated in specialized structures. Several plant families, e.g., the Lamiaceae and Asterace, have glandular trichomes with secretory cells that produce terpenes and secrete them into a shared subcuticular storage cavity (Croteau et al., 2005). Similarly, conifers accumulate oleoresin, a complex mixture of mono-, sesqui-, and diterpenes, in resin blisters or ducts, which are covered by a layer of epithelial cells that synthesize and secrete the terpenes into the lumen (Trapp and Croteau, 2001). As in the case of the conifers, many other plants accumulate monoterpenes in mixtures containing the larger sesqui- and diterpenes, rather than monterpenes alone. 

In the TRAPP procedure (Ely Hanley 1981b, 1983), the viscosity of a fluid at density p, temperature T (and for a mixture, of composition x, ) is equated to the viscosity of a hypothetical pure fluid. (The hypothetical pure fluid is obtained through the use of mixing and combining rules and is discussed later.) The hypothetical pure... 

The number of components in the mixture can be unlimited. Furthermore, if the necessary critical parameters and acentric factors are unknown, it is straightforward to incorporate a procedure to estimate them from the normal boiling point and specific gravity (Baltatu 1982 Baltatu etal. 1985). A structural method such as that of Lydersen (Reid et al. 1987) could also be used to estimate the critical properties needed in TRAPR The early work on TRAPP used a 32-term modified Benedict-Webb-Rubin equation of... 

A full discussion on the original TRAPP equations plus extensive comparisons of the method with pure fluid and mixture data were given in the papers of Ely Hanley (1981a,b, 1983) and will not be repeated here. Table 12.1 gives a comparison of experimental viscosity data for selected pure fluids with the modified TRAPP model and the SUPERTRAPP model, in terms of the average absolute percent deviation AAD and the average percentage error BIAS. For all fluids except the cyclic compounds and... 

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