Inert fluorinated gas T1 calculator

The physics of spin-rotation interaction in roughly spherical perfluorinated gas molecules has been studied extensively. But, it is difficult to calculate a spin-lattice relaxation time constant T1 for any given temperature and pressure using the published literature. We give a unified parameterization that makes use of the Clausius equation of state, Lennard-Jones collision dynamics, and a formulaic temperature dependence for collision cross section for rotational change. The model fits T1s for SF6, CF4, C2F6, and c-C4F8 for temperatures from 180 to 360 K and pressures from 2 to 210 kPa and in mixtures with other common gases to within our limits of measurement. It also fits previous data tabulated according to known number densities. Given a pressure, temperature, and mixture composition, one can now calculate T1s for common laboratory conditions with a known accuracy, typically 0.5%. Given the success of the model's formulaic structure, it is likely to apply to even broader ranges of physical conditions and to other gases that relax by spin-rotation interaction.     

Effective strategy for the preparation of indolocarbazole aglycons and glycosides: total synthesis of tjipanazoles B, D, E, and I

[reaction: see text] An effective strategy has been developed for the rapid and efficient preparation of ortho-nitrostyrenes, which can be converted to unsymmetrical 2,2'-biindoles. A unique condensation of these 2,2'-biindoles with (dimethylamino)-acetaldehyde diethyl acetal affords the indolocarbazole ring system of the tjipanazole aglycon alkaloids in three synthetic steps and good to excellent overall yield. The first total synthesis of the tjipanazole glycoside alkaloids B and E is also discussed.