sodium-chlorate and sodium-bromate

Pyrimidyl alkanol was found to act as an asymmetric autocatalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde. Asymmetric autocatalysis of 2-alkynylpyrimidyl alkanol with an extremely low enantiomeric excess (ca. 0.00005% ee) exhibits enormous asymmetric amplification to afford the same compound with >99.5% ee. This asymmetric autocatalysis with amplification of ee has been employed to examine the validity of proposed theories of the origins of homochirality. Circularly polarized light, quartz, sodium chlorate, cinnabar, chiral organic crystals and spontaneous absolute asymmetric synthesis were considered as possible candidates for the origin of chirality; each could act as a chiral source in asymmetric autocatalysis. Asymmetric autocatalysis can discriminate the isotope chirality arising from the small difference between carbon (carbon-13/carbon-12) and hydrogen (D/H) isotopes. Cryptochiral compounds were also discriminated by asymmetric autocatalysis.

Topics: Alcohols; Aldehydes; Bromates; Catalysis; Chlorates; Light; Mercury Compounds; Pyrimidines; Quartz; Sodium Compounds; Stereoisomerism; Zinc

In this investigation, salt effects on monomeric solubility and distribution are separated from self-association for caffeine. For self-associating compounds, the Setschenow equation is inadequate because it does not separate salt effects into their different contributions. Solubilities of caffeine, theophylline, and theobromine were determined in water and salt solutions at 25 degrees C. Caffeine, theophylline, and theobromine solubilities decreased with added Na(2)SO(4) or NaCl (i.e., salting-out) and increased with added NaClO(4) or NaSCN (i.e., salting-in). Caffeine distribution coefficients (D(W/O)) also decreased with added Na(2)SO(4) or NaCl and increased with added NaClO(4) or NaSCN. To separate salt-caffeine effects from salt effects on caffeine self-interaction, salting parameters (k(s)) were calculated from D(W/O) at infinite dilution instead of solubilities with the Setschenow equation. Caffeine k(s) values were smaller than the Setschenow constants (K) indicating that, for caffeine, K is not simply a salting-in/out parameter. Distribution data were used to characterize caffeine self-association using either a dimerization model (k(d), dimerization constant) or an isodesmic model (k(iso), stepwise association constant). Caffeine self-association constants (k(d) or k(iso)) decreased with NaClO(4) or NaSCN and increased with Na(2)SO(4) or NaCl.

Topics: Bromates; Caffeine; Chlorates; Phosphodiesterase Inhibitors; Salts; Sodium Chloride; Sodium Compounds; Solubility; Solutions; Sulfates; Thiocyanates