59502-05-5Relevant articles and documents
NMR in chiral polypeptide liquid crystals: the problem of amines
Solgadi, Audrey,Jean, Ludovic,Lasne, Marie-Claire,Rouden, Jacques,Courtieu, Jacques,Meddour, Abdelkrim
, p. 1511 - 1516 (2007)
It is shown that lyotropic liquid crystal mixtures made of poly-γ-benzyl-l-glutamate (PBLG) dissolved in N,N-dimethylformamide (DMF) are efficient anisotropic NMR solvents to distinguish the enantiomers of chiral amines through the effects of the differential ordering of enantiomers. This type of solvent overcomes problems often encountered when dissolving amines into the more conventional PBLG/CHCl3 or PBLG/CH2Cl2 liquid crystals. Furthermore, it is shown that perdeuterobenzyl chloride is an excellent achiral deuterated derivatizing agent for enantiomeric excess measurements of chiral amines in conjunction with the PBLG/DMF solvent.
Micellar Systems as ''Supercages'' for Reactions of Geminate Radical Pairs. Magnetic Effects
Turro, Nicholas J.,Weed, Gregory C.
, p. 1861 - 1868 (2007/10/02)
The photochemistry of dibenzyl ketone (DBK) and other molecules capable of producing benzyl radicals and substituted benzyl radicals has been investigated in micellar systems.The cage effect (percent of unscavengeable radical pairs produced by photolysis) was measured under a variety of conditions, and the results are compared with those obtained in homogeneous organic solvents.For example, parameters such as mean occupancy of ketone, detergent type and concentration, O2 concentration, additives, temperature, applied magnetic field, and pressure have been varied and investigated as to their influence on the magnitude of cage effect.In addition to modifying its environment, structural modification of the DBK by incorporation of 2H and 13C isotopes, hydrophobic groups, and heavy atoms was performed to investigate the impact of these variations on the cage effect in micellar systems.Isotopic substitution of 2H or 13C leads to results on both the quantum yields for reactions and on the percent cage that were consistent with expectations of magnetic isotope effects.Hydrophobic groups substituted in the 4-position of DBK were found to cause a substantial increase in the cage effect and yet retain the magnetic-field-dependent character found in the parent DBK.Incorporation of Br in the 4-position of DBK was found to enhance the cage effect but at the same time cause the cage effect to become magnetic field independent.Substitution of α-naphthyl for phenyl in DBK also produced magnetic-field-independent behavior, in addition to a dramatic decrease in the efficiency of photolysis.
Mechanisms of free-radical reactions. XI. Kinetic investigation of the free-radical chlorination of alkyl aromatic hydrocarbons by phenylchloroiodonium chloride
Dneprovskii, A. S.,Kasatochkin, A. N.
, p. 693 - 699 (2007/10/02)
The free-radical chlorination of meta- and para-substituted toluenes, ethylbenzene, and cumenes by phenylchloroiodonium chloride was investigated by the method of competing reactions.The good correlation between the relative reaction rate constants and the Brown ?+ constants and also the large negative values of ρ indicate separation of charges in the transition state.The values of the primary kinetic isotope effects of hydrogen decrease with increase in the reactivity of the substrate, whereas the values of the reaction parameters vary irregularly.The deviations from the inverse relation between the reactivity and the selectivity are due to the polar character of the transition state.
