Differentiation of chiral phosphorus enantiomers by P and H NMR spectroscopy using amino acid derivatives as chemical solvating agents

The ability of commercially available amino acid derivatives, especially Fmoc-Trp(Boc)-OH, to differentiate enantiomers of chiral phosphonates, phosphinates, phosphates, phosphine oxides, and phosphonamidates is demonstrated with (31)P, (13)C, and (1)H NMR spectroscopy. The chiral differentiation provided a rapid and convenient method for measuring the enantiomeric purity of these phosphorus compounds.     

Reaction of 1-arylsulfamido-2-chloroethane with amines

Conclusion The reaction of 1-arylsulfamido-2-chloroethanes with diethylamine and aniline gives 1-arylsulfamido-2-aminoethanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 943–946, April, 1987.     

The preparation and properties of low molar mass liquid crystals possessing lateral alkyl chains

The first twelve members of three new mesogenic homologous series have been characterized, each of which are composed of molecules possessing lateral alkyl chains. The n-alkyl 2,5-bis-(4-n-hexyloxy-benzoyloxy)-benzoates are purely nematic whereas both nematic and smectic behaviour is observed for the 4-cyano-4'-biphenylyl 3'-n-alkyloxybenzoates and the 4-cyano-4'-biphenylyl 3',4'-n-alkyloxybenzoates. The transitional properties of these series are similar to those of the analogous conventional mesogens and hence, can be rationalized without making any special assumptions concerning the conformational distribution of the lateral alkyl chain.     

Self-inhibition or the lack of it in the pyrolyses of neopentane and n-hexane

Published data show that in its early stages (up to 3% decomposition), the pyrolysis of n-hexane in the ranges 723–823 K and 10–100 Torr is not inhibited by the olefin products, in contrast with neopentane pyrolysis which is very strongly inhibited in similar conditions. Detailed consideration of the chain mechanisms for the two pyrolyses shows that the reactivity of the chain terminating radical towards hydrogen abstraction from an allylic C? H bond in product olefin is the factor which determines whether or not observable self-inhibition occurs. Thus, n-hexane pyrolysis, whose chain decomposition is terminated by recombination and disproportionation of ethyl, is not significantly self-inhibited, whereas that of neopentane which is terminated by recombination of methyl is very strongly inhibited because methyl is 14× more reactive than ethyl. The implications for other alkanes are briefly discussed.     

HPLC studies of isomeric chromium-N-benzoylphenylhydroxylaminates

Summary N-Benzoylphenylhydroxylarnine complexes of some metals have been investigated by HPLC. The green chromium complex formed by this reagent shows conclusive evidence of the presence of geometrical isomers. It is photosensitive and changes to a brown modification when irradiated with ultra violet or visible light. Elution behaviour of the complexes has been studied with different solvent mixtures. Attempts have been made to characterize the complexes from different measurements.

---

Untersuchung von isomeren Chrom-N-benzoylphenylhydroxylaminaten durch HPLC

     

High reliability atomic absorption spectrometry of major and minor elements in biological materials

Summary Reliable analytical information is of fundamental importance for decisions of far-reaching impact in many regulatory, medical and scientific areas and disciplines. It is however at times elusive. Although the technique of atomic absorption spectrometry (AAS) as become widely established in analytical laboratories throughout the world for the determination of inorganic elements, only few AAS-based methods have reached official status and even fewer have attained reference method status. Research is underway to delineate impacts of a number of parameters on method performance to lead to protocols for standard and reference flame AAS (FAAS) methods for the reliable measurement of major and minor levels of elements of nutritional and toxicological pertinence in clinical and biological materials. Factors investigated include preparation of standards, calibration techniques, sampling and sample decomposition, solution preparation, instrumental parameters, and measurement protocols. Examples of some pronounced effects of sample decomposition and calibration techniques are presented as well as indications of the excellent performance of well-applied AAS procedures determined by use of standard reference materials and comparison with other techniques of analysis. Reference will be made to the determination of the major and minor nutrient elements Na, K, Mg, Ca, Mn, Fe, Cu and Zn in plant biological reference materials.Formerly at Plant Research Centre, Agriculture Canada, Ottawa, Ontario K1A OC6, CanadaContribution No. 1030 from Plant Research Centre     

When maths really is rocket science

Two problems in projectiles are discussed which generate interestingloci.