Complexes of iron(III) with cyclopropanecarbo- and cyclohexyl-acetohydroxamic acids

Summary Cyclopropanecarbohydroxamic acid (CPAH) and cyclohexylacetohydroxamic acid (CHAH) were synthesized, characterized and their pK _a's determined spectro-photometrically as 9.80 and 9.85, respectively, at 25 °C and in buffers of 0.1 mol dm^–3 ionic strength (I). A spectroscopic investigation of their reactions with Fe^III in aqueous solutions revealed the sole formation of the 1:3 complexes at equilibrium. Stability constants (log ₃ at 25 °C and I = 0.1 mol dm^–3 are 34.80 and 34.22 for [Fe(CPA)₃] and [Fe(CHA)₃], respectively. Spectral and magnetic studies of the isolated complexes indicate octahedral coordination via the O atoms of the hydroxamate group.     

Computers in abstract algebra

The current emphasis on flexible modes of mathematics delivery involving new information and communication technology (ICT) at the university level is perhaps a reaction to the recent change in the objectives of education. Abstract algebra seems to be one area of mathematics virtually crying out for computer instructional support because of the availability of multi-representational tools and appropriate software that can be used to bridge the existing gap between the concrete and the abstract. This paper focuses on the use of the computer program, Excel, in teaching an introductory group theory course at the university level. Here the author describes the use of the Excel ‘fill-handle’ and ability to colour blocks of cells as cosets quickly in constructing and completing Cayley tables for abstract groups. The relation of the approach to constructivist philosophies and cooperative learning is discussed.     

Presheaves over lattices: application to twisted limits of finite groups.

The notion of “active sum of groups” appears as a special case of the notion of twisted (direct) limit of groups over partially ordered sets and lattices. This provides us with a sheaf-like theory; in fact up to introducing coverings in a lattice we obtain an extension of the theory of (pre-)sheaves over Grothendieck topologies. It is possible to introduce the point-lattice (or point-topology) and describe the transfer of structure properties from the base lattice to the point-lattice. Starting from general presheaf-action (of groups) one may then introduce a global twisted limit. Using particular functors it is then possible to define “structure sheaves” in our setting. Inspired by the theory of modules over rings, we then consider the special case of G-sets. This clears the way for application to the Burnside ring of finite groups.     

Complexes of cyclocarbohydroxamic acids with cobalt(II), nickel(II) and copper(II)

A spectroscopic investigation of the reactions of cyclopropanecarbohydroxamic acid (CPAH) with CoII and of cyclohexylacetohydroxamic acid (CHAH) with CoII, NiII and CuII in aqueous solution reveals the sole formation 1:2 complexes at equilibrium. Stability constants (log2 at 25°C and I=0.1 mol dm–3) are 9.11, 9.91, 11.70 and 24.18 for [Co(CPA)2], [Co(CHA)2], [Ni(CHA)2] and [Cu(CHA)2], respectively. Spectral and magnetic studies of the isolated complexes indicate octahedral coordination via the oxygen atoms of the hydroxamate group for the CoII and NiII complexes but a square planar geometry for the CuII complex.