Zur Chemie der Bromisocyanurs�uren: Eigenschaften und Reaktionen der Dibromisocyanurs�ure

2,3,4,5,6-Pentabromobenzoic Acid

Pentabromobenzoate is a useful fragment in organic synthesis and in coordination chemistry. Among known synthetic approaches to pentabromobenzoic acid (PBA), we have assessed and identified exhaustive bromination of benzoic acid by using 1.3-dibromoisocyanuric acid in concentrated H2SO4 solution as the most efficient method for the preparation of PBA on a multigram scale. As the crude bromination product is typically contaminated with 3,4,5,6-tetrabromobenzoic acid (TBA) and pentabromobenzene, C6Br5H, a simple purification protocol for preparation of analytically pure PBA has been developed. The molecular structure and crystal packing of PBA established by single-crystal X-ray diffractometry suggests a pattern of H-bonding and halogen bonding in solid state.

Superior bactericidal activity of N-bromine compounds compared to their N-chlorine analogues can be reversed under protein load

AIMS

To investigate and compare the bactericidal activity (BA) of active bromine and chlorine compounds in the absence and presence of protein load.

METHODS AND RESULTS

Quantitative killing tests against Escherichia coli and Staphylococcus aureus were performed both in the absence and in the presence of peptone with pairs of isosteric active chlorine and bromine compounds: hypochlorous and hypobromous acid (HOCl and HOBr), dichloro- and dibromoisocyanuric acid, chlorantine and bromantine (1,3-dibromo- and 1,3 dichloro-5,5-dimethylhydantoine), chloramine T and bromamine T (N-chloro- and N-bromo-4-methylbenzenesulphonamide sodium), and N-chloro- and N-bromotaurine sodium. To classify the bactericidal activities on a quantitative basis, an empirical coefficient named specific bactericidal activity (SBA), founded on the parameters of killing curves, was defined: SBA= mean log reductions/(mean exposure times x concentration) [mmol 1(-1) min (-1)]. In the absence of peptone, tests with washed micro-organisms revealed a throughout higher BA of bromine compounds with only slight differences between single substances. This was in contrast to chlorine compounds, whose killing times differed by a factor of more than four decimal powers. As a consequence, also the isosteric pairs showed according differences. In the presence of peptone, however, bromine compounds showed an increased loss of BA, which partly caused a reversal of efficacy within isosteric pairs.

CONCLUSIONS

In medical practice, weakly oxidizing active chlorine compounds like chloramines have the highest potential as topical anti-infectives in the presence of proteinaceous material (mucous membranes, open wounds). Active bromine compounds, on the other hand, have their chance at insensitive body regions with low organic matter, for example skin surfaces.

SIGNIFICANCE AND IMPACT OF THE STUDY

The expected protein load is one of the most important parameters for selection of a suited active halogen compound.

Active halogen compounds and proteinaceous material: loss of activity of topical anti-infectives by halogen consumption

OBJECTIVES

The activity of oxidants, such as halogens and active halogen compounds, decreases generally in the presence of proteinaceous material. A quantification of consumption effects was performed to judge the suitability of different representatives as antiseptics and their compatibility with pharmaceutical additives.

METHODS

An iodometric approach served to assess the temporal loss of oxidation capacity in the presence of peptone and fetal calf serum (FCS). The tested agents comprised active halogen compounds, well-known and in particular novel chloramine-based agents indicated for the topical treatment of infections.

KEY FINDINGS

The decrease in oxidation capacity was higher in the presence of FCS than of peptone and correlated with the reactivity of the oxidants in both cases. The highest consumption rates were for active bromine compounds followed by hypochlorous acid and heterocyclic chlorimides, such as dichloro-isocyanuric acid, while N-chlorotaurine and related amine-based analogues were least consumed. The pH dependence was only remarkable for chloramine T.

CONCLUSIONS

The observed consumption effects are the result of the differing oxidizing (chlorinating) potencies. Since consumption and irritation are founded on the very same reactions, representatives with low reactivity (N-chloro amino acids) are regarded as more tolerable and retain more oxidative capacity, which provides a more sustained antimicrobial activity.

Synthesis and Optical and Redox Properties of Core-Substituted Naphthalene Diimide Dyes

2,6-Dichloronaphthalene dianhydride has been synthesized by a modified procedure. The imidization of this dichlorinated anhydride with amines and subsequent stepwise nucleophilic exchange of the chlorine atoms by alkyl- or arylamines afforded a series of hitherto unknown monoamino- and diamino-substituted naphthalene diimides. An alternative route for the synthesis of diamino-substituted naphthalene diimides is also reported. Optical and electrochemical properties of the newly synthesized amino-functionalized naphthalene diimides were studied in detail. The absorption maxima (530-620 nm) of these dyes are appreciably bathochromically shifted compared to those of the corresponding core-unsubstituted compounds. At the naphthalene core alkylamino-substituted diimides exhibit fluorescence quantum yields up to 60%.

Flow-injection chemiluminescence determination of chlorinated isocyanuric acids

A rapid and sensitive flow-injection chemiluminescence method is described for the determination of dichloro- and trichloroisocyanuric acids based on the chemiluminescence produced during their reaction with luminol in alkaline medium. The effects of analytical and flow-injection variables on these chemiluminescence systems and determination of both oxidants are discussed. The optimized method yielded 3sigma detection limits of 8x10(-8) and 5x10(-8) mol L(-1) for the sodium dichloroisocyanurate and trichloroisocyanuric acid, respectively. The optimum conditions were found to be as follows: NaOH, 1x10(-1) mol L(-1); luminol, 5x10(-3) mol L(-1); KI, 2x10(-3) mol L(-1) and flow rate, 3.5 mL min(-1).