Counterion Exchange Selectivity in Detergent–Polymer Aggregates

In aqueous solution, the interaction between sodium dodecyl sulfate (SDS) and poly(ethylene glycol) (PEG) results in the formation of small aggregates or clusters of SDS attached to the PEG polymer chain. Selectivity coefficients for exchange of two monovalent (N-methyl-4-cyanopyridinium cation and Tl⁺) and two divalent (methylviologen cation and Cu²⁺) counterions at the surface of SDS–PEG clusters, determined employing photophysical techniques, are similar, but not identical, to those for exchange at the surface of SDS micelles in the absence of PEG. The principal factor affecting ion exchange selectivity in SDS–PEG clusters does not appear to be aggregate size or surface charge density but rather the presence of poly(oxyethylene) subunits at the aggregate surface.     

Solution Chemistry of Arsenic Anions in the Presence of Metal Cations

The interaction of arsenic(V) and arsenic(III) oxyanions with metal cations was investigated by potentiometry under temperature and ionic strength conditions approaching those prevailing in natural waters. The selection includes the major metal cations and some other ions of high environmental relevance. Ionic pairs [M(As^VO₄)]^?, [M(HAs^VO₄)] and [M(H₂As^IIIO₃)]⁺ formation is suggested for all +2 metal cations, based on the potentiometric results. These ion-pairs between arsenic anions and other metal cations are hardly ever mentioned or taken into account when arsenic speciation in natural waters is considered. These results provide the basis for studying arsenic speciation in natural aquatic systems, on which environmental fate, bioavailability and toxicity of the element depend. Some extrapolations to the conditions of the natural waters are presented as well as some insights into the adsorption process onto hydrous oxides.     

The reaction of 2-picoline N-Oxide with o-substituled benzoates and lsatoic anhydrides

The reaction of 2-picoline N-Oxide anion with o-substituted henzoates and isatoic anhydrides to give synthetically useful l-(2-methoxyphenyl)-2-(2-pyridinyl)ethanone N-oxides, I-(2-hydroxy-phenyJ)-2-(2-pyridinyl)ethanone N-oxides and I -(2-arninopheny])-2-(2-pyridinyl)ethanone N-oxides is described.     

Aureomycin nitrate,its preparation and identification

Summary Aureomycin hydrochloride does not show any promise as a reagent for qualitative detection or quantitative estimation of any of the common cations or aidons. The well developed crystals of the rather insoluble nitrate may be used for the identification of aureomycin. The low solubility of the nitrate may give a better stability as compared with the hydrochloride, which would be of interest to the pharmacist.

---

Zusammenfassung Versuche mit Aureomycinhydrochlorid gaben keine Anhaltspunkte für eine Eignung dieser Verbindung als Reagens für die Auffindung oder Bestimmung der häufig angetroffenen Kationen oder Anionen. Die gut ausgebildeten Kristalle des wenig löslichen Nitrats können für die Erkennung von Aureomycin benützt werden. Die geringe Löslichkeit des Nitrats erhöht dessen Beständigkeit im Vergleich zum Hydrochlorid, was für Pharmazeuten von Interesse sein könnte.

---

Résumé Le chlorhydrate d'auréomycine ne montre aucune propriété intéressante comme réactif de recherche qualitative ou d'estimation quantitative des cations et anions courants. On peut utiliser les cristaux bien développés de son nitrate assez peu soluble pour identifier l'auréomycine. La faible solubilité de ce nitrate peut lui conférer une meilleure stabilité que celle du chlorure ce qui est digne d'intérêt pour les pharmaciens.

---

---

Dedicated to Prof. Dr.Hans Lieb at his 70th birthday.     

Reactive properties of trans-dichlorooxirane in relation to the contrasting carcinogenicities of vinyl chloride and trans-dichloroethylen

Our objective in this work is to gain insight into the contrasting carcinogenic activities of vinyl chloride (definitely carcinogenic) and trans-dichloroethylene (apparently inactive). The initial metabolic step for each molecule is believed to be epoxidation of the double bond, and there is evidence indicating that for vinyl chloride, this epoxide (chlorooxirane) is its ultimate (direct-acting) carcinogenic form. This article presents the findings of a computational study of the reactive properties of trans-dichlorooxirane (the epoxide of trans-dichloroethylene). An ab initio SCF -MO procedure was used to determine the energy requirements for stretching the C? O and C? Cl bonds (S_N1 reactivity) and to study the epoxide's S_N2 interactions with ammonia, taken as a model nucleophile. The starting points were the oxygen- and chlorine-protonated forms of the epoxide. The structure of the system was reoptimized at each step along the various reaction pathways. The results of this work are compared to an analogous earlier study of the reactive properties of chlorooxirane. The chlorineprotonated C? Cl bonds are found to have much lower energy barriers to stretching than do the oxygen-protonated C? O bonds. In the S_N2 processes, intermediate complexes are formed with ammonia by both the oxygen- and the chlorine-protonated epoxides; the latter complexes are the more stable. Based on our results, we propose two mechanisms (one S_N1 and the other S_N2) whereby trans-dichlorooxirane can interact with N₇ of guanine to produce an adduct analogous to one formed by chlorooxirane, which has been found to be the primary in vivo DNA alkylation product of vinyl chloride and to which has been attributed the carcinogenicity of the latter. Overall, trans-dichlorooxirane is found to be chemically more reactive than chlorooxirane; this may help to account for the much lesser carcinogenic and mutagenic activities of trans-dichloroethylene, since the epoxide may be reacting with other cellular nucleophiles before it reaches the key site(s) at which the carcinogenic or mutagenic interaction would occur. We also offer some speculations concerning other possible factors related to the differing carcinogenicities of vinyl chloride and trans-dichloroethylene, such as ease of epoxide formation and the likelihood of oxygen protonation.     

The preparation of new chiral diphenyl-substituted macrocyclic polyether-diester compounds and their enantiomeric recognition of chiral organic ammonium salts

A series of chiral diphenyl-substituted macrocyclic polyether-diester ligands have been prepared from the chiral diphenyl-substituted tetraethylene glycol. Enantiomeric recogntion by the chiral diphenyl-substituted pyridino-diester-18-crown-6 compound ( 7 ) was studied by temperature dependent ¹H NMR spectroscopy in deuteriodichloromethane. This ligand exhibited chiral recognition when complexed with the hydrogen per-chlorate salts of (R)- and (S)-α-(1-naphthyl)ethylamine and (R)- and (S)-methyl phenylalaninate.     

Computational studies of the 3-Dimensional structure of cyclopenta polycyclic aromatic hydrocarbons containing a gulf region

Recently, some cyclopenta-fused polyaromatic hydrocarbons, an environmentally relevant subclass of chemicals, have been shown to have carcinogenic activity in animals. It has been suggested that benz[l] aceanthrylene ( I ), an active member of this subclass with a gulf region, has a trans dihydrodiol metabolite that is nonplanar and has two distinct spatial configurations. We have used MMP 2(85) and AM 1 to investigate the three-dimensional structure of this dihydrodiol and other similar derivatives of ( I ) and have found that although ( I ) is somewhat nonplanar the relevant derivatives are all nearly planar. Further, we have computed potential functions for the bending of the angular ring in the gulf region using MMP 2(85), AM 1, and ab initio computed energies for AM 1 spatial configurations and find that these molecules all have only a single potential minimum. We have performed the same calculations for benzo[c]phenanthren and its 1,12 dimethyl derivative, molecules with a similar gulf region for which crystallographic data exists. In agreement with that data, we find that two distinct spatial configurations exist separated by significant barries. The differences between the results generated by the three different methods of computation will be discussed.