Micellar catalysis in kinetic methods of analysis: improvement of spectrophotometric catalytic determination of copper

The combined effects of micellar and chemical catalysis were studied with a view to improving the features of catalytic kinetic determinations. For this purpose we chose the reaction between N,N-dimethyl-p-phenylenediamine (DPD) and N,N-dimethylaniline (DA) to form Bindschedler's Green leuco base, which is oxidized by hydrogen peroxide in a reaction catalysed by Cu(II). This reaction was found to be accelerated by anionic sodium dodecylsulphate (SDS) and cationic dodecyltrimethylammonium bromide (DTAB) micelles. Several advantages were gained in relation to the analytical features of the kinetic photometric determination of Cu(II) when the reaction was developed in the presence of micelles compared to that occurring in an aqueous medium. Such advantages include a lower detection limit, higher sensitivity, precision and solubility of DPD and DA, and substantially increased selectivity in some cases. A detailed study of the parameters which influence both reactions is reported. Some observations on the effect of SDS and DTAB on the reaction are also commented on.     

Synthesis of α-amino γ-butyrolactone derivatives by aziridination of α-ylidene γ-butyrolactones

The reactions of exocyclic α,β-unsaturated γ-lactones with NsONHCO₂Et and CaO produce N-(ethoxycarbonyl) spiroaziridino γ-lactones. By reaction with acetic acid these products give ring opening reaction and acetylated N-protected α-amino γ-butyrolactones are obtained. The ring opening reaction is quantitative and highly regioselective.     

Identification of the main by-products of the developing agent N-hydroxyethyl-N-ethyl-3-methyl-p-phenylenediamine in photographic effluents by liquid chromatography/mass spectrometry

N-Hydroxyethyl-N-ethyl-3-methyl-p-phenylenediamine (CD(4)) is commonly used as a developing agent in color photographic processes. The main by-products formed in developer baths used in the process were separated and identified by liquid chromatography/electron ionization mass spectrometry (LC/EI-MS) and liquid chromatography/atmospheric pressure ionization mass spectrometry (LC/API-MS). A number of side reactions, in addition to the main reactions involved in the developing process, were found to occur. Such side reactions involved in the formation of CD(4) by-products included oxidation, hydroxylation, sulfonation and the formation of coupling products. A reaction pathway for the degradation of CD(4) based on the nature of the by-products identified is proposed and discussed.     

Addition reactions of ethoxycarbonylnitrene and ethoxycarbonylnitrenium ion to allylic ethers

Ethoxycarbonylnitrene (EtOCON) generated by α-elimination adds cleanly to allylic ethers giving substituted aziridines. Similar addition via nitrenium ion (EtOCONH⁺) gives derivatives of β-amino alcohols.     

Synthesis of β,β-branched β-amino ester derivatives through spiroaziridination of (α-trimethylsilanylmethyl)cyclohexylidene esters

The reaction of (α-trimethylsilanylmethyl)cyclohexylidene esters with NsONHCO₂Et and CaO produces the N-(ethoxycarbonyl)spiroaziridines which, after ring-opening, gives the corresponding β,β-disubstituted β-amino ester derivatives. The stereochemical outcome of the reaction is influenced by substituents on the cyclohexyl group.     

N-Amination of 3-amino-1,2,4-triazole with hydroxylamine-O-sulfonic acid: Synthesis of 1,5-diamino-1,2,4-triazole

N-Amination of the 3(5)-amino-1,2,4-triazolide anion with hydroxylamine-O-sulfonic acid is studied. This method provided an access to the previously unknown 1,5-diamino-1,2,4-triazole.     

Dose-dependent inhibition of ultrasound-induced cell killing and free radical production by carbon dioxide

Previous studies have shown that if a solution for cell suspension is saturated with CO(2), ultrasound-induced in vitro cell killing and free-radical production are inhibited. However, the dose dependency of this observation has not been explored. Here, we used NaHCO(3) and HCl to produce a predictable concentration of CO(2) within the culture medium. Using 1 MHz continuous wave 4 W/cm(2) ultrasound, we sonicated U937 cells suspension for 1 min at 37 degrees C with CO(2) at different concentrations. At 2 mM, reduced cell killing was observed that further decreased with increasing CO(2) concentration until 100% protection was attained at 20 mM. Ultrasound-induced free-radical production was significantly decreased at 1 mM and became undetectable at 2 mM CO(2). This finding shows that CO(2)-mediated inhibition is concentration dependent and that the threshold for free-radical production is one order of magnitude higher than the threshold for cell killing induced by ultrasound. In addition, it also cautions researchers when adding acids and acid-based agents to a culture medium, which almost always contains NaHCO(3), in experiments related to the bioeffects of ultrasound.