Some new acridinium trifluoromethanesulfonates as spectrophotometric derivatization reagents for aromatic and aliphatic primary amines

Some new 9-substituted 10-methylacridinium trifluoromethanesuifonate (triflate) salts have been synthesized and shown to react in methanol with the model aromatic and aliphatic amines, aniline and n-butylamine, to form derivatives which absorb strongly at 445 and 439 nm, respectively. The color development is affected by heat and heating time and by the quantity of acridinium triflate used. A 10-50-fold molar excess of the triflate should be used and the solution heated at 60 degrees for 30 min. The linearity and reproducibility of the assay are improved by the presence of pyridine (for aniline) and triethylamine (for n-butylamine) in the reaction mixture. Beer's law is obeyed over the range 0-1860 ng/ml for aniline and 0-1440 ng/ml for n-butylamine, with each of the new reagents. The relative error and the precision of determination depends on the acridinium triflate used.     

Symbol dynamic maps of spatial-temporal chaotic vibrations in a string of impact oscillators

Spatially complex, temporally chaotic dynamics of N-coupled impact oscillators connected by a string are studied experimentally using a discrete measure of the motion for each of the masses. For N=8, a binary assignment of symbols, corresponding to whether or not the masses impact an amplitude constraint, is used to code the spatial pattern as a binary number and to store its change in time in a computer. A spatial pattern return map is then used to observe the change in spatial patterns with time. Bifurcations in spatial impact patterns are observed in this experiment. An entropy measure is also used to characterize the dynamics. Numerical simulation shows behavior similar to the experimental system.     

The unimolecular chemistry of [1,2-propanediol]+˙: a rationale in terms of hydrogen-bridged radical cations

By combining results from a variety of mass spectrometric techniques (metastatle ion, collisional activation, collision-induced dissociative ionization, neutralization–reionization spectrometry and appearance energy measurements) and the classical method of isotopic labelling, a unified mechanism is proposed for the complex unimolecular chemistry of ionized 1,2-propanediol. The key intermediates involved are the stable hydrogen-bridged radical cations [CH₂?C(H)? H…?O…?O(H)CH₃]⁺˙, which were generated independently from [4-methoxy, 1-butanol]⁺˙ (loss of C₂H₄) and [1-methoxyglycerol]⁺˙ (loss of CH₂O), [CH₃? C?O…?H…?O(H)CH₃]⁺˙ and the related ion-dipole complex [CH₂?C(OH)CH₃/H₂O]⁺˙. The latter species serves as the precursor for the loss of CH³˙ and in this reaction the same non-ergodic behaviour is observed as in the loss of CH³˙ from the ionized enol of acetone.     

Metastable ion studies. III—composite metastable peaks in fragmentations of some small hydrocarbon cations

Composite metastable peaks are generated in the unimolecular fragmentations (i) [C₃H₅]⁺ → [C₃H₃]⁺ + H₂ (flat-top upon flat-top) and (ii) [C₄H₉]⁺ → [C₃H₅]⁺ + CH₄ (flat-top and gaussian). The measurement of appearance potentials and kinetic energy releases lead us to conclude, in agreement with earlier proposals, that in (i) the components can arise from the generation of the isomeric cyclopropenium and propargyl daughter cations. In (ii) the components are proposed to arise from the fragmentation of tert- and sec-butyl cations yielding allyl as the common daughter ion. The composite peak observed in the fragmentation (iii) [C₃H₄]⁺· → [C₃H₃]⁺ + H· is shown to be present only if the decomposing molecular ion is large enough to also produce [C₆H₈]²⁺ ions. The second component in (iii) then arises from the reaction [C₆H₈]²⁺ → [C₆H₆]²⁺ + H₂.     

Determination of uranium and radium concentrations in the waters of the Grand Canyon by alpha spectrometry

In order to establish baseline information for current and future mining operations, water samples from the Colorado River and its tributaries have been analyzed for Ra-226 and uranium isotopes. Ra-226 was separated by coprecipitation on BaSO₄ followed by alpha spectrometry. Ba-133 was used as a tracer for yield determination. Uranium was separated by a combination of BaSO₄ precipitation and solvent extraction followed by coprecipitation on CeF₃ for alpha spectrometry.Results indicate that radium and uranium levels in the Colorado River and its tributaries, except the Little Colorado River, are below the EPA specifications [1] for drinking water of 185 mBq/liter (5 pCi/1) for Ra-226 and 433 mBq/liter (11.7 pCi/1) for U-238. However, the specific sources for elevated uranium and Ra-226 concentrations in the Little Colorado River should be identified, and the potential impacts from leaching of the naturally exposed mineralization inside the Grand Canyon should be investigated.     

On the loss of ethylene from [C3H7O]+ ions of structure \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {{\rm CHOH}}\limits^{\rm + } $\end{document}

The results of some ³C and ²H labelling experiments plus some measurements of reaction thermochemistry and translational energy releases, permit a significant simplification of the mechanistic pathways by which [C₃H₇O]⁺ ions of structure fragment by loss of C₂H₄. The relationships between these ions and some of their isomeric forms are explored and clarified.     

The solution photochemistry of αβ-unsaturated sulphones

1-Phenyl-2-(benzenesulphonyl)-ethylene and 1-phenyl-2-(benzenesulphonyl)-prop-1-ene have been shown to undergo $\text{Z}$,$\text{E}$-photoisomerisation, whereas 2-benzenesulphonylindene readily forms [_π2 + _π2] photoadducts with 2,3-dimethylbut-2-ene, cyclopentene, and cyclohexene.     

QUENCHING OF THE TRIPLET STATE OF CHLOROPHYLL a BY ASCORBIC ACID AND ASCORBATE IN ETHANOLIC SOLUTION

Abstract— Ascorbic acid and ascorbate in chlorophyll ethanol solution were found to be fairly efficient quenchers of the chlorophyll triplet state; comparable to the efficiency of ascorbic acid as a quencher in aqueous pyridine solution.
It has been well established that ascorbic acid quenches the triplet state of chlorophyll in aqueous pyridine solution.^(1,2) The bimolecular quenching constant, kQ , is very much less than that for O₂ or quinine.^(3,4)
Information regarding the quenching of the triplet state of chlorophyll by ascorbic acid in ethanolic solution is lacking. There has been some question as to whether ascorbic acid reduces photoexcited chloro-phyll-ethanolic solution because of its high oxidation potential, or because like the ascorbate ion, it acts only as a quencher; both ascorbic acid and ascorbate in high concentrations gave low quantum yields.⁽⁵⁾ The quenching of the triplet state by ascorbic acid and ascorbate was determined by the flash-photolytic method.     

Spectrophotometric determination of aromatic primary amines and nitrite by flow injection analysis

Aromatic primary amines are determined by injection into dilute hydrochloric acid carrier which merges sequentially with 4-N-methylaminophenol and dichromate. The purple-red color formed by oxidative coupling of amines with 4-N-methylaminophenol is measured at 530 nm. In contrast to the manual procedure, the flow-injection procedure avoided errors arising from the instability of the coupling intermediate, oxidation of the amine, and too great an excess of the oxidant. The method improves the selectivity for certain amines in the presence of those which are sterically hindered or have an electron-deficient aromatic nucleus. Nitrite is determined by diazotization of sulfanilamide and quantifying the residual sulfanilamide by oxidative coupling. The sample thourghout for the assay of amines (0.05–20 μg ml^?1 NH₂-N) and nitrite (1–10 μg ml^?1 NO₂^--N) was 120 h^?1. A system for the consecutive determination of aromatic primary amines and nitrite is decribed.