Carbon isotope effect studies in the mechanism of reactions of alkynes with formic acid

The¹³C fractionation has been studied in the reaction of phenylacetylene with the excess of liquid Merck formic acid at 30 and 40 °C to see the contribution of the¹³C fractionation in the formolysis of transient -formoxystyrene to the experimentally observed global¹³C fractionation. The¹³C fractionation has been investigated also in the hydration of 1 ml of PhCCH with 1 ml of formic acid in the temperature interval of 80–100°C. The¹³C KIE equal to 1.0168 at 91.75 °C and 1.0167 at 100°C indicate that the self-decomposition of formic acid in such experimental conditions is already largely suppressed. The isotope effect is discussed within the framework of the sequence of reaction steps leading to acetophenone and carbon monoxide production listed in part I.     

Synthesis of New Bidentate Phosphine Ligands Containing Saturated Phosphorus Heterocycles

The synthesis of two ethylene-bridged bidentate phosphines is described. 1,2-Bis(1-phospholano)ethane ((C(4)H(8))PCH(2)CH(2)P(C(4)H(8))) was synthesized by the stepwise addition of 2,2-dioxo-1,3,2-dioxathiepane to H(2)PCH(2)CH(2)PH(2). 1,2-Bis(1-phosphorinano)ethane ((C(5)H(10))PCH(2)CH(2)P(C(5)H(10))) was synthesized by the novel photochemical addition of 1,4-pentadiene to H(2)PCH(2)CH(2)PH(2). These bis(phosphines) form two-to-one complexes of the form Fe(PP)(2)Cl(2) when added to iron(II) chloride.     

A fluorescent high-throughput assay for double-stranded DNA: the RediPlate PicoGreen assay

The fluorescent PicoGreen reagent for detection and quantitation of double-stranded DNA has been adapted for high-throughput screening: the RediPlate PicoGreen double-stranded DNA assay format. In the RediPlate PicoGreen assay format, the PicoGreen reagent is predistributed and co-dried into either 96- or 384-well microplates with the excipient trehalose. The user resuspends the dried reagents upon adding DNA, and measures the resulting fluorescence after a five minute incubation. Replicate fluorescence measurements on nominally identical wells have less than a 5% coefficient of variation. The assay is linear from 5 to 500 ng/ml DNA in a 200 micro l volume. The RediPlate PicoGreen assay format retains the advantages of the original PicoGreen reagent - sensitivity, speed, and specificity - but in a high-throughput format.     

Photoinduced isomerisation of cis-[M(L-S,O)2](M = Pt(II) and Pd(II)) complexes of N,N-diethyl-N'-3,4,5-trimethoxybenzoylthiourea: key to preparation of the trans isomer

In acetonitrile solutions at room temperature, cis-[M(L-S,O)2] Pt(II) and Pd(II) complexes of N,N-diethyl-N'-3,4,5-trimethoxybenzoylthiourea undergo reversible photoinduced isomerisation to the corresponding trans isomer upon irradiation with visible light in the 320-570 nm range, the rate and extent of isomerisation being significantly higher for the cis-[Pd(L-S,O)2] complex compared to the Pt(II) analogue; in the dark trans-[M(L-S,O)2] cleanly reverts back to the cis complex at a rate dependent on the solution temperature, indicating a thermally controlled reverse process.     

Quantitative separation of traces of copper by electrodeposition and determination by electron probe microanalysis

Summary A combination of ion-exchange and micro-electrodeposition techniques permits the rapid separation of sub-microgram amounts of copper in a form suitable for determination with the electron probe microanalyser. Recoveries of 98% and standard deviations < 5% have been checked by other methods at the 10-g level.

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Zusammenfassung Eine Verbindung von Ionenaustausch und Elektrolyse ermöglicht die rasche Abscheidung von Submikrogrammengen Kupfer in einer für die Elektronenstrahlmikroanalyse geeigneten Form. Ausbeuten von 98% und Standardabweichungen von < 5% wurden mit anderen Verfahren im 10-g-Maßstab erwiesen.

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Presented at the VI. International Symposium on Microtechniques September 1970, Graz, Austria.     

Routine,high-sensitivity,cold vapor atomic absorption spectrometric determination of total mercury in foods after low-temperature digestion

A cold vapor atomic absorption spectrometric method was developed for the subnanogram-per-gram determination of total Hg in a wide variety of foods. Foods were weighed into 50 mL polypropylene centrifuge tubes and dried without charring at 55 degrees C in a circulating oven. Samples were then digested at 58 degrees C with HNO3, HCl, and H2O2. After matrix modification with solutions of 2% Mg(NO3)2, 0.01% Triton X-100, and Cu(II) at 10 microg/mL, samples were analyzed by using a CeTAC Technologies M-6000A dedicated Hg analyzer. Based on a 2 g sample weight, the detection limit of the method over 12 batches averaged 0.30 ng/g wet weight and ranged from 0.03 to 0.6 ng/g. Recoveries of Hg added to 17 different foods, analyzed in a routine manner, averaged 97%, and individual recoveries ranged from 77 to 107%. Accuracy was confirmed by analysis of 7 biological reference materials from the National Research Council of Canada and the National Institute of Standards and Technology. Stabilization of low concentrations of Hg in solutions containing no sample was required to prevent loss of Hg from blanks. In a comparison of NaCl, potassium dichromate, and Au(II), chloride was much more effective for stabilization than the other two, and HCl was used for subsequent stabilization.     

The number of non-isomorphic models in quasi-varieties of semigroups

Define \( n_K (\lambda )\) tobe eitherω, or the number of non-isomorphic algebras in \(K\) ] having cardinality λ, whichever cardinal is larger. It is proved here that if \(K\) ] is a quasi-variety (universal Horn class) of semigroups, then \(n_K\) is one of four functions. Each of these functions satisfies: \(n_K (\omega ) = \omega\) or \(n_K (\omega ) = 2^\omega\) . If \(n_K (\lambda )< 2^\lambda\) for some infinite λ then \(K\) ] is a residually finitevariety.     

Oxidation of a dinuclear manganese(II) complex to an oxide‐bridged dimanganese(IV) complex

Bis{μ‐2‐[bis(pyridin‐2‐ylmethyl)amino]acetato}bis[diaquamanganese(II)] bis(trifluoromethanesulfonate) monohydrate, [Mn₂(C₁₄H₁₄N₃O₂)₂(H₂O)₄](CF₃O₃S)₂·H₂O, (I), and bis{μ‐3‐[bis(pyridin‐2‐ylmethyl)amino]propionato}bis[aquamanganese(II)] bis(trifluoromethanesulfonate) dihydrate, [Mn₂(C₁₅H₁₆N₃O₂)₂(H₂O)₂](CF₃O₃S)₂·2H₂O, (II), form binuclear seven‐coordinate complexes. Oxidation of (II) with ammonium hexanitratocerate(IV), (NH₄)₂[Ce(NO₃)₆], gave the oxide‐bridged dimanganese(IV) complex di‐μ‐oxido‐bis(bis{3‐[bis(pyridin‐2‐ylmethyl)amino]propionato}manganese(IV)) bis[triaquatetranitratocerate(IV)], [Mn₂O₂(C₁₅H₁₆N₃O₂)₂][Ce(NO₃)₄(H₂O)₃]₂, (III). The manganese complexes in (II) and (III) sit on a site of symmetry.