First Direct Synthesis of Optically Active 3-Methylcyclopentene

(?)-(S)- and (+)-(R)-3-methylcyclopentene (1) has been prepared in a stereochemically unambiguous synthesis. The (S)-configuration for (?)-1 was confirmed by correlation with (?)-(S)-1-methylindane.     

Flow injection analysis for calcium in serum,water and waste waters by spectrophotometry and by ion-selective electrode

The Flow Injection technique is shown to provide fast, reliable and sensitive methods for the determination of calcium in various aqueous as well as serum samples; spectrophotometric or potentiometric detection can be used. At sampling rates of 100–110 samples per hour, with 30-μl sample injections, high reproducibility of measurement and low reagent consumption are achieved in both methods. In the spectrophotometric method, the analytical readout is available within 12 s after sample injection at a total reagent consumption of 0.75 ml per analysis. The potentiometric measurement of the calcium activity in serum is placed on a reliable basis by alternating measurements of serum samples and aqueous standards without incurring any non-reproducible changes in potential between aqueous and serum solutions. This permits the simultaneous determination of pH and pCa, the analytical readout being available within XXX s of sample injection. The good agreement between the results obtained with the Flow Injection method and those attained by atomic absorption and EDTA titrations as well as pCa stat-measurements show that the new methods are potentially suitable for routine analysis.     

Zur Photochemie von Allylaryläthern. 55. Mitteilung über Photoreaktionen

The photochemical reactions of different allyl aryl ethers (Scheme 3) were investigated in hydrocarbons (Chap. 3.1) and in alcoholic solvents (Chap. 3.2). The composition of the photoproducts depended very much on the nature of the solvent. Irradiation (3–95 h) of different methyl substituted allyl aryl ethers ( 1, 3, 5, 7 and 11 ) with a low pressure mercury lamp (λ_Emiss. = 254 nm; 6 or 15 Watt) under argon (quartz vessel) resulted in the formation of 2-, 3– and 4-substituted phenols, dienones and products of consecutive reactions (Tables 1–4 and 6). The results suggested that all products were formed by homolytic cleavage of the C? O bond in the singlet state of the ethers to intermediate radical-geminates (Scheme 5) followed by radical recombination of the two fragments. No products were formed by concerted processes (Table 5, Schemes 5 and 6). Upon irradiation of allyl aryl ethers lacking alkyl substituents at position 4 ( 1 and 5 ) in protic solvents, mainly 2- and 4-allylated phenols were obtained (Tables 1 and 4); 3-allylated phenols were formed only in small amounts (0.02%). However, in aromatic hydrocarbons or cyclohexane 3-allylated phenols were obtained from 1 , 5 and 11 in significant amounts (3–11%; Tables 1, 4 and 6). E.g., upon irradiation of allyl-2,6-dimethyl-2,4-cyclohexadien-1-one ( 6 ) besides 3- and 4-allyl-2, 6-dimethyl-phenol ( 23 and 24 ). Irradiation of 5 in methanol afforded 23 and 6 only in traces, whereas 24 was the main product.     

Photochemisches Verhalten von 1- und 2-alkylierten 1, 2-Dihydronaphthalinen bei tiefen Temperaturen

The irradiations of 1, 1-dimethyl- (8), 1, 1-di-(tri-deuteriomethyl)- (d₆– 8 ), 1, 1, 2, 2-tetramethyl- ( 9 ) and cis- and trans-1, 2-dimethyl-1, 2-dihydronaphthalenes (cis- and trans- 10 ) were investigated in 2, 2-dimethylbutane/pentane at ?100° using a mercury high-pressure lamp, and with mercury high- and low-pressure lamps at room temperature. The results were compared with one another, and those of the individual compounds are collected in schemes 2 and 4–7. The most important results are the following: 1. The 1, 2-dihydronaphthalenes undergo a conrotatory ring opening to the o-quinodimethanes on irradiation with high- or low-pressure lamps at room temperature or at ?100°. Thermal reactions ([1, 7a]H-shifts, electrocyclisations) are suppressed at ?100°. The o-quinodimethanes formed from 8 (scheme 2), 9 (scheme 5) or cis- 10 (scheme 6) undergo on irradiation with the high-pressure lamp, [1, 5]H-shifts or photochemical Diels-Alder reactions after renewed photochemical excitation, to yield the benzobicyclo[3.1.0]hex-2-ene derivatives. These Diels-Alder reactions do not proceed stereospecifically, and therefore are not orbital symmetry controlled reactions. 2. If the 1, 2-dihydronaphthalenes are irradiated at room temperature with either a high- or a low-pressure lamp, then the initially formed o-quinodimethanes undergo thermal [1, 7a]H-shifts, in preference to all other reactions, as long as this is sterically possible; the resulting products can undergo secondary photochemical transformations. Such o-quinodimethanes are formed on irradiation of 8, 9 and cis- 10 . From trans- 10 , an o-quinodimethane mixture is formed, of which one component (cis, cis- 22 ) undergoes thermal [1, 7a] H-shifts, while the other (trans, trans- 22 ) suffers a thermal disrotatory electrocyclisation to give cis- 10 . If a high-pressure lamp is used in the last experiment, then the competing photochemical Diels-Alder cyclisation to bicyclic compounds of the type 23 (scheme 7) can result in the trans, trans- 22 . As was shown by Salisbury [3], and confirmed by ourselves in other cases [2], photochemical Diels-Alder reactions or [1, 5]H-shifts in the o-quinodimethanes require light of wavelength ? 400 nm (high-pressure lamp). The present photochemical investigations amplify and confirm our earlier conclusions concerning the photochemistry of the 1, 2-dihydronaphthalenes [2].     

Säurekatalysierte Dienon-Phenol-Umlagerungen von 6-Propargyl-6-methyl-cyclohexa-2,4-dien-1-onen; ladungskontrollierte,aromatische [1s, 2s]- und [3s, 4s]-sigmatropische Reaktionen

The acid catalysed dienone-phenol rearrangement of methyl substituted o-propargyl-cyclohexadienones (scheme 3) was investigated. The rearrangements were carried out in acetic anhydride containing about 1⁰/₀₀ sulfuric acid. Under these conditions acetoxy benzenium ions are formed as intermediates. These then undergo charge-controlled [3s, 4s]- and [1s, 2s]-sigmatropic rearrangements. Thus, the [3s, 4s]-process leads to the formation of the corresponding allenyl-phenol acetates ( 19 , 21 , 23 , 25 , 28 , 30 ) whereas the [1s, 2s]-process yields propargyl-phenol acetates ( 20 , 22 , 24 , 26 , 29 ), respectively (cf. scheme 4).     

Flow injection analysis : Part IX. A New Approach to Continuous Flow Titrations

Studies of dispersion patterns in nonsegmented streams, flowing through narrow open tubes, show that it is possible to obtain highly reproducible concentration gradients within a sample zone injected into the moving stream. By varying the geometry of the flow path, low, medium and high dispersion patterns can be achieved; the high dispersion pattern forms the basis for a new approach to continuous flow titrimetry. In this type of titration, discrete samples are passed through a gradient device and are then mixed with a continuously flowing stream of titrant of fixed concentration. The new technique has been tested for potentiometric as well as spectrophotometric end-point indication. A simple one-channel system allows titrations to be performed automatically in less than 1 min.     

Fast resonance raman spectroscopy of short-lived radicals

We report the first application of pulsed resonance Raman spectroscopy to the study of short-lived free radicals produced by pulse radiolysis. A single pulse from a flash-lamp pumped tunable dye laser is used to excite the resonance Raman spectrum of the p-terphenyl anion radical with an initial concentration of 4 × 10^?5 moles per liter and a half life of 2 μs. The spectrum is recorded by an optical multichannel system consisting of an image intensifier coupled to a TV-camera.     

Self consistent field molecular orbital calculation for pyrrole

The electronic structure and spectrum of pyrrole have been studied using the semiempirical LCAO SCF MO method. With configuration interaction included, low excited singlet states are calculated to occur at 5.98 ev, 6,74 ev, 7,33 ev, and 8,20 ev, in good agreement with the experimental values of about 5.88 ev, 6.77 ev, and 7,21 ev. The dipole moment of the molecule is calculated to 1.84 D, to be compared with the experimental value 1.80 D. Tables of coreattraction integrals for combinations of carbon and nitrogen atoms are presented.

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Zusammenfassung Elektronenstruktur und -spektrum des Pyrrols wurden nach, der halbempirischen LCAO SCF MO-Methode untersucht. Unter Einschluß der Konfigurationenwechselwirkung wurden niedrigliegende angeregte Singulettniveaus bei 5,98, 6,74, 7,33 und 8,20 eV (über dem Grundzustand) errechnet, in guter Übereinstimmung mit den experimentellen Werten von etwa 5,88, 6,77 und 7,21 eV. Das Dipolmoment des Moleküls ergibt sich zu 1,84 D, bei einem experimentellen Wert von 1,80 D.Tabellen von (sphärischen) Rumpf-Elektron-Integralen für alle vier Kombinationen von C und N werden angegeben.

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Résumé La structure et le spectre électroniques du pyrrole ont été étudiés à l'aide de la méthode sémiempirique LCAO SCF MO. L'interaction de configurations inclue, le calcul donne des états excités à 5,98, 6,74, 7,33 et 8,20 eV (au-dessus de l'état fondamental), en bon accord avec les valeurs expérimentales de 5,88, 6,77 et 7,21 eV. Le moment dipolaire calculé de la molécule est 1,84 D, l'expérience donnant 1,80 D. Des tables d'intégrales d'attraction entre un coeur sphérique et un électron d'un autre atome sont données pour les quatre combinaisons d'atomes C et N.

     

Half-life measurement of <Superscript>126</Superscript>Sn isolated from Hanford nuclear defense waste

Summary Long-term risk assessment of residual and disposed nuclear fuel reprocessing waste requires good knowledge of component isotopes with long half-lives. For example, the accuracy of the accepted ¹²⁶Sn half-life of approximately 100,000 years is insufficient for desired risk assessments. From modeling and sampling, ¹²⁶Sn is known to exist in Hanford nuclear waste. Excess portions of waste characterization samples were used to isolate ¹²⁶Sn for measurement of its half-life. Isolation was performed with ion-exchange resins. The resulting ¹²⁶Sn was gamma-assayed with a hyperpure germanium spectrometer for decay photon identification and activity values. An inductively coupled plasma/mass spectrometer was used to measure the atom quantity of the isolated ¹²⁶Sn. The separation chemistry, observed gamma energies, and calculated half-life are presented. The half-life of ¹²⁶Sn estimated in this work is (2.33±0.10) ^. 10⁵ years.