Lattice Location of 12B in Single-Crystal Ni3Al Studied by β-Radiation Detected NMR

β-radiation detected nuclear magnetic resonance was applied to determine the location of ¹²B probe nuclei in a Ni₃Al single crystal. Combining our results with those of channeling experiments it turned out that more than 90% of the ¹²B ions occupy the octahedral interstitial site with six Ni ions as nearest neighbours.     

Cross relaxation of12B in single-crystal aluminium

The dipole-dipole interaction of extremely diluted probe nuclei with their surrounding host nuclei gives rise to mutual flip-flop processes of the nuclear spins. As energy has to be conserved in this so-called cross-relaxation (CR) process a transfer of polarization from the probes to the host nuclei occurs only at certain values of the inductionB leading to resonance-like dips in the probe's polarization. For the system¹²B in single-crystal aluminium CR spectra were measured forB=7...400 mT andT=310...410 K at various crystal orientations relative toB. All the spectra could be well explained by a theoretical calculation assuming the octahedral interstitial site for¹²B.     

Selective reagent ionisation‐time of flight‐mass spectrometry: a rapid technology for the novel analysis of blends of new psychoactive substances

In this study we demonstrate the potential of selective reagent ionisation‐time of flight‐mass spectrometry for the rapid and selective identification of a popular new psychoactive substance blend called ‘synthacaine’, a mixture that is supposed to imitate the sensory and intoxicating effects of cocaine. Reactions with H₃O⁺ result in protonated parent molecules which can be tentatively assigned to benzocaine and methiopropamine. However, by comparing the product ion branching ratios obtained at two reduced electric field values (90 and 170 Td) for two reagent ions (H₃O⁺ and NO⁺) to those of the pure chemicals, we show that identification is possible with a much higher level of confidence then when relying solely on the m/z of protonated parent molecules. A rapid and highly selective analytical identification of the constituents of a recreational drug is particularly crucial to medical personnel for the prompt medical treatment of overdoses, toxic effects or allergic reactions. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous ESR and optical absorption measurements of K in solid Ar

An apparatus was developed for simulataneous electron spin resonance (ESR) and optical absorption experiments on atoms imbedded in rare gas matrices. In a first application the temperature dependence of ESR signals and of optical absorption spectra of K atoms in Ar matrices were studied. One of the numerous ESR lines could be unambiguously assigned to the so-called red triplet absorption due to their identical annealing behaviour at 12–14 K. The correspondence of other ESR lines to optical absorptions is discussed.     

Enantioselective Organocatalytic Conjugate Addition of Aldehydes to Vinyl Sulfones and Vinyl Phosphonates as Challenging Michael Acceptors

Chiral framework : Chiral amines with pyrrolidine frameworks catalyze the enantioselective conjugate addition of a wide range of aldehydes to various vinyl sulfones and vinyl phosphonates in high yields and with enantioselectivities up to >99 % ee (see scheme). The high versatility of the Michael adducts is exemplified by various functionalizations with conservation of the optical purity.

     

Rapid and facile detection of four date rape drugs in different beverages utilizing proton transfer reaction mass spectrometry (PTR-MS)

In this work, we illustrate the application of proton transfer reaction mass spectrometry (PTR-MS) in the field of food and drink safety. We present proof-of-principle measurements of four different drinks (water, tea, red wine and white wine) each spiked separately with four different date rape drugs (chloral hydrate, tricholorethanol, γ-butyrolactone and butanediol). At first, the ideal PTR-MS operating conditions (reduced electric field strength and monitoring the most abundant [fragment] ion) for detection of the drugs were determined utilizing a time-of-flight-based PTR-MS instrument. We then dissolved small quantities of the drugs (below the activation threshold for effects on humans) into the various types of drinks and detected them using a quadrupole-based PTR-MS instrument via two different sampling methods: (1) dynamic headspace sampling and (2) direct liquid injection. Both methods have their advantages and drawbacks. Only with dynamic headspace sampling can rape drug contaminations be detected within a timeframe of seconds, and therefore, this method is the most promising use of PTR-MS as a fast, sensitive and selective monitor for the detection of food and drink contamination. Copyright ? 2012 John Wiley & Sons, Ltd.     

Auf eine allgemeine Reaction der mehratomigen Alkohole

Ohne Zusammenfassung     

Cross relaxation studied by β NMR

The dipole-dipole interaction between polarized β active probes implanted into a metal and the surrounding host nuclei may lead to a transfer of polarization from the probe to the host. As energy must be conserved in this cross-relaxation (CR) process, resonance-like dips show up at certainB values, if the polarization of the probes is measured as a function of magnetic inductionB. The probe isotope¹²B has been studied in several metallic stoppers. For¹²B in the fec crystals Al, Cu the three possible cubic implantation sites could easily be discriminated by means of the CR technique. The temperature dependence of the dips yielded information on the diffusion of the probes. In the case of¹²B, in Cu above 400 K a further CR structure was found due to trapping of the probe at another site. In the bcc metal VCR spectra belonging to two different¹²B trapping sites could be separately registered using a special radiofrequency technique. Both, static and dynamical properties of the CR could be quantitatively explained by theory.