Stefan Feil

Conversion of Methane to Methanol: Nickel, Palladium, and Platinum (d9) Cations as Catalysts for the Oxidation of Methane by Ozone at Room Temperature

The room-temperature chemical kinetics has been measured for the catalytic activity of Group 10 atomic cations in the oxidation of methane to methanol by ozone. Ni(+) is observed to be the most efficient catalyst. The complete catalytic cycle with Ni(+) is interpreted with a computed potential energy landscape and, in principle, has an infinite turnover number for the oxidation of methane, without poisoning side reactions. The somewhat lower catalytic activity of Pd(+) is reported for the first time and also explored with DFT calculations. Pt(+) is seen to be ineffective as a catalyst because of the observed failure of PtO(+) to convert methane to methanol.

Investigations of chemical warfare agents and toxic industrial compounds with proton-transfer-reaction mass spectrometry for a real-time threat monitoring scenario

RATIONALE Security and protection against terrorist attacks are major issues in modern society. One especially challenging task is the monitoring and protection of air conditioning and heating systems of buildings against terrorist attacks with toxic chemicals. As existing technologies have low selectivity, long response times or insufficient sensitivity, there is a need for a novel approach such as we present here. METHODS We have analyzed various chemical warfare agents (CWAs) and/or toxic industrial compounds (TICs) and related compounds, namely phosgene, diphosgene, chloroacetone, chloroacetophenone, diisopropylaminoethanol, and triethyl phosphate, utilizing a high-resolution proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOFMS) instrument with the objective of finding key product ions and their intensities, which will allow a low-resolution quadrupole mass spectrometry based PTR-MS system to be used with high confidence in the assignment of threat agents in the atmosphere. RESULTS We obtained high accuracy PTR-TOFMS mass spectra of the six compounds under study at two different values for the reduced electric field in the drift tube (E/N). From these data we have compiled a table containing product ions, and isotopic and E/N ratios for highly selective threat compound detection with a compact and cost-effective quadrupole-based PTR-MS instrument. Furthermore, using chloroacetophenone (tear gas), we demonstrated that this instruments response is highly linear in the concentration range of typical Acute Exposure Guideline Levels (AEGLs). CONCLUSIONS On the basis of the presented results it is possible to develop a compact and cost-effective PTR-QMS instrument that monitors air supply systems and triggers an alarm as soon as the presence of a threat agent is detected. We hope that this real-time surveillance device will help to seriously improve safety and security in environments vulnerable to terrorist attacks with toxic chemicals.

Structures, fragmentation, and protonation of trideoxynucleotide CCC mono- and dianions

Both quantum chemical calculations and ESI mass spectrometry are used here to explore the gas-phase structures, energies, and stabilities against collision-induced dissociation of a relatively small model DNA molecule—a trideoxynucleotide with the sequence CCC, in its singly and doubly deprotonated forms, (CCC−H)− and (CCC−2H)2−, respectively. Also, the gas-phase reactivity of these two anions was measured with HBr, a potential proton donor, using an ESI/SIFT/QqQ instrument. The computational results provide insight into the gas-phase structures of the electrosprayed (CCC−2H)2− and (CCC−H)− anions and the neutral CCC, as well as the proton affinities of the di- and monoanions. The dianion (CCC−2H)2− was found to dissociate upon CID by charge separation via two competing channels: separation into deprotonated cytosine (C−H)− and (CCC−(C−H)−2H)−, and by w1−/a2− cleavage of the backbone. The monoanion (CCC−H)− loses a neutral cytosine upon CID, and an H/D-exchangeable proton, presumably residing on one of the phosphate groups, is transferred to the partially liberated (C−H)− before dissociation. This was confirmed by MS/MS experiments with the deuterated analog. The reaction of (CCC−2H)2− with HBr was observed to be rapid, k = (1.4±0.4) × 10−9 cm3 molecule−1 s−1, and to proceed both by addition (78%) and by proton transfer (22%) while (CCC−H)− reacts only by HBr addition, k = (7.1±2.1) × 10−10 cm3 molecule−1 s−1. This is in accord with the computed proton affinities of (CCC−2H)2− and (CCC−H)− anions that bracket the known proton affinity of Br−.