PubMed · 13207067
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R M WEBSTER. 1954. Method for dispensing formalin.. https://pubmed.ncbi.nlm.nih.gov/13207067/
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We describe the application of a three-laser tunable diode laser absorption spectrometer (TDLAS), called 'tracer in-situ TDLAS for atmospheric research' (TRISTAR), to measure nitrogen dioxide (NO2), formaldehyde (HCHO) and hydrogen peroxide (H2O2), during an intensive measurement campaign on Mt. Cimone (44 degrees 11'N, 10 degrees 42'E, 2165 m asl), Northern Appenines, Italy in June 2000 as part of the EU-project 'mineral dust and tropospheric chemistry' (MINATROC). The TRISTAR instrument was a major component of an instrument package, provided by the Max-Planck-Insitut für Chemie, to investigate free tropospheric gas-phase chemistry over the Appenines. Here we discuss the optical, electronic, gas flow, and calibration setup of the TDLAS used during the campaign. We characterized extensively the instrument's performance during a preparatory phase in the laboratory and compared the laboratory results to the in-field results. Consistency checks with additional trace gas measurements obtained during the campaign create high confidence in the measured concentrations. Correlations between different trace gas species, along with other evaluation tools, allow a full chemical characterization of air masses to meet the goals of the campaign.
The C-H activation of cyclic formaldehyde aminals LCH2 (L = RN-CH2CH2CH2-NR and RNCH2CH2-NR, R = Me, Et, iPr, tBu, or Ph) with S8 proceeds at unusually low temperatures (T< 160 degrees C) and results in the formation of the respective thioureas LC=S and H2S. The reaction constitutes a new, solvent-free method for the synthesis of thioureas that eliminates the toxic and highly flammable CS2. For R = tBu, the ionic carbenium thiocyanates [LCH]+ SCN- dominate the product spectrum and the respective thioureas are obtained in low yield. The reactivity of the analogous sulfur and oxygen ring systems towards S8 was investigated. 1,3-Dithiolane is cleanly converted into 1,3-dithiolane-2-thione (S8, 14 d, 190 degrees C) and resembles the cyclic formaldehyde aminals in this respect. 1,3-Dioxolane (L = OCH2CH2O) is completely inert towards sulfur even under forceful reaction conditions (190 degrees C, 14 d). The formation of thioureas from aminals was investigated at the CBS-4 and B3LYP/6-31G(d) levels of theory.