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Furan and substituted furans were found to be atmospheric reaction products of the OH radical-initiated degradation of conjugated dienes, such as 1,3-butadiene, cis-1,3-pentadiene, and isoprene. They are also products of combustion processes. The purpose of this work is to identify the primary formed stable reaction products of the reaction of NO3 radicals toward furan and tetramethylfuran. Experiments were performed under flow conditions in the pressure range 5.5 < P (mbar) < 100 at 298 K. GC−MS/FID, direct MS, and long-path FT-IR served as detection techniques. cis-Butenedial and 3H-furan-2-one were found as main products of the reaction of NO3 radicals with furan in N2 with averaged formation yields of 0.77 and 0.19, respectively, independent of total pressure in the tube. In experiments with a maximum O2 concentration of 2.2 × 1018 molecule cm-3, an increase of the 3H-furan-2-one yield was observed up to 0.38. There were no indications for the formation of nitrates or peroxynitrates. In the reaction of NO3 radicals with tetramethylfuran, the detected reaction product was assigned to cis-3,4-dimethylhex-3-en-2,5-dione, tentatively. Using the relative rate method, the rate constant for the reaction of NO3 radicals with 3H-furan-2-one was determined to be (1.76 ± 0.23) × 10-13 cm3 molecule-1 s-1.

The gas-phase reaction of NO, radicals with 1,3-~yclohexadiene, a-terpinene, and a-phellandrene has been studied in a flow system at 298 K in the pressure range 8 < P (mbar) < 250 using GC-MS/FID, MS, and long-path FT-IR as detection techniques. At a total pressure of 15 mbar N, rate constants for the primary attack of NO, were determined with the relative rate method to be (1.08t0.02) lo-'', (1.03k0.06) lo-", and (5.98t0.20) lo-", respectively (unit: cm3 molecule-' s-').As buffer gas in the product studies served N, or He as well as O,/N, mixtures. In the case of 1,3-~yclohexadiene the formation of the corresponding oxirane (7-0xa-bicyclo[4.1 .O]hept-2-ene) up to a yield of 90Vo at P < 35 mbar and the formation of benzene (about 6%) was observed. The oxirane yield was independent on the amount of added 0, and decreased with increasing total pressure. In the case of a-terpinene and aphellandrene no indication of oxirane formation was found. However, the corresponding aromatic compound (pcymene) was detected for both terpenes, maximum yield 6% for a-terpinene and 22Vo for a-phellandrene. For all reaction systems investigated the formation of organic nitrate-compounds was proved by means of long-path FT-IR measurements. In the case of the 1,3-cyclohexadiene degradation with [O,] > 5lo" molecule cm-3 an absorption band was detected in addition assigned to a carbonylic group. There were no indications for a reaction of 0, with the adduct radical (NO,/diene).

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Bei den meisten sekundären Hydroperoxiden verläuft die Zersetzung in Gegenwart von Basen nicht einheitlich, neben Ketonen entstehen auch die entsprechenden Alkohole. Die Zersetzung sekundärer und tertiärer Hydroperoxide wird durch Basen beschleunigt; die Reaktionsgeschwindigkeiten sind sehr schlecht reproduzierbar, und sie werden durch Zusatz von Äthylendiamintetraessigsäure stark herabgesetzt. Offenbar verläuft die Hydroperoxidzersetzung in Gegenwart von Basen meist nach einem radikalischen Mechanismus, wobei Spuren von Schwermetallionen als Katalysator wirken, während die Basen nur Cokatalysatoren sind. Abweichend vom allgemeinen Fall läßt sich bei Tetralin‐ und Äthylbenzolhydroperoxid eine ionoide Zersetzung nach einem E2‐Mechanismus nachweisen. Für die durch Natronlauge katalysierte Zersetzung von α‐deuteriertem Tetralinhydroperoxid wurde ein kinetischer Isotopieefekt kH:kD = 3,9 gefunden.