Reactions of metastable diacetylene with aromatic molecules and the singlet -triplet spectroscopy of butadiene
Abstract
The reactions of metastable diacetylene with benzene, toluene, styrene, and phenylacetylene are explored using a molecular beam pump-probe time-of-flight mass spectrometer. The primary photoproducts of these reactions are detected using vacuum ultraviolet (VUV) photoionization, resonant two-photon ionization (R2PI), or UV-UV holeburning. The major products from the reaction of diacetylene and benzene have molecular formulae C8H6 and C 10H6, and are identified as phenylacetylene and phenyldiacetylene using R2PI spectroscopy. The major products from metastable diacetylene's reaction with toluene are C9H8 and C11H 8. The C9H8 product is confirmed as a mixture of ortho-, meta-, and para-ethynyl toluene, with the ortho product dominating. The C10H 8 major product of the styrene reaction is identified as a mixture of 1-phenyl-1-buten-3-yne and meta-ethynyl styrene. Mechanisms for the formation of the above products are proposed based on deuterium substitution studies of the reactions. The potential importance of these reactions is discussed as they relate to hydrocarbon growth in sooting flames. Also, the T1 ← S0 absorption spectrum of gas-phase 1,3-butadiene (C4H6) has been investigated over the region from 20,500 to 23,000 cm−1 using cavity ring-down spectroscopy. Resolved vibrational structure and partially resolved rotational structure has been observed for the first time in the gas phase. The T1 ← S 0 origin transition is located at 20,777 cm−1, with a peak absorption cross section of 2.5 × 10−26 cm2/molecule. Vibronic bands appear 249, 491, 1166, and 1617 cm−1 above the origin, and are assigned as the first overtone of the Bg symmetry CH2 torsion, and the three totally symmetric fundamentals involving stretching and bending of the carbon backbone of a planar T1 excited state. The observed Franck-Condon intensities are discussed in terms of the shape of the T1 potential energy surface.
Degree
Ph.D.
Advisors
Zwier, Purdue University.
Subject Area
Chemistry
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