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We present an experimental and theoretical investigation of the reaction of vibrationally excited CN ( v = 1) with isomers of butadiene at low temperature. The experiments were conducted using the newly built apparatus, UF-CRDS, which couples near-infrared cw-cavity ring-down spectroscopy with a pulsed Laval flow. The well-matched hydrodynamic time and long ring-down time decays allow measurement of the kinetics of the reactions within a single trace of a ring-down decay, termed Simultaneous Kinetics and Ring-down (SKaR). The pulsed experiments were carried out using a Laval nozzle designed for the 70 K uniform flow with nitrogen as the carrier gas. The measured bimolecular rates for the reactions of CN ( v = 1) with 1,3-butadiene and 1,2-butadiene are (3.96 ± 0.28) × 10 −10 and (3.06 ± 0.35) × 10 −10 cm 3 per molecule per s, respectively. The reaction rate measured for CN ( v = 1) with the 1,3-butadiene isomer is in good agreement with the rate previously reported for the reaction with ground state CN ( v = 0) under similar conditions. We report the rate of the reaction of CN ( v = 1) with the 1,2-butadiene isomer here for the first time. The experimental results were interpreted with the aid of variable reaction-coordinate transition-state theory calculations to determine rates and branching of the addition channels based on a high-level multireference treatment of the potential energy surface. H-abstraction reaction rates were also theoretically determined. For the 1,2-butadiene system, theoretical estimates are then combined with literature values for the energy-dependent product yields from the initial adducts to predict overall temperature-dependent product branching. H loss giving 2-cyano-1,3-butadiene + H is the main product channel, exclusive of abstraction, at all energies, but methyl loss forming 1-cyano-prop-3-yne is 15% at low temperature growing to 35% at 500 K. Abstraction forming HCN and various radicals is important at 500 K and above. The astrochemical implications of these results are discussed.
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Synthesis of functional 1,2-dithiolanes from 1,3-bis- tert -butyl thioethers
We report the one-step synthesis of diversely substituted functional 1,2-dithiolanes by reacting readily accessible 1,3-bis- tert -butyl thioethers with bromine. The reaction proceeds to completion within minutes under mild conditions, presumably via a sulfonium-mediated ring closure. Using X-ray crystallography and UV-vis spectroscopy, we demonstrate how substituent size and ring substitution pattern can affect the geometry and photophysical properties of 1,2-dithiolanes.
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- PAR ID:
- 10233892
- Date Published:
- Journal Name:
- Organic & Biomolecular Chemistry
- Volume:
- 18
- Issue:
- 33
- ISSN:
- 1477-0520
- Page Range / eLocation ID:
- 6509 to 6513
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d0ob01577f
