Broadband Microwave Spectroscopy of 2-Furanyloxy Radical: Primary Pyrolysis Product of the Second-Generation Biofuel 2-Methoxyfuran
- Purdue Univ., West Lafayette, IN (United States). Dept. of Chemistry
- Univ. of Florida, Gainesville, FL (United States). Dept. of Chemistry
Broadband microwave spectra over the 2–18 GHz range have been recorded for the resonance-stabilized 2-furanyloxy radical, formed in the first step of pyrolysis of the second-generation biofuel 2-methoxyfuran by methyl loss. Using a flash pyrolysis source attached to a pulsed valve, a 0.7% mixture of 2-methoxyfuran in argon was pyrolyzed at a series of temperatures ranging from 300 to 1600 K. Subsequent cooling in a supersonic expansion produced rotational temperatures of ~2 K in the interrogation region. Using chirped-pulse Fourier transform microwave (CP-FTMW) methods, combined with strong-field coherence breaking (SFCB), a set of transitions due to the radical were identified and assigned. The experimental rotational constants (A = 8897.732(93), B = 4019.946(24), C = 2770.321(84)), centrifugal distortion constants, and spin-rotation coupling constants have been determined for the radical and compared with ab initio predictions at the CCSD(T) level of theory. Compared to the 2-methoxyfuran precursor, the 2-furanyloxy radical has allylic C–C bond lengths intermediate between single and double bonds, a shortened C(5)–O(6) bond characteristic of partial double-bond character, and an O(1)–C(5)–O(6) bond angle of 121°, which resembles the O–C–O angle of an ester. Atomic spin densities extracted from the calculations confirm that the 2-furanyloxy radical is best viewed as a carbon-centered allylic lactone radical, with 80% of the spin density on the two allylic carbons and 20% on the pendant O(6) atom.
- Research Organization:
- Purdue Univ., West Lafayette, IN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- FG02-96ER14656; FG02-07ER15885
- OSTI ID:
- 1465211
- Alternate ID(s):
- OSTI ID: 1508607
- Journal Information:
- Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 122, Issue 34; ISSN 1089-5639
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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