Browsing by Author "Golec, Barbara"

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Infrared absorption of gaseous benzoylperoxy radical C(6)H(5)C(O)OO recorded with a step-scan Fourier-transform spectrometer
(2011-12-14)
Golec, Barbara
;
Chen, Jin-Dah
;
Lee, Yuan-Pern
;
應用化學系
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應用化學系分子科學碩博班
A step-scan Fourier-transform infrared spectrometer coupled with a multipass absorption cell was utilized to monitor the transient species produced in gaseous reactions of benzoyl radical, C(6)H(5)CO, with O(2). C(6)H(5)CO was produced either from photolysis of acetophenone, C(6)H(5)C(O)CH(3), at 248 nm, or from photolysis of a mixture of benzaldehyde, C(6)H(5)CHO, and Cl(2) at 355 nm. Two intense bands near 1830 and 1226 cm(-1) are assigned to the C=O stretching (nu(6)) and the C-C stretching mixed with C-H deformation (nu(13)) modes, and two weaker bands near 1187 and 1108 cm(-1) are assigned to the nu(14) (C-H deformation) and nu(16) (O-O stretching/C-H deformation) modes of C(6)H(5)C(O)OO, the benzoylperoxy radical. These observed vibrational wave numbers and relative infrared intensities agree with those reported for syn-C(6)H(5)C(O)OO isolated in solid Ar and values predicted for syn-C(6)H(5)C(O)OO with the B3LYP/cc-pVTZ method. The simulated rotational contours of the two intense bands based on rotational parameters predicted with the B3LYP/cc-pVTZ method fit satisfactorily with experimental results. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3664304]
Infrared absorption of gaseous benzoylperoxy radical C6H5C(O)OO recorded with a step-scan Fourier-transform spectrometer
(2011-12-14)
Golec, Barbara
;
Chen, Jin-Dah
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
A step-scan Fourier-transform infrared spectrometer coupled with a multipass absorption cell was utilized to monitor the transient species produced in gaseous reactions of benzoyl radical, C6H5CO, with O-2. C6H5CO was produced either from photolysis of acetophenone, C6H5C(O)CH3, at 248 nm, or from photolysis of a mixture of benzaldehyde, C6H5CHO, and Cl-2 at 355 nm. Two intense bands near 1830 and 1226 cm(-1) are assigned to the C=O stretching (nu(6)) and the C-C stretching mixed with C-H deformation (nu(13)) modes, and two weaker bands near 1187 and 1108 cm(-1) are assigned to the nu(14) (C-H deformation) and nu(16) (O-O stretching/C-H deformation) modes of C6H5C(O)OO, the benzoylperoxy radical. These observed vibrational wave numbers and relative infrared intensities agree with those reported for syn-C6H5C(O)OO isolated in solid Ar and values predicted for syn-C6H5C(O)OO with the B3LYP/cc-pVTZ method. The simulated rotational contours of the two intense bands based on rotational parameters predicted with the B3LYP/cc-pVTZ method fit satisfactorily with experimental results. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3664304]
Infrared Spectra of the 1-Pyridinium (C5H5NH+) Cation and Pyridinyl (C5H5NH and 4-C5H6N) Radicals Isolated in Solid para-Hydrogen
(2013-12-19)
Golec, Barbara
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Das, Prasanta
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Bahou, Mohammed
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Lee, Yuan-Pern
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應用化學系
Protonated pyridine and its neutral counterparts (C5H6N) are important intermediates in organic and biological reactions and in the atmosphere. We have recorded the IR absorption spectra of the 1-pyriclinium (C5H5-NH+) cation, 1-pyridinyl (C5H5NH), and 4-pyridinyl (4-C5H6N) produced on electron bombardment during matrix deposition of a mixture of pyridine (C5H5N) and p-H-2 at 3.2 K; all spectra were previously unreported. The IR features of C5H5NH+ diminished in intensity after the matrix was maintained in darkness for 15 h, whereas those of C5H5NH and 4-C5H6N radicals increased. Irradiation of this matrix with light at 365 nm diminished lines of C5H5NH+ and C but enhanced lines of 4-C5H6N slightly, whereas irradiation at 405 nm diminished lines of 4-C5H6N significantly. Observed wavenumbers and relative intensities of these species agree satisfactorily with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3LYP/6-31++G(d,p) method. Assignments of C5H5NH and 4-C5H6N radicals were further supported by the observation of similar spectra when a CI2/C5H5N5N/p-H-2 matrix was irradiated first at 365 nm and then with IR light to generate H atoms to induce the H + C5H5N reaction.
Infrared spectrum of the 2-chloroethyl radical in solid para-hydrogen
(2012)
Amicangelo, Jay C.
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Golec, Barbara
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Bahou, Mohammed
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Lee, Yuan-Pern
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應用化學系
The addition reaction of chlorine with ethylene (C(2)H(4)) is expected to proceed via a free radical intermediate, the 2-chloroethyl radical, however, this intermediate has not been previously observed spectroscopically. Irradiation at 365 nm of a co-deposited mixture of Cl(2), C(2)H(4), and p-H(2) at 3.2 K produces a series of new lines in the infrared spectrum. A strong line at 664.0 cm(-1) and weaker lines at 562.1, 1069.9, 1228.0, 3041.1 and 3129.3 cm(-1) are concluded to be due to a single carrier based on their behavior upon subsequent annealing to 4.5 K and secondary irradiation at 254 and 214 nm. The positions and intensities of these lines agree with the MP2/aug-cc-pVDZ predicted vibrational spectrum of the 2-chloroethyl ((center dot)CH(2)CH(2)Cl) radical. In order to confirm this assignment, isotopic experiments were performed with C(2)D(4) and t-C(2)H(2)D(2) and the corresponding infrared bands due to the deuterium isotopomers of this radical ((center dot)CD(2)CD(2)Cl and (center dot)C(2)H(2)D(2)Cl) have been observed. A final set of experiments were performed following irradiation of the Cl(2)/C(2)H(4)/p-H(2) mixture at 365 nm, in which the matrix was irradiated with filtered infrared light from a globar source, which has been shown to induce reactions between isolated Cl atoms and matrix H(2) to produce HCl and H atoms. In these experiments, the major products observed were HCl, the ethyl radical (center dot C(2)H(5)) and ethyl chloride (C(2)H(5)Cl) and the possible mechanisms for the formation of these species are discussed.
Reactions between chlorine atom and acetylene in solid para-hydrogen: Infrared spectrum of the 1-chloroethyl radical
(2011-11-07)
Golec, Barbara
;
Lee, Yuan-Pern
;
應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
We applied infrared matrix isolation spectroscopy to investigate the reactions between Cl atom and acetylene (C(2)H(2)) in a para-hydrogen (p-H(2)) matrix at 3.2 K; Cl was produced via photodissociation at 365 nm of matrix-isolated Cl(2) in situ. The 1-chloroethyl radical (center dot CHClCH(3)) and chloroethene (C(2)H(3)Cl) are identified as the main products of the reaction Cl + C(2)H(2) in solid p-H(2). IR absorption lines at 738.2, 1027.6, 1283.4, 1377.1, 1426.6, 1442.6, and 2861.2 cm (1) are assigned to the 1-chloroethyl radical. For the reaction of Cl + C(2)D(2), lines due to the center dot CDClCH(2)D radical and trans-CHDCDCl are observed; the former likely has a syn-conformation. These assignments are based on comparison of observed vibrational wavenumbers and (13)C- and D-isotopic shifts with those predicted with the B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ methods. Our observation indicates that the primary addition product of Cl + C(2)H(2), 2-chlorovinyl (center dot CHCHCl) reacts readily with a neighboring p-H(2) molecule to form center dot CHClCH(3) and C(2)H(3)Cl. Observation of center dot CDClCH(2)D and trans-CHDCDCl from Cl + C(2)D(2) further supports this conclusion. Although the reactivity of p-H(2) appears to be a disadvantage for making highly reactive free radicals in solid p-H(2), the formation of 1-chloroethyl radical indicates that this secondary reaction might be advantageous in producing radicals that are difficult to prepare from simple photolysis or bimolecular reactions in situ. (C) 2011 American Institute of Physics. [doi:10.1063/1.3653988]