Dewar furan and Dewar thiophene:  low-temperature matrix photolysis of furan and thiophene

Rendall, W. A.; Clement, A.; Torres, M.E.; Strausz, O. P.

doi:10.1021/ja00267a049

Cited by 29 publications

(20 citation statements)

References 4 publications

(4 reference statements)

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“…48 The observed bands of the 3FA photoproducts are collected in Table S7. The assignments were made taking into account literature data for these species isolated in argon matrices 54,[57][58][59][60] and also results of calculations made in the present study at the B3LYP/6- Figure 9). The characteristic absorptions due to CO are observed in the 2120-2140 cm -1 range: the most intense band at 2138 cm -1 corresponds to weakly interacting or well-isolated monomeric CO, whereas the lower intensity bands indicate that part of the CO molecules did not diffuse from the original cage where they were formed and interact with other species resulting from fragmentation of 3FA.…”

Section: Resultsmentioning

confidence: 99%

Photoisomerization and Photochemistry of Matrix-Isolated 3-Furaldehyde

2010

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3-Furaldehyde (3FA) was isolated in an argon matrix at 12 K and studied using FTIR spectroscopy and quantum chemistry. The molecule has two conformers, with trans and cis orientation of the OdCsCdC dihedral angle. At the B3LYP/6-311++G(d,p) level of theory, the trans form was computed to be ca. 4 kJ mol -1 more stable than the cis form. The relative stability of the two conformers was explained using the natural bond orbital (NBO) method. In fair agreement with their calculated relative energies and the high barrier of rotamerization (ca. 34 kJ mol -1 from trans to cis), the trans and cis conformers were trapped in an argon matrix from the compound room temperature gas phase in proportion ∼7:1. The experimentally observed vibrational signatures of the two forms are in a good agreement with the theoretically calculated spectra. Broad-band UV-irradiation (λ > 234 nm) of the matrix-isolated compound resulted in partial trans f cis isomerization, which ended at a photostationary state with the trans/cis ratio being ca. 1.85:1. This result was interpreted based on results of time-dependent DFT calculations. Irradiation at higher energies (λ > 200 nm) led to decarbonylation of the compound, yielding furan, cyclopropene-3-carbaldehyde, and two C 3 H 4 isomers: cyclopropene and propadiene.

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Section: Resultsmentioning

confidence: 99%

Photoisomerization and Photochemistry of Matrix-Isolated 3-Furaldehyde

2010

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“…Yellow crystals: mp 109-110 °C. NMR (250 MHz, CDCls) <5 0.9-1.0 (d, J = 6.6 Hz, 6H), 2.1 (m, 1H), 2.7 (d, J = 7.2 Hz, 2H), 7.5 (d, J = 7.7 Hz, 1H), 7.7-7.S (m, 3H), 8.3 (m, 2H), and 13 (s, 1H). 13C NMR (250 MHz,CDCls) 23,28,39,115,119,127(2) , 133(2), 134(2), 136, 138, 139, 161, 183, and 188. IR (KBr): 2956(KBr): ,1671(KBr): ,1628(KBr): ,1594(KBr): ,1358(KBr): ,1297(KBr): ,1266 cm-1.…”

Section: Methodsmentioning

confidence: 99%

“…Found: C, 72.86;H, 6.88. 13 (9, 1H). 13C NMR (250 MHz, CDC13) 6 23, 28,39,115,119,CDCl3) 6 36.2,65.3,75.8,103.6,123.7,126.0,126.5,126.6,(20) J. Org. Chem., Vol.…”

Section: General Preparation Of L-hydroxy-2-x-9lo-anthraquinone (3)mentioning

confidence: 99%

Photochemistry of 1-alkoxy- and 1-(benzyloxy)-9,10-anthraquinones in methanol: A facile process for the preparation of aldehydes and ketones

Blankespoor¹,

Smart²,

Batts³

et al. 1995

J. Org. Chem.

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The facile production of acid sensitive aldehydes and ketones via photochemical intramolecular &hydrogen atom transfer in 1-alkoxy-and l-(benzyloxy)-9,10-anthraquinones (1) was investigated. Irradiation of 1 in argon purged methanol generates the primary photoproducts, l-(RCH(OMe)O)-and l-(ArCH(OMe)O)-9,1O-anthrahydroquinones (2), respectively. Upon exposure to air, the intermediate anthrahydroquinone is rapidly converted to the corresponding aldehyde and l-hydroxy-9,lO-anthraquinone (3), which can be recycled. Aldehydes containing an acetal or ketal were prepared in high yields using this photoprocess. Apparent rate constants for the photodemethylation of l-methoxy-2-X-9,lO-anthraquinones (X = H, Me, Et, Pr, Bu, i-Bu, and benzyl) were measured and found to vary by a factor of IO separating the slowest anthraquinone (X = H) and the fastest (X = benzyl), indicating a strong dependency upon the size of the substituent at the 2-position.These rate constants are ascribed to equilibrium populations of conformers in the geometry required for reaction in the n,n* triplet state.

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“…3), which is assignable to the C^N-stretching mode like the bands of (Z)-2, syn-3 and anti-3 appearing at 2113, 2157, and 2151 cm À1 , respectively. Since species including a three-membered ring are usually produced in the photolysis of ve-membered heterocyclic compounds such as furan, 22 thiophene, 22 and isoxazole, 23 we assume that this band is due to 2-isocyanothiirane (4), which is produced by cleavage of the S1-C2 bond, hydrogen-atom migration from C2 to C5, and then electron migration to make the S1-C4 bond (see Scheme 2). The optimized geometrical parameters and the relative energy of (4) are shown in Fig.…”

Section: Identication Of 2-isocyanothiiranementioning

confidence: 99%

“…b Relative intensity is normalized to the most intense band. c Overlapped with a band of (4 thiophene, 22 and cyclopentadiene 24 were previously detected as intermediates in photolysis using the matrix-isolation technique. In addition, Dewar thiazole derivatives were theoretically proposed as candidates of the photochemical intermediates for 2-phenylthiazole and 2-acetylthiazole.…”

Section: Identication Of 2-isocyanothiiranementioning

confidence: 99%