The magnetic rotation spectrum of glyoxal

Goetz, W.; McHugh, A. J.; Ramsay, D. A.

doi:10.1139/p70-001

Cited by 51 publications

(7 citation statements)

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“…King [15] and Paldus & Ramsay [16] in rotational analyses of the 4550 A absorption have shown unambiguously that the symmetry of the excited state is A,, and that the polarization of the transition is z (perpendicular to the molecular plane). Recently, the magnetic rotation spectrum of the 5200 A band has been examined and shown to have a vibrational structure that is very similar to that of the singlet-singlet system [17]. The transition from the antisymmetric nonbonding orbital to the lowest 7c* MO is forbidden, resulting in an excited state with B, symmetry.…”

Section: Fig 2 Energy Of Two Highest Occufiied Molecular Orbitals Imentioning

confidence: 99%

The Interaction of Nonbonding Orbitals in Carbonyls

Swenson

Hoffmann

1970

Helvetica Chimica Acta

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Zusammenfassung. In Dicarbonylen wie Glyoxal oder Benzochinon bilden die nichtbindenden Sauerstofforbitale delokalisierte Molekelorbitale mit verschiedenen Energien. Wir berichten iiber EHT-und CNDO/Z-Berechnungen einiger Dione und Trione. Die berechnete Aufspaltung zwischen den Nnichtbindenden 0 Kombinationen wird auf der Grundlage der u through-space 1) und H throughbond )) Wechselwirkung analysiert. Bei den tiefliegenden nichtbindenden Orbitalen der Carbonylgruppen scheint der zweite Faktor zu dominieren. Gerust-cr-Orbitale und nichtbindende Sauerstofforbitale sind stark miteinander gemischt.An isolated carbonyl group is characterized by two 'lone-pair' orbitals, described as equivalent in the valence structure 1. In any molecular orbital description of a carbonyl group, symmetry adapted combinations of these two equivalent lone-pairs must be taken, resulting in the s and fi type lone-pairs of 2. The latter orbitals are D 1 2 nonequivalent and possess widely differing energies. There is little doubt that the highest occupied u molecular orbital of simple aldehydes and ketones is p type. It is this orbital which is most directly involved in (n, n*) electronic transitions and in the mass spectral reactions of such compounds.In molecules containing several equivalent carbonyl groups the 'nonbonding ' p orbitals must be combined into more delocalized wave functions. These molecular orbitals, degenerate in the absence of any interaction, may as a result of interaction between the individual nonbonding orbitals be differentiated in energy. The energy splitting between these molecular orbitals is the prime operational measure of the extent of orbital interaction. Experimentally, this splitting may be obtained by ascertaining the ionization potentials of the appropriate orbitals. Through the technique of photoelectron spectroscopy [l] such measurements have become feasible. Whenever nonbonding orbital interaction was considered in the past, that interaction was judged small1). This is now not in accord with either theoretical or experimental results. Lone-pairs, double bonds and other isolated subunits of a molecule interact significantly with other such units by direct through-space and indirect through-bond mechanisms. These interactions are easily analyzed See for example the considerations for glyoxal and biacetyl in [Zj.

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Section: Fig 2 Energy Of Two Highest Occufiied Molecular Orbitals Imentioning

confidence: 99%

The Interaction of Nonbonding Orbitals in Carbonyls

Swenson

Hoffmann

1970

Helvetica Chimica Acta

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“…It was also found that upon electronic excitation to the lowest singlet and triplet electronic states, the trans-conformers of glyoxal [12,13] and oxalyl halides [14][15][16][17][18][19][20], as well as the cis-conformer of glyoxal (upon singlet-singlet excitation) [21], keep a planar structure. However, no data on the structure of the second conformers of oxalyl halides in excited electronic states are available.…”

Section: Introductionmentioning

confidence: 99%

Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states. Part I: Reanalysis of the 3680Å and 4100Å absorption systems of oxalyl chloride

Godunov

Yakovlev

Bokarev

et al. 2009

Journal of Molecular Spectroscopy

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“…The ' A,-' A, (.n *-n) and A,-' A, (.n *-n) band systems of glyoxal with 0-0 bands at 4550 A and 5207 A, respectively, have been studied in considerable detail in absorption (Brand 1954;King 1957 ;Paldus and Ramsay 1967 ;Birss et al 1970), in emission (Brand 1954, and earlier references cited therein; Holzer and Ramsay 1970), and in magnetic rotation (Eberhardt and Renner 1961 ;Goetz, McHugh, and Ramsay 1970). Recently, a new band system, consisting of seven bands, was observed in the emission induced in glyoxal by the lines of an argon ion laser (Holzer and Ramsay 1970).…”

Section: Introductionmentioning

confidence: 99%

The 4875 Å Band System of cis Glyoxal

Currie¹,

Ramsay²

1971

Can. J. Phys.

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122

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The 4875 A band of glyoxal has been photographed in absorption under high resolution and a rotational analysis carried out. The band is of type C fnd the principal mqlecular constants are:, vo = 20 507.57 cm-'. The A-rotational constants are smaller by a factor of -2 than the constants found earlier for trans glyoxal. The new results are consistent with the assignment of the band to an allowed 'B1-'Al (n*-n) transition of cis glyoxal. Temperature studies indicate that the cis isomer lies 1125 , 100 cm-' above the trans isomer. This is the first time that cis glyoxal has been detected experimentally.

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The magnetic rotation spectrum of glyoxal

Cited by 51 publications

References 1 publication

The Interaction of Nonbonding Orbitals in Carbonyls

The Interaction of Nonbonding Orbitals in Carbonyls

Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states. Part I: Reanalysis of the 3680Å and 4100Å absorption systems of oxalyl chloride

The 4875 Å Band System of cis Glyoxal

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