Difference in the methyl group conformational preferences of T/sub 1/ and S/sub 1/ acetophenone. A probe of the orbital character of excited electronic states

Journal Article · Wed Mar 02 04:00:00 EST 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00213a041· OSTI ID:7256237

Tomer, J L; Spangler, L H; Pratt, D W

Ethane exists, in its electronic ground state, primarily in the staggered form because of the mutual repulsion between the filled ..pi../sub CH/sub 3// orbitals of the two methyl groups in the higher energy eclipsed form. The same considerations dictate the more stable conformation of a methyl rotor attached to an R(-C) = X group, as in propene (R = H, X = CH/sub 2/), acetaldehyde (R = H, X = O), and acetophenone (R = phi, X = 0), all of which have a C-H bond eclipsed rather than staggered with the double bond in the ground state (S/sub 0/). But, because of the sensitivity of these nonbonding interactions to the orbital occupancies of neighboring groups, the situation might be expected to be different in electronically excited states. A realization of this expectation is reported. A difference exists in the conformational preferences of the methyl group in the lowest excited triplet (T/sub 1/) and singlet (S/sub 1/) states of acetophenone, probably because of a difference in their orbital characters. The dynamic implications of this result are discussed.

• Research Organization: Univ. of Pittsburgh, PA (USA)
• OSTI ID: 7256237
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:5; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACETOPHENONE
DATA
ELECTRONIC STRUCTURE
EMISSION SPECTROSCOPY
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
FLUID FLOW
FLUORESCENCE
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JETS
KETONES
LUMINESCENCE
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOSPHORESCENCE
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STRUCTURAL CHEMICAL ANALYSIS
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