The question of an open-ring form of cyclopropanone

Olsen, John; Kang, Sungzong; Burnelle, Louis

doi:10.1016/0022-2860(71)85048-2

Cited by 22 publications

(14 citation statements)

References 23 publications

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“…Early calculations were limited to the computation of the relative energies of allene oxide, oxyallyl, and cyclopropanone. With the exception of extended Hückel calculations, in all cases cyclopropanone was found to be more stable than allene oxide with oxyallyl significantly higher in energy than either 2 or 3 . − ,12a,− In Table the relative energies of 1 − 3 , including the results of the best calculations performed to date, are summarized.…”

Section: Resultsmentioning

confidence: 99%

“…Oxyallyl ( 1 ) has long been considered as a potential intermediate or transition structure in the rearrangement of allene oxide ( 2 ) to cyclopropanone ( 3 ) − and in the ring opening and closing reactions of substituted cyclopropanones that result in racemization and isomerization. − Early experimental evidence for the existence of allene oxide as a viable species was based on the characterization of its reaction products, since its apparent high reactivity precluded its isolation. However, in 1968 Camp and Greene reported that the epoxidation of 1,3-di- tert -butylallene gave the first isolable allene oxide, 1,3-di- tert -butylallene oxide, which when heated to 100 °C underwent rearrangement to trans -2,3-di- tert -butylcyclopropanone.…”

Section: Introductionmentioning

confidence: 99%

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Rearrangements of Allene Oxide, Oxyallyl, and Cyclopropanone

1998

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A detailed theoretical study of the rearrangement of allene oxide to cyclopropanone and the racemization of substituted cyclopropanones and the isomerization of substituted cyclopropanones is presented. The rearrangement of allene oxide to cyclopropanone was found to proceed in a stepwise fashion in which allene oxide first undergoes conversion to oxyallyl via a newly found transition structure with subsequent ring closure of the oxyallyl to cyclopropanone. It is shown that a previously found transition structure is on the pathway that results in the racemization of chiral-substituted cyclopropanones. A new transition structure was also located that accounts for the previously observed conversion of cis-2,3-di-tert-butylcyclopropanone to its trans diastereomer. The discussion is based on the results of DFT and CASSCF methods. IRC calculations were carried out for all transition structures located. Single-point energies were calculated with the CASPT2N, QCISD(T), and UQCISD(T) methods. Good agreement was found between the calculated results and those available from experiment.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rearrangements of Allene Oxide, Oxyallyl, and Cyclopropanone

1998

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“…Nevertheless, we did resolve seven ionization bands in the 9-1 8-eV region, which is precisely the number expected in this region as predicted by both the ab initio and M I N D 0 / 3 calculations. There is no doubt that the lowest energy band (11) in the spectrum at 9.63 eV corresponds to removal of an electron from the predominantly nonbonding molecular orbital no. This value may be compared to a reported adiabatic first ionization potential of 9.34 f 0.05 eV obtained by mass s p e~t r o m e t r y .~~ If appropriate scaling factors are employed, both theoretical methods predict that the second ionization band at 11.88 eV should correspond to ionization of a u molecular orbital transforming under irreducible representation al in point group C2".…”

Section: Discussionmentioning

confidence: 99%

The electronic structure of cyclopropanone

Martino¹,

Shevlin²,

Worley³

1977

J. Am. Chem. Soc.

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The ultraviolet photoelectron spectrum of cyclopropanone has been investigated. Theoretical computations (ab initio, MIND0/3, and CNDO/S) together with the photoelectron spectra of other simple ketones have been used to interpret the spectrum of cyclopropanone and to probe the electronic structure of the molecule. The nonbonding molecular orbital for cyclopropanone is substantially delocalized throughout the molecule. The mode of delocalization is an interaction between the in-plane p atomic orbital on oxygen and the antibonding Walsh molecular orbital on the ring as suggested earlier by Jorgensen and Salem. It has been concluded that photoelectron spectroscopy used in conjunction with molecular orbital calculations provides an excellent means of estimating the amount of delocalization of nonbonding molecular orbitals.The simplest cyclic ketone cyclopropanone has generated considerable interest among organic and physical chemists for many years.' The parent molecule was first synthesized by Turro and Hammond2 and by DeBoer and c o -~o r k e r s .~ Its geometric structure has since been studied by microwave spectroscopy4 and by electron diffraction5 Thomas and cow o r k e r~~.~ have made an extensive study of the gas-phase photochemistry of cyclopropanone and have measured its heat of formation from the appearance potential of the CzH4+ ion.7 Several theoretical studies of cyclopropanone at various levels of approximation have been r e p~r t e d .~-l~ Of primary concern in most of the theoretical studies was whether the most stable isomer of C3H40 is the classical closed ring ketone 1 or one of the tautomers, oxyallyl 2 or allene oxide 3. The extended 1 2 3Huckel method* predicts that 2 is more stable than 1 by 23 kcal/mol and that 2 is more stable than 3 by 21 kcal/mol. However, all of the other methods predict 1 to be more stable than 2 by varying amounts (MINDO/2, 78 kcal/m01;~ INDO, 220" and 232 kcal/mol;I2 ab initio, 83 kcal/mol;I2 and MIND0/3, 66 kcal/molI3). The microwave spectral study4 also strongly indicates that the most stable isomer is 1, although the C2-C3 bond is quite long (1.575 A).Another interesting aspect of cyclopropanone chemistry is the interaction of the nonbonding electrons on oxygen with the strained u bonds of the cyclopropane ring. Jorgensen and Salem14 have pointed out that the in-plane p atomic orbital on oxygen has the proper symmetry to interact with the lowest antibonding Walsh orbital of the cyclopropane ring. The magnitude of this interaction, which lowers the energy of the nonbonding orbital while raising that of the unoccupied ucc* orbital, should become apparent from the photoelectron spectrum of 1.In view of the considerable interest in cyclopropanone among experimentalists and theoreticians, a study of its photoelectron spectrum would seem desirable. This paper reports the UV photoelectron spectrum of cyclopropanone. Theoretical computations (ab initio, MIND0/3, and CNDO/S), qualitative considerations of orbital interactions, and the photoelectron spectra of several other si...

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“…The first three were identified as C-13, C-7, and C-9, respectively, by specific decoupling of the attached protons at 1.45, 4.90, and 5.52. 6 The fourth absorption (at 169.1 ppm) was identified as the amide carbonyl (C-l) by its chemical shift, nearly identical with that of the amide carbonyl in the cmr spectrum of streptovaricin D.2'4 Labeling of C-l, C-7, C-9, and C-13 corresponds perfectly to the pattern for the amide-head2•4 direction of biosynthesis (Figure 1) but would not agree with an amide-tail direction, while labeling of C-l and C-13 argues for a continuous sequence of propionate-acetate units from C-l4 through C-l. This is the same pattern found for streptovaricin2•4 and rifamycin.5 The benzoquinone unit and its attached carbon (C-l5 through C-21) were not labeled by propionate or methionine.…”

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confidence: 99%