NMR spectrum of vinylcyclopropane

Schrumpf, G.

doi:10.1016/s0040-4039(01)98283-8

Cited by 23 publications

(10 citation statements)

References 13 publications

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“…In the gas phase and in solution, on the other hand, more than one conformer is present. Electron diffraction and vibrational, Raman, and NMR spectroscopy support a rapid equilibrium between the anti and a lesser conformer. Electron diffraction results support a 3:1 mixture (Δ E = 1.1 kcal/mol) of these conformers and a torsion angle of ∼55° for the gauche conformer 17b…”

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

“…NMR studies of 1 and derivatives have been interpreted in terms of a two-well potential surface, with minima at the syn and anti geometries,20a or a three-well potential surface, with minima at the anti and two gauche geometries 20b. The temperature dependence of coupling constants (J), chemical shifts and, particularly, the line intensities are best accommodated by the three-well potential surface 20b. Temperature-dependent changes in the Raman spectrum are compatible with both trans and gauche conformers as minima; they suggest an enthalpy difference, Δ H ∼ 1.4 kcal/mol, between the two conformers and a barrier, Δ H ‡ ∼ 4 kcal/mol …”

Section: Introductionmentioning

confidence: 99%

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Structure and Reactivity of Vinylcyclopropane Radical Cation: Electron Transfer Photochemistry andab InitioCalculations

Herbertz

Roth

1998

J. Am. Chem. Soc.

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The electron-transfer photochemistry of vinylcyclopropane (1) generates three ring-opened products, 2−4, each bearing a methoxy as well as a 4-cyanophenyl group. The products are ascribed to nucleophilic attack of methanol on the radical cation, 1 • + . The attack is regioselective but not regiospecific; attack at the secondary cyclopropane carbons, leading to 2 and trans- 3, is preferred; attack at the terminal vinylic carbon, yielding trans- 4, occurs to a lesser extent. The potential surface of 1 • + was probed by ab initio calculations; 1 • + has two minima, anti- and syn-1 • + ; both have C s symmetry and belong to the unusual structure type with two lengthened cyclopropane bonds. The calculations are in general agreement with the observed reaction pattern.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure and Reactivity of Vinylcyclopropane Radical Cation: Electron Transfer Photochemistry andab InitioCalculations

Herbertz

Roth

1998

J. Am. Chem. Soc.

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“…In addition, the s-trans conformer manifests itself in the chemical shifts of protons which are affected by the shielding of the cyclopropyl ring. In a study of the proton NMR spectra of 2-propenylcyclopropane and 1-methyl-2-propenylcyclopropane, Schrumpf observed that the resonances for the allylic protons of 2-propenylcyclopropane appear at higher frequencies relative to those of typical allylic protons. The upfield shift was explained by postulating that the dominant rotamer is s-trans, in which the allylic hydrogens lie above the cyclopropyl ring.…”

Section: Discussionmentioning

confidence: 99%

Upper Excited State Photochemistry: Solution and Gas Phase Photochemistry and Photophysics of 2- and 3-Cyclopropylindene¹

Waugh

Morrison

1999

J. Am. Chem. Soc.

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The cyclopropylcarbinyl radical rearrangement has been used to probe the photochemistry and photophysics of S2 and S1 in 2-cyclopropylindene (2CPI) and 3-cyclopropylindene (3CPI). Studies in solution and the gas phase are described. Population of S2 with 254 nm light excitation in the gas phase produces the anticipated ring expansion products 2,3,3a,8-tetrahydrocyclopenta[a]indene (1, Φ 1 = 0.1) and 1,3,3a,8-tetrahydrocyclopenta[a]indene (2, Φ 2 = 0.06) from 2CPI and 3CPI, respectively (Scheme ). Direct excitation into the S2 state (254 nm) of 2CPI in solution also produces compound 1. The efficiency of the solution phase chemistry is a function of excitation wavelength (Φ 1 = 0.022 and 0.006 for 254 and 280 nm, respectively). The solution phase excitation spectrum of 2CPI shows an anomalous dependency on monitoring wavelength which is attributed to a conformational equilibrium. The S1 singlet lifetimes of the cyclopropylindenes are quite short (0.39 and 1.0 ns for 2CPI and 3CPI, respectively) relative to the previously measured values for the corresponding methylindenes (2.3 and 13.9 ns). These shortened lifetimes are attributed to cyclopropyl ring opening in S1 with rates of 2.1 × 109 and 9.2 × 108 s-1 for 2CPI and 3CPI, respectively. Semiempirical excited state calculations support descriptions of the S2 and S1 states of alkylindenes as biradicals.

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“…From the detailed nmr and infrared studies of biisopropyl and bicyclopropyl by Liittke and coworkers (21)(22)(23), it follows that the gauche forms are favored by enthalpies of about 0.1 kcallmol. By way of contrast, for IPCP the trans conformation is distinctly favored by an energy similar to the energies favoring the trans forms in n-butane and vinylcyclopropane (,J in the latter is 8.3 Hz near room temperature (24), and is 8.6 Hz in IPCP). For an extensive discussion of the torsional potentials in all these compounds, see (3).…”

Section: Conformational Distributionmentioning

confidence: 93%

Concerning the conformational distribution in isopropylcyclopropane

Schaefer¹,

Sebastian²,

Wasylishen³

1982

Can. J. Chem.

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A partial analysis of the 400 MHz 1H nmr spectrum of isopropylcyclopropane yields 8.6 ± 0.2 Hz for the vicinal proton–proton coupling constant between a cyclopropyl proton and the methine proton of the isopropyl group. The fractional population of the s-trans conformer is estimated as 0.65 ± 0.l0 at 300 K, in reasonable agreement with molecular mechanics and INDO MO computations of the energies of the gauche and trans forms.The conformational preference of this molecule is similar to that in n-butane and in vinylcyclopropane but contrasts with that in biisopropyl and bicyclopropyl.

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NMR spectrum of vinylcyclopropane

Cited by 23 publications

References 13 publications

Structure and Reactivity of Vinylcyclopropane Radical Cation: Electron Transfer Photochemistry andab InitioCalculations

Structure and Reactivity of Vinylcyclopropane Radical Cation: Electron Transfer Photochemistry andab InitioCalculations

Upper Excited State Photochemistry: Solution and Gas Phase Photochemistry and Photophysics of 2- and 3-Cyclopropylindene¹

Concerning the conformational distribution in isopropylcyclopropane

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NMR spectrum of vinylcyclopropane

Cited by 23 publications

References 13 publications

Structure and Reactivity of Vinylcyclopropane Radical Cation: Electron Transfer Photochemistry andab InitioCalculations

Structure and Reactivity of Vinylcyclopropane Radical Cation: Electron Transfer Photochemistry andab InitioCalculations

Upper Excited State Photochemistry: Solution and Gas Phase Photochemistry and Photophysics of 2- and 3-Cyclopropylindene1

Concerning the conformational distribution in isopropylcyclopropane

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Upper Excited State Photochemistry: Solution and Gas Phase Photochemistry and Photophysics of 2- and 3-Cyclopropylindene¹