Application of vibrational spectroscopy to the estimation of electron-donating properties of organometallic groups

Epstein, Lina M.; Ashkinadze, L. D.; Shubina, Elena S.; Kravtsov, D. N.; Kazitsyna, L. A.

doi:10.1016/s0022-328x(00)86773-x

Cited by 10 publications

(3 citation statements)

References 5 publications

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“…The variation in the relative rates for ring closure of 14 (R 1 R 2 N = Me 2 N, PhNH, MeNH, and NH 2 ) of 7.5 × 10 4 :5.2 × 10 3 :140:1 is striking. The electron donor effect of the groups in stabilizing the incipient cyclobutenediones as measured by the respective σ p + constants of −1.70, −1.40, −1.81, and −1.30, respectively, would contribute to this difference, although the data for R = MeNH do not fit the trend. However, the σ p + constant for this substituent 11c was obtained in a separate study by a different laboratory than the others, and this may cause the inconsistency.…”

Section: Discussionmentioning

confidence: 97%

Amino Substituted Bisketenes: Generation, Structure, and Reactivity

Fu¹,

Allen²,

Kobayashi³

et al. 2007

J. Org. Chem.

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Hitherto unknown diamino-substituted bisketenes with both free (14) and tethered (16) amino substituents have been generated by using laser flash photolysis for ring opening of the corresponding cyclobutenediones. The time-resolved kinetics of ring closure of the amino bisketenes back to the cyclobutenediones were measured by IR or UV spectroscopy, and give first-order rate constants which vary by a factor of 7.5x10(4), and the bis(Me2N) bisketene 14 is the most reactive in ring closure that has been reported. Rate constants for ring closure of these and previously observed bisketenes vary by a factor of 10(13). The dialkylamino bisketenes 16 (R=Me, n-Bu) with tethered substituents and restricted geometries are less reactive than the bis(Me2N) bisketene 14 by factors of 1700 and 540, respectively. Computational results obtained with DFT methods suggest angle strain in the tethered cyclobutenediones 15 inhibits facile cyclization of bisketenes 16.

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Section: Discussionmentioning

confidence: 97%

Amino Substituted Bisketenes: Generation, Structure, and Reactivity

Fu¹,

Allen²,

Kobayashi³

et al. 2007

J. Org. Chem.

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“…This fact must be considered especially for hydrogen bond donating (HBD) and hydrogen bond accepting (HBA) substituents. Substituents with HBD ability (e.g., OH, NH 2 ) experience specific solvation in HBA solvents, resulting in an enhancement of the electron-donating properties . This property is explicitly exploited in solvatochromic dyes (e.g., 4-nitroanilines , ) and in acid−base indicators (e.g., 4-nitrophenol).…”

Section: Introductionmentioning

confidence: 99%

“…This is accompanied by a shift of the UV−vis absorption to lower energies . The measurement of the UV−vis absorption can be carried out either directly in the gas phase or very easily in nonpolar solvents. , In order to minimize spectral shifts, based on solvatochromic effects, the UV−vis spectra should be measured in cyclohexane. , UV−vis data of nitrobenzenes, with highly polar substituents, charged groups in particular, which are not soluble in cyclohexane, can be obtained, for instance, from dichloromethane solution. Solvents with a higher HBD or HBA capacity are less suitable, as solvatochromic effects have an increasing influence …”

Section: Introductionmentioning

confidence: 99%

Electrophilic Substituent Constant σ⁺ of Electron Donor Substituents in Nonpolar Media

et al. 2009

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The electrophilic substituent constant sigma(+) was derived from the relative rate constants of the solvolysis of substituted alpha-cumyl chlorides in an acetone/water solvent mixture in the original work by Brown and Okamoto (J. Am. Chem. Soc. 1958, 80, 4979). As an extension of this procedure, we were looking for methods to determine sigma(+) values in nonpolar media. We have calculated the exocyclic charges q(R) for alpha-cumyl cations (R-C(6)H(4)CMe(2)(+)) as a measure of the electron-donating capacity of meta and para substituents. The UV-vis absorption nu(max) of the analogously substituted nitrobenzene derivatives has been used for the experimental measurement of the electron donating capacity of substituents R in nonpolar media. A linear relationship between nu(max) and Deltaq(R) (= q(R-C(6)H(4)CMe(2)(+)) - q(C(6)H(5)CMe(2)(+))) was obtained. A description of the electron-donating capacity in nonpolar media can be achieved both for substituents investigated already and for those for which the experimental determination of sigma(+) has previously been difficult. Special interest was directed to boron-based substituents in which the electron-donating ability is dependent on the coordinational environment of the boron atom.

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2018

Vibrational Spectra of Organometallics

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Application of vibrational spectroscopy to the estimation of electron-donating properties of organometallic groups

Cited by 10 publications

References 5 publications

Amino Substituted Bisketenes: Generation, Structure, and Reactivity

Amino Substituted Bisketenes: Generation, Structure, and Reactivity

Electrophilic Substituent Constant σ⁺ of Electron Donor Substituents in Nonpolar Media

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Application of vibrational spectroscopy to the estimation of electron-donating properties of organometallic groups

Cited by 10 publications

References 5 publications

Amino Substituted Bisketenes: Generation, Structure, and Reactivity

Amino Substituted Bisketenes: Generation, Structure, and Reactivity

Electrophilic Substituent Constant σ+ of Electron Donor Substituents in Nonpolar Media

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Electrophilic Substituent Constant σ⁺ of Electron Donor Substituents in Nonpolar Media