A comparison of the radical-stabilizing ability of aromatic groups. .gamma..bul. values for aromatic groups

Creary, Xavier; Mehrsheikh-Mohammadi, M. E.; McDonald, Steven R.

doi:10.1021/jo00273a025

Cited by 34 publications

(37 citation statements)

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“…In addition, both compounds contain thienyl groups and aromatic rings. Creary and coworkers [29] found that thienyl groups had a larger radical-stabilizing effect than did phenyl groups. Therefore, the pattern observed for the enhancement of molecular ions presented in Figure 3 agrees well with the existence of molecules containing benzothiophene and dibenzothiophene groups.…”

Section: Apci and Appi Data And The Importance Of Charge-transfer Reamentioning

confidence: 99%

“…Structures with both furanyl and thiophenyl groups are proposed in Figure 6f and g. The proposed structures have DBE values of 11 and 14, which agree well with the observation in Figure 5. In addition, Creary and coworkers [29] reported that furan is a good radical-stabilizing group. Therefore, it is concluded that the SO compounds with DBE values lower than 5 are likely to contain saturated sulfoxide groups, whereas compounds with DBE values higher than 8 most likely contain furanyl and thiophenyl groups.…”

Section: Enhancement Of Molecular Ions Containing Sulfur Atomsmentioning

confidence: 99%

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Improved abundance sensitivity of molecular ions in positive-ion APCI MS analysis of petroleum in toluene

Kim

2010

J. Am. Soc. Mass Spectrom.

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Positive-ion atmospheric pressure chemical ionization (APCI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses of petroleum sample were performed with higher sensitivity by switching the solvent composition from toluene and methanol or acetonitrile to a one-component system consisting only of toluene. In solvent blends, molecular ions were more abundant than were protonated ions with increasing percentages of toluene. In 100% toluene, the double-bond equivalence (DBE) distributions of molecular ions obtained by APCI MS for each compound class were very similar to those obtained in dopant assisted atmospheric pressure photo ionization (APPI) MS analyses. Therefore, it was concluded that charge-transfer reaction, which is important in toluene-doped APPI processes, also plays a major role in positive-ion APCI. In the DBE distributions of S(1), S(2), and SO heteroatom classes, a larger enhancement in the relative abundance of molecular ions at fairly specific DBE values was observed as the solvent was progressively switched to toluene. This enhanced abundance of molecular ions was likely dependent on molecular structure.

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Section: Apci and Appi Data And The Importance Of Charge-transfer Reamentioning

confidence: 99%

Section: Enhancement Of Molecular Ions Containing Sulfur Atomsmentioning

confidence: 99%

Improved abundance sensitivity of molecular ions in positive-ion APCI MS analysis of petroleum in toluene

Kim

2010

J. Am. Soc. Mass Spectrom.

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“…Consequently, the effects of substituents depend on their radical stabilizing abilities. There have been many different Hammett-like radical substituent parameters proposed [13][14][15][16][17][18][19], to describe the effects of substituents on radical stabilities, which should also apply to aromatic nitrenes. However, the effects of substituents on the relative electronic states of aromatic nitrenes are not expected to be large.…”

Section: Introductionmentioning

confidence: 99%

“…Either mechanism accounts for the presence of triplet ground states in non-disjoint diradicals such as TMM [15,16], m-xylylene [32,33], and a,2-and a,4-dehydrotoluene [34,35], and singlet ground states in disjoint diradicals such as TME [22,23], square cyclobutadiene [24], planar D 8h cyclooctatetraene [28,36], and a,3-dehydrotoluene [34,35]. The substituent effect on the singlet-triplet splittings in aromatic nitrenes is also manifestation of the same effect.…”

Section: Introductionmentioning

confidence: 99%

Singlet stabilization of oxazole- and isoxazolenitrene-n-oxides by radical delocalization

Hossain

Wenthold

2013

Computational and Theoretical Chemistry

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“…The logarithms of the equilibrium constants K for X = H, MeO, Br, log K , were plotted against a solvent parameter E T (30) . As shown in Figure c, although the solvent effect is small, the slope is 0.020–0.036, with the solvent parameters being highly correlated with log K except in the DMF case. The equilibrium constant K decreases slightly as the solvent polarity increases.…”

Section: Resultsmentioning

confidence: 99%

1,2-Diazacyclopentane-3,5-diyl Diradicals: Electronic Structure and Reactivity

Yoshidomi

Abe

2019

J. Am. Chem. Soc.

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Localized singlet diradicals are key intermediates in bond homolysis. A thorough study of the reactive species is needed to clarify the mechanisms of the homolytic bond cleavage and formation processes. In general, the singlet diradicals are quite short-lived because of the fast radical–radical coupling reactions. The short-lived characteristic has retarded the thorough study on bond homolysis. In this study, a new series of long-lived singlet diradicals, viz., 1,2-diazacyclopentane-3,5-diyl, were identified, and their electronic structures and novel reactivities were thoroughly studied using laser-flash photolysis (LFP), product analysis, and computational studies. A direct observation of the thermal equilibration (fast process) between the singlet diradicals and the corresponding ring-closing compounds was undertaken on the submicrosecond time scale. The solvent and substituent effects on the equilibration constant and rate constants for the ring-closing reaction and ring-opening reaction clarify the novel nitrogen-atom effect on the localized singlet 1,3-diyl diradicals. Two types of alkoxy-migrated compounds, 9 and 10, were isolated with high yields as the final products. Crossover, spin-trapping, and LFP experiments for the formation of alkoxy-group migration products (i.e., 9 versus 10) revealed the unique temperature effect on the product ratio of the two types of alkoxy-migration products. The temperature-insensitive intersystem crossing process (slow process, millisecond time scale) was found to be a key step in the formation of 9, which is an entropy-controlled pathway. An intramolecular migration process was identified for the formation of 10 that was accelerated by a polar solvent in an enthalpy-controlled process. This unique heteroatom effect has opened up a new series of localized singlet diradicals that are crucial intermediates in bond homolysis.

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A comparison of the radical-stabilizing ability of aromatic groups. .gamma..bul. values for aromatic groups

Cited by 34 publications

References 0 publications

Improved abundance sensitivity of molecular ions in positive-ion APCI MS analysis of petroleum in toluene

Improved abundance sensitivity of molecular ions in positive-ion APCI MS analysis of petroleum in toluene

Singlet stabilization of oxazole- and isoxazolenitrene-n-oxides by radical delocalization

1,2-Diazacyclopentane-3,5-diyl Diradicals: Electronic Structure and Reactivity

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