Assignment of configuration to sulphoxides by use of the “shift reagent”

Fraser, Robert R.; Wigfield, Yuk Y.

doi:10.1039/c29700001471

Cited by 66 publications

(22 citation statements)

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“…However, the concept of acetylene‐like anisotropy was later criticized as being oversimplified and inadvisable 23. Other procedures for the determination of the sulfoxide group configuration have used solvent‐induced shifts,12, 23, 24 shift reagents24–26 and chiral NMR reagents 27–31…”

Section: Introductionmentioning

confidence: 99%

Observed and calculated ¹H and ¹³C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

Dračínský

Pohl

Slavětínská

et al. 2010

Magnetic Reson in Chemistry

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A series of model sulfides was oxidized in the NMR sample tube to sulfoxides and sulfones by the stepwise addition of meta-chloroperbenzoic acid in deuterochloroform. Various methods of quantum chemical calculations have been tested to reproduce the observed (1)H and (13)C chemical shifts of the starting sulfides and their oxidation products. It has been shown that the determination of the energy-minimized conformation is a very important condition for obtaining realistic data in the subsequent calculation of the NMR chemical shifts. The correlation between calculated and observed chemical shifts is very good for carbon atoms (even for the 'cheap' DFT B3LYP/6-31G* method) and somewhat less satisfactory for hydrogen atoms. The calculated chemical shifts induced by oxidation (the Delta delta values) agree even better with the experimental values and can also be used to determine the oxidation state of the sulfur atom (-S-, -SO-, -SO(2)-).

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Section: Introductionmentioning

confidence: 99%

Observed and calculated ¹H and ¹³C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

Dračínský

Pohl

Slavětínská

et al. 2010

Magnetic Reson in Chemistry

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“…To ensure correct assignments, the shift changes for individual protons were monitored at four concentrations of Eu(dpm), up to the maximum. Included in Table 4 in parentheses are the relative distance factors for each proton as measured from models, assuming 3.5 A as the europium-oxygen distance (29).…”

Section: Proton Chemical Shiftsmentioning

confidence: 99%

Conformational Studies of Substituted Trimethylene Sulfites by Proton Magnetic Resonance

Wood¹,

Buchanan²,

Miskow³

1972

Can. J. Chem.

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Proton n.m.r. chemical shifts and coupling constants are reported for trimethylene sulfite and 10 alkyl derivatives in CC14. Data are discussed in terms of possible chair and non-chair conformations and results arecompared with those from dipole moment studies. The shift reagent Eu(dpm), is used to aid configurational assignments. Conclusions from n.m.r. and dipole moments are consistent and indicate that several of the sulfites exist to a considerable degree in non-chair conformations.Les dbplacements chimiques des protons en r.m.n. et les constantes de couplage sont donntes dans CC14 pour le trimethylene sulfite et pour dix derives alkylts. Les donntes sont discutees en fonction des conformations possibles chaise et non-chaise et les resultats compares a ceux des ttudes de moment dipolaire. Le reactif de deplacement Eu(dpm), est utilisb pour faciliter les assignations de configuration. Les conclusions tirees de la r.m.n. et des moments dipolaires sont importantes et indiquent que plusieurs des sulfites existent pour une part importante sous des conformations non-chaise.

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“…It was found previously (Frackowiak et a/., 1977) that the transition moment of the main emission band of Chl a is oriented almost parallel to the direction of LC orientation. Assuming that absorption and emission transition moments of the red band are parallel to each other, a lower degree of orientation than was obtained according to Fraser (1953) that found from the spontaneous polarization of emission (Frackowiak et a/., 1977). The results obtained by the application of the procedure proposed by Thulstrup et a/.…”

Section: Absorption Spectra and Degree Of Pigment Orientationmentioning

confidence: 87%

Local Electric Field Effect on the Chlorophyll Fluorescence

Fra̧ckowiak

1978

Photochem & Photobiology

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Abstract. Polarized absorption and fluorescence of chlorophyll a and bacteriochlorophyll solutions in nematic liquid crystal mixtures have been studied in the presence of an external electric field. The electric field caused a reorientation of the pigment molecules as concluded from changes in the polarized absorption. However, no correlation was found between the change in the polarized absorption and the change in the polarized fluorescence as a function of the field strength. The field influence was much stronger than expected only from the molecular orientation. The fluorescence polarized parallel to the direction of the liquid crystal was found to increase, whereas the similarly polarized absorption decreases. As a whole, the fluorescence yield significantly increased. It is suggested that the additional electric field is reinforced by a local field, most probably due to a protonation of the liquid crystal molecules. Charged solvent molecules are reoriented in an external electric field which changes the local electric field acting on chlorophylls. Similar changes in CHI fluorescence yield due to local electric field can be created in vivo by the shift of charged molecules present in surrounding pigments. Such effects can be at least partially responsible for slow induction of fluorescence phenomena.

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Assignment of configuration to sulphoxides by use of the “shift reagent”

Cited by 66 publications

References 0 publications

Observed and calculated ¹H and ¹³C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

Observed and calculated ¹H and ¹³C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

Conformational Studies of Substituted Trimethylene Sulfites by Proton Magnetic Resonance

Local Electric Field Effect on the Chlorophyll Fluorescence

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Assignment of configuration to sulphoxides by use of the “shift reagent”

Cited by 66 publications

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Observed and calculated 1H and 13C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

Observed and calculated 1H and 13C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

Conformational Studies of Substituted Trimethylene Sulfites by Proton Magnetic Resonance

Local Electric Field Effect on the Chlorophyll Fluorescence

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Observed and calculated ¹H and ¹³C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

Observed and calculated ¹H and ¹³C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones