Relationship of aromatic nitro group torsion angles with oxygen-17 chemical shift data

Balakrishnan, P.; Boykin, David W.

doi:10.1021/jo00219a055

Cited by 56 publications

(26 citation statements)

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“…h For 2-SO 2 CH 3 substituent the steric constant E s B = -0.667 was calculated from relation [6] ∆log k = 0.021 + 2.284σ I + 0.862σ 0 R + 2.477E s B , using ∆log k = -0.309 for alkaline hydrolysis of phenyl ester of 2-(methylsulfonyl)benzoic acid in aqueous 50% DMSO. [51] i Data from References [34,35] were used. j The 2-SCH 3 derivative (E s B = -0.366 was calculated using ∆log k = -0.522 (Note h)), was excluded at confidence level t = 0.99. k For 2,6-(CH 3 ) 2 derivative the duple values of inductive, resonance and the steric constants were used.…”

Section: Discussionmentioning

confidence: 99%

“…In ortho-substituted compounds the δ( 17 O) data have been quite extensively studied for nitrobenzenes, [34,35] acetophenones, [36][37][38] benzaldehydes, [36] and benzoyl chlorides. [39][40] But to the best of our knowledge, up to now the correlation equations were not applied to describe the influence of ortho substituents on the 17 O NMR chemical shifts.…”

Section: The Values Of δ(mentioning

confidence: 99%

“…The aim of the present paper was to check the applicability of the Charton equation to describe the influence of ortho substituents on the δ( 17 O) values in phenyl esters of orthosubstituted benzoic acids, (X-C 6 H 4 CO 2 C 6 H 5 ), and to compare the substituent effects in the δ( 17 O) values with those in the alkaline hydrolysis, [6] the infrared stretching frequencies, ν CO , [9] and the 13 C NMR chemical shifts, δ CO . [8] For the comparison, the δ( 17 O) values for substituted nitrobenzenes, [34,35] acetophenones, [36,38] and benzoyl chlorides, [39][40] published in literature were correlated with the Charton equation as well.…”

Section: The Values Of δ(mentioning

confidence: 99%

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Influence of ortho substituents on ¹⁷O NMR chemical shifts in phenyl esters of substituted benzoic acids

Nummert

Mäemets

Piirsalu

et al. 2010

J of Physical Organic Chem

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Abstract17O NMR spectra for 29 phenyl esters of ortho‐, para,‐ and meta‐substituted benzoic acids, X‐C6H4CO2C6H5, at natural abundance in acetonitrile were recorded. The δ(17O) values of carbonyl and the single‐bonded oxygens for para derivatives gave good correlation with the σ+ constants. The δ(17O) values for meta derivatives correlated well with the σm constants. The influence of ortho substituents on the δ(17O) values of carbonyl oxygen and the single‐bonded oxygens was analyzed using the Charton equation containing the inductive, σI, resonance, σ+R, and steric, E, substituent constants. For ortho derivatives, excellent correlations with the Charton equation were obtained when the data treatment was performed separately for derivatives containing electron‐donating +R and electron‐attracting −R substituents. The electron‐donating substituents in ortho‐, meta‐, and para‐substituted esters resulted in shielding of the 17O signal and the electron‐withdrawing groups caused deshielding. In phenyl ortho‐substituted benzoates, the substituent‐induced positive inductive (ρI > 0), resonance (ρR > 0), and steric (δorthoE > 0) effects were found. The steric interaction of ortho substituents with ester group was found to produce a deshielding effect on the carbonyl and single‐bonded oxygens. For ortho derivatives with −R substituents, the resonance term was insignificant and the steric term was ca. twice weaker as compared to that for derivatives with +R substituents. The δ(17O) values for ortho‐substituted nitrobenzenes, acetophenones, and benzoyl chlorides showed a good correlation with the Charton equation as well. In ortho‐substituted nitrobenzenes the inductive, resonance and steric effect were found to be ca. 1.7 times stronger as compared to that for phenyl ortho‐substituted benzoates. Copyright © 2010 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Section: The Values Of δ(mentioning

confidence: 99%

Section: The Values Of δ(mentioning

confidence: 99%

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Influence of ortho substituents on ¹⁷O NMR chemical shifts in phenyl esters of substituted benzoic acids

Nummert

Mäemets

Piirsalu

et al. 2010

J of Physical Organic Chem

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“…The utility of 170 nrnr spectroscopy has been rapidly increasing (10)(11)(12), and it has been successfully used to estimate electronic characteristics (13)(14)(15) and local environment changes arising from steric interactions for a number of functional groups (16)(17)(18)(19)(20)(21), including carbonyl groups (1 8-21). For example, it has been recently demonstrated that large bulky groups (e.g., tert-butyl) cause considerable in-plane distortion of the molecular structure of phthalic anhydride when placed at the 3 position (22).…”

Section: Introductionmentioning

confidence: 99%

“…Using the slope (0.76 61" angle) of the line for the nitro group 1 7 0 chemical shift -torsion angle relationship previously reported (17,20), it is estimated that the 3-nitro group is rotated 35" from the plane of the aromatic ring. It is of interest that this torsion angle rotation is roughly equivalent to that of placing a methyl group ortho to a nitro group (17).…”

Section: Introductionmentioning

confidence: 99%

¹⁷O nuclear magnetic resonance spectroscopic study of substituted phthalic anhydrides and phthalides

Boykin¹,

Baumstark²,

Kayser³

et al. 1987

Can. J. Chem.

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IntroductionThe differential reactivity of the two carbonyl groups of unsymmetrically substituted phthalic anhydrides has been extensively studied (1-9); however, clear understanding of the factors that control the selectivity has yet to be achieved. The utility of 170 nrnr spectroscopy has been rapidly increasing (10-12), and it has been successfully used to estimate electronic characteristics (13-15) and local environment changes arising from steric interactions for a number of functional groups (16-21), including carbonyl groups (1 8-21). For example, it has been recently demonstrated that large bulky groups (e.g., tert-butyl) cause considerable in-plane distortion of the molecular structure of phthalic anhydride when placed at the 3 position (22). The steric interactions were reflected in the 170 chemical shift data of these compounds. In an effort to gain insight into the influence of substituents of varying electronic character on the properties and reactivities of the two carbonyl functions of 3-substituted phthalic anhydrides, we have studied the 170 chemical shifts of a series of phthalic anhydrides (1) and related phthalides (2 and 3).

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Radical Cyclization Reactions

et al. 1996

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Radical cyclization reactions are among the most powerful and versatile methods for the construction of mono‐ and polycyclic systems. The advantages these reactions offer to the synthetic organic chemist include high functional group tolerance and mild reaction conditions combined with high levels of regio‐ and stereochemistry. Furthermore, the recent progress in radical chemistry has led to the development of a broad range of very useful practical methods to conduct radical cyclization reactions. In general, radical cyclization reactions comprise three basic steps: selective radical generation, radical cyclization, and conversion of the cyclized radical to the product. For the generation of the initial radical a broad variety of suitable precursors can be employed, such as halides, thio‐ and selenoethers, alcohols, aldehydes and hydrocarbons. The cyclization step usually involves the intramolecular addition of a radical to a multiple bond. Most often carbon–carbon multiple bonds are employed; however, there are also examples known for the addition to carbon–oxygen and carbon–nitrogen bonds. Depending on the method employed, the cyclized radical is converted to the desired product by trapping with a radical scavenger, by a fragmentation reaction, or by an electron transfer reaction. The section Mechanism, Regio‐ and Stereochemistry provides an introduction to the key features of radical cyclization with a special emphasis on the factors controlling the regio‐ and stereochemistry. The section Scope and Limitations covers the different methods used to conduct radical cyclization. The basic principles of radical chemistry and general practical considerations when conducting radical cyclizations are not discussed in detail. Several excellent review articles and books dealing with these topics are available.

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Relationship of aromatic nitro group torsion angles with oxygen-17 chemical shift data

Cited by 56 publications

References 1 publication

Influence of ortho substituents on ¹⁷O NMR chemical shifts in phenyl esters of substituted benzoic acids

Influence of ortho substituents on ¹⁷O NMR chemical shifts in phenyl esters of substituted benzoic acids

¹⁷O nuclear magnetic resonance spectroscopic study of substituted phthalic anhydrides and phthalides

Radical Cyclization Reactions

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Relationship of aromatic nitro group torsion angles with oxygen-17 chemical shift data

Cited by 56 publications

References 1 publication

Influence of ortho substituents on 17O NMR chemical shifts in phenyl esters of substituted benzoic acids

Influence of ortho substituents on 17O NMR chemical shifts in phenyl esters of substituted benzoic acids

17O nuclear magnetic resonance spectroscopic study of substituted phthalic anhydrides and phthalides

Radical Cyclization Reactions

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Influence of ortho substituents on ¹⁷O NMR chemical shifts in phenyl esters of substituted benzoic acids

Influence of ortho substituents on ¹⁷O NMR chemical shifts in phenyl esters of substituted benzoic acids

¹⁷O nuclear magnetic resonance spectroscopic study of substituted phthalic anhydrides and phthalides