Dynamic NMR studies of phenyl formate and 2,6-dimethylphenyl formate

Mark, Hugh L.; Baker, T. N.; Noe, Eric A.

doi:10.1021/ja00199a011

J. Am. Chem. Soc.

1989

DOI: 10.1021/ja00199a011

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Dynamic NMR studies of phenyl formate and 2,6-dimethylphenyl formate

Hugh L. Mark¹,

T. N. Baker²,

Eric A. Noe³

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Cited by 11 publications

(2 citation statements)

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“…To the best of our knowledge there are practically no data on the 17 O NMR chemical shifts, δ( 17 O), for substituted phenyl benzoates, C 6 H 5 CO 2 C 6 H 4 -X, except unsubstituted phenyl benzoate [14][15][16][17][18] , X = H, available in the literature. One could find in the literature the values of the 17 O NMR chemical shifts, δ( 17 O), only for phenyl acetates 15,16,19,20 , CH 3 CO 2 C 6 H 4 -X, with X = H, 4-NO 2 , 4-OCH 3 , 2-CH 3 , 2,6-(CH 3 ) 2 , phenyl formate 21 (HCO 2 C 6 H 4 -X), with X = H, meta-substituted phenyl naphthoates 22 , and para-substituted phenylthiol acetates 23 , containing variable substituents in phenoxy part (OPh). In substituted phenyl benzoates the influence of the substituent effects from the aryl moiety on the carbonyl carbon 13 C NMR chemical shifts more thoroughly was investigated in refs [24][25][26][27] .…”

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confidence: 99%

17O NMR study of ortho and alkyl substituent effects in substituted phenyl and alkyl esters of benzoic acids

Nummert¹,

Mäemets²,

Piirsalu³

et al. 2011

Collect. Czech. Chem. Commun.

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17 O NMR spectra for 44 ortho-, meta-and para-substituted phenyl and alkyl benzoates (C 6 H 5 CO 2 C 6 H 4 -X, C 6 H 5 CO 2 R) at natural abundance in acetonitrile were recorded. Substituent effects on the 17 O NMR chemical shifts, δ( 17 O), of the carbonyl oxygen and the single-bonded phenoxy (OPh) and alkoxy (OR) oxygens have been studied. The δ( 17 O) values of the carbonyl oxygen for para derivatives showed a good correlation with the σ°con-stants. The δ( 17 O) values of carbonyl oxygen for ortho derivatives were found to be described well with the Charton equation containing the inductive, σ I , resonance, σ°R, and steric, E s B , substituent constants in case the data treatment was performed separately for electrondonating +R and electron-attracting -R substituents. The electron-donating +R ortho and para substituents in substituted benzoates caused shielding and the electron-withdrawing -R substituents produced deshielding of the O signal. The steric interaction of ortho substituents with the ester group decreased the electron density at the carbonyl oxygen. In alkyl benzoates the δ( 17 O) values were found to be described well with the inductive, σ I , and the steric, E s B , substituent constants.We have previously investigated the contribution of the inductive, resonance and steric effects of ortho, meta, para and alkyl substituents into the rates of the alkaline hydrolysis in various media (as shown in refs 1-11 ), the carbonyl carbon 13 C NMR chemical shifts 12 , δ CO , and the infrared stretching frequencies of the carbonyl group 13 , ν CO , in substituted phenyl benzoates, X-C 6 H 4 CO 2 C 6 H 5 , C 6 H 5 CO 2 C 6 H 4 -X, and alkyl benzoates, C 6 H 5 CO 2 R. In the recent paper 14 we studied the ortho substituent effect on the 17 O NMR chemical shifts, δ( 17 O), of the carbonyl oxygen and the

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mentioning

confidence: 99%

17O NMR study of ortho and alkyl substituent effects in substituted phenyl and alkyl esters of benzoic acids

Nummert¹,

Mäemets²,

Piirsalu³

et al. 2011

Collect. Czech. Chem. Commun.

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“…We have used dynamic NMR spectroscopy to study the possibility that esters, thiol acids, and thiol esters, with groups such as vinyl, phenyl, or hydrogen, which could not provide a pair of electrons to complete an “aromatic” sextet in the Z conformations, would have enhanced populations of the E isomers. The conformational equilibria for S -phenyl thioformate, phenyl formate, vinyl formate, thioacetic acid, and dithioacetic acid could be rationalized in terms of an effect of this type. The ethynyl group also could not support an aromatic sextet in the Z conformation, and an E − Z energy difference of only 1.7 kcal/mol was estimated for ethynyl formate by ab initio calculations.…”

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EandZConformations of Esters, Thiol Esters, and Amides

et al. 1998

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Populations and free-energy differences for the E and Z conformations of S-methyl, cyclopropyl, isopropyl, and cyclopentyl thioformate were determined by low-temperature 1H NMR spectroscopy, and free-energy barriers of 10.63 and 11.84 kcal/mol were obtained for interconversion of E and Z conformations of S-methyl thioformate at −52.4 °C. Populations and free-energy differences were also determined at room temperature by using 13C NMR for a series of N-substituted formamides and N-cyclopropylacetamide in 1% solutions in CD2Cl2/CH2Cl2. In both sets of compounds, electron-withdrawing groups attached to sulfur or nitrogen appear to favor the E conformations. The electronegativities of the groups are taken to increase in the order methyl < vinyl ∼ phenyl ∼ cyclopropyl < hydrogen < ethynyl. Data from the literature are discussed in these terms, including the E−Z energy differences for formic acid and its ethynyl, vinyl, and methyl esters.

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Steric as well as n→π* Interaction Controls the Conformational Preferences of Phenyl Acetate: Gas‐phase Spectroscopy and Quantum Chemical Calculations

Singh

Panwaria

Mishra

et al. 2019

Chemistry An Asian Journal

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Herein, we report that the conformational preference of phenyla cetate is governed by steric effect and n! p*i nteraction. Conformation-specifice lectronic and IR spectroscopy combined with quantum chemistry calculations confirm the presence of only the cis conformer of phenyl acetate in the experiment. The cis conformer of phenyl acetate hasn !p*i nteraction betweent he lone-pair electrons on the carbonyl oxygen atom and the p*o rbitals of the phenyl group. The n!p*i nteraction is absent in the trans conformer whichh as additional steric repulsion between the methyl group and phenyl ring. The trans conformer is higher in energyt han the cis conformer by % 3kcal mol À1 .W eh ave found the effect of methyl substitution on the strength of the n!p*i nteraction, steric repulsion, and hyperconjugation in phenyla cetate. The red-shift observed in the cis conformer of phenyl acetate with respect to the trans conformer is affected due to the influence of the methyl substituent on the strength of the n!p*i nteraction as well as hyperconjugation.T he present result demonstrates that the introduction of abulkiersubstituent can induce steric as wellase lectronic control to reduce conformational heterogeneity of a molecular system. Understanding the effect of bulkiers ubstituents to promote defined conformations having specific non-covalent interactions may have implicationi nb etter perception of the optimum structure and function of biomolecules as well as recognition of drugs by biomolecules.[a] Dr.

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Dynamic NMR studies of phenyl formate and 2,6-dimethylphenyl formate

Cited by 11 publications

References 0 publications

17O NMR study of ortho and alkyl substituent effects in substituted phenyl and alkyl esters of benzoic acids

17O NMR study of ortho and alkyl substituent effects in substituted phenyl and alkyl esters of benzoic acids

EandZConformations of Esters, Thiol Esters, and Amides

Steric as well as n→π* Interaction Controls the Conformational Preferences of Phenyl Acetate: Gas‐phase Spectroscopy and Quantum Chemical Calculations

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