Studies of chemical exchange by nuclear magnetic resonance.  II.  Hindered rotation in amides and thioamides

Neuman, Robert C.; Roark, David N.; Jonas, Violet

doi:10.1021/ja00990a007

Cited by 68 publications

(36 citation statements)

References 18 publications

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“…Neuman et al have studied N,N-dimethylcarbamoyl chloride, N,N-dimethylthiocarbamoyl chloride, and N,Ndimethylacetamide-d, by ioialline shape analysis (2,6). Inglefield et al have studied N,N-dimethylcarbamoyl chloride by the spin echo method and N,N-dimethylformamide by spin echo and total line shape analysis (5).…”

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confidence: 99%

Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives

Lemire¹,

Thompson²

1970

Can. J. Chem.

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confidence: 99%

Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives

Lemire¹,

Thompson²

1970

Can. J. Chem.

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“…(Table 5) The unsymmetrically substituted molecules both had intense resonances which exhibited normal temperature dependence, with no break in frequency dependence and no line width peculiarities (21) between 77 OK and room temperature. This suggests that CN bond reorientation (22,23) does not occur in this range of temperature. The diphenylcarbamylchloride resonance is very weak.…”

Section: The Acid Chloride Moleculesmentioning

confidence: 93%

³⁵Cl Nuclear Quadrupole Resonance of Alkyl Chloroformates, Alkyl Acid Chlorides, and Carbamyl Chlorides

Hart¹,

Whitehead²

1971

Can. J. Chem.

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The 35CI nuclear quadrupole resonance (n.q.r.) frequencies at 77 "K of twenty-two chloroformates, twenty-eight acid chlorides, two thiocarbonyl molecules, and five carbamyl chlorides are reported. Introductionchlorine by a saturated linkage. The frequency The planarity (1, 2) of the -X-COCI unit suggests n-bonding, and the difference in .nbonding when X is R, 0 , S, or N could be measured by comparing the 35C1 n.q.r. in equivalent molecules. Unfortunately, no resonances were detected in -SCOCI molecules nor in -NCSCl molecules. Frequencies were obtained for thirteen pairs of molecules, RCOCl and ROCOCI, and the frequency variation within each series was small. The frequency variation is qualitatively discussed.

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“…Both imply higher S polarisation than O. Also, 'H NMR studies for the hindered NH, rotation barriers [14,15] show that the thioamides have higher barriers than the corresponding amide by about 8.5kJmoI -1 . However, the NC bonds in gaseous HCONH 2 and HNSNH 2 are effectively identical in length, implying equal CN bond order [4], Thus we reconsider the charge distributions in amides and thioamides, ureas and thioureas and their methylated derivatives.…”

Section: Introductionmentioning

confidence: 98%

The Charge Distribution in Amides and Thioamides by Nuclear Quadrupole Coupling, Dipole Moments and Electronic Structure Calculations

Palmer

Sherwood

1996

Zeitschrift Für Naturforschung A

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The nuclear quadrupole coupling constants from microwave spectroscopy (MW) and quadrupole resonance (NQR) for amides and thioamides are discussed in relation to Hartree-Fock calculations with and without Moller-Plesset correlation effects. The view that the larger dipole moments from thioamides than the corresponding amides is a function of enhanced resonance in the former is discussed and (in effect) confirmed by the present procedures. The principal mechamism seems to be the push/pull K/C effects of the N atom with respect to the CO and CS groups, with S being a better o-donor than O; however, the effect is still present with formamidine where no electronegativity effects are important, so the overall effect is the 2,1,17t-electron contribution to the allylic system from N, C, O(S). The use of localised MO's and NO's is described, and the centroid positions are discussed in relation to the polarity of the bonds. The LMO's largely truncate the contributions to each NQCC to the three attached bonds (or 2 bonds + a lone pair orbital at O or S), as is used in the Townes-Dailey procedures. More distant LMO's generally contribute < 0.05 a. u. to the EFG, simplifying the analysis. The effects of 0(or S)-protonation of urea and thiourea is discussed.

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Studies of chemical exchange by nuclear magnetic resonance. II. Hindered rotation in amides and thioamides

Cited by 68 publications

References 18 publications

Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives

Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives

³⁵Cl Nuclear Quadrupole Resonance of Alkyl Chloroformates, Alkyl Acid Chlorides, and Carbamyl Chlorides

The Charge Distribution in Amides and Thioamides by Nuclear Quadrupole Coupling, Dipole Moments and Electronic Structure Calculations

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Studies of chemical exchange by nuclear magnetic resonance. II. Hindered rotation in amides and thioamides

Cited by 68 publications

References 18 publications

Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives

Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives

35Cl Nuclear Quadrupole Resonance of Alkyl Chloroformates, Alkyl Acid Chlorides, and Carbamyl Chlorides

The Charge Distribution in Amides and Thioamides by Nuclear Quadrupole Coupling, Dipole Moments and Electronic Structure Calculations

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³⁵Cl Nuclear Quadrupole Resonance of Alkyl Chloroformates, Alkyl Acid Chlorides, and Carbamyl Chlorides