James N. Shoolery

Proton Magnetic Resonance Studies of Chloroform in Solution: Evidence for Hydrogen Bonding

The concentration and temperature dependences of proton magnetic resonance measurements on chloroform in acetone and triethylamine solutions are presented. The behavior is similar to hydrogen bonding systems and it is concluded that there is a specific interaction involving the chloroform proton and the solvent molecule. In each system the data are consistent with the assumption of a one‐to‐one complex. Equilibrium constants and heats of formation are calculated.

Nuclear Magnetic Resonance in Concentrated Aqueous Electrolytes

The proton magnetic resonance of water has been examined in the presence of various concentrations of different diamagnetic salts. The observed shifts of the resonance frequency relative to that of pure water are interpreted in terms of the breakdown of the hydrogen‐bonded structure of water and the ability of the ions to polarize the water molecules. The concentration dependence of the shifts for the multivalent electrolytes indicates cation‐anion interactions at higher concentrations. The quite narrow single line observed for all but the Al+++, Be++, and the very concentrated ZnCl2 solutions shows that in most cases the proton exchanges faster than 104 times per second. The magnetic field dependence of the line width in the AlCl3 solution indicates that a rate of exchange of the proton of about 102 times per second is responsible for the broadening, while in the ZnCl2 and BeCl2 solutions the high viscosity appears mainly to be responsible for the increased line width. The fluorine magnetic resonance stu...

Nuclear magnetic resonance studies of hydrogen bonding in ethanol

Abstract The proton magnetic resonance of ethanol in CCl 4 solution has been studied as a function of concentration over the range pure ethanol (17 M) to 0.03 M. The shift of the OH proton frequency with concentration is interpreted in terms of hydrogen bonding between alcohol molecules, and an equilibrium constant for dimer formation is reported. The OH proton resonance of the ethanol monomer occurs slightly to the high field side of the CH 3 resonance. The value of the characteristic OH resonance frequency of the dimer (deduced from the NMR results and pertinent infrared data) suggests that the dimer is structurally different from higher polymers.

Analytical13C NMR: A rapid, nondestructive method for determining the cis,trans composition of catalytically treated unsaturated lipid mixtures

Abstract and SummaryHigh resolution natural abundance 13C Fourier transform nuclear magnetic resonance (NMR) has been found to be an effective tool for the rapid and direct determination of the cis/trans composition in partially hydrogenated and isomerized unsaturated lipids. With the eis and trans allylic carbon resonances as representative probes for double bond stereo-chemistry. Evaluation of the cis/trans composition of complex, positionally isomerized mixtures can be made without the necessity of carrying out detailed analyses of multishift olefinic carbon resonances. Migration of double bonds in monoenes and polyenes and formation of conjugated unsaturation in cata-lytically treated fats are discussed and assessed as possible sources of error in the evaluation of cis/trans isomer ratios. Carbon spin lattice relaxation times T1 were measured for both cis and trans allylic reson-ances in isomeric mixtures of varying composition to assure quantitative intensity relationships. 13C NMR compositional analysis of complex mixtures is demonstrated.

Nuclear spin-spin coupling between fluorine and hydrogen in fluorobenzene

Abstract High resolution proton and fluorine nuclear magnetic resonance (nmr) spectra of fluorobenzene, 4D-, 2,4,6-D 3− , and 2,3,5,6-D 4 -fluorobenzene have been obtained and analyzed. Double irradiation techniques were employed to eliminate the effects of the deuterium nuclear spin. The secular equation for 4D-fluorobenzene has been solved and the parameters adjusted for the best correspondence between the predicted and observed spectra. The nuclear spin couplings between the fluorine nucleus and the ortho, meta, and para protons are found to be, respectively, 9.4 ± 0.2 cps, 5.8 ± 0.2 cps, and 0.0 ± 0.5 cps. These couplings are found to have the same sign as the proton-proton couplings in the fluorobenzene molecule. This result is discussed and related to previous work on fluorobenzenes.

Structural and synthetic studies on the retrofractamides—amide constituents of Piper retrofractum

Abstract Two new unsaturated amides, retrofractamides A and C, were isolated from the total above-ground parts of Piper retrofractum . Retrofractamide A was shown to be N -isobutyl-9(3′,4′-methylenedioxyphenyl)2 E ,4 E ,8 E -nonatrienamide from spectroscopic and chemical investigations. The structure 6 for retrofractamide C was suggested from spectroscopic and chemical studies and was confirmed by a total stereoselective synthesis. The presence of sesamin and 3,4,5-trimethoxydihydrocinnamic acid as well as two higher homologues of retrofractamide A, viz. pipericide (retrofractamide B) and retrofractamide D was demonstrated. The synthesis of pipericide was also achieved.

Analytical13C NMR: Detection, quantitation, and positional analysis of butyrate in butter oil

The amount of butyrate contained in a complex mixture of butter oil triglycerides was 10.3 mole % as determined by natural abundance13C Fourier transform pulse nuclear magnetic resonance (NMR) spectroscopy. This NMR technique also demonstrated the primary isomeric positioning (>97%) of the butyrl group without the need for altering or fractionating the fat mixture.

The high resolution nmr spectrum of methyl acetylene

Abstract The proton spectrum of methyl acetylene is found to correspond to an AB3 system of nuclei with a J δ ν ratio of 1.33 at 60 Mc/sec. Analysis of this nearly accidentally degenerate multiplet is facilitated by observation of the proton spectra of all three of the molecular species containing C13 in natural abundance. Five of the six carbon-13 to proton coupling constants have been accurately measured, and the remaining one tentatively identified and measured.

New sesquiterpenoids of Bombax malabaricum

Abstract Hemigossypol-6-methyl ether, reported to be present in the root bark of Bombax malabaricum , has been shown to be isohemigossypol-1-methyl ether. Isohemigossypol-1,2-dimethyl ether, 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthaquinone, 7-hydroxycadalene and an unidentified phenolic compound have also been isolated. Long range couplings in the 1 H NMR spectrum of isohemigossypol-1-methyl ether have been established by decoupling experiments.

Hindered rotation and nonequivalent nuclear spin couplings

Abstract It is shown that the “weighted-time-average” postulate, recently proposed to explain the nonequivalence of chemically identical atoms in asymmetric molecules with hindered rotations, also predicts distinct spin-spin couplings in cases where no chemical shift is to be expected. The predicted effects have been observed in the proton magnetic resonance spectra of several molecules.