Nuclear magnetic resonance spectrum of cis-5,6-disubstituted norbornenes. Correlation of proton chemical shifts with the Taft inductive substituent constant

1969 ◽  
Vol 34 (9) ◽  
pp. 2576-2579 ◽  
Author(s):  
Martha C. Thorpe ◽  
W. C. Coburn
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrum ◽  
Resonance Spectrum ◽  
Chemical Shifts ◽  
Substituent Constant ◽  
Proton Chemical Shifts ◽  
Nuclear Magnetic

A precise analysis of the 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

1994 ◽  
Vol 72 (7) ◽  
pp. 1722-1727 ◽  
Author(s):  
Ted Schaefer ◽  
Jeremy P. Kunkel ◽  
Robert W. Schurko ◽  
Guy M. Bernard
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrum ◽  
Resonance Spectrum ◽  
Chemical Shifts ◽  
Van Der Waals ◽  
Lone Pair ◽  
Coupling Constants ◽  
Van Der Waals Interactions ◽  
Nuclear Magnetic

The 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane, as a dilute solution in a CS2–C6D12–TMS solvent mixture at 300 K, is analyzed to yield 8 chemical shifts and 22 distinct coupling constants, nJ(H,H), n = 2–6. The coupling constant between H-2 and the para proton indicates, first, that the bisected conformer (phenyl plane perpendicular to the pseudo plane of the dithiane ring) is most stable and, second, that the apparent twofold barrier to rotation about the Csp2—Csp3 bond is 9.6 kJ/mol. The AM1, STO-3G, and STO-3G* computations confirm the twofoldedness of the barrier; the AM1 barrier is 9.4 kJ/mol. The empirical equation, [Formula: see text] reproduces the vicinal coupling constants of the CH2CH2CH2 fragments and implies puckering angles [Formula: see text] of 54°, 61°, and 64°, respectively. It is implied that 3J at [Formula: see text] is larger than at [Formula: see text] This results is discussed in terms of the latest theoretical approach to 3J in the HCCH fragment. The 4J(H,H) signs and magnitudes for the CH2CH2CH2 fragment agree reasonably well with theory. For the CH2SCH fragment, 4J(H,H) values are positive, in contrast to corresponding numbers in the propanic fragment, perhaps the first experimental values for certain rigid orientations about a heteroatom. INDO MO FPT computations on propane, dimethyl ether, and dimethyl sulfide confirm the experimental trend in 4J(H,H). 2J(H,H) and 5J(H,H) values are compared to those in related molecules. The striking differential shifts of the axial and equatorial protons are attributed to differential van der Waals interactions with the 3p lone-pair orbital on sulfur. A comparison of the ring proton chemical shifts with those in phenylcyclohexane and isopropylbenzene implies that C—S bonds are weaker net electron donors by hyperconjugation than are C—C bonds. It is also proposed that the ortho protons are deshielded by intramolecular van der Waals interactions with the 3p orbitals on the sulfur atoms.

Nuclear magnetic resonance and ultraviolet studies of the effect of p2H on reduced nicotinamide–adenine dinucleotide

1970 ◽  
Vol 48 (9) ◽  
pp. 947-952 ◽  
Author(s):  
P. R. Griffith ◽  
M. J. Nye ◽  
J. C. Alexander
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrum ◽  
Nicotinamide Adenine Dinucleotide ◽  
Resonance Spectrum ◽  
Chemical Shifts ◽  
Ultraviolet Spectra ◽  
Proton Peak ◽  
Reduced Nicotinamide Adenine Dinucleotide ◽  
Nuclear Magnetic

The effect of p2H on the chemical shifts of two adenine protons and one reduced nicotinamide proton of β-NADH have been examined. The adenine protons had a single pK at a p2H 3.85. The reduced nicotinamide proton showed no pK in the range p2H 3.00 to p2H 7.00. At low p2H values a new peak appeared in the nuclear magnetic resonance spectrum 0.31 p.p.m. downfield from the nicotinamide C-2 proton of β-NADH, and the nicotinamide C-2 proton peak gradually disappeared. It is suggested that this new peak is responsible for some of the anomalies in published results. The alterations in the ultraviolet spectra also indicate a change in the structure within the reduced nicotinamide moiety of β-NADH at low p2H values.

The 31P nuclear magnetic resonance spectrum of cows' milk

1985 ◽  
Vol 52 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Peter S. Belton ◽  
Richard L. J. Lyster ◽  
Colin P. Richards
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrum ◽  
Resonance Spectrum ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Casein Micelle ◽  
Liquid Milk ◽  
Similar Solutions ◽  
Nuclear Magnetic

SUMMARYThe 31P nuclear magnetic resonance spectrum of liquid milk was examined. Of the three peaks observed, the two larger were assigned to inorganic phosphate (Pi) and the seryl phosphate (SerP) residues of casein; the third peak was assigned to a phosphodiester, which is probably glycerophosphoryl choline. The pH-dependences of the chemical shifts of the Pi and SerP were measured with and without added EDTA, and the results confirm the assignments. The width of the Pi peak in milk is significantly greater than in similar solutions lacking casein, probably because of binding to, or chemical exchange with, the casein micelle. Most of the SerP residues in milk are not sufficiently mobile to have been detected in these experiments but a significant fraction of SerP residues is able to move freely and can be titrated.

Nuclear Magnetic Resonance Chemical Shifts of some Monosubstituted Isothiazoles

1975 ◽  
Vol 53 (4) ◽  
pp. 596-603 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Thomas R. Clem ◽  
Edwin D. Becker
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Charge Densities ◽  
Monosubstituted Benzenes ◽  
Proton Chemical Shifts ◽  
Nuclear Magnetic

Carbon-13 and proton chemical shifts have been measured for several monosubstituted isothiazoles. Substituent effects upon these chemical shifts are compared with those observed for monosubstituted benzenes, pyridines, and thiophenes. In general the observed substituent effects in the isothiazoles and thiophenes closely parallel one another. Correlations between the observed carbon-13 Chemical shifts and CNDO/2 calculated charge densities are examined.

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