Quantitative Measurement of Isomer Composition in Polypentenamer Using Carbon-13 Nuclear Magnetic Resonance

1974 ◽  
Vol 7 (1) ◽  
pp. 40-43 ◽  
Author(s):  
Charles J. Carman ◽  
Charles E. Wilkes
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Quantitative Measurement ◽  
Isomer Composition ◽  
Nuclear Magnetic

Quantitative Measurement of Hydrogen Types by Intergrated Nuclear Magnetic Resonance Intensities.

1963 ◽  
Vol 35 (8) ◽  
pp. 938-942 ◽  
Author(s):  
J. L. Jungnickel ◽  
J. W. Forbes
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Quantitative Measurement ◽  
Nuclear Magnetic

Quantitative Measurement of Isomer Composition in Polypentenamer Using Carbon-13 Nuclear Magnetic Resonance

1975 ◽  
Vol 48 (2) ◽  
pp. 329-336
Author(s):  
C. J. Carman ◽  
C. E. Wilkes
Keyword(s):  
Molecular Structure ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
13C Nmr ◽  
Analytical Method ◽  
Proton Nmr ◽  
Absorption Coefficients ◽  
The Past ◽  
Isomer Composition ◽  
Nuclear Magnetic

Abstract Polypentenamer ((−CH2CH2CH=CHCH2−)n, is produced by the ring-opening polymerization of cyclopentene. In the past, the determination of the relative concentrations of cis and trans structure was based upon an infrared method developed for analyzing polybutadiene. However, inexact absorption coefficients and problems with band overlap left the resultant analyses open to question. Carbon-13 nuclear magnetic resonance spectroscopy (13C NMR) seemed ideally suited for determining the isomer composition in polypentenamers. We have used 13C NMR as the primary analytical method to precisely determine the isomer composition of a series of eight polypentenamers. These results and samples will provide standards to determine infrared absorption coefficients, and thus provide a new infrared analysis. Two recently published books clearly show that the flurry of research over the past few years has firmly established 13C NMR as a valuable spectroscopic tool for the organic chemist. Its potential for establishing polymer molecular structure has equally been exciting and encouraging. The advantage of carbon-13 over proton NMR has been the dispersion of chemical shifts over a much wider range. This has meant that unique, separate NMR peaks have been obtained which describe molecules with subtle differences in molecular structure. The analytical use of 13C NMR has been suggested and used to a limited extent to quantitatively measure stereoconfiguration and monomer sequence distribution. However, no detailed investigation has been reported on precision or accuracy if 13C NMR is used as the primary analytical method for measuring polymer microstructure. As with proton NMR, measurements of peak areas are necessary to obtain quantitative analyses. Allerhand has predicted that 13C integrated intensity should be valid as a carbon count in spectra of complex molecules. Schaefer subsequently has shown that within a polymer system the carbons undergo equal nuclear Overhauser enhancement (NOE), even though the total NOE of different polymers may not be equal or maximum. Hence one can compare relative areas within a 13C NMR spectrum without fear of inadequately accounting for all of the area of a given structural feature.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

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