A STUDY OF TAUTOMERISM IN CYCLIC β-DIKETONES BY PROTON MAGNETIC RESONANCE

1965 ◽  
Vol 43 (11) ◽  
pp. 3057-3062 ◽  
Author(s):  
Natsuko Cyr ◽  
Leonard W. Reeves
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Proton Magnetic Resonance ◽  
Enthalpy Change ◽  
Enol Form ◽  
Proton Resonance ◽  
Kcal Mole ◽  
Intensity Measurements ◽  
Acetonitrile Solutions ◽  
Monomer Form

The keto–enol equilibrium of cyclohexane-1,3-dione in chloroform is best interpreted from proton resonance measurements as[Formula: see text]K1 and K2 may be separately determined from chemical shift measurements of the enol-OH proton and intensity measurements of peaks assigned to keto and enol forms. K1 and K2 are satisfactorily independent of concentrations except in very dilute solutions where intensity measurements become unreliable. The overall equilibrium constant K = K1 × K22 can be obtained for the same molecule in acetonitrile solutions where the enol monomer form is in very low concentration. 5,5′-Dimethylcyclohexane-1,3-dione in chloroform has less enol form than the unsubstituted molecule. The enthalpy change associated with 'K' for cyclohexane-1,3-dione in chloroform is 2.05 ± 0.5 kcal mole−1.

scholarly journals ORYX-MRSI: A Fully-Automated Open-Source Software for Three-Dimensional Proton Magnetic Resonance Spectroscopic Imaging Data Analysis

2021 ◽  
Author(s):  
Sevim Cengiz ◽  
Muhammed Yildirim ◽  
Abdullah Bas ◽  
Esin Ozturk-Isik
Keyword(s):  
Data Analysis ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Open Source ◽  
Proton Magnetic Resonance ◽  
Spectroscopic Imaging ◽  
Brain Atlas ◽  
Magnetic Resonance Spectroscopic Imaging ◽  
Spectral Quality ◽  
Chemical Shift Artifact

Proton magnetic resonance spectroscopic imaging (1H-MRSI) provides noninvasive evaluation of brain metabolism. However, there are some limitations of 1H-MRSI preventing its wider use in the clinics, including the spectral quality issues, partial volume effect and chemical shift artifact. Additionally, it is necessary to create metabolite maps for analyzing spectral data along with other MRI modalities. In this study, a MATLAB-based open-source data analysis software for 3D 1H-MRSI, called Oryx-MRSI, which includes modules for visualization of raw 1H-MRSI data and LCModel outputs, chemical shift correction, tissue fraction calculation, metabolite map production, and registration onto standard MNI152 brain atlas while providing automatic spectral quality control, is presented. Oryx-MRSI implements region of interest analysis at brain parcellations defined on MNI152 brain atlas. All generated metabolite maps are stored in NIfTI format. Oryx-MRSI is publicly available at https://github.com/sevimcengiz/Oryx-MRSI along with six example datasets.

Application of proton magnetic resonance to rotational isomerism in halotoluene derivatives. III. α,α-Dichloro-2,4,6-tribromotoluene

1970 ◽  
Vol 48 (18) ◽  
pp. 2839-2842 ◽  
Author(s):  
J. Peeling ◽  
T. Schaefer ◽  
C. M. Wong
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Room Temperature ◽  
Proton Magnetic Resonance Spectrum ◽  
Methine Proton ◽  
Proton Spectrum ◽  
Kcal Mole ◽  
Ring Proton ◽  
Line Shapes ◽  
Carbon Carbon Bond

At room temperature the proton magnetic resonance spectrum of α,α-dichloro-2,4,6-tribromotoluene is ABX where the methine proton in the sidechain is X and is lying in the plane of the aromatic ring. At higher temperatures the ring proton spectrum, AB, broadens and eventually collapses to yield an A2X spectrum. From an analysis of the ring proton line shapes the barrier to rotation of the dichloromethyl group about the sp2–sp3 carbon–carbon bond is obtained; ΔG* = 17.5 ± 0.1 kcal/mole at 304°K, ΔH* = 15.67 ± 0.08 kcal/mole, ΔS* = −7 e.u., Ea = 16.38 ± 0.08 kcal/mole, log A = 11.78 ± 0.23 where the least squares errors given should probably be multiplied by a factor of from 3 to 5 to take possible systematic errors into account. The barrier is about 2 kcal/mole higher than in α,α,2,4,6-pentachlorotoluene. The barrier to rotation arises from the conformation in which chlorine and bromine atoms are eclipsed.

Carbon tetrachloride as solvent in proton magnetic resonance. Importance of size and charge effects of proximate substituents

1968 ◽  
Vol 46 (17) ◽  
pp. 2775-2781 ◽  
Author(s):  
T. Schaefer ◽  
B. Richardson ◽  
R. Schwenk
Keyword(s):  
Carbon Tetrachloride ◽  
Magnetic Resonance ◽  
Bond Length ◽  
Steric Hindrance ◽  
Proton Magnetic Resonance ◽  
Shape Effect ◽  
Proton Resonance ◽  
Charge Effects ◽  
Low Field

A model (not a theory), based on steric and charge removal characteristics of the substituents, is used to rationalize the low-field shifts caused by carbon tetrachloride (compared to cyclohexane) in the proton resonance spectra of 22 polyhalosubstituted benzenes. The low-field shifts are as large as 0.16 p.p.m. and these are found for protons situated between two ortho fluorine substituents. Larger halogens present a steric hindrance to the approach of the polarizable C—Cl bonds of the solvent and lead to smaller shifts. The charge removed from the region of the C—H bonds by the substituents is estimated by means of a function of the bond dipole divided by the bond length. A shape effect, arising when two hydrogens are ortho to each other, also appears to be present if there are bulky distant groups.

Proton Magnetic Resonance Chemical Shift Imaging ( 1 H CSI)-Directed Stereotactic Biopsy

2001 ◽  
Vol 143 (1) ◽  
pp. 45-50 ◽  
Author(s):  
B.-C. Son ◽  
M.-C. Kim ◽  
B.-G. Choi ◽  
E.-N. Kim ◽  
H.-M. Baik ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Proton Magnetic Resonance ◽  
Stereotactic Biopsy ◽  
Chemical Shift Imaging

Proton Magnetic Resonance Spectra of Some Substituted 2-Acylamino-3-arylamino-1,4-naphthoquinones

1976 ◽  
Vol 31 (2) ◽  
pp. 261-263 ◽  
Author(s):  
N. L. Agarwal ◽  
R. L. Mttal
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Proton Magnetic Resonance ◽  
Substitution Pattern ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of a number of substituted 2-acylamino-3-arylamino-1,4-naphthoquinones have been measured and discussed. The effect of various substitution pattern and hetero atoms on the chemical shift values of N-acylmethyl protons have been studied and explained.

Effect of solvent and anion upon the proton magnetic resonance spectrum of the 1-methylpyridinium ion

1968 ◽  
Vol 46 (17) ◽  
pp. 2787-2791 ◽  
Author(s):  
W. F. Reynolds ◽  
U. R. Priller
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Proton Magnetic Resonance Spectrum ◽  
Concentrated Solutions ◽  
Nonpolar Medium ◽  
Ion Proton ◽  
Acetonitrile Solutions ◽  
Proton Chemical Shifts ◽  
Pyridinium Ion

The proton magnetic resonance spectra of 1-methylpyridinium bromide and iodide have been measured over a range of concentrations in different solvents. It is found that, with the exception of acetonitrile solutions, the infinite dilution chemical shifts are related to solvent dielectric constant. Extrapolated shifts for a nonpolar medium agree with previously calculated chemical shifts for the pyridinium ion. Proton chemical shifts in concentrated solutions are affected by cation–anion interactions. These interactions are interpreted in terms of ion pair formation.

THE PROTON MAGNETIC RESONANCE SPECTRUM OF 1-FLUORO-2,4-DINITROBENZENE

1962 ◽  
Vol 40 (3) ◽  
pp. 431-433 ◽  
Author(s):  
T. Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Solvent Effects ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Previous Analysis ◽  
Proton Magnetic Resonance Spectrum ◽  
Proton Resonance ◽  
Reliable Analysis ◽  
Source Of Error

A reliable analysis of the proton resonance spectrum of 1-fluoro-2,4-dinitrobenzene is described. Solvent effects were used to obtain this analysis and a possible source of error in a previous analysis is indicated. Spectra parameters are also derived for 1,5-difluoro-2,4-dinitrobenzene. The spectrum of the latter compound confirms the assignment of peaks in the spectrum of the former.

Sign in / Sign up

Export Citation Format

Share Document