scholarly journals An Examination of Factors Influencing Small Proton Chemical Shift Differences in Nitrogen-Substituted Monodeuterated Methyl Groups

Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1610
Author(s):  
Stuart Elliott ◽  
O. Ogba ◽  
Lynda Brown ◽  
Daniel O’Leary
Keyword(s):  
Chemical Shift ◽  
Local Environment ◽  
Computational Approach ◽  
Methyl Groups ◽  
Proton Chemical Shift ◽  
Isotropic Chemical Shift ◽  
Spin States ◽  
Chemical Shift Difference ◽  
Factors Influencing ◽  
Different Populations

Monodeuterated methyl groups have previously been demonstrated to provide access to long-lived nuclear spin states. This is possible when the CH2D rotamers have sufficiently different populations and the local environment is chiral, which foments a non-negligible isotropic chemical shift difference between the two CH2D protons. In this article, the focus is on the N-CH2D group of N-CH2D-2-methylpiperidine and other suitable CH2D-piperidine derivatives. We used a combined experimental and computational approach to investigate how rotameric symmetry breaking leads to a 1H CH2D chemical shift difference that can subsequently be tuned by a variety of factors such as temperature, acidity and 2-substituted molecular groups.

scholarly journals Long-lived nuclear spin states in monodeuterated methyl groups

2016 ◽  
Vol 18 (27) ◽  
pp. 17965-17972 ◽  
Author(s):  
Stuart J. Elliott ◽  
Lynda J. Brown ◽  
Jean-Nicolas Dumez ◽  
Malcolm H. Levitt
Keyword(s):  
Chemical Shift ◽  
Nuclear Spin ◽  
Methyl Groups ◽  
Spin States ◽  
Chemical Shift Difference ◽  
Significant Chemical

It is possible to access long-lived nuclear singlet order in monodeuterated methyl groups, in the case that a significant chemical shift difference exists between the CH2D protons.

scholarly journals Origins of Small Proton Chemical Shift Differences in Monodeuterated Methyl Groups

2017 ◽  
Vol 82 (17) ◽  
pp. 8943-8949 ◽  
Author(s):  
O. Maduka Ogba ◽  
Stuart J. Elliott ◽  
David A. Kolin ◽  
Lynda J. Brown ◽  
Sebastian Cevallos ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Methyl Groups ◽  
Proton Chemical Shift

Circular dichroism spectra of tetraamminecobalt(III) complexes of amino alcohols

1978 ◽  
Vol 31 (11) ◽  
pp. 2399 ◽  
Author(s):  
CJ Hawkins ◽  
GA Lawrance ◽  
JA Palmer
Keyword(s):  
Circular Dichroism ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Amino Alcohols ◽  
Circular Dichroism Spectra ◽  
Chemical Shift Difference ◽  
Solvent Dependence ◽  
Cotton Effects ◽  
Circular Dichroïsm ◽  
Chiral Amino Alcohols

The circular dichroism spectra are reported for tetraamminecobalt(III) complexes with the chiral amino alcohols 2-aminopropan-1-ol, 2- aminobutan-1-ol, 1-aminopropan-2-ol, 2-amino-1-phenyl-ethanol, ψ- ephedrine and ephedrine with the alcohol groups protonated (OH) and deprotonated (O-). The solvent dependence of the chemical shifts of the NH protons was investigated to determine the effects of stereoselective solvation on the circular dichroism, but, in contrast to some other related systems, the chemical shift difference between the two NH2 protons was relatively insensitive to solvent. Consistent with this, the circular dichroism spectra of the tetraphenylborate salts of the deprotonated complexes were found not to be markedly dependent on solvent. Tetraammine-{(-)-ψ-ephedrine)cobalt(III) and tetraammine{(-)- ephedrine}cobalt(III) were found to have the same signs of Cotton effects for the various d-d transitions, whereas bis{(-)-ψ- ephedrine}copper(II) and bis{(-)-ephedrine}copper(II) had opposite signs. This has been explained in terms of different conformer populations in the cobalt(III) and copper(II) systems.

Aluminum Siting in the ZSM-22 and Theta-1 Zeolites Revisited: A QM/MM Study

2008 ◽  
Vol 73 (6-7) ◽  
pp. 909-920 ◽  
Author(s):  
Stepan Sklenak ◽  
Jiří Dědeček ◽  
Chengbin Li ◽  
Fei Gao ◽  
Bavornpon Jansang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Chemical Shift ◽  
Nearest Neighbor ◽  
Membered Ring ◽  
Mas Nmr ◽  
Isotropic Chemical Shift ◽  
Reaction Space ◽  
Ring Channel ◽  
T1 And T2 ◽  
Nmr Signals

The Al siting in the silicon rich ZSM-22 and Theta-1 zeolites of the TON structure was investigated analyzing already published 27Al 3Q MAS NMR experimental data using QM/MM calculations. The results of our computations show that Al atoms can be located in 6 framework T positions because the two eightfold sites (T1 and T2) split into four fourfold T sites after an Al/Si substitution. The observed resonance at 55.5 ppm corresponds to the T4 site which is predominantly occupied by Al. This site is not located on the surface of the TON ten-membered ring channel and thus the protonic sites related with the majority of Al atoms in the TON structure exhibit a significantly limited reaction space. The 27Al NMR signals centered at 57.6 and 58.7 ppm correspond to either the T2 and T3 sites, respectively, or only to T2. The T2 and T3 sites accommodate some 40% and up to 10%, respectively, of Al while the T1 site is unoccupied by Al. Isotropic shifts of 61.1 and 61.6 ppm were calculated for Al atoms located in the T1-1 and T1-2 sites, respectively. The effect of a silanol "nest" as a next-next-nearest neighbor on the 27Al isotropic chemical shift of Al located in the T4 site is calculated to be less than 1 ppm.

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