Hydrogen bond studied by nitrogen-14 nuclear magnetic resonance. II. Heteronuclear magnetic double resonance study of nitrogen-14 hydrogen-bond shifts of pyrroles and indole

1971 ◽  
Vol 93 (5) ◽  
pp. 1072-1076 ◽  
Author(s):  
Hazime Saito ◽  
Kenkichi Nukada
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Magnetic Resonance ◽  
Double Resonance ◽  
Nuclear Magnetic

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

Hydrogen bond studied by 14N nuclear magnetic resonance I.

1965 ◽  
Vol 6 (2) ◽  
pp. 111-117 ◽  
Author(s):  
Hazime Saitô ◽  
Kenkichi Nukada ◽  
Hiroshi Kato ◽  
Teijiro Yonezawa ◽  
Kenichi Fukui
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Magnetic Resonance ◽  
Nuclear Magnetic

Nuclear Magnetic Resonance Experiments on Acetals. 43. Reversal of Previous Conformational Assignment in 5-Fluoromethylated-5′-Me-1,3-dioxanes

1973 ◽  
Vol 51 (19) ◽  
pp. 3170-3172 ◽  
Author(s):  
M. Anteunis ◽  
F. Borremans
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Long Range ◽  
Double Resonance ◽  
Axial Position ◽  
Nuclear Magnetic

Additional n.m.r. investigations on 5-fluoromethylated-5′-Me-1,3-dioxanes have made it necessary for us to reverse the spectral assignments which were forwarded recently (1) in this journal. Thus, the 5-CF2H group prefers the axial position to the extent of ca. 900 cal/mol, whereas the 5-CFH2 group displays a similar preference for the axial position to the extent of ca. 200 cal/mol. An explanation for these unexpected results is advanced. Final structural assignments have been made possible by homo- and heteronuclear double resonance experiments and by ASIS-studies. The observed relative shifts for 5-CFnH3−n and 5-CH3 signals are shown to be normal (e.g. δ(5e) < δ(5a)). Also, the previously reported 4J(F,H) long range couplings follow a classical M-path.

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