1.3.4.4 Nuclear magnetic resonance and electron double resonance (ENDOR)

2006 ◽  
pp. 295-297
Author(s):  
W. Gunsser ◽  
U. Wolfmeier ◽  
J. Fleischhauer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Double 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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