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Predominance of resonance over polar effects on 1H, 13C and 15N NMR substituent chemical shifts in N-arylglycines

✍ Scribed by Ryszard Gawinecki; Erkki Kolehmainen; Zdzisław Kucybała; Borys Ośmiałowski; Reijo Kauppinen

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
260 KB
Volume
36
Category
Article
ISSN
0749-1581

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✦ Synopsis

1H, 13C and 15N NMR spectra of the ring-substituted N-phenylglycines (1) and their ethyl esters (2) were measured in

The chemical shift determinations and assignments are based on modern inverse 2D DMSO-d 6 . techniques (HMQC, HMBC). Dependences between chemical shifts and substituent constants show that the substituent e †ect is well transmitted to some side-chain atoms. There is a good correlation between and linear d N 1 H combinations of the inductive, and resonance substituent constants, for compounds 2. Similar results were p I , p R (~), obtained when the carbonyl carbon chemical shifts in both Series 1 and 2 were related to the substituent constants. Excellent linear dependences were obtained for nitrogen chemical shifts. The correlation coefficient for the linear dependence vs. linear combination of inductive and resonance substituent constants is high and it becomes d 15 N even higher when a correction for the solvent e †ect is included. In general, the contribution of resonance to chemical shifts is much higher than that of polar e †ects. The results obtained show to be a strong electron NHCH 2 CO 2 R donor.

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