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Predominance of resonance over polar effects on 1 H, 13 C and 15 N NMR substituent chemical shifts in N ‐arylglycines
Author(s) -
Gawinecki Ryszard,
Kolehmainen Erkki,
Kucybała Zdzisław,
Ośmiałowski Borys,
Kauppinen Reijo
Publication year - 1998
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(1998110)36:11<848::aid-omr379>3.0.co;2-o
Subject(s) - substituent , chemical shift , chemistry , resonance (particle physics) , polar , inductive effect , carbon 13 nmr , computational chemistry , ring (chemistry) , linear correlation , stereochemistry , crystallography , organic chemistry , atomic physics , statistics , mathematics , physics , astronomy
1 H, 13 C and 15 N NMRspectra of the ring‐substituted N ‐phenylglycines (1) and theirethyl esters (2) were measured in DMSO‐ d 6 . Thechemical shift determinations and assignments are based on moderninverse 2D techniques (HMQC, HMBC). Dependences between chemicalshifts and substituent constants show that the substituent effect iswell transmitted to some side‐chain atoms. There is a good correlationbetween δ N1H and linear combinations of theinductive, σ I , and resonance substituent constants,σ R (‐) , for compounds 2. Similar resultswere obtained when the carbonyl carbon chemical shifts in both Series1 and 2 were related to the substituent constants. Excellent lineardependences were obtained for nitrogen chemical shifts. Thecorrelation coefficient for the linear dependenceδ 15N vs . linear combination of inductive andresonance substituent constants is high and it becomes even higherwhen a correction for the solvent effect is included. In general, thecontribution of resonance to chemical shifts is much higher than thatof polar effects. The results obtained showNHCH 2 CO 2 R to be a strong electron donor. ©1998 John Wiley & Sons, Ltd.