1H and 13C dynamic NMR study of the E, Z isomers of vinylogous diamides. Effect of conjugation and electrostatic and steric repulsion on the C(O)N rotation barriers and low‐temperature conformation

Gábor Szalontai, Péter Sándor, Felix Bangerter, L. Kollár

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

A 1H dynamic NMR study was carried out on N,N‐diethylmethacrylamide (1a), N,N,N′,N′‐tetraethylitaconamide (2), N,N,N′,N′‐tetraethylcitraconamide (3) and N,N,N′,N′‐tetraethylmesaconamide (4) over a wide temperature interval. Amide rotational barriers were determined from the coalescence temperatures. In 3 a second dynamic process was observed below 240 K, which made the geminal methylene protons non‐equivalent. The phenomenon is interpreted in terms of a non‐planar conformation caused by electrostatic and/or steric repulsion of the amide carbonyls. Homonuclear NOE experiments revealed an s‐cis, s‐cis′ conformation for the compounds studied.

Original languageEnglish
Pages (from-to)216-222
Number of pages7
JournalMagnetic Resonance in Chemistry
Volume27
Issue number3
DOIs
Publication statusPublished - 1989

Fingerprint

Diamide
Amides
Isomers
Conformations
Electrostatics
Nuclear magnetic resonance
Coalescence
Protons
Temperature
Experiments

Keywords

  • H and C dynamic NMR
  • Low‐temperature conformational analysis
  • Methylene proton non‐equivalence
  • Vinylogous diamide rotational barriers

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

Cite this

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title = "1H and 13C dynamic NMR study of the E, Z isomers of vinylogous diamides. Effect of conjugation and electrostatic and steric repulsion on the C(O)N rotation barriers and low‐temperature conformation",
abstract = "A 1H dynamic NMR study was carried out on N,N‐diethylmethacrylamide (1a), N,N,N′,N′‐tetraethylitaconamide (2), N,N,N′,N′‐tetraethylcitraconamide (3) and N,N,N′,N′‐tetraethylmesaconamide (4) over a wide temperature interval. Amide rotational barriers were determined from the coalescence temperatures. In 3 a second dynamic process was observed below 240 K, which made the geminal methylene protons non‐equivalent. The phenomenon is interpreted in terms of a non‐planar conformation caused by electrostatic and/or steric repulsion of the amide carbonyls. Homonuclear NOE experiments revealed an s‐cis, s‐cis′ conformation for the compounds studied.",
keywords = "H and C dynamic NMR, Low‐temperature conformational analysis, Methylene proton non‐equivalence, Vinylogous diamide rotational barriers",
author = "G{\'a}bor Szalontai and P{\'e}ter S{\'a}ndor and Felix Bangerter and L. Koll{\'a}r",
year = "1989",
doi = "10.1002/mrc.1260270304",
language = "English",
volume = "27",
pages = "216--222",
journal = "Magnetic Resonance in Chemistry",
issn = "0749-1581",
publisher = "John Wiley and Sons Ltd",
number = "3",

}

TY - JOUR

T1 - 1H and 13C dynamic NMR study of the E, Z isomers of vinylogous diamides. Effect of conjugation and electrostatic and steric repulsion on the C(O)N rotation barriers and low‐temperature conformation

AU - Szalontai, Gábor

AU - Sándor, Péter

AU - Bangerter, Felix

AU - Kollár, L.

PY - 1989

Y1 - 1989

N2 - A 1H dynamic NMR study was carried out on N,N‐diethylmethacrylamide (1a), N,N,N′,N′‐tetraethylitaconamide (2), N,N,N′,N′‐tetraethylcitraconamide (3) and N,N,N′,N′‐tetraethylmesaconamide (4) over a wide temperature interval. Amide rotational barriers were determined from the coalescence temperatures. In 3 a second dynamic process was observed below 240 K, which made the geminal methylene protons non‐equivalent. The phenomenon is interpreted in terms of a non‐planar conformation caused by electrostatic and/or steric repulsion of the amide carbonyls. Homonuclear NOE experiments revealed an s‐cis, s‐cis′ conformation for the compounds studied.

AB - A 1H dynamic NMR study was carried out on N,N‐diethylmethacrylamide (1a), N,N,N′,N′‐tetraethylitaconamide (2), N,N,N′,N′‐tetraethylcitraconamide (3) and N,N,N′,N′‐tetraethylmesaconamide (4) over a wide temperature interval. Amide rotational barriers were determined from the coalescence temperatures. In 3 a second dynamic process was observed below 240 K, which made the geminal methylene protons non‐equivalent. The phenomenon is interpreted in terms of a non‐planar conformation caused by electrostatic and/or steric repulsion of the amide carbonyls. Homonuclear NOE experiments revealed an s‐cis, s‐cis′ conformation for the compounds studied.

KW - H and C dynamic NMR

KW - Low‐temperature conformational analysis

KW - Methylene proton non‐equivalence

KW - Vinylogous diamide rotational barriers

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U2 - 10.1002/mrc.1260270304

DO - 10.1002/mrc.1260270304

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JF - Magnetic Resonance in Chemistry

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