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Conformational studies by nuclear magentic resonance—II: The effect of steric factors on hindered rotation in enamino aldehydes and ketones

✍ Scribed by J. Dabrowski; L. J. Kozerski

Publisher: John Wiley and Sons
Year: 1972
Tongue: English
Weight: 423 KB
Volume: 4
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1270040116

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✦ Synopsis

Rotational barriers of the dimethylamino group in different enamino aldehydes and ketones have been applied for evaluation of their conformation. It has been maintained that repulsion between bulky substituents causes twisting of the molecule rather than planar deformations.

Arguments for and against these alternative concepts based on the analysis of JAH and J(13CH) coupling constants in different fragments of the molecule have been discussed. 'J*-cis CH,=CCI, 27 13.51 & 0.05 12.37 & 0.05 CH3 (2) CH,CI, 33 13.5 i 0.1 12.5 & 0.1 (CD3),CO 50 13.8 i 0.1 12.6 i 0.1 CD,OD 64 13.3 0.1 12.5 & 0.1

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Conformational studies by nuclear magnet

Conformational studies by nuclear magnetic resonance—III: ASIS and protonation studies of the rotational isomerism of enamino aldehydes and ketones

✍ Lech Kozerski; Janusz Dąbrowski 📂 Article 📅 1972 🏛 John Wiley and Sons 🌐 English ⚖ 323 KB

The s-cis + s-trans equilibrium of several enamino ketones and aldehydes, has been evaluated based on the results of aromatic solvent induced shift measurements and of protonation of the title compounds. In contrast to cc,p-unsaturated ketones bearing no heteroatom, the A&,,,, value but not the A.83