13C NMR Chemical Shifts of Heterocycles: Empirical Substituent Effects in 5-Halomethylisoxazoles
作者:
MarcosA. P. Martins,
Rogério Freitag,
Nilo Zanatta,
期刊:
Spectroscopy Letters
(Taylor Available online 1994)
卷期:
Volume 27,
issue 9
页码: 1227-1240
ISSN:0038-7010
年代: 1994
DOI:10.1080/00387019408006976
出版商: Taylor & Francis Group
关键词: 13C NMR of Isoxazoles;Substituent Effects;13C NMR of heterocycles
数据来源: Taylor
摘要:
Evaluation by empirically derived equations for the Substituent effect (α, β, γ, δ) on the13C NMR chemical shifts for C-3, C-4. C-5 and halomethyl-substituent carbon (C-6) in isoxazoles 1-5 [where C-3 substituent (R1) = H, alkyl or phenyl, C-4 Substituent (R2) = H, alkyl, and C-5 substituent (R3) = di-or trihalomethyl, methyl and H], taking as reference the compound la, is reported. From the calculated values for the α, β, γ, δ effects for each substituent it was possible to estimate the chemical shift of each carbon of the compounds 1–5. The13Cchemical shifts of the C-3, C-4, C-5, C-6 of these compounds, can be estimated with good precision: 94% of the calculated chemical shifts are found to be within ±1.0ppm, and 100% are found to be within ±1.5ppm.
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