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Type: Artigo de periódico
Title: The alpha-substituent effect of alkyl groups in the C-13 NMR and IR data of some aliphatic nitriles
Author: Rittner, R
Tormena, CF
Carniero, PIB
Abstract: Carbon-13 NMR spectra of some aliphatic nitriles, from acetonitrile to octanonitrile, were recorded, and unequivocal assignments of the chemical shifts through the use of HSQC and gHMBC sequences were performed. Cyano group stretching frequencies (nu(CN)), C-13 NMR chemical shifts for the CN and alpha-CH2 carbon atoms were correlated with electronic and steric parameters and also with calculated charge densities. No correlation between NMR and IR values was observed. However, it was observed a decrease of nu(CN) with the increase in the substituent polarizability. Opposite tendencies were observed for the delta(CN) and delta(alpha-CH2) values. delta(alpha-CH2) increases with the increase in substituent steric effect and with the decrease of calculated charge densities. A reasonable agreement between the methylene and methyl carbon experimental and theoretically calculated (HF) chemical shifts is observed, and also for the cyano carbon when MP2 or B3LYP methods were used. The unique properties of the ethyl group drive the delta(CN), delta(alpha-CH2) I and nu(CN) to apparently unexpected values, which. 2 is noted in all linear and non-linear correlations here presented, and may be due to the absence of a carbon atom in the gamma-position in relation to the CN or to the alpha-CH2 group.
Subject: aliphatic nitriles
substituent effects
carbon-13 NMR
infrared spectra
theoretical calculation
Country: Canadá
Editor: Spectroscopy Soc Canada, Ottawa
Rights: fechado
Date Issue: 2002
Appears in Collections:Unicamp - Artigos e Outros Documentos

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