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|Type:||Artigo de periódico|
|Title:||The α-substituent Effect Of Alkyl Groups In The 13c Nmr And Ir Data Of Some Aliphatic Nitriles|
|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 (νCN), 13C NMR chemical shifts for the CN and α-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 νCN with the increase in the substituent polarizability. Opposite tendencies were observed for the δCN and δα-CH2 values. δα-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 δCN, δα-CH2 and νCN to apparently unexpected values, which is noted in all linear and non-linear correlations here presented, and may be due to the absence of a carbon atom in the γ-position in relation to the CN or to the α-CH2 group.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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