Abstract

SILVA, João Bosco P. da et al. Principal component analysis for verifying ¹H NMR spectral assignments: the case of 3-aryl (1,2,4)-oxadiazol-5-carbohydrazide benzylidenes. Quím. Nova [online]. 2005, vol.28, n.3, pp.492-496. ISSN 1678-7064.  http://dx.doi.org/10.1590/S0100-40422005000300022.

The ¹H NMR data set of a series of 3-aryl (1,2,4)-oxadiazol-5-carbohydrazide benzylidene derivatives synthesized in our group was analyzed using the chemometric technique of principal component analysis (PCA). Using the original ¹H NMR data PCA allowed identifying some misassignments of the proton aromatic chemical shifts. As a consequence of this multivariate analysis, nuclear Overhauser difference experiments were performed to investigate the ambiguity of other assignments of the ortho and meta aromatic hydrogens for the compound with the bromine substituent. The effect of the 1,2,4-oxadiazol group as an electron acceptor, mainly for the hydrogens 12,13, has been highlighted.

Keywords : PCA; ¹H NMR assignment; 1,2,4-oxadiazol.

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