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- Title
Linear Free Energy Relationships of the <sup>13</sup>C NMR chemical shifts in 5-(3- and 4-substituted arylazo)-4,6-dimethyl-3-cyano-2-pyridones.
- Authors
Valentić,, Nataša V.; Vitnik, željko J.; Mijin, Dušan Ž.; Ušćumlić, Gordana S.; Todorović, Nina; Juranić, Ivan O.
- Abstract
The 13C NMR chemical shifts of the C2 carbon atom in the heteroaromatic nuclei of seventeen 5-(3- and 4-substituted arylazo)-4,6-dimethyl-3-cyano-2-pyridones were determined in deuterated DMSO solution. For quantitative assessment of the substituent effects on the 13C NMR chemical shifts simple and extended Hammett equations and Swain-Lupton equation were used. The mode of transmission of substituent effects have been discussed in a relation to the geometry of investigated molecules. The geometry data were obtained using semiempirical MNDO-PM6 energy calculations. The observed 13C NMR substituent chemical shifts were correlated with literature 13C NMR data for the corresponding 3- and 4-substituted-2′,6′-dimethylazobenzenes and 3- and 4-substituted azobenzenes. A good linear dependence obtained in this way, provided a basis to discuss the influence of the ortho-methyl groups on the degree of coplanarity of azobenzene and pyridone systems, and on the efficiency of transmission of electronic substituent effect from one ring to the other one.
- Subjects
ETHANES; HAMMETT equation; LINEAR free energy relationship; LINEAR dependence (Mathematics); CONDITIONS &; laws of chemical reaction; GIBBS' free energy; AZO compounds; TEXTILE fibers; ORGANIC solvents; SWAIN-Lupton equation
- Publication
ARKIVOC: Online Journal of Organic Chemistry, 2009, p227
- ISSN
1551-7004
- Publication type
Article