Abstract

SALVATELLA, Luis. The alkyl group is a -I + R substituent. Educ. quím [online]. 2017, vol.28, n.4, pp.232-237. ISSN 0187-893X.  https://doi.org/10.1016/j.eq.2017.06.004.

Electronic substituent effects are usually classified as inductive (through 𝜎-bonds) and resonance effects (via 𝜋-bonds). The alkyl group has been usually regarded as a 𝜎-electron donor substituent (+I effect, according to the Ingold’s classification). However, a 𝜎-withdrawing, 𝜋-donor effect (‒I + R pattern) allows explaining the actual electron-withdrawing behavior of alkyl groups when bound to sp3 carbon atoms as well as their well-known electron-releasing properties when attached to sp2 or sp atoms. Alkyl substitution effects on several molecular properties (dipole moments, NMR, IR, and UV spectra, reactivity in gas phase and solution) are discussed.

Keywords : Second-year undergraduate; Organic chemistry; Misconceptions; Textbooks; Acids/bases; Covalent bonding; IR spectroscopy; NMR spectroscopy; UV-Vis spectroscopy.

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