Utilizing the relative electronegativity value of 2.1 for hydrogen and 2.5 for carbon, the H—C may be represented as follows: Hδ+ -> Cδ-. Thus, the larger the number of such bonds, as in the i-butyl group, the greater the combined electron release effect would be expectedAs the combined electron release effect increases, the greater the destabilizing effect on the alkoxide anion, which thus accounts for the observed order of reactivity: 1º>2º>3º.