The ground state basicities of a series of substituted acetophenones: A theoretical study

Abstract

<span style="font-size:12.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">MNDO calculations with complete geometry optimization are carried out on a series of <i style="mso-bidi-font-style:normal">p</i>-substituted acetophenones and their <i style="mso-bidi-font-style:normal">o</i>-protonated counterparts. The gas phase <i style="mso-bidi-font-style:normal">o</i>-protonation turns out to be exothermic case and the local stereochemical disposition of the proton is found to be almost the same in each case. The presence of <i style="mso-bidi-font-style: normal">p</i>-substituent is seen to cause very little change of the protonation energies (PE) relative to the unsubstituted acetophenones. Electron releasing <i style="mso-bidi-font-style:normal">p</i>-substituents increase PE by 0.3 eV and the electron withdrawing <i>p- </i>substituents decrease it by 0.5 eV. Computed protonation energies are sought to be correlated with a number or computed system parameters such as, the net charge on the carbonyl oxygen, charge on the proton and the computed hardness of the unprotonated species.</span>