利用B3LYP/6-31G＊計算去質子的X-C6H4COOH及X-C6H4NH(CH3)2+結構。由NBO分析所得到的最佳化路易士結構顯示，C6H5COOH苯基上有三個共軛雙鍵及羰基(COOH基)穩定電子，脫氫前後分子的總能及穩定度會改變；而在接上取代基後X-C6H4COOH及X-C6H4NH(CH3)2+，其總能及穩定度大小，會受到取代基及取代基取代的位置(鄰位、間位、對位)所影響，其總能、酸度、pka值、鍵長、E(2)值、電荷及s-character百分比均會有改變，特別在脫氫後穩定負電荷的因素，在取代基、取代基取代位置、苯環共振效應、超共軛及負超共軛穩定作用是非常重要的因素。
當取代基氟原子的數目愈多時其穩定度愈高，在取代基氟原子的數目相同時，直鏈取代的穩定度高於支鏈取代，且取代基上含氫氧基比氟原子對穩定度的貢獻更大，取代基上不同取代位置影響穩定度，幾乎是對位取代>間位取代>鄰位取代。利用理論計算所得苯甲酸及二甲苯胺衍生物Isodesmic Reaction的DEreaction值，對Sheppard的實驗結果pkawater ethanol值作圖，有很好的線性關係，此乃表示DE0值愈小，其化合物較穩定，酸度也愈高。苯甲酸羰基的穩定度影響酸度，而穩定度由取代基、取代基取代位置及負電荷決定。取代基的誘導效應、共振效應、超共軛、＋R character及p-π interaction都會影響到分子的穩定度。

B3LYP/6-31G* calculations have been employed to optimize two series of compounds: X-C6H4COOH and X-C6H4NH(Me)2+ {X=CF3，C2F5, n-C3F7, iso-C3F7, n-C4F9, C(OH)(CF3)2}, followed by Natural Bond Orbital studies. Deprotonated counterparts have also been under studies in order to acquire for supplementary and/or comparative information concerning effects (1) the nature of X and (2) the substitution sites of X on acidity. It is also our goal to probe how valid the hyperconjugation argument can account for the substitution effects of X on the acidity of the two series of compounds.
In the fluorinated alkyl substituents, the number of F-atoms will uniformly lead to higher stabilization energies, an observation predicted by hyperconjugation effects.
The site effects generally follow the order para > meta > ortho, which is also well rationalized by the combination of hyperconjugation with the well-known mesomeric effects. The latter contains +R character and p-p interaction between X and the phenyl system. It is also found, for the CnF2n+1 substituents, branched alkyl groups exert fewer enhancements on the acidity than the non-branched.
Moreover, the OH group shows higher enhancements of the acidity than the F-atom does. The relative acidities are well contrasted to the isodemic reaction energies: a more negative isodemic energy results in a more stable product-system, which in return accompanied by a lower reported pKa value.

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