## 3 Results and Discussion
From our results, the only Log \(P\) value for that can be cited for an effective fluorinated compound on _E.coli_ (Gram negative) is 2.00 for compound **5**. For the Gram positive bacteria, a range of Log \(P\) values of 1.15-2.19 apparently relate to efficacy. For the non-fluorinated compounds, optimal Log \(P\) values cover a wider range 1.61-3.41, and becomes wider 1.15-3.41 with the inclusion of _C.albicans_. The plots of the MIC-K\({}_{\rm D}\) for the twelve \(\beta\)-methyl-\(\beta\)-nitrostyrenes investigated for their antibacterial activities against _E. coli_ and _E. faecalis_ presented in Figure 1 reflect the poor correlation between the effectiveness against _E.coli_ and the partition coefficients of the compounds tested (r\({}^{2}\) = 0.0498 for _E.coli_, r\({}^{2}\) = 0.1416 for _E. faecalis_). There were no correlations between MIC value and K\({}_{\rm D}\) value for _S. aureus_, _B. subtilis_, and _C. albicans_ (graphs not shown). \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline Strain & **5** & **9** & **10** & **11** & **12** & **13** & **14** & **15** & **16** & **17** & **18** & **19** & **20** & **21** \\ _S. aureus_ & 2 & 128 & 3 & 8 & 2 & 2 & 16 & 16 & 2 & 16 & 3 & 2 & 256 & 8 \\ _B. subtilis_ & 2 & 256 & 3 & 16 & 2 & 2 & 8 & 8 & 4 & 8 & 2 & 2 & 256 & 16 \\ _E. faecalis_ & 5.5 & 64 & 5 & 16 & 6 & 4 & 32 & 16 & 8 & 16 & 4 & 5 & 128 & 16 \\ _E. coli_ & 27 & 256 & 42 & 256 & 45 & 96 & 512 & 256 & 512 & 256 & 256 & 128 & 256 & 96 \\ _C. albicans_ & 2 & 32 & 3 & 8 & 3 & 4 & 16 & 8 & 8 & 8 & 3 & 4 & 32 & 6 \\ Meas. **K\({}_{\rm D}\)** & 88 & 73 & 207 & 23 & 155 & 68 & 74 & 213 & 66 & 132 & 354 & 247 & 44 & 133 \\ Meas. **logP** & 1.94 & 1.86 & 2.32 & 1.36 & 2.19 & 1.83 & 1.87 & 2.33 & 1.82 & 2.12 & 2.55 & 2.39 & 1.64 & 2.12 \\
**Calc. logP** & 2.34 & 2.27 & 2.34 & 2.34 & 3.49 & 3.08 & 3.08 & 3.08 & 3.63 & 3.63 & 1.82 & 1.88 & 2.13 & 2.20 \\ \hline \end{tabular}
\end{table} 
Table 1: Antibacterial/fungus assays of various \(\beta\)-_E_-nitrostyrene compounds, their MIC [\(\mu\)g/mL] and K\({}_{\rm D}\), logP values. MIC and K\({}_{\rm D}\) values are the means of two determinations. The low K\({}_{\rm D}\) for fluorine containing compound **5** [K\({}_{\rm D}\) = 88] may be accounted by the presence of fluorine atom back bonding, leading to polar resonance structures and a gain in solvation energy in a hydrophilic compared to lipophilic medium, as shown in Scheme 2. Similarly, the 2,4-difluoro substituted compound **12** results in additional fluorine back bonding resonance structures with an overall increase in polarity and solvation in the aqueous solvent, significantly lowering its partition coefficient value. **Scheme 2. ** Fluorine back-bonding in fluorine substituted \(\beta\)-methyl-\(\beta\)-\(E\)-nitrostyrene compounds. Can aromatic ring fluorine/hydrogen exchange influence membrane permeability? Generally, aromatic F/H substitution tends to increase compound lipophilicity, in direct contrast to what is observed. Alternatively, the reason for the effectiveness of fluorine substitution on the aromatic ring may be connected with the high electronegativity of fluorine, although size factors could also be important. Perhaps the electronegativity of fluorine could affect binding affinity to the binding site of the bacteria, thus causing inhibition of the enzyme. Further investigations with other fluorine-substituted compounds to determine the structural features required for the optimal anti-bacterial activity of \(\beta\)-methyl-\(\beta\)-nitrostyrene compounds are currently being carried out.