## 3 Results and Discussion  
The preparation of the \(\beta\)-methyl-\(\beta\)-nitrostyrenes involved the Henry condensation reaction [22] of the aromatic aldehyde with nitroethane under basic conditions followed by dehydration of the resultant alcohol. The NMR analysis of the \(\beta\)-methyl-\(\beta\)-nitrostyrene fluorine derivatives indicated that the \(\beta\)-methyl-\(\beta\)-\(E\)-nitrostyrene conformation was predominant in most of the compounds prepared. For example, for 13 the \(E\)/\(Z\) ratio is 14/1. The antibacterial activity of \(\beta\)-nitrostyrene derivatives and related compounds has been well known for a number of years. Their resurgence is attributed to the strong antibacterial/antifungal activity of some compounds with applications in veterinary and human medicine. It has been established from SAR studies that their lipophilicity plus the nucleophilic addition of thiol groups of some enzymes to the exocyclic double bond of these compounds are critical for the development of their antimicrobial activity. The antimicrobial efficacy of the \(\beta\)-nitrostyrenes was assessed by their activity against a panel of bacteria and a fungus (_Candida albicans_). The results appear as the minimum inhibitory concentration (MIC) for each compound. The partition coefficient (\(\mathrm{K_{D}}\)) between octanol and water for each compound, representing its degree of lipophilicity, was also determined in order to access the extent of its interaction with the surface of the microorganism. The measured and calculated log P values are also included. Compounds with the incorporation of fluorine were of considerable interest as earlier studies had indicated an improvement of antibacterial activity [9]. The antibacterial assays shown in Table 1 indicated that the \(\beta\)-nitrostyrene compounds **20** and **9** displayed significantly lower activity towards all the tested bacteria relative to all the \(\beta\)-methyl-\(\beta\)-nitrostyrene analogues that were studied. This is exemplified by comparing the activity values of **20** and **21** as well as **9** and **5** that differ by at least an order of magnitude. The \(\beta\)-nitropropenyl side chain deviates 28\({}^{\circ}\) from coplanarity with the benzene ring [4] and the relative higher \(\mathrm{K_{D}}\) values of the \(\beta\)-methyl-\(\beta\)-nitrostyrene compounds provides evidence that the steric effect and presence of the \(\beta\)-methyl group is substantial. However, the reasons for their enhanced antibacterial potency are unclear. It is also difficult to correlate the position of fluorine substitution on the benzene ring or the effect of multiple fluorine substituents with activities and \(\mathrm{K_{D}}\) values of **5**, **10 11** and **12**. The activity order of the four most potent antibacterial compounds \(\mathbf{5}>\mathbf{10}>\mathbf{12}>\mathbf{13}\) does not correlate with their \(\mathrm{K_{D}}\) values. The data also provides evidence of the apparent tendency for fluorine functionalized \(\beta\)-methyl-\(\beta\)-nitrostyrenes to show considerable hydrophilic properties. The results also suggest that the more hydrophilic nature of the fluorine functionalized-\(\beta\)-methyl-\(\beta\)-nitrostyrenes with \(\mathrm{K_{D}}\) values in the lowest range (23-132) is more effective against _E.coli._ It is interesting to note that substituent size appears to affect antibacterial activity against _E. coli._, since for F-, the potency order is \(p>o>m\) and for \(\mathrm{CF_{3}}\)-, its \(p>m>o\). Of all the substances tested, compound **5** was most active against _E.coli_ (27 \(\mathrm{\SIUnitSymbolMicro g/mL}\)) and the MIC values against the other microorganisms were 6 \(\mathrm{\SIUnitSymbolMicro g/mL}\) or less, making it also the most effective against the three Gram positive bacteria and _C.albicans_. We deduce from this that for many Gram negative bacteria (such as _E. coli_) that are known to have polysaccharide structures, hydrophilic compounds more readily penetrate the bacterial cell wall to inhibit bacterial enzymes.