## 1 Introduction
_E.coli_ was suppressed effectively by chlorine or fluorine C\({}_{4}\)-aryl-substituents relative to the unsubstituted or the 3-4-methylenedioxy ring compounds. 2. _S.aureus_ was suppressed effectively by a wide range of nitropropenyl arenes including \(\beta\)-methyl-\(\beta\)-nitrostyrene, the 4-fluorine and 4-chlorine substituted \(\beta\)-methyl-\(\beta\)-nitrostyrene, imidazolyl, benzothiazole and the 3,4-methylenedioxy derivatives. An important finding was that when two hydroxy groups were present on the ring in the 2- and 4- positions or the 2- or 5- positions, activity against this microorganism noticeably reduced. The fact that this also occurred with substitution by \(N\),\(N\)-dimethyl and \(N\),\(N\)-diethyl groups indicated that the more polar nature of these substituents was detrimental to activity. This was supported by the K\({}_{\rm D}\) values of the latter compounds being relatively low compared with the unsubstituted and halogenated-substituted compounds. 3. _B.subtilis_ was suppressed by a wide range of compounds in a similar fashion to _S.aureus_. The 2,4- and 2,5- dihydroxyarly substituted compounds exhibited poor bacterial inhibition whereas the 3,4-dihydroxy derivative gave high activity. 4. _C.albicans_ was suppressed by the 3,4-dichloro, 4-chloro, 4-fluoro, derivatives. However 2,4-dihydroxy, 2,5-dihydroxy and the benzimidazole derivatives were very unreactive. The introduction of 'fluorine functionality' into molecular architecture has proved to be invaluable for modulation of the molecular properties of medicinal compounds [15]. The substitution of hydrogen and other functional groups with fluorine can have multiple molecular impacts, including electronic, lipophilic, \(H\)-bonding, chemical, metabolic stability and steric factors, which can influence the pharmacodynamic and pharmacokinetic properties of pharmaceuticals [16]. When fluorine atoms or trifluoromethyl groups were introduced into either the peptidic chain or the C-terminal end of cationic pentapeptides, the antimicrobial activity always improved by diminishing the minimal inhibitory concentration (MIC) [17]. A recent report on the structure activity relationships of antitubercularnitroimidazoles highlighted the high activity achieved by the inclusion of trifluoromethoxybenzyl substituents in the nitroimidazoles [18]. Carbon films with a high fluorine content exhibited excellent antibacterial properties against _E. coli_ growth [19]. Furthermore, a simple super hydrophobic coating composed of nano-structured fluorinated silica colloids with fluoroalkoxysilane on a silane structure demonstrated that the adhesion of _Staphylococcus aureus_ and _Pseudomonas aeruginosa_ was reduced by \(2.08\pm 0.25\) and \(1.76\pm 0.12\) log over controls, respectively [20]. The fluorine containing 4-(substituted-2-hydroxybenzoyl) pyrazoles **6**, **7**, **8** showed promising antibacterial activity [21]. Based on the discoveries that fluorine substituted \(\beta\)-nitrostyrene enhanced antimicrobial activity, this investigation was undertaken to study the effects on antimicrobial activity offluoro-, trifluoromethyl- and trifluoromethoxy- substituted \(\beta\)-methyl-\(\beta\)-nitrostyrenes and related compounds that were prepared via the Henry reaction [22]. For an antimicrobial agent to be effective, it must penetrate the bacterial cell first to reach its target enzymes, therefore the lipophilicity of the prepared compounds was determined from the octanol-water partition coefficients. The antimicrobial activities of all products were measured by minimum inhibitory concentration (MIC). Three Gram positive bacteria (_Staphylococcus aureus_, _Bacillus subtilis_ and _Enterococcus faecalis_), one Gram negative bacterium (_Escherichia coli_) and a fungus (_Candida albicans_) were tested.