5-Nitroanilines hydrophobicity

Deutsch and Hansch applied this principle to the sweet taste of the 2-substituted 5-nitroanilines. Using the data available (see Table VII), the calculated regression Eqs. 5-7 (using the method of least squares) optimally expressed the relationship between relative sweetness (RS), the Hammett constant, cr, and the hydrophobic-bonding constant, ir. 

Nitroanilines 1x103-50 Nonconjugated polar groups large molecules strong hydrophobic forces... 

Symmetry Shield is more hydrophobic than the low covered XTerra (see the values for isobutyl/isopropyl methyl ketone and 3-/4-nitroaniline), but, like Symmetry, has more surface silanol groups than XTerra. 

Mandal et al. (in preparation) incorporated p-cyclodextrin in an aqueous solution (0.7 M P-cyclodextrin, 7.5% NaOH, 37.5% urea, pH = 12) and employed it as a CLM in a permeator containing 300 symmetric hydrophobic feed fibers and 300 similar strip fibers. The feed was an equimolar (0.005 M) mixture of structural isomers o-nitroaniline and /7-nitroaniline in 80% octanol-20% heptane with the same solvent mixture as the strip liquid (Figure 3a). They obtained a selectivity of almost 5 for /7-nitroaniline over the ortho isomer. The operation was stable. The longest run continued for a period of almost two days with the feed solution and the strip solvent in coxmtercurrent flow. This successful separation indicated that employing a reflux arrangement at the end of the extraction cascade, it would be possible to continuously separate structural isomers into high purity (99%). ... 

Currently, these molecular systems are studies as SAMs on a metal surface. An additional method of preparing ordered monolayers of molecular devices is the use of Langmuir-Blodgett (LB) films. Therefore, a compound with hydrophilic and hydrophobic subunits with the central nitroaniline core similar to 70 was synthesized as in Scheme 3.40. n-Hexylbenzene was easily brominated on neutral alumina and coupled to TMSA followed by silyl removal and coupling to the nitroacetanilide core intermediate, 68, to afford 88. The methyl ester, intermediate 90, was synthesized by the coupling of methyl 4-ethynylbenzoate (89) to 88. The amine was unmasked and the methyl ester was saponified with lithium hydroxide to afford molecular scale device 91. Compound 91 is suitable for the formation of a LB film due to its hydrophilic carboxylic acid end-group and the hydrophobic n-hexyl end-group. 

MOFs can also be used as the stationary phase for both NP- and RP-HPLC. Fu et alP explored MIL-lOO(Fe) as a novel stationary phase for both NP and RP HPLC. Two groups of analytes (benzene, toluene, ethylbenzene, naphthalene, and 1-chloronaphthalene aniline, acetanilide, 2-nitroaniline, and 1-naphthylamine) were used to test the performance of MIL-lOO(Fe) in RP mode, whereas chloroaniline and toluidine isomers were employed to evaluate its performance in NP mode. Baseline separation of all the tested analytes was achieved on MIL-100(Fe)-packed colunm with good precision. The hydrophobic property stemmed from the aromatic ring walls of the pores in MIL-100(Fe) frameworks dominates the selective separation of neutral analytes and basic anilines in RP mode, whereas the interactions between the nitrogen atoms in the analyte and the Fe active sites in MIL-1 OO(Fe) govern the separation of chloroaniline and toluidine isomers in NP mode. The mesoporous cages, accessible windows, excellent chemical and solvent stability, metal active sites, and aromatic pore walls... 

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