Traube s rule

Traube s rule accommodates the balance between hydrophobicity and hydro-philicity. It has been extended somewhat and formalized with the development of quantitative methods to estimate the surface area of molecules based on their structures [19, 237]. The molecular surface area approach suggests that the number of water molecules that can be packed around the solute molecule plays an important role in the theoretical calculation of the thermodynamic properties of the solution. Hence, the molecular surface area of the solute is an important parameter in the theory. In compounds other than simple normal alkanes, the functional groups will tend to be more or less polar and thus relatively compatible with the polar water matrix [227,240]. Hence, the total surface area of the molecule can be subdivided into functional group surface area and hydro carbonaceous surface area . These quantities maybe determined for simple compounds as an additive function of constituent groups with subtractions made for the areas where intramolecular contact is made and thus no external surface is presented. 

Traube s rule phys chem In dilute solutions, the concentration of a member of a homologous series at which a given lowering of surface tension is observed decreases threefold for each additional methylene group in a given series. trau-baz, rtil ) tretamlne See triethylenemelamine. tred-3,men ... 

It has been shown 8) that VT, the molar volume calculated from Traube s rule 4), VM, the molar volume of Exner 3), and the parachor,5) P all give significant correlation with the equation... 

Mark and Saito 31) attempted fractionating polymers by means of chromatography as early as 1936. They filtered solutions of cellulose acetate in acetone through a column with a charcoal-like adsorbent made from blood. The eluate contained the fraction of highest molar mass the rest of the sample was trapped in the column. It could be extracted by dioxane from separated portions of the packing. The largest molecules had travelled farthest. This was in contrast to expectation from Traube s rule and indicated size exclusion. 

For organic compounds consisting of hydrocarbon chains, solubility in water decreases with an increase in chain length of the homologous series (i.e., Traube s rule), because the compounds become more hydrophobic and nonpolar. More hydro-phobic adsorbates are expelled from water and thus allow an increasing number of water-water bond to be reformed. A nonpolar adsorbate will be strongly adsorbed from a polar solvent by a nonpolar adsorbent but will not be adsorbed much on a polar adsorbent in a nonpolar solvent. Therefore, an increase in the polarity of an adsorbate decreases its adsorption on activated carbon, which is a relatively polar adsorbent, in water. 

Thus the work of adsorption increases by a constant amount for each CH2 added to the hydrocarbon chain of the molecules. This must mean that each CH2 group is situated in the same relation to the surface as every other such group in the chain, and this can only be the case if the chains lie parallel to the surface. Hence Langmuir concluded that Traube s rule—for this is the name given to the effect of increasing length of chain... 

D. C. Jones and Cutting (unpublished 1937) have very recently confirmed the predominance of the lateral adhesion in these adsorbed films, and also the validity of Traube s rule. When the vapour phase is nearly saturated with the hydrocarbon they find films more than one molecule thick. Adsorption on heavy water is rather less than on ordinary water. 

Traube s rule does not hold for adsorption from organic solvents. While, on charcoal, from aqueous solution, the adsorption of organic compounds increases as the hydrocarbon chains are lengthened,2 this rule is reversed in the case of fatty acids on silica. Holmes and McKelvey3 found much greater adsorption of the shortest chain acids, from toluene on silica, than of longer chain acids and Bartell and Fu4 obtained similar results with solutions in carbon tetrachloride. 

There is no reason to expect Traube s rule to hold good except for aqueous solutions it is only an expression of the tendency of long hydrocarbon chains to escape from solution in water. 

Schulze-Hardy rule.1 Specific properties of the ions promoting easy adsorption are also important e.g. with a series of sodium salts of aromatic sulphonic acids, the introduction of an aliphatic side chain decreases the concentration necessary to diminish the potential by a given amount, by a factor of three for each additional CH2 group in the side chain2 this is another case of Traube s rule in adsorption. 

The absence of pmportionality between AG and increase of the hydrocarbon radical length indicates that for polar organic liquids Traube s rule is not valid. 

Komori et al. [490] analyzed the adsorptivities of substituted benzoic acids on two commercial activated carbons. They concluded that Traube s rule was applicable to the adsorption of the m-substituted benzoic acid except isophthalic acid. The trends for the o-substituted compounds were difficult to rationalize and were attributed to ortho effects. suggesting the importance of both electron-withdrawing and electron-donating substituents in affecting adsorbate acidity. El-Dib and Badawy [491] reported Freundlich-type behavior of o-xylene, ethylbenzene, toluene, and benzene on a commercial activated carbon (in the... 

Mostafa et al. [416] noted that the uptake of substituted phenols did not follow Traube s rule but instead did decrease in the order of their increasing pK values o-chlorophenol > hydroquinone > resorcinol > phenol > catechol > pyrogallol. Even though the experiments were performed at (unspecified) pH where the adsorbates were predominantly in an undissociated form, the authors noted that the acidity of the adsorbate is an important factor in determining its adsorption capacity this was not surprising to them because, presumably, the ability [of steam-activated and thus alkaline carbons] to remove phenols is expected to... 

Zaror [497] compared the uptakes of four phenols on a commercial activated carbon at a pH of 2 and reported both relatively low uptakes (<0.1 mmol/g at 0.3 mmol/L) and relatively small differences, in spite of the substantial differences in the nature of the substituents. Wang et al. [439] reported that the uptakes of p-nitrophenol, p-chlorophenol, and phenol were consistent with the notion that materials of high molecular weight are adsorbed to a more considerable extent than those of low molecular weight for compounds of similar chemical constitution Traube would be happy to learn that a century later [498] his rule lives on and that, under certain (perhaps very limited) conditions, the complexities discussed elsewhere in this review can be ignored. A clear example of the inapplicability of Traube s rule, however, is the study of Mostafa et al. [416] the authors did not attribute this to electrostatic effects or to changes in 7t- electron density (see below) but to the difference in the ability of hydrogen bond formation of the different phenols. ... 

The relationship between hydrocarbon chain length and surface activity is expressed by Traube s rule, which states that in dilute aqueous solutions of surfactants belonging to any one homologous series, the molar concentrations required to produce equal lowering of the surface tension of water decreases threefold for each additional CH2 group in the hydrocarbon chain of the solute. Traube s mle also applies to the interfacial tension at oil/water interfaces. 

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