Diffusion of Aromatic Isomers in Acetone: An Investigation on the Effects of Intramolecular and Intermolecular Hydrogen Bonding

Abstract

Limiting mutual diffusivities of o- and m-isomers of methylaniline, nitroaniline, nitrophenol, and aminophenol were measured in acetone at 298.2 K by the Taylor dispersion method. The data reveal that all of the o-substituted solutes capable of intramolecular hydrogen bonding diffuse faster than their m-counterparts without such bonding. By taking into account of the small corrections for the differences in molecular shape and steric hindrance between the o- and m-isomers that can form solute-solvent complexes, the net effects of intramolecular hydrogen bonding were uncovered to render the o-isomers greater in diffusivity by 3-15% as compared to their m-isomers in this study. For aromatic amines and phenols diffusing in acetone, the overall effects of intermolecular hydrogen bonding on diffusivity were ascertained by comparing the available diffusivity data of the associated aromatic solutes with those of the nonassociated ones. The intermolecular effects that cause solutes to diffuse slower were found to vary from approximately 12-39% in the present work. The results indicate that both of the opposite intra- and intermolecular effects are significant. In addition, the quantified effects were analyzed to show that they are closely related to the nature and position of the functional groups contained in the aromatic solutes, including those that are unable to form hydrogen bonds with acetone. A relation that can correlate the diffusivities of the hydrogen-bonded aromatic amines and phenols in acetone with the overall acidities of the compounds is also presented.

Effects of Hydrogen Bonding on Diffusion of Aromatic Compounds in Acetone: An Experimental Investigation from 268.2 to 328.2 K

“…The limiting mutual diffusivities of the basically nonpolar aromatic compounds ( D 12 N ) in acetone, together with their precisions, are presented in Table for the temperature range from 268.15 to 328.15 K. All of the reported data were measured in this work by the Taylor dispersion technique, except those at 298.15 K that were mainly collected from previous studies. ,,,− Also given in the table are the van der Waals volumes ( V 1 ) of the solute molecules, which were obtained by the method of group increments. ,,, Note that the 10 aromatic solutes listed in Table are all disc-shaped hydrocarbons that are incapable of H-bonding with acetone, as they do not have any proton-donating (H-donating) groups. For solutes that are similar in shape, many investigations ,,,,,− have shown that a linear relationship exists between the reciprocal of D 12 N and V 1 at constant temperature, i.e., where a and b are constants for a given temperature. It is noteworthy that eq actually originates from the rough-hard-sphere theory with simplification for the diffusion of nonassociated solutes of the same shape in a given solvent at constant temperature. , This equation is generally applicable for a fairly wide range of solute sizes.…”

“…Reviews of the fundamental principles of the Taylor dispersion technique have been given by Cussler and by Tyrrell and Harris . The experimental setup and procedure in this work were basically the same as those reported earlier in our previous studies. − Actually, the equipment and instruments resembled those constituting a common HPLC (high-performance liquid chromatography) system, i.e., a solvent delivery pump, a sample injector, a column, and a detector. Instead of an HPLC column, however, a diffusion tube of length 91.4 m was used for the diffusivity measurements in this work.…”

“…The mutual diffusivities at infinite dilution (limiting mutual diffusion coefficients) of the solutes in acetone were measured at 15 degree intervals from 268.15 to 328.15 K in this study by applying the Taylor dispersion technique. This technique, also known as the chromatographic peak-broadening method, is currently widely employed for measurement of mutual diffusivities. − Many advantages of using this technique have recently been noted by Rossi et al and by Shevtsova et al Mainly, it is a quick, precise, and reliable technique for obtaining diffusivity data. Reviews of the fundamental principles of the Taylor dispersion technique have been given by Cussler and by Tyrrell and Harris .…”

“…Hills et al used the overall acidity and basicity values of different compounds for predicting the diffusivity data of 58 solutes in ethanol and of 133 solutes in water. Recently, we have extended the study of the diffusivities in acetone to include the aromatic compounds containing two polar functional groups that can form not only intermolecular but also intramolecular H-bonding . The results of the above investigations are generally satisfactory, indicating that the approach of utilizing the OHAB scales for probing the effects of H-bonding on diffusion is useful.…”

Nanometer-Scale Heterogeneous Interfacial Sapphire Wafer Bonding for Enabling Plasmonic-Enhanced Nanofluidic Mid-Infrared Spectroscopy

“…Phenomena of mass transport by diffusion are ubiquitous in chemical and biological science and engineering. , Among them, molecular diffusion in hydrogen-bonding associated system has always been recognized as a challenging problem. , However, few studies have been reported to learn molecular diffusion in nanoscale. Combining the advantages of our Al 2 O 3 -based 3D sensing platform, we have conducted a real-time observation for the acetone molecular diffusion in DI water in nanospace.…”