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Interfacial enhancements of chemical reaction equilibria and rates in liquid droplets are predicted using a combined theoretical and experimental analysis strategy. Self-consistent solutions of reaction and adsorption equilibria indicate that interfacial reactivity enhancement is driven primarily by the adsorption free energy of the product (or activated complex). Reactant surface activity has a smaller indirect influence on reactivity due to compensating reactant interfacial concentration and adsorption free energy changes, as well as adsorption-induced depletion of the droplet core. Experimental air-water interfacial adsorption free energies and critical micelle concentration correlations provide quantitative surface activity estimates as a function of molecular structure, predicting an increase in interfacial reactivity with increasing product size and decreasing product polarity, aromaticity, and charge (but less so for anions than cations). Reactions with small, neutral, or charged products are predicted to have little reactivity enhancement at an air–water interface unless the product is rendered sufficiently surface active by, for example, interactions with interfacial water dangling OH groups, charge transfer, or voltage fluctuations. [ABSTRACT FROM AUTHOR]

Aggregate size distributions in an aqueous solution containing either charged or neutral surfactants are investigated using Raman multivariate curve resolution (Raman-MCR) spectroscopy and analyzed with the aid of a multi-aggregation chemical potential surface (MCPS) modeling strategy. Total least squares decompositions of the concentration-dependent Raman-MCR spectra are used to quantify the free and micelle surfactant populations, and the surfactant's C–H stretch frequency is used as a measure of its average aggregation state. MCPS predictions relate the experimental measurements to the underlying surfactant aggregate size distribution by fitting either the component concentrations or the average C–H frequency to MCPS predictions, and thus determine the critical micelle concentration (CMC) and estimate the corresponding micelle size and polydispersity. The Raman-MCR spectra of aqueous 1,2-hexanediol, sodium octanoate, and sodium dodecyl sulfate, measured both below and above CMC, provide critical tests of the assumed functional form of the MCPS and the presence of low-order premicellar aggregates. Our results indicate that the low-order aggregate population gradually emerges as the CMC is approached and then remains nearly concentration-independent after the appearance of micelles. [ABSTRACT FROM AUTHOR]

The derivations based on the use of deficit functions provide a simple means of demonstrating the extremism conditions that are applicable to various thermodynamics function. The method shows that the maximum quantity of work is available from a system only when the processes are carried out reversibly since irreversible (spontaneous) transformations not only produce less than optimum quantity of work, but also increase the entropy of the universe.

The rule of corresponding states, which shows the connection between the thermodynamic properties of various liquids is re-examined. The overall likeness is observed by using an updated scaling technique of Lennard-Jones corresponding states (LJ-CS).

Hydrophobic hydration is considered to have a key role in biological processes ranging from membrane formation to protein folding and ligand binding (1). Historically, hydrophobic hydration shells were thought to [...]

A new isotope edited internal standard (IEIS) method for quantitative surface-enhanced Raman spectroscopy (SERS) is demonstrated using rhodamine 6G (R6G-[d.sub.0]) and rhodamine 6G (R6G-[d.sub.4]) edited with deuterium. The reproducibility and accuracy of the IEIS method is investigated both under optical resonance (SERRS) and nonresonance (SERS) conditions. A batch-to-batch concentration measurement reproducibility of better than 3% is demonstrated over a concentration range of 200 pM-2 [micro]M with up to a factor of 3 difference between the concentration of the analyte and its IEIS. The superior performance of the IEIS method is further illustrated by comparing results obtained using absolute SERS/SERRS intensity calibration (with no internal standard) or using adenine (rather than R6G-[d.sub.4]) as an internal standard for R6G concentration quantization. Potential biomedical gene expression and comparative proteomic applications of the IEIS method are discussed.

Potential distribution and coupling parameter theories are combined to interrelate previous solvation thermodynamic results and derive several new expressions for the solvent reorganization energy at both constant volume and constant pressure. The results are used to extract numerical values of the solute-solvent mean interaction energy and associated fluctuation entropy directly from experimental solvation thermodynamic measurements.

The compatibility of nonenhanced Raman spectroscopy with chromatographic and mass spectroscopic proteomic sensing is demonstrated for the first time. High-quality normal Raman spectra are derived from protein solutions with concentrations down to 1 [micro]M and 1 fmol of protein nondestructively probed within the excitation laser beam. These results are obtained using a drop coating deposition Raman (DCDR) method in which the solution of interest is microdeposited (or microprinted) on a compatible substrate, followed by solvent evaporation and back-scattering detection. Representative applications include the DCDR detection of insulin derived from an HPLC fraction, nondestructive DCDR followed by MALDI-TOF of lysozyme, the DCDR detection of protein spots deposited using an ink-jet microprinter, and the identification of spectral differences between glycan isomers of equal mass (such as those derived from posttranslationally modified proteins).

The conformational equilibrium of the trans-gauche isomerization of 1,2-dichloroethane (DCE) and the axial, axial-equatorial, equatorial isomerization of trans-1,2-dichlorocyclohexane (T12D), both dissolved in diethyl ether, are studied using Raman spectroscopy. The results reveal the different impact of attractive and repulsive perturbations on various thermodynamic functions.

A comparison of experiment and theory has been carried out relative to educational applications of infrared (IR) and Raman spectroscopy. No justification for not introducing these topics into the undergraduate curricula of chemistry departments now exists, given advances in low-cost array detectors and lasers and inexpensive commercial Raman systems and availability of powerful computers and software. Combining the spectroscopies and quantum theoretical methods offers an educational picture of molecular vibrational structure. IR and Raman spectroscopies are complementary.