Raman Spectroscopy as the Method of Detection for Constructing a Binary Liquid–Vapor Phase Diagram

Abstract

b S Supporting Information T he physical chemistry laboratory course is an essential experience to the student wishing to pursue an advanced degree in chemistry or a career in a chemistry related field. A study in 2004 on physical chemistry curriculum points out that physical chemistry bridges physics, chemistry, and mathematics and develops complex critical-thinking skills required by scientists working on projects with interdisciplinary foci. 1 Physical chemistry now encompasses subareas too numerous to list and contributes to the study of almost all the other disciplines in chemistry. Today in a growing number of universities, however, the physical chemistry lab has been scaled back from the traditional two-semester period to just one semester. For example, in a recent informal survey of chemistry programs in the Southern Universities Group, approximately a quarter of the schools now only require one semester of physical chemistry lab to obtain a B.S. degree in chemistry. The loss of a whole semester has different roots, such as the desire to reduce the number of hours in a major or to make room for other new specialty courses such as environmental or forensic chemistry. The problem, therefore, arises in being able to provide students with enough lab experience to encompass the important areas of physical chemistry. Moore pointed out that it is extremely important to make sure the physical chemistry curriculum reflects what physical chemists really do. 2 With this in mind, in 1999, the University of Maryland integrated a program of physical and analytical techniques to investigate significantly more complex systems than those incorporated with one curriculum. 3 In 2004, Grand Valley State University sought to incorporate both computational and traditional physical chemistry laboratories in their curriculum, stating that the coupling of laboratories allows students to experience an experiment from a macroscopic, empirical point of view as well as an abstract, theoretical level that considers molecular-level events. 4 Combining multiple laboratory procedures into fewer multidimensional lab exercises allows students to be provided with opportunities encompassing multiple facets of physical chemistry in a constrained time frame. 5 Constructing a binary liquidÀvapor phase diagram is a classic physical chemistry experiment that is still taught in many chemistry departments and serves to illustrate an important physical concept. Here, we show that two other important concepts can be taught concurrently in this laboratory exercise, specifically molecular spectroscopy and quantum chemistry.The classic binary liquidÀvapor phase diagram experiment utilizes Raoult's law, which states that vapor pressure of an ideal solution is directly proportional to the mole fraction of each component. This law is a good approximation for a component only when its mole fraction is close to unity. Deviations, positive or negative, from Raoult's law give insight into the thermodynamic properties of the components involved. There have been...

Noncovalent Interactions between Trimethylamine N-Oxide (TMAO), Urea, and Water

“…All calculations were performed using the Gaussian09 software . Simulated Raman spectra were created by summing Lorentzian profiles for each normal mode …”

“…This concentration was chosen to maximize the number of osmolytes present in solution. We showed previously that increasing dilution does not affect features in the Raman spectra of TMAO. , At first glance, the spectra are additive . However, when comparing the locations of normal modes for TMAO and urea in the three solutions, there is a noticeable +11 cm –1 blue shift in the broad feature centered at 1591 cm –1 .…”

“…66 Simulated Raman spectra were created by summing Lorentzian profiles for each normal mode. 67 Spectroscopic Results. Figure 2 compares the Raman spectra of saturated aqueous solutions of TMAO and urea to that of a 1:1 mixture of these solutions.…”

Raman spectroscopic and quantum chemical investigation of the effects of trimethylamine N‐oxide on hydrated guanidinium and hydrogen‐bonded water networks

“…[ 79–82 ] Lorentzian‐type functions for each normal mode were combined in order to create simulated Raman spectra. [ 68,83 ] Zero point energy (ZPE) corrections were applied for the comparison of relative energetics.…”

Characterizing the BP Stretching Vibration in Phosphorus‐Substituted Phosphine Boranes

“…Default convergence criteria and numerical integration grids were employed for all calculations. Simulated spectra were created by summing Lorentzian functions for each normal mode by using a custom program developed with National Instruments LabView 44. The INTDER200545 program was employed to determine the TEDs characterizing the normal modes.…”