Peer Mentoring in the General Chemistry and Organic Chemistry Laboratories. The Pinacol Rearrangement: An Exercise in NMR and IR Spectroscopy for General Chemistry and Organic Chemistry Laboratories

Abstract

Collaborative work in the laboratory is valued at Wofford College (1-3), as it is at many other institutions. Earlier collaborations at Wofford have allowed students in our physical chemistry classes to share data and to work with students from other institutions on computational chemistry projects. We now wish to report on preliminary efforts in establishing a program involving laboratory collaboration of another sort-between students enrolled in organic chemistry and those studying general chemistry.Organic chemistry and spectroscopic analysis methods have begun to find their way into the general chemistry laboratory. These experiments range from studies of electronegativity influences on chemical shift (4), to solving unknown structures (5-6), to the preparation of aspirin and spectroscopic confirmation of the product's structure and purity by FTIR and FT-NMR (7-8). A number of labs have been developed for organic chemistry classes, which are more discovery-based than traditional synthesis labs. Experiments such as these tend to pique students' interest since they are less like following a "cookbook" (9-16) and don't require three to four hours to reproduce a known result.Recognizing that we are better students of chemistry now that we are educators in the field, and further recognizing that mentorships can be fun and informative for all parties involved (17-18), we began a program involving the use of organic chemistry students as peer-mentors for general chemistry laboratory students. We felt that it was important that the labs we developed as part of this project should all contain an element of discovery. OverviewWe introduce organic chemistry students to interpretation of IR and NMR ( 1 H and 13 C) spectra during the first semester of organic chemistry. We then require these students to interpret spectra of several unknown compounds as an out-of-lab exercise. Throughout the first term, we reinforce spectroscopic interpretation on lecture tests and as a normal analysis of reaction products. The first lab of the second semester for the organic chemistry students involves a dehydration of cyclohexanol. During this lab we require students to obtain IR and NMR ( 1 H and 13 C) spectra of the cyclohexanol and of the cyclohexene formed. This experience allows the organic chemistry students to learn to operate an NMR spectrometer for the first time.During the week in which organic chemistry students are performing the dehydration of cyclohexanol we present an introduction to molecular spectroscopy to the general chemistry students. Although this topic is not typically covered in general chemistry textbooks, we introduce molecular spectroscopy after our textbook chapters on molecular bonding. Providing experimental evidence for molecular structure helps reinforce the abstract subject of molecular bonding. From IR spectroscopy students see evidence of the effect of a double bond on the vibrational spectra, noting that the stronger double bond has a greater vibrational frequency than does a single bond. We present 1 ...

Examination of Bond Properties through Infrared Spectroscopy and Molecular Modeling in the General Chemistry Laboratory

“…Students are guided toward discovering the relationship between bond strength, bond order, and vibrational frequency through a series of exercises that include observing masses oscillating on springs, modeling bond stretching computationally, and obtaining IR spectra of several related compounds. Although several previously published general chemistry experiments use IR spectroscopy as an educational component, − only a few examine bond properties. − Of these, one is somewhat similar to the laboratory described herein in that IR spectra are obtained and Hooke’s law is demonstrated via masses and springs . However, this experiment extends the learning as students build and conduct molecular modeling experiments on their own molecules in a computational chemistry program, animate the molecular vibrations of their compounds, and generate a theoretical IR spectrum for them.…”

Implementation of a Program for Mentoring Students in a Two-Year Chemical Technology Program by an Alumnus Enrolled in Graduate School

“…Another successful model involves organic chemistry students mentoring general chemistry students on using molecular spectroscopy to identify an unknown organic compound they had synthesized. It was reported that this was one of the general chemistry students’ favorite laboratories; further the authors felt that the experience motivated the general chemistry students to continue their studies in chemistry . It was similarly reported that seventh grade students’ interest and level of participation increased after using newly developed technology-based modules and receiving instruction from college mentors, connecting the seventh grade girls with women who shared similar backgrounds and chose to study science in college .…”

“…It was reported that this was one of the general chemistry students' favorite laboratories; further the authors felt that the experience motivated the general chemistry students to continue their studies in chemistry. 8 It was similarly reported that seventh grade students' interest and level of participation increased after using newly developed technology-based modules and receiving instruction from college mentors, connecting the seventh grade girls with women who shared similar backgrounds and chose to study science in college. 9 In another mentoring program, high school and middle school students benefited from enriching exposure to polymers and material sciences and, additionally, because they "may not have the opportunity to interact with college students; the exposure to college mentors...may inspire them to pursue college degrees in science and engineering."…”

Introducing NMR to a General Chemistry Audience: A Structural-Based Instrumental Laboratory Relating Lewis Structures, Molecular Models, and 13C NMR Data

“…Over the past 15 years or so, there have been several NMR based experiments/activities suitable for the first year chemistry experience described in the literature. Some focus on the analysis of student prepared samples, some relate NMR data to electronegativity, periodic trends, or pH, , some are multi-week, multi-instrument spectroscopy experiences which involve the use of spectra from known compounds, , and some focus on the identification of unknowns following some pre-lab component (handout or tutorial) where students are introduced to spectral identification prior to the actual laboratory activity. − We believe we have developed a unique cooperative learning hands-on laboratory experience relating information acquired from the 13 C NMR experiment to molecular structure without the use of known compounds, or without prior student knowledge of NMR details and methods of spectroscopic interpretation.…”