Adapting NMR for the Modern Classroom Laboratory Class

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Godson C. Nwokogu, a Professor of Chemistry and Biochemistry at Hampton University, discusses the changing environment of the laboratory classroom.

Prof. Nwokogu at his desk
Prof. Nwokogu at his desk

With many years of experience overseeing and instructing laboratory classrooms, it is safe to say that Prof. Nwokogu knows the secret to preparing students for the next steps on their academic pursuits. For over 30 years Prof. Nwokogu has taught and undertaken research at the university. He also trains users on the use of NMR.

Below is a summary of an interview with Prof. Nwokogu.

Changes in undergraduate programs in recent years, facilitated through NMR

Turner Hall
Turner Hall, location of the Chemistry Department and the 400 MHz NMR

The Hampton University Chemistry Department has a JEOL 400 MHz NMR, purchased in 2008, through a grant from the National Science Foundation. It is primarily used for undergraduate organic chemistry laboratory studies as modern chemistry degree programs require the use of high-field NMR for laboratory exercises. With the acquisition of this new NMR, 2nd semester laboratory classes at Hampton University regularly use the 400 MHz NMR. Specifically, undergraduate laboratory classes are adopting a new way of learning. Here Prof. Nwokogu describes in more detail how, “we have been moving away from recipe type laboratory activities towards more project based activities”.

For example, whereas formerly students would be given an unknown organic compound and then asked to figure out what it is through the application of different spectroscopic and other analysis methods, instead, in the current laboratory practices, students are provided information to synthesize a compound in a 2-3 step scheme and then try to figure out what they have obtained using analytical methods.

Students and Instructors
Prof. Nwokogu with his students

Here NMR plays an important role. Instead of taking too much time with distillation or recrystallization methods, students can with minimal work-up directly analyze the product obtained from synthesis using a high-field 400MHz NMR, which takes only 5 minutes to run the sample. If only Mass Spectroscopy was available, or a low-field NMR, purification steps would be needed that would force an exercise to run over multiple lab periods. This newer more synthetic based laboratory practice is more enjoyable for students and heightens their curiosity.

Electrophilic Aromatic Nitration of Alkylbenzenes

Recently, Prof. Nwokogu and co-authors, Michelle Waddell, Charles Bump, and Edmund Ndip have published a paper illustrating a specific example of the use of NMR being more favorable and accurate over mass spectrometry for quantitative analysis when determining the p/o-isomer product ratios after electrophilic aromatic nitration of Alkylbenzenes.1

The paper describes how the use of recrystallization, trituration, or distillation would lead to a change in the p/o-isomer product ratio after synthesis of the nitrated alkylbenzene. (The alkylbenzenes are nitrated through a traditional mixed acid nitration reaction.) With NMR, the crude mixture can be immediately analyzed and the results used for calculating the isomeric ratio.

The results obtained correlate well with previously reported results using other methods. This new method from the paper gives detailed instructions which can be used by other instructors for their laboratory programs.

Classroom Lecturer and Research Scientist

Setting a sample up in the Carousel
Setting a sample up in the Carousel

Prof. Nwokogu originally hails from Nigeria, which he describes as the most populous and one of the largest countries in Africa. After graduating from high school in Nigeria he was awarded a scholarship by the Government of Bulgaria to study chemical technology at the Higher Institute for Chemical Technology of Sofia State University in Sofia, Bulgaria. Thereafter, he came to the United States to undertake his PhD studies in organic chemistry at Michigan State University. After some post-doctoral positions at the Ohio State University and University of Maine at Orono, he was at Virginia Tech when he received his appointment at Hampton University in 1988. Since then he has been teaching organic chemistry for undergraduates and also advanced organic chemistry for those who are undertaking a Masters in Chemistry at Hampton University, along with doing extensive advanced research in the field of organic synthesis.

Hands-on teaching

All students taking the lab course learn to use the 400 MHz NMR for both 1H and 13C analysis. The Delta application includes an automated protocol for the battery of experiments including DEPT, COSY and HETCOR which complement the basic spectroscopic data required for identifying and confirming chemical structures at this level. Prof. Nwokogu says “the Delta software used for JEOL NMR instruments is very easy for students to use”. With so many students needing to be taught how to use the NMR, this makes the job of teaching NMR spectroscopy much easier.

New methods for the laboratory classes are also extensively vetted by a team of instructors to ensure that students will undertake exercises that will be completed in the allotted time. Most students in these organic chemistry laboratory classes are often pre-med and biology majors, that are planning on applying to medical schools and as such, take organic chemistry in their sophomore or junior year. For those who are not biology or pre-med majors, Hampton University offers degrees in chemistry and biochemistry; a concentration in forensic chemistry is also available. In recent years, Hampton University students have graduated to go on to PhD programs in organic chemistry, biochemistry, neuroscience, and toxicology.

Prof. Nwokogu also describes how he has learned other newer ways to increase the pace of the laboratory classes while maintaining and enhancing the quality of the student experience. He describes how some older reactions generate too much waste, therefore the use of microwave heating can be quicker and also give cleaner results.

Despite all this hands-on teaching, Prof. Nwokogu also has time for more advanced research, he is currently working on new synthetic schemes for compounds that may be medically significant such as derivatives of resveratrol that will be more soluble in non-aqueous media.  He is also researching dipolar materials with optimized anisotropic properties for electronic use.

Authors
Laboratory team and co-authors
Left to right: Edmund Ndip, Michelle Waddell, Prof. Nwokogu
  1. Determination of the p/o-Isomer Product Ratios in Electrophilic Aromatic Nitration of Alkylbenzenes Using High Resolution 1H NMR Spectroscopy. Waddell M. K., Bump C. M., Ndip E. M., Godson C. Nwokogu G. C. World J. Chem. Educ. 2019, 7 (3), 216-224.

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