I was drawn to Joel Karty’s textbook because of its innovative mechanistic organization.  I remembered my own undergraduate experience and the power that mechanisms held in the learning process to illuminate the reasoning behind the overwhelming number of transformations and seemingly random sets of reagents.  Now, most of all, I want my students to see that the underlying reactivity follows the same basic rules and that the complexity of organic chemistry becomes simplified and interconnected when considering the mechanisms.

Better understanding with less memorization was my goal.  Better retention was the byproduct.

It makes sense – if the nine common mechanistic steps presented in Chapter 7 describe the reactivity presented in the majority of the textbook, students must constantly reinforce earlier concepts when learning new material.  These connections mean students don’t need to start fresh at the beginning of each chapter.  Instead, they continue to build a more thorough network of applications of basic principles.  At the end of the two-semester course sequence, early chapters aren’t easily forgotten because the material has never truly been left behind.

Still, I was shocked to see how this change in textbook from functional group organization to mechanistic organization played out on the standardized ACS exam in organic chemistry that serves as the final exam in my second semester course.  The words “cumulative exam” have always been intimidating for students, even more so when the material can come from two courses.  It is nearly impossible to re-learn everything from both semesters, so retention of concepts is the key to success.  I have used the statistics released by ACS Exams to analyze student performance relative to the national percentile since I began teaching.  There is one caveat: I allow students to use the full 3 hours allotted by the college for final exam periods rather than the recommended 110 minutes, so the numbers presented here cannot be directly compared to national performance.  However, the details of year-to-year performance in my classroom are in Table 1 and can easily be compared in graph below.

Graph1

Graph2

In analyzing the data, there are several important factors to note.  This span includes three ACS exams: the 2008, 2012, and 2016 versions. Precautions are taken to prevent information from passing on to future students, and the change from the 2008 to 2012 and then to 2016 exam did not correlate with a significant change in the distribution of scores, nor did using the same exam two years in a row.  The class size remained consistent, college admissions standards didn’t change, and I will admit that my teaching didn’t vastly improve between my third and fourth year on the job.

The factor that did change?  In the fall of 2014, I started using Joel’s textbook and the mechanistic organization.  Ever since this change, more students are achieving scores that correspond to the top 90-100th percentile using ACS norms.  On top of that, the middle two quartiles in the class are elevated.  As the graph shows, 80% of the students in my course are consistently scoring in the 70th percentile or above.  While there are still a small number of students that are scoring below average, which is to be expected in a difficult course, this change in organization seems to benefit the whole class, not just the brightest students.

Interestingly, the grade distribution in the first semester course over these years has been consistent, as well as the first-semester performance level of the student population that continues from Organic I to Organic II.  In my experience, students still struggle in the first semester to learn the language of organic chemistry.  But their performance in the second semester improves significantly when they understand through mechanisms rather than memorizing categories of functional group reactivity.  Once the mechanistic reasoning foundation is laid, new information can be incorporated within a student’s existing understanding, the mountain of possible reagents becomes easier to navigate, and retention improves.

-Laura Wysocki, Wabash College

Click here to learn more about Dr. Wysocki.

Photo credit: VGstockstudio/Shutterstock

3 thoughts on “By the Numbers: Teaching the Mechanism and the ACS Exam

  1. GOALS! I’ve seen improvement too, but not to this amazing degree! Congrats to you and your students, and Joel for the great tool.

    1. Thanks Beth! I’m wondering if you, too, might have a story to share? If so, please don’t hesitate to email me.

    2. Thank you! The students certainly put in the hard work to get there, but year after year the mechanistic organization continues to support their efforts. I’m glad you’ve seen improvement too!

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