Our goal as scientists is to help students make sense of the world by building on their prior knowledge and engaging with what they already understand. Undergraduate students bring with them a whole host of experiences from their prior educations and their prior experiences in the world. To be successful in their coursework and in future courses, students must make connections between their knowledge and the core ideas of a discipline. These connections are necessary for students to be successful in many of their courses as they move from a novice with disconnected understanding to a more integrated expert like understanding. Undergraduate organic chemistry is one such course and is often a prerequisite to many courses that are required for pre professional schools, such as medical and veterinary school. However, previous research shows that students often rely on surface level features and memorization to be successful in organic chemistry. In particular, prior research has found that students struggle with using mechanistic arrows, a tool used to predict the movement of electrons and predict reaction mechanisms. My work seeks to characterize and understand better ways to support students learning mechanistic arrows in organic chemistry.This dissertation focuses on how students use mechanistic arrows in both familiar and unfamiliar reactions. This work was situated within a transformed organic chemistry course that emphasizes students constructing explanations and developing and using models and explicitly making connections to structure property relationships and electrostatic and . However, students can take many combinations of courses throughout their time as undergraduates, and I explored how these different course types and backgrounds affected how students draw mechanistic arrows for both familiar and unfamiliar reactions.The studies in this dissertation used both quantitative and qualitative techniques to examine students use and understanding of reaction mechanisms. Student participants were sampled from both the two-semester transformed organic curriculum and a course that has not undergone a transformation, referred to in this dissertation as a traditional curriculum. By sampling students multiple times throughout both semesters and both course types, this allowed me to investigate the effect various course types and combinations had on students' responses.Findings suggest that students who took two semesters of the transformed course use their arrows to predict a plausible product more frequently that traditional students do for both a familiar and unfamiliar reaction. Furthermore, when exploring the different course combinations students take for organic chemistry, I found that students' ability to draw arrows varies depending on their organic chemistry course background. Students who most recently took the transformed curriculum were better able to make plausible predictions with their mechanistic arrows than the traditional students. While students who had the transformed curriculum for the first semester and switched to the traditional curriculum for the second semester did not draw plausible mechanisms as frequently as students who took the transformed curriculum for both semesters. This emphasizes the importance of consistent course environments that support students' engagement with the core ideas of a discipline. Additionally, I describe the process of developing a task designed to elicit students' explanations and understandings of an unfamiliar intramolecular reaction. Implications of this work on instructional coherence and future directions will be discussed.
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