Supporting students in building well-grounded explanations plays a crucial role in scientific practice. Research in organic chemistry education on students' mechanistic explanations, however, has revealed various challenges. When solving mechanistic tasks, students experience difficulties when (I) deriving implicit properties from structural formulas, (II) inferring the influence of these properties on the reaction process, (III) comparing and weighing multiple variables,(IV) using structural properties to make a claim, and (V) linking a structural consideration to energetic considerations. Reasoning steps, namely, (I) and (II), can be considered essential for mechanistic explanations, whereas the other steps depend on the task format. One way of supporting learners in these reasoning steps is to provide an instructional explanation that in a guided manner models these steps in tutorial videos. In this study, the design of tutorial videos on substitution reactions, which addresses known students' challenges, is reported. The tutorial videos were put to test in a qualitative pre/post-interview study with students of an undergraduate organic chemistry course (N = 12). While tutorial videos are widely used, little is known about the impact of explicitly designed instructional explanations in videos on students' ability to build mechanistic explanations. Hence, the findings of this study aim to contribute to the growing area of mechanistic reasoning by analyzing how students alter their mechanistic explanations after watching explicitly designed tutorial videos. Differentiated content analysis reveals that students adapt different aspects outlined in the tutorial videos. Overall, students infer more structural properties and use these to make a claim after watching the videos. However, linking this claim to the energetics of a reaction seems to remain challenging. Recommendations for the use in teaching as well as further development possibilities of the videos are presented.