The study presented here is a follow-up to a previous report in which we investigated how general-chemistry students in a transformed curriculum reason about simple acid-base reactions. In the present study, we use and adapt the previously developed coding scheme for a longitudinal study in which we follow students from general chemistry through organic chemistry. We find that (i) generally, the manner in which students reason about acid-base reactions increases in sophistication over the course of a two-semester sequence of organic chemistry; (ii) there is little difference in reasoning between students at the end of a transformed general-chemistry course and a similar cohort at the beginning of organic chemistry; (iii) the nature of a student's general-chemistry experience has a profound effect on the sophistication of their reasoning in that students from a transformed general-chemistry course are more likely to provide causal mechanistic explanations for simple acid-base reactions than students with other general-chemistry experiences; and (iv) the type of acid-base reaction that the students discuss impacts the type of reasoning they exhibit. We find that when asked to explain a Lewis acid-base reaction, students are less likely to invoke electrostatic ideas.