This study was conducted to analyze the conceptual understanding of students and their struggle on Polycyclic Aromatic Hydrocarbons (PAHs) compounds topic through the implementation of the RADEC Model. Respondents consisted of 37 students from Chemistry Education Department and 33 students from the Chemistry Department at a university in Bandung, Indonesia. This study is an experimental study with a pre-experimental type. Data on conceptual understanding were obtained through pre-tests and post-tests, while data on students’ difficulties were obtained through survey. The data were analyzed using SPSS 24. It was found that there was an increase in the conceptual understanding of the students of Chemistry Education and Chemistry Department in the medium category with n-gain values of 0.33 and 0.38, respectively. The results of inferential analysis through the Wilcoxon Test with Asymp. Sig. (2-tailed) were <0.05 for the two groups of students indicating differences in the pre-test and post-test results with a higher average post-test score. Friedel-Crafts acylation is a concept that is difficult to understand by students from the Chemistry Education Department and the Chemistry Department with the same percentage of 33%. Chemistry Department students also have difficulty understanding the electrophilic substitution concept with a percentage of 33%. As a practical implication, this study successfully showed the effective implementation of the RADEC model, serving as an innovative and beneficial learning approach. The model offered substantial support to students in grasping complex topic such as PAHs compounds.

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