Beyond Chemistry Knowledge: Embedding Pedagogical Content Knowledge through an AI-Augmented Retrosynthesis Program for Chemistry Education

Abstract Synthetic route planning is a core learning objective in university organic chemistry, yet a challenging one requiring the development of advanced problem-solving skills. Existing computational tools often propose routes beyond the intended curriculum, limiting their suitability as learning resources. In this work, we introduce Retro-Learn, an educational retrosynthesis platform that integrates a curriculum-aligned reaction template library with large language model interfaces. The platform incorporates selected aspects of pedagogical content knowledge by aligning available reactions with the scope and sequence of instruction. An agent skill and a web-based chatbot enable route generation and visualization through natural language interaction. Evaluation using cumulative chapter-specific template libraries showed how the addition of reaction knowledge enables new routes and shorter solutions. Blind assessments of undergraduate examination problems showed higher mean chemical correctness scores than those of database-derived routes and scores comparable to or higher than those of general-purpose language models. Student survey responses indicated a plurality preference for Retro-Learn over general-purpose tools as a synthesis-planning learning aid. These findings illustrate how curriculum-specific chemical informatics and language model interfaces can translate pedagogical considerations into computational support for organic chemistry learning.