Yes, it is beneficial to revise the diagrams and structures in UPSC Chemistry Optional subject.

Overview
Revising the diagrams and structures in UPSC Chemistry Optional subject can greatly enhance the understanding and retention of key concepts. It helps in visualizing complex chemical reactions, mechanisms, and molecular structures, making it easier to comprehend and remember.

Enhances Understanding
1. Visual Representation: Diagrams and structures provide a visual representation of chemical reactions, mechanisms, and molecular structures. This helps in understanding the spatial arrangement, bond angles, and interactions between different atoms and molecules.

2. Clarity: Well-drawn diagrams and structures provide a clear and concise representation of complex concepts, making it easier to understand their intricacies. They help in breaking down complex information into simpler components, facilitating better comprehension.

Aids Retention
1. Memory Recall: Visual learning is known to enhance memory recall. Revising diagrams and structures helps in creating strong mental associations between the visual representation and the underlying concepts. This aids in recalling the information during exams or while answering questions.

2. Organization: Diagrams and structures provide a structured and organized way of representing information. This helps in organizing and categorizing knowledge, making it easier to remember and retrieve when needed.

Facilitates Problem Solving
1. Interpretation: Diagrams and structures are crucial for interpreting chemical reactions, mechanisms, and molecular structures. They help in identifying key functional groups, reaction intermediates, and transition states, allowing for a better understanding of the underlying principles and mechanisms.

2. Analysis: Revising diagrams and structures enables students to analyze and predict the outcome of chemical reactions, based on their understanding of the molecular structures and bonding. This is particularly helpful in solving numerical problems that require a deep understanding of the concepts.

Conclusion
Revising the diagrams and structures in UPSC Chemistry Optional subject is highly beneficial as it enhances understanding, aids retention, and facilitates problem-solving. It is essential to practice drawing and interpreting diagrams to develop a strong conceptual understanding of the subject.