Hello. I apologize for the delay in my response. I have been away.
The sample pages you sent are in UEB. If you are transcribing technical material in UEB, you should not be following the rules in the Braille Code for Chemical Notation -- that resource is an adjunct to the Nemeth Code.
I am not at all an expert in UEB technical. I suggest that you post your question to the UEB Technical thread. Please include an image of the print for this chemical diagram. The best advice can be given when the print is shared.
Thank you for your question. I will learn something when I read the reply.
- Lindy Walton