21182
Biological results demonstrated that the introduction of a fluorine atom at the ortho position of the 9 - benzyl group generally enhanced affinity toward A1 subtype and did not significantly affect A2A and A3 affinity .
 Chemical: fluorine; Chemical: 9 - benzyl
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: fluorine; Chemical: 9 - benzyl