18562
Structure - activity investigations determined that replacing the fluorines of the difluoromethyl ketone with hydrogens resulted in an inactive analogue .
 Chemical: fluorines; Chemical: difluoromethyl ketone; Chemical: hydrogens
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: fluorines; Chemical: difluoromethyl ketone; Chemical: hydrogens