7603
The difference of the activities is considered to be due to differences in the flexibility of the carboxylic acid - containing substituent on the diphenylamine skeleton .
 carboxylic acid, diphenylamine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 carboxylic acid, diphenylamine