7531
Moreover , we demonstrate that ET precedes PT in PyCOOH ( 0 ) formation , confirming PyH ( 0 ) ' s pK ( a ) as irrelevant for predicting PT from PyH ( 0 ) to CO ( 2 ) .
 PyCOOH ( 0 ), PyH ( 0 ), PyH ( 0 ), CO ( 2 )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 PyCOOH ( 0 ), PyH ( 0 ), PyH ( 0 ), CO ( 2 )