7557
Values of - ( 376 . 2 +/- 2 . 6 ) , - ( 355 . 9 +/- 3 . 0 ) , and - ( 381 . 7 +/- 2 . 8 ) kJ . mol ( - 1 ) for the gas - phase enthalpies of formation at T = 298 . 15 K of 5 , 6 - dimethyluracil , 1 , 3 , 5 - trimethyluracil , and 1 , 3 , 5 , 6 - tetramethyluracil , respectively , were obtained from the experimental thermochemical study .
 5 , 6 - dimethyluracil, 1 , 3 , 5 - trimethyluracil, 1 , 3 , 5 , 6 - tetramethyluracil
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 5 , 6 - dimethyluracil, 1 , 3 , 5 - trimethyluracil, 1 , 3 , 5 , 6 - tetramethyluracil