12377
A structure - activity relationship was established : Antiviral activity versus VACV was highest with an ether side chain with an optimum of n - C ( 9 ) H ( 18 ) - O - n - C ( 5 ) H ( 11 ) .
 ether, n - C ( 9 ) H ( 18 ) - O - n - C ( 5 ) H ( 11 )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 ether, n - C ( 9 ) H ( 18 ) - O - n - C ( 5 ) H ( 11 )