19521
However , while some general rules have been revealed , a comprehensive understanding of the function played by the attached alkyl chains is still lacking , and current methodology is system - specific in many cases .
 Chemical: alkyl
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: alkyl