24034
The experimental and theoretical results strongly suggest that , at moderate temperatures , aromatic ring formation from chlorinated ethylenes normally follows a Diels - Alder coupling of C4 and C2 molecular units followed by internal shifts ; the one exception is the C4Cl4 + C2Cl2 system , where steric factors lead to the formation of non - aromatic products .
 Chemical: chlorinated ethylenes; Chemical: C4; Chemical: C2; Chemical: C4Cl4; Chemical: C2Cl2
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: chlorinated ethylenes; Chemical: C4; Chemical: C2; Chemical: C4Cl4; Chemical: C2Cl2