How many letters does the top answer for “any of three isomeric hydrocarbons c4h8; all used in making synthetic rubbers” have?

The most common answer is butene (6 letters).

Crossword clue: any of three isomeric hydrocarbons c4h8; all used in making synthetic rubbers

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

butene 6 letters wn-def

any of three isomeric hydrocarbons C4H8; all used in making synthetic rubbers

butylene 8 letters wn-def

any of three isomeric hydrocarbons C4H8; all used in making synthetic rubbers