A three-carbon alkane, which is unlucky enough to have a name which does not specify how many carbons it has (like hexane or nonane do).
Confuses orgo students.
Formula is C3H8.
Pyromaniacs are fond of this stuff.
And again, confuses orgo students. A lot.
OWL: "Draw a structural formula for cis-1,2-diethylcyclopropane"
Orgo student: "Huh? WTF???!"
OWL: "Both I and Marvin Sketch despise you equally, and a lot."
Orgo student: *cries* "Whyyyy?...."