2-Methyl-1,3-pentadiene1118-58-7100 % similar Isoprene78-79-545 % similar Polyisoprene9003-31-045 % similar Methacrolein78-85-343 % similar Methyl propenyl ketone3102-33-836 % similar 3-Penten-2-one625-33-236 % similar