Explanatory notes
… - - Propene (propylene) 2901.23 - - Butene (butylene) and isomers thereof 2901.24 - - Buta-1,3-diene and isoprene 2901.29 - - Other Acyclic hydrocarbons are … by alkyl radicals (e.g., methyl, ethyl, propyl); thus isobutane (2-methylpropane, trimethylmethane) has the same …