Acrolein is prepared industrially by oxidation of propene. Likewise, 1-chloropropane and 2-chloropropane give propene. HD-5 is a specification that establishes a maximum concentration of 5% propene in propane. This process starts from "m"-cresol which is alkylated with propene to thymol. MAPD interferes with the catalytic polymerization of propene. Isobutyraldehyde is produced industrially by the hydroformylation of propene. Vinyl acetate is produced similarly, using ethylene in place of propene. The yield of propene is about 85 m%. So acetylene is faster than ethylene, and ethylene is faster than propene, etc. It is a byproduct in the chlorination of propene to make allyl chloride. Propane containing too much propene is not suited for most vehicle fuels. Hydroquinone is prepared by dialkylation of benzene with propene to give 1,4-diisopropylbenzene. Allyl chloride is generally produced directly by the chlorination of propene. The concentration of the propene at the explosion site was abnormally high at 13,000 ppm. It is also used in refrigerant blends with e.g. ammonia, carbon dioxide, butane and propene.