Fifteen milliliters of gaseous hydrocarbon $C_3{H}_8$ was required for complete combustion 357ml of air (21% oxygen by volume) and gaseous products occupied 327 ml(all volumes measured at STP). When this gaseous hydrocarbon on chlorination with $C{l}_2$in presence of sunlight gives N number of isomeric products and then dichlorination with $C{l}_2$ in presence of sunlight gives M number of isomers including stereo isomers.