Notam hidrocarbura CaHb
m,H=12a/6--> b=2a----> CaH2a===>alchena
derivat monoclorurat al unei alchene se obtine prin substitutie alilica; compusul are formula generala CaH2a-1Cl
masa lui rezulta din densitatea relativa d=M/M,aer
3,13= M/29--> M=90,77g/mol
90,77= 14n-1+35,5---> n=4----> butena
izomeri : 1 butena CH2=CH-CH2-CH2-CH3
2metil 1 propena CH2=CCH3-CH3
2 butena ,cu izomerii cis,trans CH3-CH=CH-CH3