The deuterium/hydrogen exchange reaction was performed under iron-catalyzed Fischer-Tropsch reaction conditions using a mixture of deuterated octane, nonane, decane, tridecane, and pentadecane as the probes. The results indicated that deuterium/hydrogen exchange does not occur in alkanes under these conditions. Under the same reaction conditions, 1-octene-d(16) was used as the probe to study the isomerization of l-alkene. The 1-octene-d(16) was reduced to deuterated octane, and isomerized to deuterated trans-2-octene and cis-2-octene with approximately equal amounts of the two isomers. No other internal deuterated octene and C-7 products were obtained. The deuterium/hydrogen exchange reaction occurred in deuterated 1-octene as well as in the products formed from it. The maximum number of deuterium atoms that can be replaced by hydrogen is 5. There is no C8D16 isotopomer of 2-octenes. To account for these experimental facts, a mechanism was proposed for the isomerization of I-alkene under iron-catalyzed Fischer-Tropsch reaction conditions.