2, 2, 4-trimethylpentane ( octane异辛烷) CH3 CH3 H3C—c—CH2-CH—CH3 CH3 Isooctane burns very smoothly without knocking, but heptane Burns to produce much knocking. A mixture of 87% isooctane and 13% heptane would be rated as 87-octane gasoline2,2,4-trimethylpentane (isooctane 异辛烷) H3C C CH3 CH3 CH2 CH CH3 CH3 Isooctane burns very smoothly without knocking, but heptane Burns to produce much knocking. A mixture of 87% isooctane and 13% heptane would be rated as 87-octane gasoline