Final answer:
3-ethylhexane is a structural isomer of octane with a base chain of six carbons and an ethyl group as a substituent. Benzene displays a resonance structure and sp2 hybridization due to its ring with alternating double bonds, a conversion enhancing octane levels in gasoline.
Step-by-step explanation:
A structural isomer of octane with a base chain that is six carbons long could be 3-ethylhexane. In order to create an isomer of octane, which has a base chain of eight carbons, we need to shorten the main chain to six carbons and add substituents to make up the total number of eight carbons. The isomer begins with the base name hexane, indicating a six-carbon chain. Positioning an ethyl group (2 carbons) at the third carbon creates 3-ethylhexane. The carbon atoms are numbered from the end nearest the substituent to ensure the substituents have the lowest possible numbers.
Furthermore, for benzene, the molecule contains a six-carbon ring with alternating double bonds, and each carbon atom bonded to one hydrogen atom. The carbons in benzene are sp2 hybridized. The presence of a resonance structure in benzene indicates that its actual structure is a hybrid of multiple Lewis structures, where the double bonds are not fixed but are delocalized around the ring.
In the case of 3C₂H2 being converted to C6H6, we describe the catalytic process where three molecules of acetylene react to form one molecule of benzene, enhancing the octane level in unleaded gasoline. Lewis structures for acetylene would show a triple bond between the two carbon atoms and each carbon bonded to one hydrogen atom. When converting to benzene, these triple bonds are altered to form a ring with alternating double bonds.