A confused student was doing an isomer problem and listed the following six names as different structural isomers of C7H16. a. 1-sec-butylpropane b. 4-methylhexane c. 2-ethylpentane d. 1-ethyl-1-methylbutane e. 3-methylhexane f. 4-ethylpentane How many different structural isomers are actually present in these six names?

In case of heptane (C7H16) the following structural isomers are possible

shown in figure

a. 1-sec-butylpropane : this is actually 3-methyl hexane

b. 4-methylhexane : this is actually 3-methylhexane

c. 2-ethylpentane : this is actually 3-methyl hexane

d. 1-ethyl-1-methylbutane: 3-methylhexane

e. 3-methylhexane: correct IUPAC

f. 4-ethylpentane: This is actually 3-methylhexane

Hence all represent single isomer