Which one of the following hydrocarbon does not show positional isomerism and has three chain isomers ?
Alkanes show only one type of structural isomerism which is chain isomerism ;
Number of structural isomers (all chain isomers) :
C4H10 — 2 ; C5H12 — 3 ; C6H14 — 5 ; C7H16 — 9 ; C8H18 — 18 ; C9H20 — 35 ; C10H22 — 75 ;
C5H12 ---- n-pentane , isopentane and neopentane ;