The Narumi-Katayama topological indes S of a hydrocarbon is the product of vertex degrees of the respective molecular graph. If PH is a phenylene and HS is its hexagonal squeeze, then the respective Narumi-Katayama indices are related as S(PH) = 9h 1 S(HS), where h is the number of hexagons of PH and HS, or as S(PH) = αS(HS)β. where α = 0.078 and β = 1.613.
- Benzenoid hydrocarbons
- Hexagonal squeeze
- Narumi-Katayama topological index