Research on the standard enthalpies of formation of alkyl derivatives based on molecular connectivity index of atomic ordinal number

Atomic ordinal number (f(i)), which is coloured for non-carbon atom in, molecular topological graph, appears solity for every non-hydrogen atom in molecule. A novel connectivity index ((m) F) based on the adjacency matric and f(i) is proposed in this paper. F-1 among F-m has excellent selectivity for alkanes and its derivatives. Satisfactory linear and curve equations between F-1 and - Delta(f)H(m)(theta) of 42 alkyl derivatives (such as F, Cl, Br, I, OH, NH2, and SH) are developed as follows: - Delta(f)H(m)(theta) = - 131.98 + 101.76 F-1, r = 0.9884; - Delta(f)H(m)(theta) = - 24.55 + 27.34 F-1(1.75), r = 0.9956. Their correlativities are all even more ideal than that in the reported literature which r is equal to 0.2930.