NOPR Collection:

On the structure-dependence of the largest eigenvalue of the distance matrix of an alkane

1998-07-01T00:00:00Z

Title: On the structure-dependence of the largest eigenvalue of the distance matrix of an alkane Authors: Gutman, Ivan; Medeleanu, Mihai Abstract: The distance matrix of an alkane has a unique positive eigenvalue A., which has recently been applied as a topological index and used for ordering alkane isomers with respect to their branching and for calculating their boiling points. We have now determined the main structural features of the alkane molecule, on which A depends. These are the number of vertices of the molecular graph (n) and the sum of the squares of the distances between all pairs of vertices (S). A good linear correlation between Ʌ and (nS)^1/2 is shown to exist. Lower and upper bounds of Ʌ are deduced, both depending solely on n and S. Because S = 2 WW - W, there exists a connection between A, the Wiener index (W) and the hyper- Wiener index (WW). Page(s): 569-573

New topological matrices and their polynomials

1998-07-01T00:00:00Z

Title: New topological matrices and their polynomials Authors: Ivanciuc, Ovidiu; Diudea, Mircea V.; Khadikar, Padmakar V. Abstract: New polynomials and molecular graph spectra are derived on the basis of recently proposed matrices, D_A, D_P, and RD_P, and of the previously defined RD_e (reciprocal distance) matrix. The new molecular graph descriptors are exemplified on a collection of path-graphs L_2-L₅ and cyclic-graphs C_3-C₃•. The polynomials for the last two matrices (both based on a reciprocal relationship) are the first defined polynomials with non-integer coefficients. The sum of their absolute values, denoted as SumCh(RD_e) and SumCh(RD_p) can be viewed as global descriptors (i.e. topological indices), by analogy with the Hosoya's number Z. Values of the two indices as well as the minimum, MinSp(M), and maximum, MaxSp(M), eigenvalues are listed for nonane isomers. The new structural descriptors have been tested for correlation with some physico-chemical properties and are found to give good results in modeling the properties of alkanes. Page(s): 574-585

Topological investigations of molecular interactions in binary mixtures containing methylene bromide

1998-07-01T00:00:00Z

Title: Topological investigations of molecular interactions in binary mixtures containing methylene bromide Authors: Sharma, V.K.; Singh, Jaibir; Singh, Bhup Abstract: Molar excess volumes and molar excess enthalpies of methylene bromide(i)+ cyclohexane (j) and methylene bromide(i) + m-nitrotoluene(j) mixtures have been determined diiatometrically andcalorimetrically as a function of composition at 308.15 K. The analysis of V^E data by graph-theoretical approach reveals that methylene bromide + m-nitrotoluene mixture is characterised by interactions between the delocalised p - electron cloud over nitrogen and oxygen atoms of nitro group in m-nitrotoluene and vacant 3d orbitals of bromine atom in methylene bromide. IR studies lend additional support to the nature and extent of interactions for the proposed structure in the mixture. The observed data have also been analysed in terms of Sanchez and Lacombe's theory [J phys Chem, 80(1976)2352; 80(1976)2568]. Page(s): 586-591

Kinetics and mechanism of reaction of sulphur(lV) with pyruvate (pentaammine) cobalt(III).

1998-07-01T00:00:00Z

Title: Kinetics and mechanism of reaction of sulphur(lV) with pyruvate (pentaammine) cobalt(III). Authors: Dash, Anadi C; Patnaik, Ajay K; Das, Nigamananda Abstract: The reaction of S(lV) with pyruvato(pentaamrnine)cobalt(III) has been studied in the range of pH (3.2 - 6.5) and temperatures (15 - 30°C). There is no evidence of substitution of bound carboxylate by sulphite. However, the keto form of the pyruvato complex reacts with HSO₃- and SO₃^2-yielding the S(IV) addition product, (NH₃)₅CoO₂CC(SO₃)(OH)CH₃. The rate constants and activation parameters for both HSO_3- and SO₃ ^2- reaction paths are reported. The pyruvato complex and also its sulphite addition product do not undergo reduction of cobalt(III) centre by sulphite. Page(s): 592-595