A hexagonal patch is a plane graph in which inner faces have length 6, inner vertices have degree 3, and boundary vertices have degree 2 or 3. We consider the following counting problem: given a sequence of twos and threes, how many hexagonal patches exist with this degree sequence along the outer face? This problem is motivated by the study of benzenoid hydrocarbons and fullerenes in computati...

A method for the calculation of the hyper–Wiener index (WW ) of a benzenoid system B is described, based on its elementary cuts. A pair of elementary cuts partitions the vertices of B into four fragments, possessing nrs , r, s = 1, 2 vertices. WW is equal to the sum of terms of the form n11 n22 + n12 n21 . The applicability of the method is illustrated by deducing a general expression for WW of...

In this paper, the infra-red absorption spectra of a number of crystalline natural estrogens are presented and considered in relation to chemical structure. As a group, the natural estrogens are distinguished chemically from other steroids by the benzenoid structure of Ring A, which gives rise to certain infra-red absorption bands by which their spectra may be differentiated from those of other...

Tessellations of kekulenes and cycloarenes have a lot potential as nanomolecular belts for trapping transporting heavy metal ions chloride because they the best electronic properties pore sizes. The aromaticity, superaromaticity, chirality, novel electrical magnetic class known been subject several experimental theoretical studies. Through topological computations superaromatic structures with ...

In this paper, Kekule structures of benzenoid chains are considered. It has been shown that the coefficients of a B_n (x) Morgan-Voyce polynomial equal to the number of k-matchings (m(G,k)) of a path graph which has N=2n+1 points. Furtermore, two relations are obtained between regularly zig-zag nonbranched catacondensed benzenid chains and Morgan-Voyce polynomials and between regularly zig-zag ...

In 1972 Erich Clar formulated his aromatic π-sextet rule that allows discussing qualitatively the aromatic character of benzenoid species. Now, 40 years later, Clar's aromatic π-sextet rule is still a source of inspiration for many chemists. This simple rule has been validated both experimentally and theoretically. In this review, we select some particular examples to highlight the achievement ...

Hydrodistilled essential oil of the aerial parts of Laggera crispata (Vahl) Hepper & Wood, collected from the Kumaon region of the western Himalayas was analysed by gas chromatography and gas chromatography–mass spectrometry. Eighty constituents, accounting for 83.9 % of the total oil composition, were identified. The oil was mainly dominated by sesquiterpenoids (45.3 %) and benzenoid compounds...