Lignin selective dyes: quantum-mechanical study of their characteristics

Abstract

The mechanism of dye-bonding to the lignin component of the fibre was checked using the quantum-mechanical and crystallographic approach. The calculated data support the conclusion that for the selectivity of cationic dyes for lignin, a high partial negative charge on accessible substituents on the periphery of the molecule is the most important, but not an exclusive factor. Besides the delocalized positive charge, what is also important for the interaction of a dye with hemicellulose, is the dye's ability to be involved in hydrogen bonds, whereas for the interaction with lignin also its ability of stacking to it.

Vertex Degree Weighted Path Indices

“…If we present the path indices 1,2 in the way used to derive a variety of indices from the Universal matrix U(a, b, c), 9,11 we see that they can be presented in the following way: …”

“…To assess where approximately are positioned the maxima in absolute values of correlation coefficient R in the space of exponents a, b, ..., a multidimensional grid of values of exponents was applied in the way presented earlier 9,11 and the values of correlation coefficients at those combinations of exponent values were derived. The exponent values -5, -4, -3, -2, -1, -0.5, -0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3, 0.5, 1, 2, 3, 4, and 5 were chosen as the grid points in all dimensions of exponents.…”

“…in 0.231, improves the value of the fifth or higher decimal of the correlation coefficient. 9 For our purpose, in the first step of assessment, three decimals in the correlation coefficient are sufficient, therefore in our first step we use onedigit grid values of exponents. For optimization, five decimals in the value of the correlation coefficient are considered sufficient, therefore only two digits in the value of exponents a, b, ... are needed.…”

“…In a private discussion about topological indices, Prof. M. Randi} suggested to study the path indices in a similar way as there were studied the indices derived from the Universal matrix U(a, b, c), 9 and there should be tested also the combinations of them. The results of this approach are presented below.…”

Topological indices are not necessarily invariant to graph labeling

“…[1][2][3][4][5][6][7] However, on inclusion of vertex-degree vertex-distance weighted indices, [8][9][10][11][12][13][14] especially with variation of value of exponents on vertex degrees and vertex distances, [11][12][13][14] there appear situations, where some combinations of exponents give rise to invariance to molecular labeling, whereas other combinations do not. Some of the latter ones give rise to better correlations with physicochemical properties of alkanes in general or of octanes in particular.…”