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Kinetic and Calorimetric Studies of Reactive Dye Hydrolysis and Alcoholysis Reactions
Author(s) -
Iyer S. R. Sivaraja,
Ramaseshan G.,
Chourishi N. K.
Publication year - 1981
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1981.tb03592.x
Subject(s) - chemistry , hydrolysis , enthalpy , methanol , exothermic reaction , sorbitol , reactivity (psychology) , reaction rate constant , alcohol , tetramethylurea , solvent , reaction rate , organic chemistry , nuclear chemistry , kinetics , catalysis , thermodynamics , physics , quantum mechanics , medicine , alternative medicine , pathology
Kinetic and calorimetric studies have been carried out to determine rate constants and enthalpy changes for the hydrolysis and alcoholysis reactions as a function of pH, for some reactive dyes at a given temperature, in the temperature range 25–35°C. The alcoholysis reactions were carried out in homogeneous media using glucose, sorbitol, methanol, r–propyl alcohol and ho–propyl alcohol respectively. The calorimetric data have been obtained using a sensitive rating–period calorimeter. The results indicate that, irrespective of whether the rate constants k“–or k”AO–are independent of pH or not, the heat of hydrolysis HH which is exothermic, increases with pH, whereas the heat of alcoholysis HA which is also exothermic, decreases with increase in pH for glucose and sorbitol for all the dyes studied. For the reaction with methanol, on the other hand, while k“AO– decreases with increase in pH, HA increases for the two dyes studied, namely, Procion Brilliant Red MX–2B (ICI) and Procion Red MX–G (ICI). The HA values, using n–propyl and iso–propyl alcohol, indicate that the interaction of these reactive dyes with secondary alcohol groups leads to a lowering of HA. Studies on HH in buffered and unbuffered solutions of the dyes indicate that the presence of buffer decreases the heat of hydrolysis. Taking into cons/deration both the kinetic and thermodynamic data, it is suggested that, for the hydrolysis reaction, the changes in reactivity and heat of reaction with pH are Influenced by the changes in the solvent environment at different pH values. In the case of alcoholysis reactions using glucose and sorbitol, the decrease in HA with increase in pH could be attributed to an Increase in the interaction of the dye with secondary alcohol groups. Other factors which could influence the heats of such reactions are steric factors associated with the dye and carbohydrate molecule, changes in the structure of water around these molecules and changes in activity coefficients.