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Spectrophotometric Study on Kinetics of Solvatochromism of Methyl Violet in Aqueous Methanol
Author(s) -
Saeed Rehana,
Ashfaq Maria
Publication year - 2010
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201090167
Subject(s) - chemistry , solvatochromism , bathochromic shift , methanol , gibbs free energy , enthalpy , activation energy , iodide , kinetics , entropy of activation , aqueous solution , solvent , inorganic chemistry , methyl violet , photochemistry , reaction rate constant , organic chemistry , fluorescence , thermodynamics , physics , quantum mechanics
The kinetics of the reaction of methyl violet with iodide in aqueous methanol system was studied by spectrophotometric method. The rate of reaction of methyl violet in different alcoholic composition in presence of potassium iodide was observed at pH 4 and 6 at various temperatures (298–318 K). Solvatochromic effect was studied in different percentages of methanol (0–50%). Bathochromic shift was observed with the decrease in polarity of solvent. The color change was attributed to molecule's structure, the delocalization of unit electrical charge causes deepening of color and decrease of delocalization causes fading of color due to reduction of dye. Increase in the rate of reaction was observed with increase in alcoholic content and also affected by potassium iodide salt and increased with increase in concentration of potassium iodide. Energy of activation ( E a ) and transition energy ( E T ) were calculated with the help of kinetic data. Thermodynamic parameters such as enthalpy change of activation (Δ H *), Gibbs free energy change of activation (Δ G *) and entropy change of activation (Δ S *) were evaluated as a function of concentration of solvent and salt.