Volume 25 , Issue 2 , December 2023 , Pages 50-68
Sirwan A. Ahmad 1 ; Mohammad T. Kareem 1
1 Department of Chemistry, College of Science, University of Sulaimani, 46001 Sulaymaniyah, Kurdistan, Iraq
A spectrophotometric method has been established for the reaction kinetics of phenol
oxidative coupling with 4-amino-N, N-dimethylaniline in the presence of potassium
dichromate as an oxidant to form C14H14N2O, known as phenol blue. Optimum
conditions for the reaction were investigated: maximum wavelength (λ max), linear
range, molar absorbtivity, and stability constant. The kinetic models were applied to
the reaction, indicating that it is a first-order reaction. The activation energy (Ea) and
Arrhenius constant (A) were calculated from the Arrhenius equation as 14.89
kJ·mol−1
and 3.75 × 105
s
-1 respectively. Thermodynamic parameters were ΔH*
12.37 Kj·mol−1
, ΔG* 5.47 kJ·mol−1
and ΔS* 22.77 J·mol−1
·K−1
at 30oC.. Results
indicate that the formation of the product phenol blue is non-spontaneous and
endothermic in nature. Density function theory (DFT) has been done for the
comparison between experimental and theoretical results using the common 6-
311G(d,p) basis set. The results are in good agreement with each other, proving the
reliability of the method.Finally,some preliminary test has been performed to check
possibility of the product as dye.