Thionine sensitized areobic photooxidation of thiourea in acidic medium

doi:10.1007/s11458-011-0235-8

Front Chem Chin

2011, Vol. 6

Issue (2) : 120-126 https://doi.org/10.1007/s11458-011-0235-8

RESEARCH ARTICLE

Thionine sensitized areobic photooxidation of thiourea in acidic medium

Rafia AZMAT(

), Nida SALEEM

Department of Chemistry, Jinnah University for Women, Karachi 74600, Pakistan

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Abstract

An investigation of the thionine sensitized aerobic photooxidation of thiourea was observed spectrophotometrically at a wavelength of 598 nm. Articles reported two types of reactions which generally occur in the presence of oxygen: 1) Singlet oxygen, produced by dye sensitization due to the hydrolysis that reacts with thiourea to form oxidative products like urea and other sulfur-containing fragments and 2) bleaching of dye, which leads to the reduction. The rate of reaction in all studied parameters followed first order kinetics with respect to maximum absorption of the dye in the visible band region. Reaction kinetics was significantly dependent upon the medium and the reaction accelerated more rapidly at low pH. A direct relation was exhibited between the thiourea concentration and dye sensitizer, which was not pragmatic with the concentration of dye. The reaction was effected by the temperature, and the values of energy parameters suggested that the energy of activation was low while the entropy of activation increases with the rise in temperature, which indicated a highly solvated state of intermediate complex. Lower value of ΔBoldItalic* and ΔBoldItalic* at elevated temperature showed that free energy is the driving force for the completion of reaction. A mechanism based on the above findings has been suggested.

Keywords thionine sensitized photo oxidation thiourea singlet oxygen fragment

Corresponding Author(s): AZMAT Rafia,Email:rafiasaeed200@yahoo.com

Issue Date: 05 June 2011

Cite this article:

Nida SALEEM,Rafia AZMAT. Thionine sensitized areobic photooxidation of thiourea in acidic medium[J]. Front Chem Chin, 2011, 6(2): 120-126.

URL:

https://academic.hep.com.cn/fcc/EN/10.1007/s11458-011-0235-8
https://academic.hep.com.cn/fcc/EN/Y2011/V6/I2/120

Fig.1

Fig.2 Spectral changes of thionine at different initial concentrations

Fig.3 A plot of optical density vs. time at different concentrations of dye for thionine – thiourea reduction reaction in acidic medium.

Tab.1 Redox reaction of thionine and thiourea with different concentrations of dye

Tab.2 Redox reaction of thionine and thiourea with different concentrations of reductant

Tab.3 Effect of acid concentration on redox reaction of thionine

Fig.4 Spectral changes of thionine at different initial concentrations of acid

Fig.5 A plot of ln / vs. time for redox reaction of thionine and thiourea

Fig.6

Fig.7

Fig.8

Fig.9

Tab.4 Effect of pH on redox reaction of thiourea and dye

Tab.5 Effect of salt on redox reaction between thiourea and thionine

Tab.6 Effect of temperature on rate of redox reaction and energy parameters

Fig.10

Fig.11

Fig.12

Fig.13

Fig.14

Fig.15 A plot of ln vs. thiourea concentration for thionine – thiourea reduction reaction in acidic medium

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