Study of Oxidative Degradation of Anthranilic Acid by Di-tertiary Butyl Chromate

 

Renuka Thakur1, Rajeev Ranjan2*

1PG Department of Chemistry, Ranchi Women’s College, Ranchi-834001

2PG Department of Chemistry, Ranchi College, Ranchi-834008

*Corresponding Author E-mail: rajeevran7@yahoo.com

 

ABSTRACT:

Di-tertiary butyl chromate has been used to oxidize anthranilic acid in different molar proportions and the solid products obtained have been isolated and analyzed. Elemental analysis, IR and thermal studies have been carried out. Results of thermogravimetric analysis have been used to ascertain the proposed composition. Characterization of these complexes helps in ascertaining the products formed by the oxidation of anthranilic acid.

 

KEYWORDS: TBC, DTA, TLC, TGA,TBA.

 

 


INTRODUCTION:

A number of Cr(VI) based oxidants are being used to carry out oxidation of a wide variety of organic substrates.1-9  Important among these are di-tertiary butyl chromate, di-isopropyl chromate, chromium peroxide etherate, pyridine chromium peroxide and 2,2-bipyridyl chromium peroxide. But due to various merits di-tertiary butyl chromate (TBC) has got an edge over other Cr (VI) based oxidants and therefore it is not only used to carry out oxidation but also for complex formation with advantage of the associated degradation during the process.10-23 The thermal-decomposition pattern, mechanism of decomposition and evaluation of kinetic parameters of complexes were reported in this paper. The simultaneous TG/DTA curves of the complexes were recorded. Thermal analysis involves linear heating of the complexes. On increasing the temperature there are various chemical and physical changes at definite temperature range.

The physical and chemical changes were associated with the change in mass and the change of heat.

 

MATERIAL AND METHODS:

A molar solution of tertiary butyl chromate (TBC) was prepared by dissolving 1 gm of dry CrO2 in 1.5 ml of tertiary butyl alcohol (TBA). This clear brown solution of the TBC was added to the anthranilic acid dissolved in minimum volume of dioxan in different substrate and oxidant ratio with constant stirring. The solid products RBB1, RBB2 and RBB3 were isolated. The obtained solid products were washed several times with dioxan, benzene and finally with acetone. Purification of these compounds ware done by TLC. Thermogravimetric analysis has been done by NETZSCH Thermal Analysis STA 409. Elemental analysis, IR and thermogravimetric analysis of these products have been carried out. On elemental and spectral analysis of these products, RBB1, RBB2 and RBB3 were identified as complexes of chromium involving the products of oxidation as ligands (Table-1). The results have been supported by the thermal analysis, TG and DTA. The weight loss and corresponding heat changes confirms the expected sequence of reaction on heating.

 

DISCUSSION:

The products depend on strength of the oxidant.

 

 

Above mentioned compounds have been analysed thermogravimetrically for the evaluation of their decomposition kinetic parameters and thermal decomposition mechanism by NETZSCH Simultaneous Thermal Analyser STA 409. These complexes decomposed in two or three steps involving elimination of water, forming acid etc. The regular decomposition of RBB1 started at 100°C. First step involves loss of three molecules of water at 100°C, second step involves loss of one molecule of formic acid at 278°C and the third step involves  loss of rest whole unit leaving behind CrO at 300°C (table-2, fig-1).

 

In the complex RBB2 the decomposition started at 110°C. First step involves loss of one molecule of HCOO- at 120°C and second step involves loss of one molecule of water at 240°C. The third step involves the loss of whole unit leaving behind 2CrO residue at 800oC. The DTA curve in the thermal analyzer shows two distinct exothermic peaks, one major at 160oC due to the loss of HCOO- and the other major at about 240oC due to loss of one molecule of water (table-3, fig-2).

 

In the complexes RBB3 the DTA curve show one distinct exothermic peak. This peak appears near 3400C. At this temperature the whole unit starts breaking.

 

Chromium takes five oxygen atoms from heating atmosphere. At 740°C the above mentioned unit was lost leaving behind CrO5 (table-4).


 

 

 

Thermal analysis report of RBB1:

The thermal analysis report of RBB1 shows the proposed formulation. The percentage of the substance left after experiment, corresponds to the theoretical percentage of the residue and support the presence of CrO as residue. The presence of CrO, support the proposed formula.

 

Thermal analysis report of RBB2 :

The thermal analysis of RRB2 shows the proposed formulation. The percentage of substance left after experiment, corresponds to the theoretical percentage of the residue and support the presence of 2CrO as the residue. The presence of 2CrO, support the proposed formula.

 

DTA/TG Graph of RBB1

Fig-1

 

 

DTA/TG Graph of RBB2

Fig-2

 


Thermal analysis report of RBB3:

In the complex RBB3 the DTA curve show one distinct exothermic peak. This peak appears near 340°C. At this temperature the whole unit was starting breaking. Chromium takes five oxygen atoms from heating atmosphere forming CrO5. At 740oC the whole unit was lost leaving behind CrO5 (table-4).

 

RESULTS :

From the result of thermal analysis the total theoretical loss percentage corresponds to the total experimental loss percentage in the proposed formula of the complex. Hence the thermal of RBB3 show the proposed formulation. The presence of coordinated water in some complexes were indicated by broad band in the region 3500-3200 cm-1.24-25 A number of polynuclear complexes of Cr have been reported previously with carboxylate anion with many different framework.26-28

 

ACKNOWLEDGEMENT :

We are thankful to the Head, CIF, BIT Mesra, Ranchi, for providing IR Spectra and elemental analysis. We are also thankful to the Director, RDCIS, SAIL, Ranchi, for DTA/TG analysis.

 

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Received on 10.11.2015         Modified on 11.12.2015

Accepted on 18.12.2015         © AJRC All right reserved

Asian J. Research Chem. 8(12): December 2015; Page 721-725

DOI: 10.5958/0974-4150.2015.00116.9