Study of the oxidation of Salicylic acid by CrO3 (VI)

 

M. Alam*, A . Prameela

Department of Chemistry, Ranchi University, Ranchi,  Jharkhand

*Corresponding Author E-mail:

 

ABSTRACT:

Oxidation of Salicylic acid (in solvent t–butyl alcohol) was carried out by chromium trioxide, i.e. Cr (VI) in solvent t-butyl alcohol and using different (substrate: oxidant) molar ratios. Solid product, with oxidized fragments are obtained in the form of chromium complexes. During the process of oxidation, ligands were obtained in the process itself. After purification , the formulae of these complexes were studied and analyzed.

 

KEYWORDS: Salicylic acid , TBC.

 

 

INTRODUCTION:

The use of  a number of oxidants  in non aqueous medium in recent years has given us the potential to use the process of degradation as a method of preparing complexes of defined structures  and  properties1-3.  To carry out such oxidative degradation and result in complexation, some of the workers have used oxidants like pyridine chromium peroxide, di-tertiary butyl chromate, di-isopropyl chromate etc.  Among the various  Cr (VI) based oxidants CrO3 appears to be the most suitable one, as others suffer from a no. of disadvantages viz. thermal stability, hygroscopic nature, large excess requirements, poor selectivity; non effectiveness for acid sensitive substrates etc. M. Alam, et al4. have prepared complexes of chromium with various organic substrates and TBC in different solvents. Some mixed ligand complexes of chromium had been prepared by the interaction of CrO3 with lactic acid and hydrazine hydrate by G. Mishra, M. Alam and coworkers5.

 

OBJECTIVE:

In the present work , action of CrO3 on salicylic acid has been studied by employing different reaction conditions , as mentioned in the abstract with following objectives:

a)    Whether the process of oxidation is selective; will arresting the reaction up to different stages (by taking different molar ratios) result into same product or not?

b)   Whether any change in medium affects the reaction?

 

EXPERIMENTAL:

1.    In each case, CrO3 (oxidant) was dissolved in suitable medium of t- butyl alcohol .

2.    Substrate (Salicylic acid) was dissolved in t-butyl alcohol.

3.    These two solutions were mixed together, stirred, refluxed and each case solid products separated out.

4.    Solid products isolated were washed with acetone for four to five times respectively.

5.    Pure solid products obtained were then subjected  to  Elemental and IR Analysis.

6.    Empirical formulae of the products were determined .

7.    Thermal analysis was carried out and TG, DTA peaks were recorded.

8.    Finally possible molecular formulations of the complexes were proposed.

 

RESULTS AND DISCUSSION

On the basis of quantitative and spectroscopic analysis , the products were found to be the complexes of chromium involving oxidized fragments of the substrate as ligands along with water molecules (in some cases) that might have been formed during the oxidation process. With variation of the relative amount of the substrate and the reagent, the degree of oxidation, however, varies. Thermal analysis  further supported the results.

 

 

Findings are given below:

Sample

Subs : CrO3

Composition of the product

Structural formulae

AP – 1

1 : 1.5

 

 

 

C7H13O9Cr2

 

AP – 2

1 : 1

 

 

 

C7H11O7Cr2

                     

 

AP – 3

1 : 0.75

 

 

 

C7H9O5Cr

 

AP – 4

1 : 0.5

 

 

 

C14H13O8Cr

 

 

Results of thermodynamic analysis :

Sample / Empirical formula mass

% left

No. of gm per formula left

Wt. loss

Diff. in wt. loss

Formula left after the loss of fragments

AP – 1

345

a) 87

b) 22.03

301

76

44

225

-

181

CO2  lost

½ Cr2O3 left

AP – 3

225

a) 84

b) 30.2

189

68

36

121

-

85

2 H2O lost

CrO left

                                                                                           

 

 

The degree of oxidation , however , varies with variation of the relative amount of the substrate and the reagent . The results have been supported by thermal analysis .

 

CONCLUSION:

The oxidation state of Cr in the complexes appears to be influenced by the molar substrate and oxidant ratio . In general excess of oxidant appears to give complexes in which chromium has higher oxidation state . The complexes of Chromium  with salicylic acid  and their degradation products are stable to heating but volatile since finally only chromium oxide complex is left out .

 

IR of Sample AP-1

 

IR of Sample AP-2

 

IR of Sample AP-3

 

IR of Sample AP-4

 

TG, DTA GRAPH of Sample AP-1

 

TG, DTA GRAPH of Sample AP-3

REFERENCES :

1.       J. Fugita, K. Nakamoto and M. Kobyashy, J. AM. Chem. Soc . 98. 3963, (1956)

2.       A. K. Laha and A. B. Kulkarni, J. Sc. Ind . Res.506 (1985)

3.       G. Mishra , M. Alam , Renuka Thakur and N. Mishra, J. Inst. Chem. (Ind.) 63,!66 (1991)

4.       G. Mishra, M. Alam, N. Dwivedi and N. N. Mishra, J. Inst. Chem. (Ind.) 63, 169 (1991)

5.       R. K. Dubey, U. K. Dubey, C. M. Mishra “Synthesis and physiochemical characterization of some Schiff base complexes of Cr (III) complexes”. Indian J. Chem. 45A : 1638 – 1642 (2006)

 

 

 

Received on 05.06.2015         Modified on 06.01.2016

Accepted on 15.01.2016         © AJRC All right reserved

Asian J. Research Chem. 9(1): Jan., 2016; Page 01-05

DOI: 10.5958/0974-4150.2016.00001.8