Thermal studies on the sodium salts of aminosalicylic acids

M. Rotich; M. Brown; B. Glass

doi:10.1023/a:1025469827599

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Journal of Thermal Analysis and Calorimetry

Volume/Issue:: Volume 73: Issue 2

Thermal studies on the sodium salts of aminosalicylic acids

Authors:

M. Rotich

M. Rotich Rhodes University Chemistry Department Grahamstown 6140 South Africa Grahamstown 6140 South Africa

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M. Brown

M. Brown Rhodes University Chemistry Department Grahamstown 6140 South Africa Grahamstown 6140 South Africa

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B. Glass

B. Glass James Cook University Glass School of Pharmacy Townsville Queensland 4811 Australia Townsville Queensland 4811 Australia

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Pages:: 499–508

Online Publication Date:: 31 Oct 2004

Publication Date:: 01 Aug 2003

Article Category:: Research Article

DOI:: https://doi.org/10.1023/a:1025469827599

Keywords:: TG-FTIR; DSC; aminosalicylic acids; sodium salts

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Abstract

The effect on the stability of the isomers of aminosalicylic acid of formation of their sodium salts has been studied by use of differential scanning calorimetry and thermogravimetry, coupled with evolved gas analysis by Fourier transform infrared spectroscopy. X-ray powder diffraction and infrared spectroscopy provided complementary information. The DSC curves for the sodium salts of all of the isomers showed complex dehydration/decomposition endotherms. From the initial mass losses of the TG curves, the amounts of water per mole of salt were estimated as 0.5, 2.4 and 1.4 moles for the sodium salts of 3-aminosalicylic acid, 4-aminosalicylic acid and 5-aminosalicylic acid, respectively. TG-FTIR results for the sodium salt of 3-aminosalicylic acid showed the evolution of carbon dioxide in three stages: below 150C, between 200 and 300C and continuous formation up to 500C. This behaviour differs from that of 3-aminosalicylic acid itself, which forms CO₂ between 225 and 290C. For the sodium salt of 4-aminosalicylic acid, the formation of carbon dioxide starts from 250C and is still being formed at about 650C. 4-aminosalicylic acid decarboxylates above 150C. 5-aminosalicylic acid and its sodium salt showed no evolution of carbon dioxide below 600C.

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Journal of Thermal Analysis and Calorimetry

Print ISSN:: 1388-6150

Online ISSN:: 1572-8943

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Journal of Thermal Analysis and Calorimetry
Language	English
Size	A4
Year of Foundation	1969
Volumes per Year	1
Issues per Year	24
Founder	Akadémiai Kiadó
Founder's Address	H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher	Akadémiai Kiadó Springer Nature Switzerland AG
Publisher's Address	H-1117 Budapest, Hungary 1516 Budapest, PO Box 245. CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible Publisher	Chief Executive Officer, Akadémiai Kiadó
ISSN	1388-6150 (Print)
ISSN	1588-2926 (Online)