ABSTRACT

We studied the thermochemical behaviour of five commonly used drugs namely naproxen, atenolol, methocarbamol (ML), acetaminophen and mephenesin (MP) using dielectric spectroscopy (10-3 Hz 1 MHz) and differential scanning calorimeter (DSC) down to liquid nitrogen temperature. The first two samples quickly crystallized during cooling, and we are able to study the glass transition phenomena in the latter three drugs only. The dielectric spectroscopy reveals the glass transition process as a pronounced relaxation process identifiable with so called primary relaxation process, or a- process, which is non-Debye in nature, and can be described well using Hevriliak- Negami (HN) equation. One sub-Tg process is found with activation energy of about 27-34 kJ/mol in temperature range is about 150K 250 K and it does not appear to be of Johari-Goldstein type. Interestingly the three samples studied here can be classified as very fragile liquids.

Compounds

#	Formula	Name
1	C14H14O3	(S)-(+)-naproxen
2	C14H22N2O3	2-(4-(2-hydroxy-3-(isopropylamino)propoxy)phenyl)acetamide
3	C11H15NO5	2-hydroxy-3-(2-methoxyphenoxy)propyl carbamate
4	C8H9NO2	N-acetyl-p-aminophenol
5	C10H14O3	3-(2-methylphenoxy)-1,2-propanediol

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Phase	Method	#Points
POMD	1	Molar enthalpy of transition or fusion, kJ/mol ; Crystal	Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	1	Normal melting temperature, K ; Crystal	Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	2	Molar enthalpy of transition or fusion, kJ/mol ; Crystal	Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	2	Normal melting temperature, K ; Crystal	Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal	Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	3	Normal melting temperature, K ; Crystal	Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	3	Triple point temperature, K ; Glass	Glass Liquid Gas	DTA	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Metastable crystal	Metastable crystal Liquid Air at 1 atmosphere	DSC	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1	Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	4	Normal melting temperature, K ; Metastable crystal	Metastable crystal Liquid Air at 1 atmosphere	DTA	1
POMD	4	Normal melting temperature, K ; Crystal 1	Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	4	Triple point temperature, K ; Glass	Glass Liquid Gas	DTA	1
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1	Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	5	Normal melting temperature, K ; Crystal 1	Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	5	Triple point temperature, K ; Glass	Glass Liquid Gas	DTA	1

Thermodynamics Research Center / ThermoML | Thermochimica Acta

Study of Glass Transition Phenomena in the Supercooled Liquid Phase of Methocarbamol, Acetaminophen and Mephensin

Saini, M. K.[Manoj K.], Murthy, S. S. N.

ABSTRACT