ABSTRACT

Considerable efforts have recently been made to investigate how the structure of protic ionic liquids determines some of their most important properties for technological applications (e.g. low vapour pressure, conductivity). In contrast, the assessment of cohesive energies (which are also linked to those properties) based on thermodynamic results is still practically unexplored. This problem is addressed here for 1,1,3,3- tetramethylguanidinium nitrate, 1/2Htmg 1/2NO3 , through a combination of experimental and computational chemistry results at the reference temperature of 298.15 K. The standard molar enthalpies of formation, DfHo mo1/2Htmg 1/2NO3 ; crP 1/4 o311:8 2:3P kJ mol 1, and fusion, DfusHo mo1/2Htmg 1/2NO3 P 1/4 16:2 3:8 kJ mol 1, of solid 1,1,3,3-tetramethylguanidinium nitrate (form I polymorph) were obtained by combustion and differential scanning calorimetry, respectively. From these results DfHo mo1/2Htmg 1/2NO3 ; lP 1/4 o295:6 4:4P kJ mol 1 could be derived. Also determined were the standard molar enthalpies of formation, DfHo motmg; lP 1/4 7:7 2:8 kJ mol 1, and vaporisation, DvapHo motmg; lP 1/4 50:0 1:2 kJ mol 1, of 1,1,3,3-tetramethylguanidine, by reaction solution and Calvet-drop microcalorimetry, respectively, leading to DfHo motmg; gP 1/4 57:7 3:0 kJ mol 1. This result is in excellent agreement with DfHo motmg; gP 1/4 58:4 4:0 kJ mol 1, obtained from the ab initio calculation of the standard molar enthalpy of atomization of tmg using the W1-F12 procedure. From the above results, the cohesive energy of 1/2Htmg 1/2NO3 (l) could be evaluated. Finally, the nature of a solid to solid phase transition observed for 1/2Htmg 1/2NO3 at 221.4 +- 1.2 K using DSC was investigated by single crystal X-ray diffraction. The structural results indicate that complete proton transfer from HNO3 to tmg only occurs above the phase transition temperature

Compounds

#	Formula	Name
1	CO2	carbon dioxide
2	N2	nitrogen
3	H2O	water
4	O2	oxygen
5	C5H13N3	1,1,3,3-tetramethylguanidine
6	C5H14N4O3	tetramethylguanidinium nitrate
7	HNO3	nitric acid

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	Variable	Constraint	Phase	Method	#Points
POMD	5	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid		Liquid Gas	Static calorimetry	1
POMD	5	Mass density, kg/m3 ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	Vibrating tube method	5
POMD	6	Mass density, kg/m3 ; Crystal 1	Temperature, K; Crystal 1 Pressure, kPa; Crystal 1		Crystal 1	X-ray diffraction	1
POMD	6	Mass density, kg/m3 ; Crystal 2	Temperature, K; Crystal 2 Pressure, kPa; Crystal 2		Crystal 2	X-ray diffraction	1
POMD	6	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DSC	1
POMD	6	Triple point temperature, K ; Crystal 1			Crystal 1 Liquid Air at 1 atmosphere	DTA	1
POMD	6	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	6	Triple point temperature, K ; Crystal 2			Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	7 3 6	Molar enthalpy of solution, kJ/mol ; Liquid	Mole fraction - 6; Liquid Pressure, kPa; Liquid Temperature, K; Liquid Solvent: Amount concentration (molarity), mol/dm3 - 7; Liquid		Liquid	Calvet calorimetry	1
POMD	5 7 3	Molar enthalpy of solution, kJ/mol ; Liquid	Mole fraction - 5; Liquid Pressure, kPa; Liquid Temperature, K; Liquid Solvent: Amount concentration (molarity), mol/dm3 - 7; Liquid		Liquid	Calvet calorimetry	1
RXND	6 1 2 3 4	Specific internal energy of reaction at constant volume, J/g				Static bomb calorimetry	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Thermochemistry of 1,1,3,3-tetramethylguanidine and 1,1,3,3-tetramethylguanidinium nitrate

Vitorino, J.[Joana], Agapito, F.[Filipe], Piedade, M. F. M., Bernardes, C. E. S.[Carlos E.S.], Diogo, H. P.[Herminio P.], Leal, J. P.[Joao P.], Piedade, M. E. M. d.[Manuel E. Minas da]

ABSTRACT