Synthesis, characterization and thermochemical properties of N-acyl-N′,N′-diethylthioureas

Abstract

Three N-acyl-NЈ,NЈ-diethylthioureas, RCONHCSNEt 2 , R = i Pr, i Bu, t Bu, have been prepared and characterised. The standard ( p o = 0.1 MPa) molar enthalpies of combustion in oxygen of the three crystalline compounds, at T = 298.15 K, have been measured by rotating bomb-combustion calorimetry, and the standard molar enthalpies of sublimation of the compounds by microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively. The derived standard molar enthalpies of formation in the gaseous state are discussed comparatively. Acid constants and some complex stabilities have been measured pH-potentiometrically in dioxane-water mixture. The crystal structure of N,N-diethyl-NЈ-isovaleroylthiourea is presented and shows a delocalization of the π electrons of the C᎐ ᎐ S group over the carbon-amine nitrogen bond, CS-NEt 2 , stabilising the molecule, in accordance with the thermochemical results.

Thermochemistry of 2,5-Thiophenedicarboxylic Acid

“…Over the past years, we have been involved in a thermochemical study of the energetic effects of sulfur compounds, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] among them thiophene derivatives. 6,9,16,17 The fundamental interest in this work is the understanding of structural effects on thermodynamic stabilities that are reflected on the enthalpies of formation for the compounds studied.…”

“…Over the past years, we have been involved in a thermochemical study of the energetic effects of sulfur compounds, − among them thiophene derivatives. ,,, The fundamental interest in this work is the understanding of structural effects on thermodynamic stabilities that are reflected on the enthalpies of formation for the compounds studied. If benzenes are the paradigm of aromatic molecules, thiophenes are the simplest representatives of stable aromatic structures bearing sulfur…”

Enthalpies of combustion of two bis(N,N-diethylthioureas)

“…Unfortunately, experimental values for the standard molar enthalpies of formation in the gas phase, D f H m ðgÞ, for both compounds, are not known. Applying bondenergy schemes with the previously established [23] parameters C-(H) 3 …”

Thermochemistry of Cu(II) and Ni(II) complexes with N,N-di-n-butyl-N′-thenoylthiourea and N,N-di-iso-butyl-N′-thenoylthiourea

“…More recently, the thermochemistry of this class of compounds became the subject of interest [3], including transition metal complexes [4]. The extraction properties of N,N-di-n-butyl-N 0 -benzoylthiourea are very well established and exhibit some advantages when compared with b-diketones or b-thioxoketones.…”