Solution and solid state thermal stability of morpholinedithiocarbamates

Abstract

Estudos termogravimétricos e calorimétricos diferenciais de morfolinoditiocarbamatos de NH 4 + , Mn 2+ , Co 2+ , Ni 2+ e Cu 2+ foram realizados em atmosferas de ar e nitrogênio, para avaliar a influência da presença do oxigênio como heteroátomo no anel da amina na decomposição térmica. Produtos de decomposicão térmica foram caracterizados através de difratogramas de raios X, sendo predominantemente formados por sulfetos metálicos, sob atmosfera dinâmica de nitrogênio e óxidos metálicos, sob ar. Usando espectrofotometria, também foram determinados o pKa = 3,56 para o ácido morfolinoditiocarbâmico em força iônica 0,50 mol dm -3 (NaClO 4 ) à 25,0 °C e parâmetros cinéticos de decomposição em diferentes valores de pH (k lim = 0,14 ± 0,04 s -1 e t ½ lim = 5,3 ± 1,2 s).Thermogravimetric and differential scanning calorimetric investigation of the thermal behavior of NH 4 + , Mn 2+ , Co 2+ , Ni 2+ e Cu 2+ morpholinedithiocarbamates were performed under nitrogen and air atmospheres in order to investigate the effect, in the thermal decomposition, of the presence of an oxygen as the heteroatom in the amine ring. Decomposition products were identified by their X-ray diffraction patterns. Metal sulfites and oxides were the major residues under nitrogen and air atmospheres, respectively. Spectrophotometric measurements were used to estimate the pKa =3.56 for the morpholinedithiocarbamic acid at 0.50 mol dm -3 ionic strength (NaClO 4 ) at 25.0 °C and kinetic parameters of decomposition at different pH values (k lim = 0.14 ± 0.04 s -1 e t ½ lim = 5.3 ± 1.2 s).

Thermoanalytical and solution stability studies of hexamethylenedithiocarbamates

“…91 This is in total agreement with our previous findings for other cyclic DTC complexes with the same metal cations. 24,25,90 The characteristic C-N stretching vibrational mode is observed at 1474-1503 cm -1 and is less intense than that observed for alkyl DTC derivatives due to the low double bond character caused by the rigid ring system. 92 Table 1.…”

“…The limiting half life (t 1/2lim ) suggests that hex is more stable than piperidinedithiocarbamate (pip) and morpholinedithiocarbamate (mor) and much less stable than pyrrolidinedithiocarbamate (pyr). 23,90 The thermal analytical studies revealed that sulfides were the main residues obtained under nitrogen atmosphere, which were reduced to the elementary metals in the case of the copper(II) and zinc(II) complexes. Oxysulfates were observed in air as intermediates of the decomposition of Ni(hex) 2 , Cu(hex) 2 and Cd(hex) 2 , while oxides were obtained as final decomposition products.…”

“…23,90 All the spectrophotometric measurements were carried at 25.0 ± 0.1 °C, using the buffered solution as a blank. Stock HMA-hex solutions (1.0 × 10 -2 mol dm -3…”

“…7 This is in agreement with previous findings for other cyclic dithiocarbamate derivatives. [23][24][25]90 Thermal decomposition in air…”

Estudos termoanalíticos de sais de sódio e potássio de ditiocarbamatos em atmosfera oxidante

“…15,16 Os sais de sódio e potássio são costumeiramente usados na preparação de complexos de ditiocarbamatos com íons metálicos, cujo comportamento térmico foi descrito previamente. [17][18][19][20][21][22][23] Considerando a relevância e os poucos dados descritos na literatura, o presente trabalho trata da síntese e caracterização, assim como do estudo termoanalí-ticos envolvendo TG/DTG e DSC de sais de Na[S 2 CNR] e K[S 2 CNR] derivados de aminas cíclicas (R = pirrolidina (pyr), piperidina (pip), morfolina (mor), hexametileno (hex)), em atmosfera de ar.…”