3271-87-2Relevant academic research and scientific papers
Characterisation of metal carboxylates by Raman and infrared spectroscopy in works of art
Otero, Vanessa,Sanches, Diogo,Montagner, Cristina,Vilarigues, Mrcia,Carlyle, Leslie,Lopes, Joo A.,Melo, Maria J.
, p. 1197 - 1206 (2015/02/19)
This work introduces the complementary use of μ-Raman and μ-Fourier transform infrared (IR) spectroscopy for the detection of specific carbon chains and cations for the identification of metal carboxylates within oil paint microsamples. Metal carboxylates (metal soaps) form naturally when free fatty acids react with metal cations and may also be found as additives or degradation products. Twenty-two metal carboxylates were synthesised, and their spectra assembled in a reference database. Metal salts of cations commonly present in oil paintings were used, including lead, zinc, calcium, cadmium, copper and manganese. The fatty acids selected were the saturated acids palmitic (C1 6:0) and stearic (C18:0) and the polyunsaturated oleic acid (C1 8:1). Azelaic acid (C9 diacid), a product resulting from autoxidation of polyunsaturated acids, was also included. Metal carboxylates were characterised by Raman and IR spectroscopy, and their structures were confirmed by X-ray diffraction. Raman and IR spectroscopy proved to be complementary techniques for a full identification of the metal carboxylates in complex aged paint. Raman enables the differentiation of the carbon chain length in the C-C stretching region (1120-1040 cm-1), and IR distinguishes the metal cation in the COO- stretching absorption region (1650-1380cm-1). Principal component analysis was applied to the spectra in order to facilitate a fast and accurate method to discriminate between the different metal carboxylates and to aide in their identification. Finally, spectra from case studies were successfully projected in the principal component analysis models built, enabling a higher confidence level for the identification of copper palmitate and copper azelate in two 19th-century Portuguese oil paintings.
Liquid Phase Oxidation of s-Butyltoluene
Kulsrestha, Girendra N.,Pathania, Bikram S.,Sharma, Krishna G.,Sharma, Jaipal S.,Negi, Janaki,Bhattacharyya, Kshitindra K.
, p. 636 - 638 (2007/10/02)
Oxidation of s-butyltoluene (SBT) to its hydroperoxide (ROOH) by oxygen has been studied in the presence and absence of catalysts in aqueous suspension at 80 deg to 116 deg C and 1 to 8.5 kg/cm2 O2 pressure.The oxidation rate is higher at higher pressures and the selectivity to ROOH formation is the highest when no catalyst is used.Effects of various reaction parameters have been studied in the absence of catalyst.A reaction temperature of 100 deg, SBT-water ratio of 1:2 and oxygen pressure of more than 3 kg/cm2 are found to be the most suitable for ROOH formation.Oxidation above 11.5percent ROOH level leads mainly to byproducts including s-butylbenzoic acid.
