4991-47-3Relevant articles and documents
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.
Zinc carboxylic salts used as catalyst in the biodiesel synthesis by esterification and transesterification: Study of the stability in the reaction medium
Reinoso, Deborath M.,Damiani, Daniel E.,Tonetto, Gabriela M.
, p. 88 - 95 (2013/02/23)
Biodiesel is produced by the catalytic transesterification of renewable sources such as vegetable oils and animal fats. It is an attractive alternative to diesel fuel because of its environmental benefits. In this work, the transesterification of soybean
Compact metal-organic frameworks for anti-corrosion applications: New binary linear saturated carboxylates of zinc
Mesbah, Adel,Jacques, Sophie,Rocca, Emmanuel,Francois, Michel,Steinmetz, Jean
, p. 1315 - 1321 (2011/06/10)
Zinc-based metal-organic frameworks (MOFs), binary zinc carboxylates ZnCnCn′ with Cn and Cn′ = CH3(CH2)n - 2COO-, have been synthesised and characterised for anti-corrosion applications. The crystallographic structures of ZnC10C14 and ZnC 10C16 were determied from synchrotron powder diffraction data and refined by the Rietveld method. Protective coatings on electrogalvanised steel composed of ZnC12C16 have been developed by formulating a particular "carboxylating" bath. The ZnC12C16 coating exhibits better anti-corrosion behaviour than the pure Zn(C16)2 and Zn(C12)2 coatings, according to electrochemical and non-electrochemical measurements. The crystallographic results and corrosion measurements demonstrate the great flexibility of the zinc carboxylate lamellar structures in modifying the insolubility and hydrophobicity of the protective coatings. In addition, the conditions for the ZnC12C16 coating process fulfil the specifications for the surface treatment of zinc. Finally, these new compounds, which can be easily synthesised in water, provide a new and environmentally friendly anti-corrosion treatment for metals. New zinc-based metal-organic frameworks (MOFs), binary zinc carboxylates ZnCnCn′ with Cn and Cn′ = CH3(CH2)n - 2COO-, have been synthesised and characterised for anti-corrosion applications on zinc. The crystallographic structures demonstrate the great flexibility of these MOFs in modifying the insolubility and hydrophobicity of the protective coatings on metals in an aqueous solvent process. Copyright
Room temperature molecular and lattice structures of a homologous series of anhydrous zinc(II) n-alkanoate
Taylor, Richard A.,Ellis, Henry A.
, p. 99 - 107 (2008/02/13)
The room temperature structures and lattice arrangements of a homologous series of zinc(II) n-alkanoates from chain length, nC = 4-20, inclusive, have been studied using infrared spectroscopy, X-ray diffraction and polarizing light microscopy. Lattice parameters from single crystal and powder diffraction data, for zinc(II) hexanoate, are compared to validate the use of the powder method. Since they are in excellent agreement, the powder data are analyzed by a software programme to determine lattice parameters for all the homologues. These are used, in conjunction with infrared, X-ray, density and molecular model calculations to determine molecular and lattice structures. The compounds are isostructural, in that, each zinc atom is tetrahedrally coordinated to oxygen atoms from four different carboxylate groups and each ligand forms a Z,E-type bidentate bridge with two tetrahedral zinc atoms resulting in a syn-anti arrangement. The hydrocarbon chains are in the fully extended all-trans configuration and are tilted at an average angle of 60° to the zinc basal plane. For the short chain length compounds with nC ≤ 8, a double bilayer in-plane-perpendicular-perpendicular-in-plane arrangement of hydrocarbon chains, with two molecules per unit cell, is indicated. For the others, an interdigitating in-plane-in-plane bilayer with head-to-tail interactions, with one molecule per unit cell, is proposed. A geometric model is presented to account for odd-even chain effects and to explain the differences in melting points and densities between these adducts. All the compounds crystallize in the monoclinic space group with P symmetry and are arranged in a two-dimensional network along the ac plane within the unit cell.
Melting of saturated fatty acid zinc soaps
Barman,Vasudevan
, p. 22407 - 22414 (2008/10/09)
The melting of alkyl chains in the saturated fatty acid zinc soaps of different chain lengths, Zn(CnH2n-1COO)2; n = 11, 13, 15, and 17, have been investigated by powder X-ray diffraction, differential scanning calorimetry, and vibrational spectroscopy. These compounds have a layer structure with the alkyl chains arranged as tilted bilayers and with all methylene chains adopting a planar, all-trans conformation at room temperature. The saturated fatty acid zinc soaps exhibit a single reversible melting transition with the associated enthalpy change varying linearly with alkyl chain length, but surprisingly, the melting temperature remaining constant. Melting is associated with changes in the conformation of the alkyl chains and in the nature of coordination of the fatty acid to zinc. By monitoring features in the infrared spectra that are characteristic of the global conformation of the alkyl chains, a quantitative relation between conformational disorder and melting is established. It is found that, irrespective of the alkyl chain length, melting occurs when 30% of the chains in the soap are disordered. These results highlight the universal nature of the melting of saturated fatty acid zinc soaps and provide a simple explanation for the observed phenomena.
