Thermal Analyses of Diorganotin dl-Mandelates

The compounds [(LR₂Sn)₂O] {R=CH₃ (Me), n-C₄H₉(Bⁿ); L=C₆H₅CH(OH)COO⁻}were studied by thermogravimetric and differential scanning calorimetry in a dynamic atmosphere of helium. The thermal decomposition mechanisms are similar for both compounds and occur in two consecutive steps. The TG curves of the complexes suggest the liberation of the ligand L in the first step, with probable formation of a tin oxide R₂SnO intermediate. At the end of the second step free tin is obtained in accordance with the stoichiometry of the related compounds. An inverse relation betweenΔH _fusion and solubility of the compounds suggests a polymeric structure for the compound with Bⁿ ligand in relation to the compound with M ligand. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal stability of high-energy compounds

The influence of molecular structure on the stability of high-energy compounds is considered. The kinetic parameters of the decomposition of various energy-rich groups in monofunctional compounds are established. Data on decomposition of compounds with mixed functional groups are described. The sites of primary breakdown are determined and the mutual influence of functional groups on the stability is considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 231–234, February, 2000.     

Thermal stability of new zinc acetate-based complex compounds

New zinc acetate based complex compounds (of general formula Zn(CH₃COO)₂·1?2L·nH₂O) containing one or two molecules of urea, thiourea, coffeine and phenazone were prepared namely: Zn(CH₃COO)₂·2.5H₂O, Zn(CH₃COO)₂·2u·0.5H₂O, Zn(CH₃COO)₂·tu·0.5H₂O, Zn(CH₃COO)₂·2tu, Zn(CH₃COO)₂·cof·2.5H₂O, Zn(CH₃COO)₂·2cof·3.5H₂O, Zn(CH₃COO)₂·2phen·1.5H₂O. The compounds were characterized by IR spectroscopy, chemical analysis and thermal analysis. Thermal analysis showed that no changes in crystallographic modifications of the compounds take place during (heating in nitrogen before) the thermal decompositions. The temperature interval of the stability of the prepared compounds were determined. It was found that the thermal decomposition of hydrated compounds starts by the release of water molecules. During the thermal decomposition of anhydrous compounds in nitrogen the release of organic ligands take place followed by the decomposition of the acetate anion. Zinc oxide and metallic zinc were found as final products of the thermal decomposition of the zinc acetate based complex compounds studied. Carbon dioxide and acetone were detected in the gaseous products of the decomposition of the compounds if ZnO is formed. Carbon monoxide and acetaldehyde were detected in the gaseous products of the decomposition, if metallic Zn is formed. It is supposed that ZnO and Zn resulting from Zn acetate complex compounds here studied, possess different degree of structural disorder. Annealing takes place by further heating above 600°C.     

Analytical Methods for Speciation of Organotins in the Environment

The growing awareness over the environmental fate of organotin compounds is reflected in the large number of analytical methods developed for their separation. Organotin compounds have varying degrees of toxicological properties, depending on the nature and number of alkyl groups bonded to the tin atom. Most of the analytical speciation methods applied to actual environmental media have involved prior derivatization to transform organotin compounds into volatile hydrophobic analytes amenable to separation and identification by gas chromatography coupled to a sensitive and selective tin-detector. Evidence exists that members of the same homologous series are related by environmental degradation pathways. Chemical treatment prior to analysis, or high temperatures associated with gas chromatography separation, may alter the relative amounts of organotins in samples and blur the true environment picture. To avoid species redistribution that may occur during derivatization or gas speciation analysis, methods based on liquid chromatography and supercritical fluid chromatography have been investigated. This review documents analytical methods for determination of tin and speciation of organotin compounds, in the hope that it will be of value to those interested in initiating a programme for assessing the impact of such species on the environment.     

HPTLC analysis of organotin compounds in preservative solutions and preservative-treated wood

A high-performance thin-layer chromatographic (HPTLC) method is described for the determination of tributyltin compounds (bis(tri-n-butyltin) oxide, TBTO, and tri-n-butyltin naphthenate, TBTN) and their degradation products (dibutyltin and monobutyltin compounds). The organotin compounds are extracted from wood with ethanol containing 0.5% (v/v) of hydrochloric acid and the separation of the defferent kinds of organotin compounds is achieved by thin-layer chromatography. The sample spots are measured using a scanning densitometer after decomposing the organotin compounds to inorganic tin by ultraviolet irradiation and visualization of the spots with pyrocatechol violet. Applications of the method to detection and quantification of organotin compounds in preservative solutions, in recently impregnated wood, and in wood samples from five-year-old window frames are described.     

Thermal analysis of thione compounds

The thermal behavior of thiourea (Tu), N-methylthiourea (MeTu), N, N-dimethylthiourea (Me₂Tu) and N, N, N, N-tetramethylthiourea (Me₄Tu) was investigated by means of conventional thermal analysis in O₂ and N₂ and IR spectroscopy of the residues on heating in air at various temperatures.At ordinary pressure, the compounds are thermally stable up to the melting points. After melting, they show high vapor pressure, combustion in O₂ atmosphere and isomerization to ammonium thiocyanate, with the exception of Me₄Tu.Financially supported by the Italian MURST.     

Decomposition of aliphatic α-fluorodinitro compounds in the liquid phase

The decomposition of compounds Y[CH₂C(NO₂)₂X]₂ (X=NO₂ and F; Y=CH₂C(O)O and OCH₂O) in the liquid phase (melt, solution) was found to proceedvia the same mechanism (homolytic cleavage of the C−N bond) as in the gas phase. Some stabilizing effects of the O_β atom and independence of the gas evolution rate constant (measured by the yield of final products) on the number of the −C(NO₂)₂X groups were found and interpreted. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2455–2458, December, 1998.     

Thermal stability and decomposition of pharmaceutical compounds

Thermal analysis of fusion and decomposition processes were carried out on recently synthetized pharmaceutical compounds in order to establish thermal stability criteria. This study was carried out using thermogravimetry, TG, and differential scanning calorimetry, DSC. Degradation and fusion temperatures have been produced as thermal data with the aim of to study the thermal stability of the compounds. Relationship is found among stability and a series of effects of structure of the compounds. The compounds which present an amide functional group in the central molecule are more stable because they have a comparatively higher fusion and degradation temperature. In addition, the stability of this type of compounds depends on the position of the electrophilic substitution (in ortho, meta or para). Likewise, the groups linked to the aromatic ring with high electronic density give stability, and therefore are able to delocalize the charge in a greater spacial interval. Therefore, criteria for the selection of substituents have established that improve the stability of compounds     

Thermal stability evaluation of doping compounds before GC-MS analysis by DSC

The Medical Commission of the International Olympic Committee forbids the use of anabolic androgenic steroids, β-agonists, stimulant and narcotic compounds to improve athletic performance. In this work, we evaluated the thermal stability of 17 compounds by the use of the DSC for their potential GC-MS analysis either under free form or under TMS derivative form. In DSC, esterified and unesterified anabolic steroids were characterized by a true melting peak, followed by a large exothermic peak at about 251–316°C due to oxidative degradation. They could be analysed by GC-MS mainly under TMS derivatives. Hydroxylated and unhydroxylated stimulant compounds (xanthines) seemed to be more stable at high temperature. As unhydroxylated xanthines were not silylated with BSTFA - TMCS, their GC analysis would be done under their free forms. TMS derivatisation of albuterol hemisulfate and codeine phosphate is preferable. In our conditions, to analyse by GC-MS all 17 doping compounds in the same GC-MS run, the optimal silylation temperature and best column initial temperature were determined at both 60°C.     

Structure and thermal stability of difluoroamino compounds in the liquid state

The kinetics of decomposition of 15 difluoroamino compounds with NF₂ groups at primary, secondary, and tertiary carbon atoms in the liquid state was investigated. Activation energies (E _a) for all of the compounds were in the interval 100–120 kJ · mol^–1. The reaction rate does not depend on the electronic effects of the substituents and decreases only in the case of steric shielding of the NF₂ group. ForN-difluorobenzylamine it was shown that the gas-phase elimination of HF is characterized byE = 176 kJ·mole^–1, while the rate of decomposition in a solution depends on the dielectric constant of the medium. Based on the results obtained, a mechanism for liquid-phase decomposition, which involves heterolysis of the N-F bonds, is suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 336–338, February, 1994.     

Non-isothermal Kinetic Study of the Heterogeneous Thermal Decomposition of a Mannich Compound

The authors present data concerning the evaluation of kinetic parameters of the decomposition of a Mannich compound by using the classical method of constant heating rate thermal analysis and the new one of controlled rate thermal analysis (CRTA). The data processed using the CRTA method allow to obtain more reliable kinetic parameters according to the proposed reaction mechanism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition kinetics of lanthanum and neodymium bromide complexes with glycine or alanine

Four complexes of rare earth bromides with amino acids, REBr₃·3L·3H₂O (RE=La, Nd;L=glycine or alanine) were prepared and characterized by means of chemical analysis, elemental analysis, molar conductivity, thermogravimetry, IR spectra and X-ray diffraction. Their thermal decomposition kinetics from ambient temperature to 500°C were studied by means of TG-DTG techniques under non-isothermal conditions. The kinetic parameters (activation energyE and pre-exponential constantA) and the most probable mechanisms of thermal decomposition were obtained by using combined differential and integral methods. The thermal decomposition processes of these complexes are distinguished as being of two different types, depending mainly on the nature of the amino acid.     

Thermal behaviour of g-zirconium phosphate intercalation compounds with template surfactants

Long chain alkylammonium cations can be exchanged into a preswelled phase of g-zirconium phosphate, a layered inorganic ion-exchanger. The derived materials are used as templates to give organic-inorganic composite materials. The cationic exchange occurs very quickly. These intercalation compounds behave in a very similar way. They are still layered and exhibit an interlayer distance d notably greater than that of its precursor whose behavior depends on the chain length. By thermal and microanalyser characterizations it can be observed that the surfactant is lost in two stages, the second one as a result of the fragmentation of the chain. The layered structure with the expanded interlayer distance is maintained up to ~350°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal analysis of cyclodextrins and their inclusion compounds

This review examines the literature concerning the thermal properties of natural and semisynthetic cyclodextrins and their inclusion compounds. Particular emphasis is given to recent results of investigations by thermal methods of the hydrated forms of cyclodextrins. The limitations and advantages of the applications of thermal analyses concerning water- and drug-cyclodextrin interactions are also discussed.     

A multicriteria ranking of organotin(IV) compounds with fungicidal properties

The application of multicriteria decision‐making methods to the results of in vitro antifungal properties of organotin compounds of the type Ph_xSnX_z (x = 2 or 3; X = O₂CC₆H₄OH, O₂CC₆H₄OCOCH₃, Cl or O₂CCH₃; z = 1 or 2) and of free 2‐hydroxybenzoic and 2‐acetoxybenzoic acids against Aspergillus niger, Aspergillus flavus, Candida albicans, Penicillium citrinum, Trichophyton rubrum and Trichophyton violaceum have been described. Ranking information necessary to select one toxicant in preference to others and to assess the properties influencing the preference has been obtained. Patterns in the multivariate analyses suggest that cationic and anionic moieties of the toxicant play some roles in their fungicidal activities. The triphenyltin compounds were generally more active than their diphenyltin analogues, but the acetoxybenzoates were more active than the corresponding hydroxybenzoates, acetates or chlorides. Thus, triphenyltin acetoxybenzoate is up to 7.5 times as active as the corresponding acetate, which is commercially marketed as a fungicide. The results of the analyses have been discussed in the light of the mechanism of antifungal activity of organotin compounds and the potential of multivariate data analysis techniques to facilitate the screening and ranking of antifungal agents. Copyright © 2003 John Wiley & Sons, Ltd.     

Theoretical model and experimental study of pore growth during thermal expansion of graphite intercalation compounds

Summary A new technique, which allows one to simultaneously follow the mass and volume of graphite intercalation compounds (GICs) during thermal transformation into expanded graphite, was developed. This enabled us to elucidate the mechanism for the thermal expansion of GICs and formulate a quantitative model for the process. Effective activation parameters of the thermal decomposition of new GICs were obtained by using non-isothermal kinetics procedure. Thermal decomposition was described as a break of intermolecular bonds followed by diffusion.     

Solid-state compounds of 4-methoxybenzylidenepyruvate and cinnamylidenepyruvates with thorium (IV)

By close control of experimental variables affecting precipitation, solid-state compounds of the type Th(OH)_mL_4-m·nH₂O, where L stands for 4-methoxy-benzylidenepyruvate, cinnamylidenepyruvate or 4-dimethylaminocinnamylidene-pyruvate; m=0 to 3 andn=0.5-3 were isolated. Chemical analysis, TG, DTG, DSC and X-ray powder diffractometry have been employed to characterize and to study the thermal behavior of these compounds in dynamic air atmosphere. In all cases, hydration water is slowly lost between 30 and 160°C; a continuous, slow rate, mass loss is observed thereafter and beyond 280-400°C the rate of decomposition/oxidation increased rapidly, to give ThO₂as the final product, beginning at 412-510°C. The results associated with the hydroxo-compounds indicate that the loss of constitution water (OH ions) and the decomposition / oxidation of the organic moieties occur as simultaneous process. This revised version was published online in August 2006 with corrections to the Cover Date.     

Organotin–Oxido Cluster‐Based Multiferrocenyl Complexes Obtained by Hydrolysis of Ferrocenyl‐Functionalized Organotin Chlorides

Three organotin–oxido clusters were formed by hydrolysis of ferrocenyl‐functionalized organotin chloride precursors in the presence of NaEPh (E=S, Se). [R^FcSnCl₃?HCl] ( C ; R^Fc = CMe₂CH₂C(Me)?N?N?C(Me)Fc) and [SnCl₆]^2? formed {(R^FcSnCl₂)₃[Sn(OH)₆]}[SnCl₃] ( 3 a ) and {(R^FcSnCl₂)₃[Sn(OH)₆]}[PhSeO₃] ( 3 b ), bearing an unprecedented [Sn₄O₆] unit, in a one‐pot synthesis or stepwise through [(R^FcSnCl₂)₂Se] ( 1 ) plus [(R^FcSnCl₂)SePh] ( 2 ). A one‐pot reaction starting out from FcSnCl₃ gave [(FcSn)₉(OH)₆O₈Cl₅] ( 4 ), which represents the largest Fc‐decorated Sn/O cluster reported to date.     

Thermal behavior of zinc γ-zirconium phosphate intercalation compounds

Summary The layered ion-exchangers γ-zirconium phosphate and γ-zirconium phosphate containing intercalated diamines, obtained by exchanging zinc ions, have been synthesized and characterized. Zinc ions are able to form coordination compounds between the layers of the host matrix and consequently form zinc complexes formed in situ. The zinc ions uptake, the thermal behavior and the structural characterization of the compounds obtained have also been examined. The thermal stability and X-ray spectra of these compounds depend on the type of isomeric diamine precursor. The zinc fully exchanged γ-zirconium phosphate is able to form ZnS particles in the host matrix. The X-ray spectra of this obtained material matched those of the initial γ-zirconium phosphate precursor.     

Divalent silicon,germanium, and tin compounds with element--heteroatom bonds

Principal results and trends in chemistry of organic derivatives of divalent silicon, germanium, and tin containing bonds between these elements and the halogen, nitrogen, oxygen, and sulfur atoms are briefly surveyed. Selected characteristics of compounds with the element--phosphorus and element--arsenic bonds are discussed for comparison. Data on the synthesis and structures of new types of these compounds, viz., germanium(ii) diacylates, the alkoxy derivatives E¹⁴(OR)₂ and E¹⁴(OR)Y (E¹⁴ = Ge, Sn; R = Me₂NCH₂CH₂; Y = Cl, AcO, (Me₃Si)₂N), and the ate-complexes Li⁽⁺⁾[E¹⁴(OCH₂CH₂NMe₂)₃]^(–) and [Li(thf)₂]⁽⁺⁾[TsiE¹⁴(SBu)₂]^(–) (E¹⁴ = Ge, Sn; Tsi = (Me₃Si)₃C), are presented. It was established for the first time that germanium(ii) and tin(ii) derivatives can be stabilized in the monomeric form only through the intramolecular N_sp3E¹⁴ coordination bonds and the -acceptor effect of the oxygen atoms without introduction of bulky substituents.