Dairy aroma compounds recovery by pervaporation

Original pervaporation experiments with two dairy aroma compounds diluted in model aqueous solutions through GFT silicalite-filled silicone composite membrane and GKSS PEBA homogeneous membrane (0.1 m² effective area) were carried out on a pilot-plant. A systematic approach was done, studying the influence of various operating parameters (feed temperature and permeate pressure). The permeabilities of the membranes were calculated for each permeant, based on the estimation of the driving force as a fugacities difference. The pervaporation membranes tested showed a good selectivity for the extraction of methylthiobutanoate (hydrophobic molecule with cheese fragrance) at high dilution rate. However, these membranes proved to be less selective for the recovery of diacetyl (hydrophilic butter aroma). For this component, the coupling of pervaporation and two-stage condensation improved significantly the selectivity of the whole process. The thermodynamic properties in the liquid feed (real dairy media) as well as in the permeate (vapour-liquid equilibria at low pressure) have to be well known in order to optimize the recovery of the aroma compounds     

Redox-controlled, reversible rearrangement of a tris(2-pyridylthio)methyl ligand on nickel to an isomer with an “N,S-confused” 2-pyridylthiolate arm

Interchange between the nickel +2 and +3 oxidation states precisely controls the reversible rearrangement of the tris(2-pyridylthio)methanide (tptm) ligand in the organometallic nickel(II) complex [{Ni(μ-Br)-(tptm)}(2)] (2). Oxidation of 2 first gives the corresponding Ni(III) complex [{Ni(μ-Br)(tptm)}(2)][PF(6)](2) (4). However, in solution the tptm ligand in 4 slowly undergoes a rearrangement, in which the N and S atoms of one of the pyridylthiolate arms exchange Ni and C bonding partners, thereby resulting in an "N,S-confused" isomer of tptm in the product, [NiBr(bpttpm)]PF(6) (5; bpttpm= bis(2-pyridylthio)(2-thiopyridinium)-methyl). Reduction of 5 reverses this ligand rearrangement and 2 is reformed quantitatively. The individual steps involved in these unusual ligand rearrangements were investigated by a number of methods, including voltammetric analysis, and a mechanism for this process is proposed. X-ray crystal structure determinations of the key compounds 2, 4 and 5 have been obtained.     

Palladium(II) complexes containing cytokinins derived from 6-benzylaminopurine

A series of palladium(II) complexes of general formula [Pd(LH⁺)Cl₃] (1–12) containing 6-benzylaminopurine derivatives has been prepared [L?=?6-(2-methoxybenzylamino)purine (1), 6-(3-methoxybenzylamino)purine (2), 6-(4-methoxybenzylamino)purine (3), 6-(2-hydroxy-benzylamino)purine (4), 6-(3-hydroxybenzylamino)purine (5), 6-(4-hydroxybenzylamino) purine (6), 6-(2-fluorobenzylamino)purine (7), 6-(3-fluorobenzylamino)purine (8), 6-(4-fluorobenzylamino)purine (9), 6-(2-chlorobenzylamino)purine (10), 6-(3-chlorobenzylamino) purine (11) and 6-(4-chlorobenzylamino)purine (12)]. The compounds have been characterized by elemental analysis, IR, ES+ MS and ¹H- and ¹³C-NMR spectroscopy, and two of them, 6 and 12, also by TG/DSC analyses. The complexes have been screened in vitro against the four human tumour cell lines G-361, HOS, K-562 and MCF7.     

MASS SPECTRAL FRAGMENTATION STUDIES ON THIOPHENOTROPONE AND THIOPHENOTROPILIDENE DERIVATIVES AND THEIR METAL TRICARBONYL COMPLEXS

Abstract

The mass spectral fragmentation of thiophenotropone, thiophenotropilidene derivatives and their iron and chromium tricarbonyl complexes are fully reported and discussed. The fragmentation patterns of the complexes are characterised by successive loss of three carbonyl groups. In general, the resulting ions after elimination of the metal behave in the same manner as the organic ligand. The iron complexes behave differently from their corresponding chromium complexes. The thiopheno[b]tropilidene iron tricarbonyl complex and its isomer thiopheno[c]tropilidene iron tricarbonyl complex could not be differentiated by mass spectrometry, such differentiation was achieved by proton magnetic resonance.