A 4D view on the evolution of metamorphic dehydration reactions

Metamorphic reactions influence the evolution of the Earth's crust in a range of tectonic settings. For example hydrous mineral dehydration in a subducting slab can produce fluid overpressures which may trigger seismicity. During reaction the mechanisms of chemical transport, including water expulsion, will dictate the rate of transformation and hence the evolution of physical properties such as fluid pressure. Despite the importance of such processes, direct observation of mineral changes due to chemical transport during metamorphism has been previously impossible both in nature and in experiment. Using time-resolved (4D) synchrotron X-ray microtomography we have imaged a complete metamorphic reaction and show how chemical transport evolves during reaction. We analyse the dehydration of gypsum to form bassanite and H2O which, like most dehydration reactions, produces a solid volume reduction leading to the formation of pore space. This porosity surrounds new bassanite grains producing fluid-filled moats, across which transport of dissolved ions to the growing grains occurs via diffusion. As moats grow in width, diffusion and hence reaction rate slow down. Our results demonstrate how, with new insights into the chemical transport mechanisms, we can move towards a more fundamental understanding of the hydraulic and chemical evolution of natural dehydrating systems

Sinteza i biološko djelovanje derivata 3-{[5-(6-metil-4-aril-2-okso-1,2,3,4-tetrahidropirimidin-5-il)-1,3,4-oksadiazol-2-il] -imino}-1,3-dihidro-2H-indol-2-ona

Reaction of ethyl-6-methyl–2-oxo-4-aryl-1,2,3,4-tetrahydropyrimidin-5-carboxylates (1a-i) with hydrazine hydrate yielded 6-methyl-2-oxo-4-aryl-1,2,3,4-tetrahydropyrimidin-5-carbohydrazides (2a-i). These products on reaction with cyanogen bromide gave 5-(5-amino-1,3,4-oxadiazol-2-yl)-6-methyl-4-aryl-3,4-dihydropyrimidin-2(1H)-one (3a-i). The resultant aminooxadiazolylpyrimidinones were condensed with isatin to obtain various 3-{[5-(6-methyl-4-aryl-2-oxo-1,2,3,4-tetrahydropyrimidin-5-yl)-1,3,4-oxadiazol-2-yl]-imino}-1,3-dihydro-2H-indol-2-ones (4a-i). These products were characterized by IR, 1H NMR, mass spectra and elemental analysis. Products 4a-i revealed promising antibacterial, antifungal and antioxidant activity.Derivati 6-metil-2-okso-4-aril-1,2,3,4-tetrahidropirimidin-5-karbohidrazida (2a-i) pripravljeni su reakcijom etil-6-metil–2-okso-4-aril-1,2,3,4-tetrahidropirimidin-5-karboksilata (1a-i) i hidrazin hidrata. Iz njih su sa cijanogen bromidom priređeni 5-(5-amino-1,3,4-oksadiazol-2-il)-6-metil-4-aril-3,4-dihidropirimidin-2(1H)-oni (3a-i). Kondenzacijom nastalih aminooksadiazolilpirimidinona s izatinom dobiveni su 3-{[5-(6-metil-4-aril-2-okso-1,2-tetrahidropirimidin-5-il)-1,3,4-oksadiazol-2-il]-imino}-1,3-dihidro-2H-indol-2-oni (4a-i). Produkti 4 karakterizirani su uobičajenim spektroskopskim metodama (IR, 1H NMR, spektar masa) i elementarnom analizom. Biološko vrednovanje ukazuje da spojevi 4a-i imaju potencijalno antibakterijsko, antimikotsko i antioksidativno djelovanje