To determine more accurately the amount of polyflavanoids in tannin extracts from radiata pine bark, which react with formaldehyde, it is important to elucidate chemical structures of (﹢)-catechin-formaldehyde reaction products (Stiasny precipitates). The Stiasny value of 106.4% for (﹢)-catechin was obtained from the reaction with formaldehyde under strong acid conditions. This value is almost identical to the value calculated from the Stiasny precipitates, which were formed in the ratio of two molecules of (﹢)-catechin to three molecules of formaldehyde.
The solid-state 13C NMR spectrum was measured to elucidate the structures of the Stiasny precipitates, and analysed on the basis of the chemical shifts of (﹢)-catechin. The NMR results indicate that C-6 and C-8 in the A-ring are bonded by methylene bridges to form polymers, and also form methylene bridges with C2′, C5′ or C6′ in the B-ring of a catechin unit.
Consequently, the reaction products of (﹢)-catechin-formaldehyde under strong acid conditions (Stiasny precipitates) are (﹢)-catechin-polymers, which consist of two moles of (﹢)-catechin and three moles of formaldehyde. The methylene bridges are formed mostly between A-rings, and less frequently, between A- and B-rings and between B-rings of the catechin units.
Florenskyite is a new phosphide species from the Kaidun chondritic meteorite, which fell in South Yemen in 1980. Kaidun is a unique chondritic breccia containing a huge variety of fragments of different chondritic types. Florenskyite was found as four dispersed grains with a maximum dimension of 14 μm within a single mass of Fe-rich serpentine within one Kaidun clast. Florenskyite is associated with submicrometer-sized grains of pentlandite and small (up to 1.5 μm in width) laths of a still uncharacterized Fe-Cr phosphide. Florenskyite is creamy white in reflected light, and its luster is metallic. The average of three electron microprobe analyses gave (wt%) Fe 40.52, Ti 30.08, Ni 5.47, Cr 0.93, V 0.91, Co 0.60, P 21.69, Si 0.59, sum 100.79, corresponding to Fe1.01(Ti0.87Ni0.13Cr0.03V0.02Co0.01)1.06(P0.97Si0.03). Single-crystal structure analysis was performed on florenskyite using a Laue pattern collected from a multiple crystal by in-situ synchrotron X-ray diffraction. Florenskyite crystallizes in the space group Pnma, and has the anti-PbCl2 structure. Previously determined cell constants of synthetic material [a = 6.007(1), b = 3.602(1), c = 6.897(1) Å] were used in the single-crystal data reduction. We used the POWD12 program to calculate a powder XRD pattern; the 5 most intense reflections are d = 2.301 (I = 100), 2.188 (88), 2.307 (47), 1.938 (45), and 1.801 Å (45). Florenskyite is only the fourth phosphide to be described from nature. Its paragenesis may be unique, and may be due to melting of a mineral assemblage including Fe-Ni metal, schreibersite, daubreelite, osbornite, or heideite and subsequent crystallization of phosphides from the melt.