57Fe Mössbauer spectroscopy study of organic rich sediment (source rocks) from test well K-263 of Cambay Basin, India

⁵⁷Fe Mössbauer Spectroscopy study was carried out on the samples collected from different depth interval of a representative well K-263 of the North Cambay basin (India). The results obtained were compared with the basins already studied. Comparison show that general trend of relative distribution of iron containing minerals as a function of depth for well K-263 is more or less similar to that reported for Eastern Krishna Godavari Basin. Interestingly both these basins have similar hydrocarbon prospecting (hence nature of organic content) also. On the other hand we found that distribution pattern of iron minerals of Cambay basin is markedly different from the basins (viz North Sea and Jaisalmer) having different prospecting and organic properties in comparison to Cambay Basin. So some correlation exists between distribution of iron minerals and prospects of a basin.     

Equivalent particle diameter and length scale for pressure drop in porous metals

The internal architecture of metal foam is significantly different from that of traditional porous media. This provides a set of challenges for understanding the fluid flow in this relatively new class of materials. This paper proposes that despite the geometrical differences between metal foam and traditional porous media, the Ergun correlation is a good fit for the linear pressure drop as a function of the Darcian velocity, provided that an appropriate equivalent particle diameter is used. The paper investigates an appropriate particle diameter considering the physics of energy dissipation, i.e. the viscous shear and the form drag. The above approach is supported by wind tunnel steady-state unidirectional pressure drop measurements for airflow through several isotropic open-cell aluminum foam samples having different porosities and pore densities. For each foam sample, the equivalent particle diameter correlated well with the surface area per unit volume of the foam. This was also very well valid for previous porous metal pressure drop data in the open literature.     

Physical & thermal properties of model polysiloxane rubbers: impact of crosslink density and tin concentration

The influence of the tin octanoate catalyst on the physical and thermal properties of RTV 5370 polysiloxane rubbers has been studied. To assess the likely influence of crosslinking on a number of physical and thermal properties in polysiloxanes, “model siloxane networks” (representing networks of well defined composition/structure) have been formulated by the hydrosilylation of polysiloxane diols of known average molecular weight with tetraethoxysilane curing agent. It was found that linear swell and the crystallisation melting transitions of these systems were both significantly affected by changes in crosslink density. A selection of RTV5370 foamed rubbers with different tin concentrations were prepared in a similar manner to assess the influence of the tin catalyst. For these materials it was found that the area of the crystalline melting transition decreased with increasing tin concentration, an effect indicative of increased crosslinking. Samples with double the standard amount of tin (10% wt catalyst) show a shift in the crystallisation transition to higher temperature with no further effect beyond this concentration. Furthermore, the storage modulus (E') of the rubbers at room temperature appears to be independent of the tin catalyst concentration. Through correlation with the data from the model siloxanes, these results suggests that increasing the catalyst concentration appears to induce additional crosslinking interactions that are stable at low temperatures but not stable at room temperature.     

Crystal and Molecular Structure of Sulfadimethoxine,Polymorph III

Crystal structure of sulfadimethoxine, C₁₂H₁₄N₄O₄S, has been determined and refined to an R‐value of 0.043 using direct methods. It crystallizes in the triclinic space group P with a = 7.946(1), b = 9.330(1), c = 10.407(1)Å, α = 93.46(1), β = 95.43(1), γ = 114.62(1)° and Z = 2. The dihedral angle between the two six ‐ membered rings of the molecule is 77.6(8)°. Molecule adopts a gauche conformation about S8‐N11 bond with torsional angle of 60.0(2)°. The structure is mainly stable due to strong hydrogen bonds, amino nitrogen plays the role of donor in two different intermolecular hydrogen bonds where sulfonyl oxygen and pyrimidine nitrogen act as acceptor.     

PVT and CVT Growth and Characterization of SnSxSe2-x (0 ⩽ <x 2) Single Crystals

Single crystals of solid solutions of tin sulphoselenide have been grown in the same ampoule. Specific conditions for growing single crystals of SnSSe have also been identified. A study of microstructures on the growth surfaces responds to the mechanism of growth of these crystals. The dependence of electrical resistivity, Hall mobility, carrier concentration with the values of the configuration parameter x has been studied.     

Al–SnSe2 Schottky Barrier

Shottky barrier diodes are fabricated on SnSe₂ crystal grown by direct vapour transport method. The barrier is produced by thermal evaporation of aluminium on as grown single crystal of SnSe₂. The barrier height of Schottky diodes are estimated using current-voltage characteristics, and activation energy measurement. The barrier height is estimated about 0.49 eV. The implications are discussed.     

Hydroxy-directed fluorination of remote unactivated C(sp3)–H bonds: a new age of diastereoselective radical fluorination

We report a photochemically induced, hydroxy-directed fluorination that addresses the prevailing challenge of high diastereoselectivity in this burgeoning field. Numerous simple and complex motifs showcase a spectrum of regio- and stereochemical outcomes based on the configuration of the hydroxy group. Notable examples include a long-sought switch in the selectivity of the refractory sclareolide core, an override of benzylic fluorination, and a rare case of 3,3′-difluorination. Furthermore, calculations illuminate a low barrier transition state for fluorination, supporting our notion that alcohols are engaged in coordinated reagent direction. A hydrogen bonding interaction between the innate hydroxy directing group and fluorine is also highlighted for several substrates with ¹⁹F–¹H HOESY experiments, calculations, and more.

We report a photochemical, hydroxy-directed fluorination that addresses the prevailing challenge of high diastereoselectivity. Numerous motifs showcase a range of regio- and stereochemical outcomes based on the configuration of the hydroxy group.

The hydroxy (OH) group is treasured and versatile in chemistry and biology.¹ Its ubiquity in nature and broad spectrum of chemical properties make it an attractive source as a potential directing group.² The exploitation of the mild Lewis basicity exhibited by alcohols has afforded several elegant pathways for selective functionalization (e.g., Sharpless epoxidation,³ homogeneous hydrogenation,⁴ cross-coupling reactions,⁵ among others⁶). Recently, we reported a photochemically promoted carbonyl-directed aliphatic fluorination, and most notably, established the key role that C–H⋯O hydrogen bonds play in the success of the reaction.⁷ Our detailed mechanistic investigations prompt us to postulate that other Lewis basic functional groups (such as –OH) can direct fluorination in highly complementary ways.⁸ In this communication, we report a hydroxy-directed aliphatic fluorination method that exhibits unique directing properties and greatly expands the domain of radical fluorination into the less established realm governing high diastereoselectivity.⁹Our first inclination that functional groups other than carbonyls may influence fluorination regiochemical outcomes was obtained while screening substrates for our published ketone-directed radical-based method (Scheme 1).^8a In this example, we surmised that oxidation of the tertiary hydroxy group on substrate 1 cannot occur and would demonstrate functional group tolerance (directing to C11, compound 2). Surprisingly, the two major regioisomers (products 3 and 4) are derivatized by Selectfluor (SF) on C12 and C16 – indicative of the freely rotating hydroxyl directing fluorination. Without an obvious explanation of how these groups could be involved in dictating regiochemistry, we continued the mechanistic study of carbonyl-directed fluorination (Scheme 2A). We established that the regioselective coordinated hydrogen atom abstraction occurs by hydrogen bonding between a strategically placed carbonyl and Selectfluor radical dication (SRD).⁷ However, we noted that the subsequent radical fluorination is not diastereoselective due to the locally planar nature of carbonyl groups. Thus, we posed the question: are there other directing groups that can provide both regio- and diastereoselectivity? Such a group would optimally be attached to a sp³ hybridized carbon; thus the “three dimensional” hydroxy carbon logically comes to mind as an attractive choice, and Scheme 1 illustrates the first positive hint.Open in a separate windowScheme 1Observed products for the fluorination of compound 1.Open in a separate windowScheme 2(A) Proposed mechanism, (B) β-caryophyllene alcohol hypochlorite derivative synthetic probe, (C) isodesmic relation of transition states showing the general importance of the hydroxy group to reactivity (ωB97xd/6-31+G*), and (D) ¹H NMR experiment with Selectfluor and various additives at different concentrations.We began our detailed study with a simple substrate that contains a tertiary hydroxyl group. Alcohol 5 was synthesized stereoselectively by the reaction of 3-methylcyclohexanone, FeCl₃, and 4-chlorophenylmagnesium bromide;¹⁰ the 4-chlorophenyl substituent allows for an uncomplicated product identification and isolation (aromatic chromophore). We sought to determine optimal reaction conditions by examination of numerous photosensitizers, bases, solvents, and light sources (7 Although we utilize cool blue LEDs (sharp cutoff ca. 400 nm), CFLs (small amount of UVB (280–315 nm) and UVA (315–400 nm)) are useable as well.¹¹ A mild base additive was also found to neutralize adventitious HF and improve yields in the substrates indicated (

Spirals on flux-grown plates of CaWO4

Thin and transparant single crystalline plates of calcium tungstate have been grown by using the method of isothermal flux evaporation at 840°C. The floating plates exhibited spiral depression on their top as-grown surfaces as revealed by high resolution (20 A°) electron-optical plant. It is believed that the spiral pattern results from thermal etching at the sites of helical dislocations.     

Textural properties of AISb films

Textural studies have been carried out in AlSb films deposited by coevaporation method under high vacuum at different substrate temperatures between 450° to 625 °C. The films have been examined by X-ray and electron diffraction techniques. It was observed that the films deposited around 550 °C were found to exhibit [110] and [111] textures and the films deposited at higher substrate temperatures (above 600 °C) were found to exhibit only [111] textures.