Titanium Tetraiodide Research Articles

Polymorphic transformations in iodine titanium

Based on the analysis of differential scanning calorimetry data, the possibility of classifying the observed endothermic or exothermic transformations as phase transformations of the first oder is considered. Two approaches have been implemented. The first is based on the correspondence between the temperatures of the maximum conversion rate and the temperatures of the extrema on the second derivative of the differential scanning calorimetry signal with respect to temperature. In the second approach, the phase transformation is considered as a kind of kinetic reaction of a chemical process with the determination of some parameters included in the kinetic equations. In this case, the order parameter of such reaction n is obtained from the analysis of the differential scanning calorimetry signal shape in the region of phase transformation registration temperatures. Using the example of experiments carried out during thermal cycling of titanium iodide samples, it is shown that both the first and second approaches make it possible to fairly adequately attribute the processes that cause calorimetric effects on the dependences of differential scanning calorimetry to first-order phase transitions. In particular, the obtained results of differential scanning calorimetry during heating and cooling of iodide titanium show that polymorphic transformations in it are realized by various mechanisms depending on the rate of thermal cycling and the thermal history of the metal. Keywords: activation energy, titanium, calorimetry, polymorphism, structure, approximation.

Полиморфные превращения в йодидном титане

Based on the analysis of differential scanning calorimetry data, the possibility of classifying the observed endothermic or exothermic transformations as phase transformations of the first oder is considered. Two approaches have been implemented. The first is based on the correspondence between the temperatures of the maximum conversion rate and the temperatures of the extrema on the second derivative of the differential scanning calorimetry signal with respect to temperature. In the second approach, the phase transformation is considered as a kind of kinetic reaction of a chemical process with the determination of some parameters included in the kinetic equations. In this case, the order parameter of such reaction n is obtained from the analysis of the differential scanning calorimetry signal shape in the region of phase transformation registration temperatures. Using the example of experiments carried out during thermal cycling of titanium iodide samples, it is shown that both the first and second approaches make it possible to fairly adequately attribute the processes that cause calorimetric effects on the dependences of differential scanning calorimetry to first-order phase transitions. In particular, the obtained results of differential scanning calorimetry during heating and cooling of iodide titanium show that polymorphic transformations in it are realized by various mechanisms depending on the rate of thermal cycling and the thermal history of the metal.

Analysis of the Structural State Formed in Titanium at the Final Severe Plastic Deformation Stage

The structural state of iodide titanium after deformation by drawing at 77 K, which is the final stage of severe plastic deformation (SPD), has been analyzed and estimated in this work. The SPD has been implemented by a sequential combination of deformation techniques (compression-squirting-extrusion-drawing) that provide different stress epures. The temperature dependence of the logarithmic damping decrement of torsional oscillations in the 77–250 K temperature range has been studied to give a physical interpretation of the nonmonotonic change in the strength of the iodide titanium after SPD and to compare the calculated strength with that obtained for low purity titanium.

Gas‐solid displacement reactions in the Ti–W–C system

AbstractDisplacement reactions between binary and ternary ceramics in the Ti–W–C system and reactive gaseous atmospheres are investigated in this work. Specifically, WC and 50:50 wt% TiC:WC solid solution powders were exposed to flowing hydrogen gas, or equilibrated against an excess of titanium in the presence of iodine, to form metallic tungsten and TiC solid products. In the case of pure WC reacting with hydrogen, transformation to metallic tungsten occurred as a result of removal of chemically bound carbon as gaseous hydrocarbons. In the case of pure WC reacting with titanium iodide vapors, transformation was accompanied by the appearance of TiC as a solid product formed at the gas‐solid interface. In the case of 50:50 wt% TiC:WC solid solution powders, hydrogen was generally found to be an ineffective displacing reagent, whereas reaction with titanium iodide vapors was observed to proceed virtually to completion, resulting in a two phase product mixture comprising metallic tungsten and TiC. For the latter case, a variety of microstructures could be observed within a given batch, including tungsten platelets and/or lamellae in a TiC matrix, or coarse tungsten grains interspersed with TiC grains. These morphological variations are speculated to arise from compositional variation in the starting material and the occurrence of local rapid coarsening along fast diffusion pathways within reacting agglomerates and polycrystalline primary particles. The observed reaction products and relative efficacy of gaseous reagents to promote displacement reactions in the Ti–W–C system are rationalized on the basis of thermodynamic predictions. The reaction between 50:50 wt% TiC:WC solid solution powders and titanium iodide vapors constitutes the first known report of an internal displacement reaction proceeding via gaseous intermediates in a nonoxide ceramic system.

Titanium Tetraiodide/Trimethylsilyl Iodide Synergistically Induced Cyclization of N-(2-Cyanophenyl)benzamides into 2-Aryl-4-iodoquinazolines.

Synthesis of 2-aryl-4-iodoquinazolines is developed using titanium tetraiodide/trimethylsilyl iodide synergistically induced cyclization of N-(2-cyanophenyl)benzamides. The cyclization reactions proceeded to give the 2-aryl-4-iodoquinazolines in moderate to high yields. Remarkable synergetic effect of titanium tetraiodide and trimethylsilyl iodide was observed to promote the cyclization. The method was applied to the formal synthesis of a potent analgesic agent.

Micromechanical properties of single crystals and polycrystals of pure α-titanium: anisotropy of microhardness, size effect, effect of the temperature (77–300 K)

The anisotropy of microhardness of pure α-Ti single crystals, indentation size effect in single-crystal, course grained (CG) pure and nanocrystalline (NC) VT1-0 titanium, as well as the temperature dependences of the microhardness of single-crystal and CG Ti in the temperature range 77–300 K were studied. The minimum value of hardness was obtained when indenting into the basal plane (0001). The indentation size effect (ISE) was clearly observed in the indentation of soft high-purity single-crystal iodide titanium while it was the least pronounced in a sample of nanocrystalline VT1-0 titanium. It has been demonstrated that the ISE can be described within the model of geometrically necessary dislocations (GND), which follows from the theory of strain gradient plasticity. The true hardness and others parameters of the GND model were determined for all materials. The temperature dependence of the microhardness is in agreement with the idea of the governing role of Peierls relief in the dislocation thermally-activated plastic deformation of pure titanium as has been earlier established and justified in macroscopic tensile investigations at low temperatures. The activation energy and activation volume of dislocation motion in the strained region under the indenter were estimated.

四ヨウ化チタンのヨードチタン化能力を活用する新規合成反応

四ヨウ化チタンのヨードチタン化能力を活用する新規合成反応

Titanium tetraiodide-mediated diastereoselective iodo-aldol and Mannich reactions of γ-alkoxy-α,β-alkynyl ketone derivatives

The development of the stereoselective synthesis of vinyl halides plays an important role in organic chemistry. The multi-functionalized vinyl iodide is one of the most important intermediates in functional organic compounds. We investigated stereoselective iodo-aldol and iodo-Mannich reactions using γ-alkoxy-α,β-alkynyl ketones. Characteristic features of titanium tetraiodide involve iodination ability and moderate Lewis acidity, which are successfully used for the present stereoselective synthesis of multi-functionalized vinyl iodides. Furthermore, we have succeeded in the synthesis of a useful tetra-substituted furan, via a Sonogashira coupling of the vinyl iodide moiety. The factors to control diastereoselectivity of the iodo-aldol reactions are explained in terms of theoretical calculations. Consequently, the obtained activation free energy and reaction energy indicate the experimentally observed E/Z-selectivity.

Titanium Tetraiodide Induced Cyclization of Cyanoketones into 3-Aryl-1-iodoisoquinolines

Titanium Tetraiodide Induced Cyclization of Cyanoketones into 3-Aryl-1-iodoisoquinolines

Structural transformations in single-crystalline titanium under high-pressure cold and cryogenic deformation

The structure of an iodide titanium pseudo-single crystal subjected to severe plastic deformation in Bridgman anvils under a pressure of 8 GPa at room (293 K) and cryogenic (80 K) temperatures has been examined using methods of X-ray diffraction analysis and electron microscopy. It has been shown that, in the course of deformation, the original α titanium pseudo-single crystal undergoes the α→ ω transition. A decrease in the temperature of deformation to 80 K leads to the activation of twinning. At degrees of deformation lower than e = 6 titanium deformed at 293 K experiences more substantial strain hardening. In the course of subsequent deformation at 293 K, when e > 6, dynamic recrystallization begins, which is accompanied by the softening of the titanium. A decrease in the temperature of deformation to 80 K suppresses the recrystallization; therefore, the titanium deformed in liquid nitrogen shows a higher increase in the microhardness at degrees of deformation 6 < e < 10.

Evolution of the structure of an α-titanium single crystal during high-pressure torsion

The microstructure of an iodide titanium single crystal subjected to severe plastic deformation in Bridgman anvils at a pressure of 8 GPa and room temperature or the liquid-nitrogen temperature is studied by electron microscopy and X-ray diffraction. The initial α-titanium single crystal undergoes the baric α→ω transformation during compression and deformation under pressure. A decrease in the deformation temperature to 80 K is found to activate twinning. Upon deformation up to a strain e = 6, the strain hardening at room temperature exceeds the low-temperature strain hardening. At higher strains, the room-temperature strain hardening begins to decrease as compared to the low-temperature strain hardening due to the development of dynamic and postdynamic recrystallization. A decrease in the deformation temperature to 80 K suppresses recrystallization; correspondingly, titanium deformed in liquid nitrogen exhibits a larger microhardness increment in the strain range 6 < e < 10.

ChemInform Abstract: Titanium Tetraiodide‐Mediated Organic Reactions

AbstractReview: 54 refs.

ChemInform Abstract: Chemoselective Reductions and Iodinations Using Titanium Tetraiodide

AbstractReview: [48 refs.

Titanium Tetraiodide-Mediated Organic Reactions

A variety of organic transformations using titanium tetraiodide are described, in which iodotitanation, reduction, and use as a Lewis acid are discussed in detail. The iodotitanation reactions make possible the diastereoselective iodoaldol reactions and iodo olefin synthesis. The ability of iodide anion to reduce various substrates was utilized in many of chemoselective organic transformations. The mild Lewis acidity of titanium tetraiodide induces the catalytic aldol and Mannich-type reactions.

ChemInform Abstract: Diastereoselective Iodoaldol Reaction of γ‐Alkoxy‐α,β‐alkynyl Ketone Derivatives Promoted by Titanium Tetraiodide.

ChemInform Abstract: Diastereoselective Iodoaldol Reaction of γ‐Alkoxy‐α,β‐alkynyl Ketone Derivatives Promoted by Titanium Tetraiodide.

Diastereoselective Iodoaldol Reaction of γ‐Alkoxy‐α,β‐Alkynyl Ketone Derivatives Promoted by Titanium Tetraiodide

I, aldol: The iodoaldol reaction of γ-alkoxy-α,β-alkynyl ketones with aldehydes promoted by titanium tetraiodide proceeds to give the iodoaldol products in good yields with good to high diastereoselectivities. The iodinated addition products were transformed into tetrasubstituted furans by palladium-catalyzed Sonogashira coupling and subsequent cyclization. MOM=methoxymethyl ether.

Features of forming structure of titanium pseudosingle crystal during β → α (bcc → hcp) polymorphic transformation

The structure of a titanium iodide single crystal obtained by zone melting has been studied by metallography, X-ray diffraction, and electron microscopy. It has been shown that the initial bcc titanium single crystal becomes a pseudosingle crystal upon cooling below the temperature of the β → α polymorphic transition. The pseudosingle crystal consists of macroscopic packets, i.e., crystals of lath morphology with a size of 0.1–0.5 cm2 in different crystal sections. Each packet consists of α-phase laths of the same orientation, which are separated by dislocation boundaries. A total of six different types of packets in the pseudosingle crystal volume is realized in accordance with the Burgers orientation relationships. The structural heredity in the titanium pseudosingle crystal after the cycle of the α → β → α transformations is confirmed.

ChemInform Abstract: Regioselective Ring‐Opening Reaction of 2‐Mono‐Substituted Azetidin‐3‐ones Promoted by the Combined Use of Titanium Tetraiodide and Its Chloro or Bromo Counterpart.

AbstractThe ring‐opening reaction of azetidinones (I) in the presence of a combination of titanium iodide and titanium chloride occurs at the more substituted bond to afford the ketones (II) and (III) in moderate to high yields with high regioselectivity.

Regioselective Ring-Opening Reaction of 2-Mono-Substituted Azetidin-3-ones Promoted by the Combined Use of Titanium Tetraiodide and Its Chloro or Bromo Counterpart

Regioselective Ring-Opening Reaction of 2-Mono-Substituted Azetidin-3-ones Promoted by the Combined Use of Titanium Tetraiodide and Its Chloro or Bromo Counterpart

Titanium Tetraiodide-promoted Tandem Prins Reaction of Alkynes with Acetals: Synthesis of (Z,Z)-1,5-Diiodo-1,3,5-triarylpenta-1,4-dienes

Abstract In the presence of titanium tetraiodide, a tandem Prins reaction of alkynes proceeded with acetals to give (Z,Z)-1,5-diiodo-1,3,5-triarylpenta-1,4-dienes in good yields, where an intriguing reversal of the stereoselectivity was observed among titanium tetrahalides.