Hydride chemical reactions

In contrast to alcohols with their nch chemical reactivity ethers (compounds contain mg a C—O—C unit) undergo relatively few chemical reactions As you saw when we discussed Grignard reagents m Chapter 14 and lithium aluminum hydride reduc tions m Chapter 15 this lack of reactivity of ethers makes them valuable as solvents m a number of synthetically important transformations In the present chapter you will learn of the conditions m which an ether linkage acts as a functional group as well as the methods by which ethers are prepared... 

Miscellaneous Atomization Methods A few elements may be atomized by a chemical reaction that produces a volatile product. Elements such as As, Se, Sb, Bi, Ge, Sn, Te, and Pb form volatile hydrides when reacted with NaBH4 in acid. An inert gas carries the volatile hydrides to either a flame or to a heated quartz observation tube situated in the optical path. Mercury is determined by the cold-vapor method in which it is reduced to elemental mercury with SnCb- The volatile Hg is carried by an inert gas to an unheated observation tube situated in the instrument s optical path. 

Hardness on the Mohs scale is often above 8 and sometimes approaches 10 (diamond). These properties commend nitrides for use as crucibles, high-temperature reaction vessels, thermocouple sheaths and related applications. Several metal nitrides are also used as heterogeneous catalysts, notably the iron nitrides in the Fischer-Tropsch hydriding of carbonyls. Few chemical reactions of metal nitrides have been studied the most characteristic (often extremely slow but occasionally rapid) is hydrolysis to give ammonia or nitrogen ... 

Complexes 79 show several types of chemical reactions (87CCR229). Nucleophilic addition may proceed at the C2 and S atoms. In excess potassium cyanide, 79 (R = R = R" = R = H) forms mainly the allyl sulfide complex 82 (R = H, Nu = CN) (84JA2901). The reaction of sodium methylate, phenyl-, and 2-thienyllithium with 79 (R = R = r" = R = H) follows the same route. The fragment consisting of three coplanar carbon atoms is described as the allyl system over which the Tr-electron density is delocalized. The sulfur atom may participate in delocalization to some extent. Complex 82 (R = H, Nu = CN) may be proto-nated by hydrochloric acid to yield the product where the 2-cyanothiophene has been converted into 2,3-dihydro-2-cyanothiophene. The initial thiophene complex 79 (R = R = r" = R = H) reacts reversibly with tri-n-butylphosphine followed by the formation of 82 [R = H, Nu = P(n-Bu)3]. Less basic phosphines, such as methyldiphenylphosphine, add with much greater difficulty. The reaction of 79 (r2 = r3 = r4 = r5 = h) with the hydride anion [BH4, HFe(CO)4, HW(CO)J] followed by the formation of 82 (R = Nu, H) has also been studied in detail. When the hydride anion originates from HFe(CO)4, the process is complicated by the formation of side products 83 and 84. The 2-methylthiophene complex 79... 

In chemical storage, a chemical reaction is used that releases hydrogen, for example, by thermal decomposition of a hydride, but chemical decomposition of... 

In an irreversible metal hydride, hydrogen is generated through a chemical reaction, which is not easily reversible onboard a vehicle. Common reactant is water or an alcohol. For example, sodium borohydride can produce hydrogen as... 

There is a marked difference in chemical reactivity between bridging and terminal hydrogens. Terminally bonded hydrogens readily react in a similar manner to that observed for mononuclear hydrides. Thus reactions with chlorinated hydrocarbons such as carbon tetrachloride yield the chloro cluster complexes and chloroform. In contrast, bridging hydrides are stable and may be studied in chlorinated sol-... 

Dications 222+ and 232+ were synthesized by hydride abstraction reaction of the corresponding hydro derivatives as stable dark-brown powder. The p/CR+ values for these dications are also extremely high for doubly-charged systems (222+ 11.7 and 232+ 11.7). The electrochemical reduction of 222+ and 232+ exhibited a reduction wave at less negative potentials than that of dication 212+. This wave corresponds to the reduction of two cation units by a one-step, two-electron reduction to form thienoquinoid products. Chemical reduction of 222+ and 232+ afforded the closed-shell thienoquinoid compounds (22 and 23), which exhibited high electron-donating ability. The formation of the closed-shell molecules is in contrast with the result from reduction of dication 212+connected via a / -phenylenediyl spacer. 

Hydride generation Light absorbed by atoms derived from hydrides that are generated by chemical reaction are measured An excellent technique for a limited number of analytes that are difficult to measure otherwise... 

The hydride generation technique is a technique in which volatile metal hydrides are formed by chemical reaction of the analyte solutions with sodium borohydride. The hydrides are guided to the path of the light, heated to relatively low temperatures, and atomized. It is useful because it provides an improved method for arsenic, bismuth, germanium, lead, antimony, selenium, tin, and tellurium. 

Saita et al. [80] applied hydriding chemical vapor deposition (HCVD) for preparing MgH. They used commercial Mg, which was heated to 600°C and vaporized in a hydrogen atmosphere at a pressure of 4 MPa. The reaction product was deposited on a cooled Inconel substrate and subsequently collected for further investigation. Quite remarkably, the obtained morphology was nanofibrous, as shown in Fig. 2.47, and is very similar to the one fabricated by Zlotea et al. [79]. Each fiber was less than 1 jm in diameter and 10 or more micrometers in length. 

The preferential chemical reaction of a reagent with one of two or more different functional groups. For example, sodium borohydride exhibits greater chemoselectivity as a reducing agent than does lithium aluminum hydride, because the latter reacts with a wider spectrum of substances. 

Bio)chemical reactions may take place prior to or after the continuous separation module and are intended to enhance or facilitate mass transfer, detection or both. The earliest and simplest approach to integrated analytical steps in continuous-flow systems involves a combination of chemical reactions and continuous separations [4,5]. Such is the case with the formation of soluble organic chelates of metal ions in liquid-liquid extractions with the ligand initially dissolved in the organic stream [6], the formation and dissolution of precipitates [7], the formation of volatile reaction products in gas difiusion [8] and that of volatile hydrides in atomic absorption spectro-... 

The related elements, proton hydrogen (H ), and hydride (H ) change their physical properties (including their size) drastically by the change of the number of electrons. Hydrogen-bond and proton-transfer interactions are the key to understanding many chemical reactions, biological activities, structure of molecular assemblies and supramolecules, functionalities in the solid state, etc. 

The reversibility of the metal-hydrogen reaction (Eq. l) and the heat of chemical reaction (Eq. 2) provides the basis for hydride heat pumps. These devices are closed units in which hydrogen serves as an energy carrier between two or more hydride beds. By selecting appropriate hydriding alloys, heat sources and heat sinks, heat can be pumped over wide temperature differentials with no moving parts except possibly check valves. 

P.I. Gold, Chemical species and chemical reactions of importance in nonequilibrium propellant performance calculations, NASA Accession No N66-33714, Rept No NASA-CR-65442, avail CFSTI, SciTechAerosp Rept 4 (19), 3722 (1966) CA 67, 4484 (1967) 47) S.S. Cherry L.J. van Nice, Pyrodynamics 6 (3-4), 275 (1969) CA 70, 98394 (1969) 48) R.E. Lo, Theoretical performance of the multicomponent rocket propellant system (oxygen, fluorine/ beryllium, lithium hydride)/hydrogen, Deutsche Versuchsanst Luft- und Raumfehri Rept11968, DLR-Mitt-68-21 (Ger), avail CFSTI, SciTech Aerosp Rept 7 (1), 161 (1969) CA 71,... 

Ullrafine particles (UFPs) of metal and semiconductor nitrides have been synthesized by two major techniques one is the reactive gas condensation method, and the other is the chemical vapor condensation method. The former is modified from the so-called gas condensation method (or gas-evaporation method) (13), and a surrounding gas such as N2 or NII2 is used in the evaporation chamber instead of inert gases. Plasma generation has been widely adopted in order to enhance the nitridation in the particle formation process. The latter is based on the decomposition and the subsequent chemical reaction of metal chloride, carbonate, hydride, and organics used as raw materials in an appropriate reactive gas under an energetic environment formed mainly by thermal healing, radiofrequency (RF) plasma, and laser beam. Synthesis techniques are listed for every heal source for the reactive gas condensation method and for the chemical vapor condensation method in Tables 8.1.1 and 8.1.2, respectively. 

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