Temperature yield

A connnon approach has been to measure the equilibrium constant, K, for these reactions as a fiinction of temperature with the use of a variable temperature high pressure ion source (see section (Bl.7.2)1. The ion concentrations are approximated by their abundance in the mass spectrum, while the neutral concentrations are known from the sample mlet pressure. A van t Hoff plot of In K versus /T should yield a straight Ime with slope equal to the reaction enthalpy (figure B1.7.11). Combining the PA with a value for basicityG at one temperature yields a value for A.S for the half-reaction involving addition of a proton to a species. While quadnipoles have been tire instruments of choice for many of these studies, other mass spectrometers can act as suitable detectors [19, 20]. 

Titanium trifluoride is prepared by dissolving titanium metal in hydrofluoric acid (1,2) or by passing anhydrous hydrogen fluoride over titanium trihydrate at 700°C or over heated titanium powder (3). Reaction of titanium trichloride and anhydrous hydrogen fluoride at room temperature yields a cmde product that can be purified by sublimation under high vacuum at 930—950°C. 

When water activity is low, foods behave more like mbbery polymers than crystalline stmctures having defined domains of carbohydrates, Hpids, or proteins. Water may be trapped in these mbbery stmctures and be more or less active than predicted from equiUbrium measurements. As foods change temperature the mobiUty of the water may change. A plot of chemical activity vs temperature yields a curve having distinct discontinuities indicating phase... 

Light or heavy magnesium carbonate is exposed to a red heat, and carbon dioxide and water are expelled leaving light or heavy magnesium oxide. The density is also influenced by the calcining temperature higher temperatures yield more compact forms. 

Melt Viscosity. Viscosities of resins at standard temperatures yield information about molecular weight and molecular weight distribution, as weU as valuable information with respect to appHcation logistics. Some customers prefer to receive resins in molten form. Melt viscosities help to determine the required temperature for a resin to be pumpable. Temperature—viscosity profiles are routinely suppHed to customers by resin manufacturers. In general, a molten viscosity of 1—1.1 Pa-s (1000—1100 cP) or less at process temperatures is convenient for the pumping and handling of molten resin. 

AHyl alcohol can be easily oxidized to yield acrolein [107-02-8] and acryhc acid [79-10-7]. In an aqueous potassium hydroxide solution of RuQ., aHyl alcohol is oxidized by a persulfate such as K2S20g at room temperature, yielding acryhc acid in 45% yield (29). There are also examples of gas-phase oxidation reactions of ahyl alcohol, such as that with Pd—Cu or Pd—Ag as the catalyst at 150—200°C, in which ahyl alcohol is converted by 80% and acrolein and acryhc acid are selectively produced in 83% yield (30). 

Improved materials, coatings, and cooling techniques permit newer machines to operate at higher turbine inlet temperatures, yielding both increased output and efficiency. Further efficiency gains result from improved aerodynamics in the hot gas path, compressor, and turbine sections. Use is also made of variable inlet guide vanes (IGV). 

Measurements of stress relaxation on tempering indicate that, in a plain carbon steel, residual stresses are significantly lowered by heating to temperatures as low as 150°C, but that temperatures of 480°C and above are required to reduce these stresses to adequately low values. The times and temperatures required for stress reUef depend on the high temperature yield strength of the steel, because stress reUef results from the localized plastic flow that occurs when the steel is heated to a temperature where its yield strength is less than the internal stress. This phenomenon may be affected markedly by composition, and particularly by alloy additions. 

Benzene. The reaction of sulfur trioxide and ben2ene in an inert solvent is very fast at low temperatures. Yields of 90% ben2enesulfonic acid can be expected. Increased yields of about 95% can be reali2ed when the solvent is sulfur dioxide. In contrast, the use of concentrated sulfuric acid causes the sulfonation reaction to reach reflux equiUbrium after almost 30 hours at only an 80% yield. The by-product is water, which dilutes the sulfuric acid estabhshing an equiUbrium. 

Vanadium (IV) Chloride. Vanadium(IV) chloride (vanadium tetrachloride, VCy is a red-brown hquid, is readily hydrolyzed, forms addition compounds with donor solvents such as pyridine, and is reduced by such molecules to trivalent vanadium compounds. Vanadium tetrachloride dissociates slowly at room temperature and rapidly at higher temperatures, yielding VCl and CI2. Decomposition also is induced catalyticahy and photochemically. This instabihty reflects the difficulty in storing and transporting it for industrial use. 

CgH BiBr2, and diphenylbromobismuthine [39248-62-9] C22H2QBiBr, respectively, with lithium aluminum hydride or sodium borohydride at low temperatures yielded only black polymeric substances of empirical formula C H Bi (33). It has been claimed (34) that dimethylbismuthine and diphenylbismuthine can be used as cocatalysts for the polymerisation of ethylene (qv), propylene (qv), and 1,3-butadiene. The source of these bismuthines, however, was not mentioned. 

The butanols undergo the typical reactions of the simple lower chain aUphatic alcohols. For example, passing the alcohols over various dehydration catalysts at elevated temperatures yields the corresponding butenes. The ease of dehydration increases from primary to tertiary alcohol /-butyl alcohol undergoes dehydration with dilute sulfuric acid at low temperatures in the Hquid phase whereas the other butanols require substantially more stringent conditions. 

Equation (4-18) may first be divided by dT and restric ted to constant pressure, and then be divided by dP and restricted to constant temperature, yielding the two equations ... 

Benzal chloride and benzotnchloi ide are also decomposed by water, the foimer in presence of calcium carbonate, and the latter at a high temperature, yielding in the one ca e, ben/alde-hyde, and in the other, benzoic acid,... 

Combination of stoichiometric amounts of H2S and SO2 at low temperature yields the white crystalline adduct H2S.SO3 which is isomeric with thiosulfuric acid. 

The compound tends to dissociate into AUF3 and, when treated with Xe 2 in anhydrous HF solution below room temperature, yields yellow-orange crystals of the complex [Xe2F3][AuFfi] ... 

Similarly, iV,A/ -dimethyl-3,3 -bisindolylmethane (169) has been used in a related experiment, where treatment thereof with trifluoroacetic fflihydride (TFAA) in diethyl ether at room temperature yielded a mixture of products from which the trifluoromethyl-substituted indolo[3,2-b]carbazole 170 was isolated as the major pentacyclic component, accompanied by the hydroxy derivative 171 as well as small amounts of the indolo[2,3-h]carbazole 146 (Scheme 20). The precursor 169 could also be prepared in situ from A-methylindol-3-methanol under... 

Phospholes 78 were obtained (67AG58) from diacetylene and phenylphosphine in pyridine (yield up to 29%) and with butyllithium in benzene at room temperature (yield up to 90%). 

Acidic and basic hydrolysis of ethyl 4-oxo-4//-pyrido[l, 2-u]pyrimidin-3-carboxylates gave 3-carboxylic acid derivatives (OlMIPl). Stirring rerr-butyl ( )-3-(2-hydroxy-8-[2-(4-isopropyl-l, 3-thiazol-2-yl)-l-ethenyl]-4-oxo-4//-pyrido[l,2-u]pyrimidin-3-yl)-2-propenoate in CF3CO2H at room temperature yielded ( )-3-substituted 2-propenoic acid. 

The only exception is represented by isoxazole-3-carboxylic acid in which the N—O bond is the only one to be broken, other bonds remaining unaffected hydrolysis of the intermediate (not isolated) gave carbethoxypyruvic acid. Quilico et al, reported the peculiar degradation of 3,3 -diisoxazolyl (124) ° treatment with sodium ethylate even at room temperature yields diacetyl with the evolution... 

The treatment of 8-hydroxy-11-isopr opoxy-7,8,9,10-tetrahydropyr-ido[l,2-A][l,2]benzothiazin-10-ones 42 with eone. H2SO4 at ambient temperature yielded 7,10,10n,ll-tetrahydropyrido[l,2-A][l,2]benzothiazin-9,10-diones 40 (67JMC223, 68USP3408347). 

Treatment of 8-fluoro-l,2-dihydro-4 7,67/-[l,4]oxazino[4,3-a]quinoline-4,6-dione with 6N aqueous NaOH and PhCH2Br under reflux overnight and with NaOMe in DMF at ambient temperature yielded l-(2-benzyloxyethyl)- and l-vinyl-6-fluoro-l, 4-dihydroquinoline-2-carboxylic acids, respectively (01SL833). 

Reduction of a perhydropyrido[l,2-c][l,4]oxazin-l-one with BH3 in anhydrous THF at room temperature yielded a perhydropyrido[l,2-c] [l,4]oxazine (OOMIPl). 

Reduction of ethyl 3-[(2-fcrf-butoxycarbonylperhydropyrido[l,2-a]pyra-zin-7-yl)methoxy]benzoate with LAH in THF at room temperature yielded... 

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