Alternative Routes

The correlation functions provide an alternate route to the equilibrium properties of classical fluids. In particular, the two-particle correlation fimction of a system with a pairwise additive potential detemrines all of its themiodynamic properties. It also detemrines the compressibility of systems witir even more complex tliree-body and higher-order interactions. The pair correlation fiinctions are easier to approximate than the PFs to which they are related they can also be obtained, in principle, from x-ray or neutron diffraction experiments. This provides a useful perspective of fluid stmcture, and enables Hamiltonian models and approximations for the equilibrium stmcture of fluids and solutions to be tested by direct comparison with the experimentally detennined correlation fiinctions. We discuss the basic relations for the correlation fiinctions in the canonical and grand canonical ensembles before considering applications to model systems. 

Here we suggest an alternative route to the problem in which the equations of motion are formulated as a boundary value problem. This limits the... 

The Japp-Klingeraann coupling of aryidiazonium ions with enolates and other nucleophilic alkenes provides an alternative route to arylhydrazones. The reaction has most frequently been applied to P-ketoesters, in which deacylation follow S coupling and the indolization affords an indole-2-carboxylate ester. 

These methods were not applicable to all acids, and various alternative routes were investigated. The conversion of an acid to its methri ester by diazomethane is a method of choice when other methods are unsatisfactory (6, 30, 61, 65). With appropriate alcohols thiazoleanhydrkies give the esters or diesters in good yield (64), dimethyl 2-phoiyl-4,5-thiazoledicarboxylate (13) has been prepared in this way (Scheme 8) (17). 

An alternative route to 6a- uorosteroids was developed by treating the enol acetate (93) of a A -3-one with perchloryl fluoride ia aqueous dioxane to obtain a mixture of the 6-fluoro-epimers (94) which were converted iato the 6a-fluoro-A -3-ones (95) on treatment with. ... 

Rhoda.mines, Rhodamines are commercially the most important arninoxanthenes. If phthalic anhydride is used in place of formaldehyde in the above condensation reaction with y -dialkylarninophenol, a triphenyknethane analogue, 9-phenylxanthene, is produced. Historically, these have been called rhodamines. Rhodamine B (Basic Violet 10, Cl45170) (17) is usually manufactured by the condensation of two moles of y -diethylaminophenol with phthahc anhydride (24). An alternative route is the reaction of diethylamine with fluorescein dichloride [630-88-6] (3,6-dichlorofluoran) (18) under pressure. 

Ma.nufa.cture. Most butanediol is manufactured in Reppe plants via hydrogenation of butynediol. Recendy an alternative route involving acetoxyiation of butadiene has come on stream and, more recendy, a route based upon hydroformylation of allyl alcohol. Woddwide butanediol capacity has climbed steadily for many years. In 1990 it was estimated to be 428,000 metric tons (141), as compared to a Htde more than 70,000 metric tons in 1975... 

Isobutyl alcohol [78-83-1] forms a substantial fraction of the butanols produced by higher alcohol synthesis over modified copper—zinc oxide-based catalysts. Conceivably, separation of this alcohol and dehydration affords an alternative route to isobutjiene [115-11 -7] for methyl /-butyl ether [1624-04-4] (MTBE) production. MTBE is a rapidly growing constituent of reformulated gasoline, but its growth is likely to be limited by available suppHes of isobutylene. Thus higher alcohol synthesis provides a process capable of supplying all of the raw materials required for manufacture of this key fuel oxygenate (24) (see Ethers). 

H. Storen, "The Nitrophosphate Process—an Alternative Route to Phosphate Fertilizers," ia proceedings of Phosphate Eertilicyers and the Environment, International Fertilizer Development Center, Muscle Shoals, Ala., 1992. 

Preparation. Thermal elimination of HCl from l-chloro-l,l-difluoroethane (HCFC-142b) [75-68-3] is the principal industrial route to VDF covered by numerous patents (8—19). Dehydrohalogenation of l-bromo-l,l-difluoroethane (20), or 1,1,1-trifluoroethane (HFC-143a) (21—25), or dehalogenation of l,2-dichloro-l,l-difluoroethane (26—28) are investigated alternative routes (see Fluorine compounds, organic-fluorinated aliphatic compounds). 

The polymerization of A/-(2-tetrahydropyranyl)aziridine with subsequent hydrolysis of the resulting polymers has been described as an alternative route for the synthesis of linear polyethyleneimine (359). Linear polyethyleneimine, in contrast to branched polyethyleneimines, is only sparingly soluble in water at room temperature. 

Dow Chemical Company purchased the rights to MacaHum s patents (14), initiated a detailed study of the process and other improved syntheses of PPS in the 1950s and early 1960s, and pubUshed the results of their investigation (9,15,16). Clearly, alternative routes to PPS were desirable and the most promising of these involved the nucleophilic self-condensation of cuprous -bromothiophenoxide, carried out at 200—250°C in the soHd state or in the presence of pyridine (16) ... 

Other Synthesis Routes. Several alternative routes to the nucleopbilic substitution synthesis of polysulfones are possible. Polyethersulfone can be synthesized by the electrophilic Eriedel-Crafts reaction of bis(4-chlorosulfonylphen5l)ether [121 -63-1] with diphenyl ether [101-84-8] (11—13). 

A ruthenium-based catalyst is used but low yields resulting from unexpected side reactions are stiU a problem. Refinement of alternative route ammonia manufacture and advances in genetic engineering, allowing a wider range of plant life to fix nitrogen in situ should provide assurance for long term world food needs. 

An alternative route to 5-nitro-2-furancarboxaldehyde requires nitration of 2-furancarboxaldehyde oxime [1121 -47-7] with mixed acid to give the nitrated oxime [555-15-7] and concomitant hydrolysis (22). Furthermore, 2-furan-carboxaldehyde derivatives with the R-substituent in place have been nitrated to the desired product (23). 

The introduction of tritium into molecules is most commonly achieved by reductive methods, including catalytic reduction by tritium gas, PH2], of olefins, catalytic reductive replacement of halogen (Cl, Br, or I) by H2, and metal pH] hydride reduction of carbonyl compounds, eg, ketones (qv) and some esters, to tritium-labeled alcohols (5). The use of tritium-labeled building blocks, eg, pH] methyl iodide and pH]-acetic anhydride, is an alternative route to the preparation of high specific activity, tritium-labeled compounds. The use of these techniques for the synthesis of radiolabeled receptor ligands, ie, dmgs and dmg analogues, has been described ia detail ia the Hterature (6,7). 

An alternative route of manufacture is from siUcon tetrafluoride that is generated ia large quantities as a by-product of the production of phosphate fertilizers. The reaction is... 

An alternative route is the reaction of iodine or bromine in pyhdine with Hquid sulfur dioxide at 20°C, which gives good to high yields of sulfites (106). 

In contrast with the well-known Embden-Meyerhof-Pamass glycolysis pathway for the conversion of hexose sugars to alcohol, the steps in conversion of ethanol to acetic acid remain in some doubt. Likely, ethanol is first oxidized to acetaldehyde and water (39). For further oxidation, two alternative routes are proposed more likely, hydration of the acetaldehyde gives CH2CH(OH)2, which is oxidized to acetic acid. An alternative is the Cannizzaro-type disproportionation of two molecules of acetaldehyde to one molecule of ethanol and one molecule of acetic acid. Jicetobacter... 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

Reaction with Amines and Ammonia. Carbonates react with amines and ammonia to produce carbamates or ureas. This reaction can be used as an alternative route to producing carbamate pesticides. 

From Allyl Alcohol. An alternative route to dichlorohydrias from aHyl chloride begias with the hydrolysis to aHyl alcohol. Significant yields of 2,3-dichloropropanol can be obtained from the reaction of chlorine with allyl alcohol if the reaction is performed ia the presence of concentrated hydrochloric acid (65). Several patents for the manufacture of 2,3-dichloropropanol by the chlorination of allyl alcohol at low temperature, —30° to +20° C, ia 25—40% HCl solution have appeared (66—68). Product yields as high as 98% are claimed. 

Chloroanthraquinone [82-44-0] (41) is an intermediate for manufacturing vat dyes such as Cl Vat Brown 1. 1-Chloroanthraquinone is prepared by chlorination of anthraquinone-l-sulfonic acid with sodium chlorate in hydrochloric acid at elevated temperature (61). An alternative route from 1-nitroanthraquinone (18) using elemental chlorine at high temperature has been reported (62). 

An alternative route from l-aminoanthraquinone (17) has been proposed. Methylation is preferably carried out usiag dimethyl sulfate or methyl iodide ia an organic solvent ia the presence of alkah metal hydroxide and a catalytic amount of quaternary ammonium compound (98). 

An alternative route for the formation of diethyl ether from ethanol is by dehydration ... 

Pyrimidine N-oxides may be made directly or via their N-alkoxy analogues by means of the Principal Synthesis or other primary synthesis. The alternative route is peroxide oxidation of the parent pyrimidine but this can lead to a mixture of 1- and 3-oxides if the substrate is unsymmetrical about the 2,5-axis of the molecule. 

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