Route a

Of little use commercially except as a route to anthraquinone. For this purpose it is oxidized with acid potassium dichromate solution, or better, by a catalytic air oxidation at 180-280 C, using vanadates or other metal oxide catalysts. 

Oldham K B 1991 Steady-state microelectrode voltammetry as a route to homogeneous kinetics J. Electroanal. Chem. 313 3... 

Filippi C and Umrigar C J 2000 Correlated sampling in quantum Monte Carlo a route to forces Phys. Rev. B 61 R16 291... 

Merkle R C 1999 Bioteohnology as a route to nanoteohnology Trends Biotechnol. 17 271... 

All these routes use known reactions and are about the same length. Do you notice that no less than three have the unsaturated acid 353A as an intermediate. If we need to try out new reactions it is best to choose a route with a common intermediate (353A here) so that if one route fails we can use the same intermediate for another. We can then choose between the three routes on cost. The 1977 prices of the starting materials are p-chlorobenzaldehyde 9.80/500g diethyl rnalonate 2.80/500g... 

Treatment of 2-imino-3-phenyl-4-amino-(5-amido)-4-thiazoline with isocyanates or isothiocyanates yields the expected product (139) resulting from attack of the exocyclic nitrogen on the electrophilic center (276). Since 139 may be acetylated to thiazolo[4,5-d]pyrimidine-7-ones or 7-thiones (140). this reaction provides a route to condensed he erocycles (Scheme 92). 

Nitrile groups m cyanohydrins are hydrolyzed under conditions similar to those of alkyl cyanides Cyanohydrin formation followed by hydrolysis provides a route to the preparation of a hydroxy carboxylic acids... 

Hydrogenation of the aromatic ring to form naphthenic compounds has been proposed as a route to faciUtate the separation of the Cg aromatic isomers (31). The spread in boiling points of the naphthenic compounds is 12°C vs a spread of 8°C for the aromatic compounds. However, the cycloparaffinic products obtained from OX and EB boil only 3°C apart, impeding the separation. 

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... 

Manufacture Various methods for the manufacture of acrylates are summarized in Figure 1, showing thek dependence on specific raw materials. For a route to be commercially attractive, the raw material costs and utilization must be low, plant investment and operating costs not excessive, and waste disposal charges minimal. 

Dehydrogenation of Propionates. Oxidative dehydrogenation of propionates to acrylates employing vapor-phase reactions at high temperatures (400—700°C) and short contact times is possible. Although selective catalysts for the oxidative dehydrogenation of isobutyric acid to methacrylic acid have been developed in recent years (see Methacrylic ACID AND DERIVATIVES) and a route to methacrylic acid from propylene to isobutyric acid is under pilot-plant development in Europe, this route to acrylates is not presentiy of commercial interest because of the combination of low selectivity, high raw material costs, and purification difficulties. 

Olefin—Paraffin Separation. The catalytic dehydrogenation of / -paraffins offers a route to the commercial production of linear olefins. Because of limitations imposed by equiUbrium and side reactions, conversion is incomplete. Therefore, to obtain a concentrated olefin product, the olefins must be separated from the reactor effluent (81—85), and the unreacted / -paraffins must be recycled to the catalytic reactor for further conversion. 

The lime—soda process is practiced mainly in isolated areas in some process operations, in the Kraft recovery process, and in the production of alurnina. It is not as efficient a route as electrolytic production. 

Akzo Process. Akzo Zout Chemie has developed a route to vinyl chloride and soda ash from salt usiag an amine—solvent system catalyzed by a copper—iodide mixture (13). This procedure theoretically requires half the energy of the conventional Solvay processes. 

Bicomponent fibers have also provided a route to self-texturing (self-crimping) fibers. The crimp results from the length differential developed during processing caused by differential shrinkage in the two polymers in side-by-side or eccentric core—sheath configurations (50). 

Akylsilanes undergo highly regioselective acylation to give P,y-unsaturated ketones (177). Acylation of y,y-dialkylallyltrialkylsilane provides a route to the constmction of difficulty accessible quaternary carbon centers. 

In general, the aluminohydrides are more active and powerful reducing agents than the corresponding borohydrides. They decompose vigorously with water. Reaction also occurs with alcohols, although more moderately, providing a route to substituted derivatives. 

Polymerization of methacrylates is also possible via what is known as group-transfer polymerization. Although only limited commercial use has been made of this technique, it does provide a route to block copolymers that is not available from ordinary free-radical polymerizations. In a prototypical group-transfer polymerization the fluoride-ion-catalyzed reaction of a methacrylate (or acrylate) in the presence of a silyl ketene acetal gives a high molecular weight polymer (45—50). 

Functional Olefin Hydroformylation. There has been widespread academic (18,19) and industrial (20) interest in functional olefin hydroformylation as a route to polyfiinctional molecules, eg, diols. There are two commercially practiced oxo processes employing functionalized olefin feedstocks. Akyl alcohol hydroformylation is carried out by Arco under Hcense from Kuraray (20,21). 1,4-Butanediol [110-63 ] is produced by successive hydroformylation of aHyl alcohol [107-18-6] aqueous extraction of the intermediate 2-hydroxytetrahydrofuran, and subsequent hydrogenation. 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

Although the concept of polymer blends is sometimes a route for a voiding the development of new polymers, it often has been an integral part of the utiliza tion of new polymer chemistry, eg, the commercial success of PPO hinged on the advantages of its blends with PS. 

The principal iadustrial production route used to prepare fatty amines is the hydrogenation of nitriles, a route which has been used since the 1940s. Commercial preparation of fatty amines from fatty alcohols is a fairly new process, created around 1970, which utilizes petrochemical technology, Ziegler or Oxo processes, and feedstock. 

Direct halogenation of S-hydroxyquiaoline has been used as a route to 5,7-dihalo derivatives. Compounds of this type reported iaclude... 

Sulfur dichloride undergoes many of the same reactions with organic compounds as described for sulfur monochloride. Addition to olefins affords a route to bis(2-chloroalkyl) sulfides and, ia certain cases, heterocycHc sulfides (159,160). 

Monolayers of alkyl chains on siUcon are a significant addition to the family of SAMs. An abiUty to directly connect organic materials to siUcon allows a direct coupling between organic materials and semiconductors. The fine control of supedattice stmctures provided by the self-assembly technique offers a route for building organic thin films with, for example, electrooptic properties on siUcon. 

The kidney is an important organ for the excretion of toxic materials and their metaboHtes, and measurement of these substances in urine may provide a convenient basis for monitoring the exposure of an individual to the parent compound in his or her immediate environment. The Hver has as one of its functions the metaboHsm of foreign compounds some pathways result in detoxification and others in metaboHc activation. Also, the Hver may serve as a route of elimination of toxic materials by excretion in bile. In addition to the Hver (bile) and kidney (urine) as routes of excretion, the lung may act as a route of elimination for volatile compounds. The excretion of materials in sweat, hair, and nails is usually insignificant. 

Ring contraction of 2-thiocephems has also been examined as a route to penems. Desulfurization of (82, n = 0) using triphenylphosphine gave mixtures of 5(R)- and 5(5)-penems (121). The stereochemical problem was neatiy overcome by regioselective oxidation to the thiosulfonate (82, n = 2) which underwent stereospecific thermal extmsion of sulfur dioxide (122) to give the S(R)-penem (83). 

Electrode kinetics lend themselves to treatment usiag the absolute reaction rate theory or the transition state theory (36,37). In these treatments, the path followed by the reaction proceeds by a route involving an activated complex where the element determining the reaction rate, ie, the rate limiting step, is the dissociation of the activated complex. The general electrode reaction may be described as ... 

Ce(IV) extracts more readily iato organic solvents than do the trivalent Ln(III) ions providing a route to 99% and higher purity cerium compounds. Any Ce(III) content of mixed lanthanide aqueous systems can be oxidi2ed to Ce(IV) and the resultiag solutioa, eg, of nitrates, contacted with an organic extractant such as tributyl phosphate dissolved in kerosene. The Ce(IV) preferentially transfers into the organic phase. In a separate step the cerium can be recovered by reduction to Ce(III) followed by extraction back into the aqueous phase. Cerium is then precipitated and calcined to produce the oxide. 

Hexachloroethane is considered to be one of the more toxic chlorinated hydrocarbons. The 1991 ACGIH recommended time-weighted average (TWA) for hexachloroethane was 1 ppm or 10 mg /m of air. Skin adsorption is a route of possible exposure ha2ard. The primary effect of hexachloroethane is depression of the central nervous system (147). Pentachloroethane and tetrachloroethylene are primary metaboHtes of hexachloroethane in sheep (148). 

The Michael addition reaction has attracted many researchers as a route to convert high melting BMI building blocks into resins with improved processibihty as compared with the BMI precursors. Heat-resistant resin compositions are prepared from BMI and para- or y /i7-aminophenol (38). The idealized stmcture of such a BMI—y -aminophenol adduct follows. 

Amino-2-chloto-4-hydtoxyanditaquinone is prepared via a route from chlorobenzene and phthalic anhydride as the taw materials (35) (see Fig. 2). 

Conventional 1,5-dichloroanthraquinone has also been used as a starting material. A route via 1,5-diaminoanthraquinone has also been proposed (127) treatment of this compound with Br2 in H2SO4 and H BO gives (11). 

Polyisobutylene has the chemical properties of a saturated hydrocarbon. The unsaturated end groups undergo reactions typical of a hindered olefin and are used, particularly in the case of low mol wt materials, as a route to modification eg, the introduction of amine groups to produce dispersants for lubricating oils. The in-chain unsaturation in butyl mbber is attacked by atmospheric ozone, and unless protected can lead to cracking of strained vulcanizates. Oxidative degradation, which leads to chain cleavage, is slow, and the polymers are protected by antioxidants (75). 

In contrast to the above, the reaction of a heterocyclic thione with an a-halogenoketone (Scheme 3) has been widely exploited as a route to [5,6] ring-fused systems with a heteroatom at a ring fusion point. 

Acylation of 3-alkyl-6-hydroxy-l,2-benzisoxazole has also been reported (77JIC875) under Friedel-Crafts conditions to give the 7-acyl product. Fries rearrangement of 6-acetoxy-3-methyl-1,2-benzisoxazole in the presence of AICI3 at 140 °C also provides a route to the 7-acetyl-6-hydroxy derivatives (73UC541). Reactions of these kind are rare in this series. 

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