One-step processing

The Wittig reaction is one that IS still undergoing mech anistic investigation An other possibility is that the oxaphosphetane intermedi ate IS formed by a two step process rather than the one step process shown in Figure 17 13... 

The mechanism of enolization involves two separate proton transfer steps rather than a one step process m which a proton jumps from carbon to oxygen It is relatively slow m neutral media The rate of enolization is catalyzed by acids as shown by the mechanism m Figure 18 1 In aqueous acid a hydronium ion transfers a proton to the carbonyl oxygen m step 1 and a water molecule acts as a Brpnsted base to remove a proton from the a car bon atom m step 2 The second step is slower than the first The first step involves proton transfer between oxygens and the second is a proton transfer from carbon to oxygen... 

Triethylaluminum Preparation. Triethyl aluminum [97-93-8], C H Al, can be prepared by a two-step or a one-step process. In the former, aluminum [7429-90-5], Al, powder is added to recycled triethylaluminum and the slurry reacts first with hydrogen [1333-74-0], to produce diethylaluminum hydride [871-27-2], which in the second step reacts with ethylene [74-85-1], to produce triethylaluminum. In the one-step process,... 

Depending on the ring substituent, trifluoromethoxyben2enes can be made by the sequential chlorination—fluorination of anisole(s) (351—354). A one-step process with commercial potential is the BF (or SbF2)-cataly2ed reaction of phenol with carbon tetrachloride/hydrogen fluoride (355). Aryl trifluoromethyl ethers, which may not be accessible by the above routes,may be made by fluorination of aryl fluoroformates or aryl chlorothioformates with sulfur tetrafluoride (348) or molybdenum hexafluoride (356). 

Wea.kA.cid Cation Exchangers. The syathesis of weak acid catioa exchangers is a one-step process when acryHc acid or methacrylic acid is copolymetized with DVB. If an acryHc ester is used as the monomer iastead of an acryHc acid, the ester groups must be hydrolyzed after polymerization usiag either an acid or base (NaOH) to give the carboxyHc acid functionaHty, or the sodium salt (4) of it. 

Much of the work with regard to this process was done by the French Petroleum Institute (113) and by the Kuraray Co. (108). In the CIS, a sinulat process which begins with cmde C s was developed (114). A one-step process that begins with isobutylene and methanol has been disclosed (108,115). This process is beheved to have significant economic advantages over the original route. 

Soft-drink bottles made from poly(ethylene terephthalate) (PET) are usuady made by stretch-blow mol ding in a two-step process. Eirst, a test-tube-shaped preform is molded, which is then reheated to just above its glass-transition temperature, stretched, and blown. Stretching the PET produces biaxial orientation, which improves transparency, strength, and toughness of the botde (54,56). A one-step process is used for many custom containers that are injection stretch-blow molded. 

In a patented process, a stirred suspension of sodium sulfite is continuously treated with aqueous sodium hydroxide and a sulfur dioxide-containing gas at 60—85°C, and 96% pure anhydrous sodium sulfite is removed by filtration (336). In another continuous one-step process, substantially anhydrous sodium carbonate and sulfur dioxide are concurrently introduced into a saturated solution of sodium sulfite at pH 6.5—7.6 and above 35°C with continuous removal of sodium sulfite (337). 

Because PEA is such an important fragrance material this simple, essentially one-step process has been exhaustively studied to optimize reaction conditions and purification procedures. Because of the high reactivity of the iatermediates and the tendency toward polymer formation, critical factors such as throughput, temperature, molar ratios of reactants, addition rates, reactor materials and design, and agitation rate must be carefully balanced to provide an economical product with acceptable odor properties. 

Other Cellulosics. Rayon is bleached similarly to cotton but under milder conditions since the fibers are more easily damaged and since there is less colored material to bleach. Cellulose acetate and triacetate are not usually bleached. They can be bleached like rayon, except a slightly lower pH is used to prevent hydrolysis. The above fibers are most commonly bleached with hydrogen peroxide. Linen, dax, and jute requite more bleaching and mil der conditions than cotton, so multiple steps are usually used. Commonly an acidic or neutral hypochlorite solution is followed by alkaline hypochlorite, peroxide, chlorite, or permanganate, or a chlorite step is done between two peroxide steps. A one-step process with sodium chlorite and hydrogen peroxide is also used. 

The pattern of commercial production of 1,3-butadiene parallels the overall development of the petrochemical industry. Since its discovery via pyrolysis of various organic materials, butadiene has been manufactured from acetylene as weU as ethanol, both via butanediols (1,3- and 1,4-) as intermediates (see Acetylene-DERIVED chemicals). On a global basis, the importance of these processes has decreased substantially because of the increasing production of butadiene from petroleum sources. China and India stiU convert ethanol to butadiene using the two-step process while Poland and the former USSR use a one-step process (229,230). In the past butadiene also was produced by the dehydrogenation of / -butane and oxydehydrogenation of / -butenes. However, butadiene is now primarily produced as a by-product in the steam cracking of hydrocarbon streams to produce ethylene. Except under market dislocation situations, butadiene is almost exclusively manufactured by this process in the United States, Western Europe, and Japan. 

Methoxycarbonyl and cyano derivatives One-step process mechanism 75LA449... 

Phenolics or phenol-aldehydes include the important commercial phenolic resin bakelite based on phenol and formaldehyde. A one-step process produces resol resin from more than one molecule of formaldehyde per phenol molecule. A two-step process uses an excess of phenol to produce novolacs - resins that have no reactive methylol groups and must be mixed with an aldehyde o undergo further reaction. 

The syntheses of pyrylium salts will be classified into three groups, according to the number of building blocks required to form the ring in a one-step process (see Scheme 1). 

In contrast to S l reactions, the Sn2 type represent a one-step process. The rate-determining stage, and hence the formation of the new bond, depends on the nucleophilicity of the anion (the nucleo-philicity is essentially a function of the polarizability ). In the Sn2 reaction under discussion, Eq, (7), the nitrogen in CH3—is replaced by the atom of the mesomeric anion which possesses the greatest nucleophilicity. 

Mechanistically the 1,3-dipolar cycloaddition reaction very likely is a concerted one-step process via a cyclic transition state. The transition state is less symmetric and more polar as for a Diels-Alder reaction however the symmetry of the frontier orbitals is similar. In order to describe the bonding of the 1,3-dipolar compound, e.g. diazomethane 4, several Lewis structures can be drawn that are resonance structures ... 

Notice that the overall reaction, obtained by summing the individual steps, is identical with that for the one-step process. The rate expressions are quite different, however ... 

Production of D-gluconolactone from glucose in several fungi is a one-step process catalysed by glucose oxidase. 

No single mechanism accounts for all the reactions. One pathway involves a concerted one-step process involving a cyclic transition state. This of necessity affords a c -product. Another possibility, more favoured in polar solvents, involves a cationic 5-coordinate intermediate [IrX(A)(CO)L2]+, which undergoes subsequent nucleophilic attack by B-. Other possibilities include a SN2 route, where the metal polarizes AB before generating the nucleophile, and radical routes. Studies are complicated by the fact that the thermodynamically more stable isolated product may not be the same as the kinetic product formed by initial addition. 

Poly(arylene ether ketone) Synthesis 6.2.2.4.1 Common One-Step Process... 

Sn2 stands for substitution nucleophilic bimolecular. The lUPAC designation (p. 384) is AnDn- In this mechanism there is backside attack The nucleophile approaches the substrate from a position 180° away from the leaving group. The reaction is a one-step process with no intermediate (see, however, pp. 392-393 and 400). The C—Y bond is formed as the C—X bond is broken ... 

A simple one-step process involving a three-center cyclic transition state ... 

For the characterization of Langmuir films, Fulda and coworkers [75-77] used anionic and cationic core-shell particles prepared by emulsifier-free emulsion polymerization. These particles have several advantages over those used in early publications First, the particles do not contain any stabihzer or emulsifier, which is eventually desorbed upon spreading and disturbs the formation of a particle monolayer at the air-water interface. Second, the preparation is a one-step process leading directly to monodisperse particles 0.2-0.5 jim in diameter. Third, the nature of the shell can be easily varied by using different hydrophilic comonomers. In Table 1, the particles and their characteristic properties are hsted. Most of the studies were carried out using anionic particles with polystyrene as core material and polyacrylic acid in the shell. 

Phenol is the starting material for numerous intermediates and finished products. About 90% of the worldwide production of phenol is by Hock process (cumene oxidation process) and the rest by toluene oxidation process. Both the commercial processes for phenol production are multi step processes and thereby inherently unclean [1]. Therefore, there is need for a cleaner production method for phenol, which is economically and environmentally viable. There is great interest amongst researchers to develop a new method for the synthesis of phenol in a one step process [2]. Activated carbon materials, which have large surface areas, have been used as adsorbents, catalysts and catalyst supports [3,4], Activated carbons also have favorable hydrophobicity/ hydrophilicity, which make them suitable for the benzene hydroxylation. Transition metals have been widely used as catalytically active materials for the oxidation/hydroxylation of various aromatic compounds. 

A similar one-step process was employed successfully [66] to prepare well-crystallized CdS thin films of optical quality on Au(lll) from an aqueous solution of CdSOa, EDTA, and Na2S at room temperature. A phase transition from cubic (zinc blende) to hexagonal (wurtzite) CdS structure was observed with decreasing pH below 5, while highly preferential orientation along [11.0] directions for the... 

Intermediate of increased One-step process Intermediate of reduced coordination number coordination number... 

Examples for necessary process improvements through catalyst research are the development of one-step processes for a number of bulk products like acetaldehyde and acetic acid (from ethane), phenol (from benzene), acrolein (from propane), or allyl alcohol (from acrolein). For example, allyl alcohol, a chemical which is used in the production of plasticizers, flame resistors and fungicides, can be manufactured via gas-phase acetoxylation of propene in the Hoechst [1] or Bayer process [2], isomerization of propene oxide (BASF-Wyandotte), or by technologies involving the alkaline hydrolysis of allyl chloride (Dow and Shell) thereby producing stoichiometric amounts of unavoidable by-products. However, if there is a catalyst... 

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