Industrial syntheses

The industrial scale fermentative synthesis of PHA uses these pathways to convert the typical nutrients sugar or starch to PHB, but glycerol or palm-oil can also be applied. In addition, copolymers can be produced in this way but special microorganisms, growing condition, and additives are needed. Thus a statistic comonomer distribution starting from 0% (pure PHB) up to 90% co-monomer content can be achieved [35-38]. 

For the production of PHB, a specially selected bacteria is used. They grow in aqueous media during air injection at 35°C. At the end of the fermentation process about 80% of cell dry weight consists of PHB. Production is about 100 kg PHB/m of medium (Fig. 7). 

The next step in the process is the extraction of the product. The bacteria are washed and then concentrated. The polymer is extracted by the use of organic solvents such as hot alcohols and decanted from the non-PHA cell matter. The solution is pressed into water to precipitate the polymer as a white solid. In most 

Production this way is thus complex and time consuming, therefore generating an extremely expensive material. Even if new and low-cost feedstocks are applied successfully in future, fermentative synthesis will remain high priced due to this work-up process, which cannot compete with a simple poly(olefin) production (Fig. 9). 

Adolf von Baeyer s first synthetic efforts on the preparation of indigo - for which the question of its correct structure remained unanswered - were not exploitable on an industrial scale due to the inaccessibility of the starting materials. Already in 1870, following his seven-stage isatin synthesis, Baeyer (Fig. 2.11) had succeeded in converting this material with phosphorus pentachloride into isatin chloride reductive dehalogenation of the latter with zinc yielded indigo directly. 

The accessibility of o-nitrobenzaldehyde was the problem. Toluene, which served as a starting material and could be isolated from coal tar, was restricted in availability, and its chlorination and nitration were considered unsatisfactory on the grounds of selectivity and yield. 

In the meantime, Hoechst and BASF had teamed up to form what nowadays would be described as a joint ventme - they had acquired the patent rights from Baeyer and set up enormous research activities. In the end, those efforts remained unsuccessful. 

Starting from aniline and chloroacetic acid, phenylgycine was accessible, and this, when melted with solid potassium hydroxide, gave indigo. 

Unfortunately it very quickly became clear, that even under optimised reaction conditions, the yield was only 10 %. 

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Since (A) does not contain any other functional group in addition to the formyl group, one may predict that suitable reaction conditions could be found for all conversions into (A). Many other alternative target molecules can, of course, be formulated. The reduction of (H), for example, may require introduction of a protecting group, e.g. acetal formation. The industrial synthesis of (A) is based upon the oxidation of (E) since 3-methylbutanol (isoamyl alcohol) is a cheap distillation product from alcoholic fermentation ( fusel oils ). The second step of our simple antithetic analysis — systematic disconnection — will now be exemplified with all target molecules of the scheme above. For the sake of brevity we shall omit the syn-thons and indicate only the reagents and reaction conditions. 

The industrial synthesis of acetaldehyde from ethylene IS shown on page 644... 

A similar reaction in which ammonia and carbon dioxide are heated under pres sure IS the basis of the industrial synthesis of urea Here the reactants first combine yielding a salt called ammonium carbamate... 

The most widely used industrial synthesis of phenol is based on isopropylbenzene (cumene) as the starting material and is shown m the third entry of Table 24 3 The eco nomically attractive features of this process are its use of cheap reagents (oxygen and sulfuric acid) and the fact that it yields two high volume industrial chemicals phenol and acetone The mechanism of this novel synthesis forms the basis of Problem 24 29 at the end of this chapter... 

Material System. There are two basic techniques for the industrial synthesis of Si3N powder, although other methods are available (36). The older and most widely used method is the nitridation of siHcon. SiHcon is heated in a nitrogen [7727-37-9] atmosphere at temperatures of 1100—1450°C in... 

R. A. Sheldon, Chirotechnology Industrial Synthesis of Optically Active Compounds, Marcel Dekker, Inc., New York, 1993. 

A Methylamino)phenol. This derivative (15) is easily soluble ia ethyl acetate, ethanol, diethyl ether, and benzene. It is also soluble ia hot water, but only spatingly soluble ia cold water. Industrial synthesis is by heating 3-(A/-methylamino)benzenesulfonic acid with sodium hydroxide at 200—220°C (179) or by the reaction of resorciaol with methylamiae ia the presence of aqueous phosphoric acid at 200°C (180). 

A A Diethylamino)phenol. This derivative (16) forms rhombic bipyramidal crystals. Industrial synthesis is analogous to the previously described synthesis of 3-(/V,/V-dimethy1amino)pheno1 from resorciaol and diethylamiae, by reaction of 3-(Ai,A/-diethylamiQo)benzenesulfonic acid with sodium hydroxide, or by alkylation of 3-amiaophenol hydrochloride with ethanol. 

A Methylamino)phenol. This derivative, also named 4-hydroxy-/V-methy1ani1ine (19), forms needles from benzene which are slightly soluble in ethanol andinsoluble in diethyl ether. Industrial synthesis involves decarboxylation of A/-(4-hydroxyphenyl)glycine [122-87-2] at elevated temperature in such solvents as chlorobenzene—cyclohexanone (184,185). It also can be prepared by the methylation of 4-aminophenol, or from methylamiae [74-89-5] by heating with 4-chlorophenol [106-48-9] and copper sulfate at 135°C in aqueous solution, or with hydroquinone [123-31 -9] 2l. 200—250°C in alcohoHc solution (186). 

Although the industrial synthesis of vitamin remains largely unchanged from its early beginnings, significant effort has been devoted to improvements in the condensation step, the oxidation of dihydrovitarnin to vitamin K, and in economical approaches to vitamin (vide infra). Also, several chemical and biochemical alternatives to vitamin have been developed. 

As compared to vitamin K, vitamin K2 is relatively unimportant industrially with only a few producers, such as Teikoku Kagaku Sangyo and Eisai, and is dominated by the manufacture of vitamin K2 20) industrial synthesis parallels that of vitamin and involves as a key step alkylation of monosubstituted menadione with an appropriate (all-E) reagent (44,45). Several academic syntheses have been described (46—49). 

Hexametbyipbospboric triamide (HMPA) [680-31-9] M 179.2, f 7.2°, b 68-70°/lmm, 235°/760mm, d 1.024, n 1.460. The industrial synthesis is usually by treatment of POCI3 with excess of dimethylamine in isopropyl ether. Impurities are water, dimethylamine and its hydrochloride. It is purified by refluxing over BaO or CaO at about 4mm pressure in an atmosphere of nitrogen for several hours, then distd from sodium at the same pressure. The middle fraction (b ca 90°) is collected, refluxed over sodium under reduced pressure under nitrogen and distd. It is kept in the dark under nitrogen, and stored in solid CO2. Can also be stored over 4A molecular sieves. 

Write a chemical equation for this industrial synthesis. 

The industrial synthesis uses the strongly exothermic reaction between urea and anhydrous H2SO4 (or dilute oleum) ... 

Heterocycles in industrial synthesis of fragrant and flavoring substaces in Czech Republic 99CLY412. 

An important industrial synthesis of cyclohexanone is by partial hydrogenation of phenol over palladium, carried out in either liquid or vapor phase. 

We had a brief introduction to radical reactions in Section 5.3 and said at that time that radicals can add to alkene double bonds, taking one electron from the double bond and leaving one behind to yield a new radical. Let s now look at the process in more detail, focusing on the industrial synthesis of alkene polymers. 

Phenols occur widely throughout nature and also serve as intermediates in the industrial synthesis of products as diverse as adhesives and antiseptics. Phenol itself is a general disinfectant found in coal tar methyl salicylate is a flavoring agent found in oil of wintergreen and the urushiols are the allergenic constituents of poison oak and poison ivy. Note that the word phenol is the name both of the specific compound hydroxybenzene and of a class of compounds. 

Figure 20.7 The industrial synthesis of ascorbic acid from glucose.

Diels-Alder reaction of, 575 electrostatic potential map of, 576 evidence for, 575 structure of, 576 Bergman, Torbern, 2 Bergstrom, Sune K., 1068 Beta anomer, 984 Beta-carotene, structure of, 172 industrial synthesis of, 722 UV spectrum of, 504 Beta-diketone, 851... 

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