Anhydrous conditions

Also, in anhydrous conditions, silver reacts with fluorine and forms silver difluoride AgFj and cobalt gives cobalt(III) fluoride, C0F3, these metals showing higher oxidation states than is usual in their simple salts. 

Although the acetylation of alcohols and amines by acetic anhydride is almost invariably carried out under anhydrous conditions owing to the ready hydrolysis of the anhydride, it has been shown by Chattaway (1931) that phenols, when dissolved in aqueous sodium hydroxide solution and shaken with acetic anhydride, undergo rapid and almost quantitative acetylation if ice is present to keep the temperature low throughout the reaction. The success of this method is due primarily to the acidic nature of the phenols, which enables them to form soluble sodium derivatives, capable of reacting with the acetic... 

R NHa + C.HjNCO = RNH CO NHC,Hj Traces of water will contaminate the product with diphenylurea (p. 336) if the solution is boiled hence the need for anhydrous conditions. i-Naphthylisocyanate reacts more slowly with water, and the i-naphthyl-urea derivative can often be obtained using a cold aqueous solution of an aliphatic amine it is particularly necessary in such cases to purify the product by recrystallisation from, or extraction with, boiling petroleum, leaving behind any insoluble di i-naphthylurea. Note that the amine must also be free from alcohols (p. 335) and phenols (p. 337). 

The ureas are less soluble than the corresponding urethanes, but their separation is not always easy. For this reason the urethanes are generally prepared from alcohols which are insoluble in water and can therefore be easily obtained in the anhydrous condition. 

Olah s original preparative nitrations were carried out with mixtures of the aromatic compound and nitronium salt alone or in ether, and later with sulpholan as the solvent. High yields of nitro-compounds were obtained from a wide range of aromatic compounds, and the anhydrous conditions have obvious advantages when functional groups such as cyano, alkoxycarbonyl, or halogenocarbonyl are present. The presence of basic fimctions raises difficulties with pyridine no C-nitration occurs, i-nitropyridinium being formed. ... 

Palladium-catalyzed coupling reactions of organic halides with olefins or dienes (R. F. Heck, 1979) are broad in scope and simple to carry out. Anhydrous conditions or any special technique are not required and most functional groups are tolerated. 

In contrast to oxidation in water, it has been found that 1-alkenes are directly oxidized with molecular oxygen in anhydrous, aprotic solvents, when a catalyst system of PdCl2(MeCN)2 and CuCl is used together with HMPA. In the absence of HMPA, no reaction takes place(100]. In the oxidation of 1-decene, the Oj uptake correlates with the amount of 2-decanone formed, and up to 0.5 mol of O2 is consumed for the production of 1 mol of the ketone. This result shows that both O atoms of molecular oxygen are incorporated into the product, and a bimetallic Pd(II) hydroperoxide coupled with a Cu salt is involved in oxidation of this type, and that the well known redox catalysis of PdXi and CuX is not always operalive[10 ]. The oxidation under anhydrous conditions is unique in terms of the regioselective formation of aldehyde 59 from X-allyl-A -methylbenzamide (58), whereas the use of aqueous DME results in the predominant formation of the methyl ketone 60. Similar results are obtained with allylic acetates and allylic carbonates[102]. The complete reversal of the regioselectivity in PdCli-catalyzed oxidation of alkenes is remarkable. 

Anthralin [1143-38-0] is acetylated using acetyl chloride in toluene and a pyridine catalyst to furnish 1,8-dihydroxy-lO-acetylanthrone [3022-61-5], an intermediate in the preparation of medications used in treating skin disorders, such as warts, psoriasis, and acne (38). Sugar esters can be similarly prepared from acetyl chloride under anhydrous conditions (39). 

Oxidative Carbonylation of Ethylene—Elimination of Alcohol from p-Alkoxypropionates. Spectacular progress in the 1970s led to the rapid development of organotransition-metal chemistry, particularly to catalyze olefin reactions (93,94). A number of patents have been issued (28,95—97) for the oxidative carbonylation of ethylene to provide acryUc acid and esters. The procedure is based on the palladium catalyzed carbonylation of ethylene in the Hquid phase at temperatures of 50—200°C. Esters are formed when alcohols are included. Anhydrous conditions are desirable to minimize the formation of by-products including acetaldehyde and carbon dioxide (see Acetaldehyde). 

Inasmuch as the gas hydroly2es readily, all equipment should be purged repeatedly using inert dry gas before admitting boron trifluoride. Under anhydrous conditions, carbon steel equipment is satisfactory. Stainless steel and aluminum siUcon bron2e may also be used. Stainless steel tubing is recommended for both temporary and permanent connections. 

Under neutral or slightly alkaline conditions, only the unstable hemiformal (CH O—CH2OH, methoxymethan0I) is produced. Alpha-chloromethyl ether is synthesized from aqueous formaldehyde, methanol, and hydrogen chloride (54). However, under anhydrous conditions, a carcinogenic by-product, bis(chloromethyl)ether is also formed (55). 

This method, however, is not industrially practical because a large amount of dehydrating agent, such as ethyl orthoformate, is required to remove water formed in the reaction. Because water is an inhibitor of the reaction, the reaction system has to be kept under substantially anhydrous conditions. 

Consequendy, most organomineral peroxides must be prepared and stored under anhydrous conditions. In addition, anhydrous hydrogen chloride converts alkyl-substituted organomineral peroxides to alkyl hydroperoxides (33). 

A related but distinct rhodium-catalyzed methyl acetate carbonylation to acetic anhydride (134) was commercialized by Eastman in 1983. Anhydrous conditions necessary to the Eastman acetic anhydride process require important modifications (24) to the process, including introduction of hydrogen to maintain the active [Rhl2(CO)2] catalyst and addition of lithium cation to activate the alkyl methyl group of methyl acetate toward nucleophilic attack by iodide. 

Lactams can also be polymerized under anhydrous conditions by a cationic mechanism initiated by strong protic acids, their salts, and Lewis acids, as weU as amines and ammonia (51—53). The complete reaction mechanism is complex and this approach has not as yet been used successfully in a commercial process. 

Refluxing linoleic acid and a primary or secondary alkyl amine with -toluenesulfonic acid in toluene for 8—18 h also yields the substituted amides (32—34). The reaction of methyl esters with primary or secondary amines to make substituted amides is catalyzed with sodium methoxide. Reactions are rapid at 30°C under anhydrous conditions (35). Acid chlorides can also be used. Ai,A/-dibutyloleamide [5831-80-17 has been prepared from oleoyl chloride and dibutyl amine (36). 

N -Heterocyclic Sulfanilamides. The parent sulfanilamide is manufactured by the reaction of A/-acetylsulfanilyl chloride with excess concentrated aqueous ammonia, and hydrolysis of the product. Most heterocycHc amines are less reactive, and the condensation with the sulfonyl chloride is usually done in anhydrous media in the presence of an acid-binding agent. Use of anhydrous conditions avoids hydrolytic destmction of the sulfonyl chloride. The solvent and acid-binding functions are commonly filled by pyridine, or by mixtures of pyridine and acetone. Tertiary amines, such as triethylamine, may be substituted for pyridine. The majority of A/ -heterocycHc sulfanilamides are made by simple condensation with A/-acetylsulfanilyl chloride and hydrolysis. 

Friedel-Crafts. 2-Phenylpropanol results from the catalytic (AlCl, FeCl, or TiCl reaction of ben2ene and propylene oxide at low temperature and under anhydrous conditions (see Friedel-CRAFTS reactions). Epoxide reaction with toluene gives a mixture of 0-, m- and -isomers (75,76). 

Unlike simple, unhindered carbonyl compounds, the quinones do not yield bisulfite addition products, but undergo ring addition. Another significant carbonyl reaction is the addition of tertiary phosphites under anhydrous conditions (98). The ester product (99) is easily hydroly2ed, and the overall sequence produces excellent yields of hydroquinone monoethers. 

Hydration and Dehydration. Succinic anhydride reacts slowly with cold water and rapidly with hot water to give the acid. For this reason it must be carefully stored in anhydrous conditions. Succinic acid can be dehydrated to the anhydride by heating at 200°C, optionally in the presence of a solvent (31). Dehydration can also be performed with clay catalysis in the presence of isopropenyl acetate under microwave irradiation (32) or with his (trichi oromethyl) carbonate at room temperature (33). 

Stannic Chloride Pentahydrate. Stannic chloride pentahydrate [10026-06-9] is a white, crystalline, deHquescent soHd that is soluble in water or methanol and stable at 19—56°C. It is used in place of the anhydrous chloride where anhydrous conditions are not mandatory. It is easier to handle than the fuming anhydrous Hquid form. The pentahydrate is prepared by dissolving stannic chloride in hot water, thereby forming the pentahydrate at a temperature above the melting point and crystallizing by cooling. The cake is broken into small lumps for packaging. 

Alkoxides. Zirconium alkoxides are part of a family of alcohol-derived compounds (219). The binary zirconium compounds have the general formula ZRX — (OR). They are easily hydrolyzed and must be prepared under anhydrous conditions. They are prepared by the reaction of zirconium tetrahahdes and alcohols ... 

The zirconium—nitrogen bond is weaker than the zirconium—oxygen bond even under anhydrous conditions. When zirconium tetrachloride reacts with carbonyl-containing amides such as... 

Conversion to a more facile, sulfur-derived, leaving group can be achieved by treatment with sodium thiosulfate or salts of thio and dithio acids (75,87). Under anhydrous conditions, boron tribromide converts the 3 -acetoxy group to a bromide whereas trimethyl silyl iodide gives good yields of the 3 -iodide (87,171,172). These 3 -halides are much more reactive, even when the carboxyl group is esterified, and can be displaced readily by cyano and by oxygen nucleophiles (127). 

Dimethyl carbonate [616-38-6] and dimethyl oxalate [553-90-2] are both obtained from carbon monoxide, oxygen, and methanol at 363 K and 10 MPa (100 atm) or less. The choice of catalyst is critical cuprous chloride (66) gives the carbonate (eq. 20) a palladium chloride—copper chloride mixture (67,68) gives the oxalate, (eq. 21). Anhydrous conditions should be maintained by removing product water to minimize the formation of by-product carbon dioxide. 

Many of the surfactants made from ethyleneamines contain the imidazoline stmcture or are prepared through an imidazoline intermediate. Various 2-alkyl-imidazolines and their salts prepared mainly from EDA or monoethoxylated EDA are reported to have good foaming properties (292—295). Ethyleneamine-based imida zolines are also important intermediates for surfactants used in shampoos by virtue of their mildness and good foaming characteristics. 2- Alkyl imidazolines made from DETA or monoethoxylated EDA and fatty acids or their methyl esters are the principal commercial intermediates (296—298). They are converted into shampoo surfactants commonly by reaction with one or two moles of sodium chloroacetate to yield amphoteric surfactants (299—301). The ease with which the imidazoline intermediates are hydrolyzed leads to arnidoamine-type stmctures when these derivatives are prepared under aqueous alkaline conditions. However, reaction of the imidazoline under anhydrous conditions with acryflc acid [79-10-7] to make salt-free, amphoteric products, leaves the imidazoline stmcture essentially intact. Certain polyamine derivatives also function as water-in-oil or od-in-water emulsifiers. These include the products of a reaction between DETA, TETA, or TEPA and fatty acids (302) or oxidized hydrocarbon wax (303). The amidoamine made from lauric acid [143-07-7] and DETA mono- and bis(2-ethylhexyl) phosphate is a very effective water-in-od emulsifier (304). 

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

Bu4N F , THF, 25°, 1 h, >90% yield. Fluoride ion is very basic especially under anhydrous conditions and thus may cause side reactions with base-sensitive substrates. ArOTBDMS ethers can be cleaved in the presence of alkyl OTBDMS ethers. ... 

Bu4N" Cr, KF-H20, CH3CN, 25°, 4 h, 95% yield. This method generates fluoride ion in situ and is reported to be suitable for reactions that normally require anhydrous conditions. 

Under anhydrous conditions, cesium carbonate or bicarbonate quantitatively cleaves an aryl dibenzoate or diacetate to the monoester yields are considerably lower with potassium carbonate. ... 

CH2Br2, NaOH, H2O, Adogen, reflux, 3 h, 76-86% yield. Adogen = R3N CH3C1 , phase-transfer catalyst (R — Cg-C,o straight-chain alkyl groups). Earlier methods required anhydrous conditions and aprotic solvents. 

Aluminium bromide [7727-15-3] M 266.7, m 97°, b 114°/10mm. Refluxed and then distilled from pure aluminium chips in a stream of nitrogen into a flask containing more of the chips. It was then distd under vacuum into ampoules [Tipper and Walker 7 Chem Soc 1352 1959], Anhydrous conditions are essential, and the white to very light brown solid distillate can be broken into lumps in a dry-box (under nitrogen). Fumes in moist air. 

The compound known as 18-crown-6 is one of the simplest and most useful of the macrocyclic polyethers. Its synthesis in low yield was first reported by Pedersen. Greene and Dale and Kristiansen" have reported syntheses of the title compound from triethylene glycol and triethylene glycol di-p-toluenesulfonate. Both of these procedures use strong base and anhydrous conditions and achieve purification by more or leas classical methods. The combination of distillation and formation of the acetonitrile complex affords crown of high purity without lengthy chromatography or sublimation. ... 

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