Benzene, dehydration

Prepared by the dehydration of benzamide. Hydrolysed by dilute acids and alkalis to benzoic acid. Good solvent. benzopheDone,C]3HioO,PhC(0)Ph. Colourless rhombic prisms, m.p. 49 C, b.p. 306°C. Characteristic smell. It is prepared by the action of benzoyl chloride upon benzene in the presence of aluminium chloride (Friedel-Crafts reaction) or by the oxidation of di-phenylmethane. It is much used in perfumery. Forms a kelyl with sodium. 

It is a dibasic acid, and forms stable metallic salts. Distillation with soda lime gives benzene. Readily dehydrated to phthalic anhydride. Its reactions are similar to phthalic anhydride in which form it is almost invariably used. 

Place 24 ml. (24 5 g.) of aniline, 13 ml. (15 5 g.) of nitro-benzene,t and 62 ml. (75 g.) of the anhydrous glycerol in the flask and mix thoroughly. (If the glycerol is still warm from the dehydration, cool the mixture in water.) Now add slowly 36 ml. (66 g.) of concentrated sulphuric acid, shaking the mixture thoroughly during the addition. The mixture at first... 

Pinacol (tetramethylethyleneglycol). Pinacol hydrate may be dehydrated in the following manner (compare Section 11,39). Mix 100 g. of pinacol hydrate with 200 ml. of benzene and distil a mixture of water and benzene passes over. Separate the lower layer and return the upper layer... 

Fig. 2.19 Adsorption isotherm of benzene on (I) hydrated, and (II) dehydrated siliea gel. (After Kiselev .)...

A typical phenol plant based on the cumene hydroperoxide process can be divided into two principal areas. In the reaction area, cumene, formed by alkylation of benzene and propylene, is oxidized to form cumene hydroperoxide (CHP). The cumene hydroperoxide is concentrated and cleaved to produce phenol and acetone. By-products of the oxidation reaction are acetophenone and dimethyl benzyl alcohol (DMBA). DMBA is dehydrated in the cleavage reaction to produce alpha-methylstyrene (AMS). 

Amino-4-nitrophenol. This derivative, 2-hydroxy-5-nitroani1ine (9), forms orange prisms from water. These prisms are hydrated with one water of crystallization, mp 80—90°C, and can be dehydrated over sulfuric acid to the anhydrous form, mp 143 —145°C. The compound is soluble in ethanol, diethyl ether, acetic acid, and warm benzene and slightly soluble in water. 

Pyrrohdinone (2-pyrrohdone, butyrolactam or 2-Pyrol) (27) was first reported in 1889 as a product of the dehydration of 4-aminobutanoic acid (49). The synthesis used for commercial manufacture, ie, condensation of butyrolactone with ammonia at high temperatures, was first described in 1936 (50). Other synthetic routes include carbon monoxide insertion into allylamine (51,52), hydrolytic hydrogenation of succinonitnle (53,54), and hydrogenation of ammoniacal solutions of maleic or succinic acids (55—57). Properties of 2-pyrrohdinone are Hsted in Table 2. 2-Pyrrohdinone is completely miscible with water, lower alcohols, lower ketones, ether, ethyl acetate, chloroform, and benzene. It is soluble to ca 1 wt % in aUphatic hydrocarbons. 

Styrene. Commercial manufacture of this commodity monomer depends on ethylbenzene, which is converted by several means to a low purity styrene, subsequendy distilled to the pure form. A small percentage of styrene is made from the oxidative process, whereby ethylbenzene is oxidized to a hydroperoxide or alcohol and then dehydrated to styrene. A popular commercial route has been the alkylation of benzene to ethylbenzene, with ethylene, after which the cmde ethylbenzene is distilled to give high purity ethylbenzene. The ethylbenzene is direcdy dehydrogenated to styrene monomer in the vapor phase with steam and appropriate catalysts. Most styrene is manufactured by variations of this process. A variety of catalyst systems are used, based on ferric oxide with other components, including potassium salts, which improve the catalytic activity (10). 

Dicyanoacetylene, 2-hiitynedinitri1e, is obtained from dimethyl acetylenedicarboxylate by ammonolysis to the diamide, which is dehydrated with phosphoms pentoxide (44). It bums in oxygen to give a flame with a temperature of 5260 K, the hottest flame temperature known (45). Alcohols and amines add readily to its acetylenic bond (46). It is a powerhil dienophile in the Diels-Alder reaction it adds to many dienes at room temperature, and at 180°C actually adds 1,4- to benzene to give the bicyclo adduct (7) [18341 -68-9] C QHgN2 (47). 

Consider azeotropic distillation to dehydrate ethanol with benzene. Initial steady-state conditions are as shown in Fig. 13-108. The overhead vapor is condensed and cooled to 298 K to form two hquid phases that are separated in the decanter. The organic-rich phase is returned to the top tray as reflux together with a portion of the water-rich phase and makeup benzene. The other portion of the water-rich phase is sent to a stripper to recover organic compounds. Ordinarily, vapor from that stripper is condensed and recycled to the decanter, but that coupling is ignored here. 

Ethanol [64-17-5] M 46.1, b 78.3 , d 0.79360, d 0.78506, n 1.36139, pK 15.93. Usual impurities of fermentation alcohol are fusel oils (mainly higher alcohols, especially pentanols), aldehydes, esters, ketones and water. With synthetic alcohol, likely impurities are water, aldehydes, aliphatic esters, acetone and diethyl ether. Traces of benzene are present in ethanol that has been dehydrated by azeotropic distillation with benzene. Anhydrous ethanol is very hygroscopic. Water (down to 0.05%) can be detected by formation of a voluminous ppte when aluminium ethoxide in benzene is added to a test portion. Rectified... 

Thioglycollic acid [68-11-1] M 92.1, b 95-96 /8mm, d 1.326, n 1.505, pK 3.42, pK j 10.20. Mixed with an equal volume of benzene, the benzene is then distd to dehydrate the acid. After heating to 100° to remove most of the benzene, the residue was distd under vacuum and stored in sealed ampoules at 3°. [Eshelman et al. Anal Chem 22 844 I960.]... 

Merck and Maeder have patented the manufacture of arecaidine by loss of water from l-methyl-4-hydroxypiperidine-3-carboxylic acid. A method of producing the latter has been describd by Mannich and Veit and has been developed by Ugriumov for the production of arecaidine and arecoline. With the same objective, Dankova, Sidorova and Preobrachenski use what is substantially McElvain s process,but start by converting ethylene oxide, via the chlorohydrin and the cyanohydrin, into -chloropropionic acid. The ethyl ester of this with methylamine in benzene at 140° furnishes methylbis(2-carbethoxyethyl) amine (I) which on refluxing with sodium or sodium Moamyloxide in xylene yields l-methyl-3-carbethoxy-4-piperidone (II). The latter is reduced by sodium amalgam in dilute hydrochloric acid at 0° to l-methyl-3-carbethoxy-4-hydroxypiperidine (III) which on dehydration, and hydrolysis, yields arecaidine (IV R = H), convertible by methylation into arecoline (IV R = CH3). 

That the sulphuric. acid act.s in the. ihove in.inner, md not merely as a dehydrating apciit appears not only fioin the form.ation of iniKccl ethers, but al.so fiom the f.ii t that the sulphuric acid m.ay be replaced by phiisphonc, arsenic and benzene sulphonic acids. 

Isoborneol yields camphor on oxidation, but it yields camphene on dehydration much more readily than borneol does. If a solution of isoborneol in benzene be heated with chloride of zinc for an hour, an almost quantitative yield of camphene is obtained. Pure borneol under the same conditions is practically unchanged. 

Ethyl 1-bromocyclohexanecarboxylate, when treated with magnesium in anhydrous ether-benzene with subsequent addition of cyclohexanone, yields ethyl l-(l-hydroxycyclohexyl)cyclo-hexanecarboxylate. Dehydration and saponification give rise to l-(l-cyclohexenyl)cyclohexanecarboxylic acid, which upon decarboxylation at 195° yields cyclohexylidenecyclohexane in 8% overall yield, m.p. 540.4 This olefin has also been prepared by the debromination of 1,1 -dibromobicyclohexyl with zinc in acetic acid. ... 

Dehydration of 9,10-dihydro-4//-thieno[3,2-b]-l-benzazepin-10-ols, e.g. 57, to the thienobenz-azcpines, e.g. 58, is best carried out with neutral alumina in refluxing benzene.137 Dehydration can also be accomplished by heating the alcohol 57 with fumaric acid in ethanol. 

The hydroxy lactams 1 are converted into the 2//-2,4-benzodiazepin-l(3//)-ones 3 in refluxing benzene in the presence of p-toluenesulfonic acid. The reaction proceeds by ring opening to the oxo amides 2, followed by dehydration.16,166... 

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