Ethylene chain dehydration

The hrst step in the preparation of the antidepressant maprotiline (33-5) takes advantage of the acidity of anthrone protons for incorporation of the side chain. Thus treatment of (30-1) with ethyl acrylate and a relatively mild base leads to the Michael adduct saponihcation of the ester group gives the corresponding acid (33-1). The ketone group is then reduced by means of zinc and ammonium hydroxide. Dehydration of the hrst-formed alcohol under acidic conditions leads to the formation of fully aromatic anthracene (33-2). Diels-Alder addition of ethylene under high pressure leads to the addition across the 9,10 positions and the formation of the central 2,2,2-bicyclooctyl moiety (33-3). The hnal steps involve the construction of the typical antidepressant side chain. The acid in (33-3) is thus converted to an acid chloride and that function reacted with methylamine to form the amide (33-4). Reduction to a secondary amine completes the synthesis of (33-5) [33]. 

Initially, ethylene was obtained by the dehydration reaction of ethanol. Nowadays, ethylene is obtained by steam cracking from naphtha as a basic chemical. Steam cracking degrades longer aliphatic chains and introduces the double bond. Steam cracking is done at temperatures up to 900°C and leaves a wide variety of products behind. Ethylene is recovered by distillation processes. 

The preparation of various alkenylbenzo[6]thiophenes by dehydration of side-chain alcohols is discussed in Section VI, J. l,l-Di(2-benzo[6]thienyl)ethylene may be prepared by treating 2-benzo[6]-thienyllithium with acetyl chloride,132 and the olefins (158a-d) may... 

The multiple bond structures of importance in side chain modification reactions are carbonyl and ethylenic groups and the processes frequently involved in the formation and elimination of such groups are reduction, hydrogenation, oxidation, and dehydration, here arbitrarily restricted to reactions in which no accompanying carbon-carbon fragmentation occurs. 

To apply the phase inversion principle, the transitional inversion method should be used, as demonstrated by Shinoda and coworkers [11, 12] when using nonionic surfactants of the ethoxylate type. These surfactants are highly dependent on temperature, becoming lipophilic with increasing temperature due to dehydration of the poly(ethylene oxide) (PEO) chain. When an O/W emulsion that has been prepared using a nonionic surfactant of the ethoxylate type is heated, at a critical temperature - the PIT - the emulsion will invert to a W/O emulsion. At the PIT, the droplet size reaches a minimum and the interfacial tension also reaches a minimum, but the small droplets are unstable and coalesce very rapidly. Rapid cooling of an emulsion that has been prepared close to the PIT results in very stable and small emulsion droplets. 

More recently, calcium sulfate was applied to the dehydration of glycols into unsaturated carbonyls 31), cupric sulfate mounted on alumina was used for the conversion of aUyl ether to allyl alcohol 32), and some metal sulfates were used for the open-chain polymerization of ethylene oxide 33). 

Isobutylene, CH2=C(CH3)2, is predominantly produced from cracked petroleum gases, and also, partially, by the dehydration of /-butanol. In industrial polymerizations, isobutylene is liquefied on addition of some diisobutylene, and mixed with about the same quantity of liquid ethylene and then cationically polymerized at -80°C with BF3/H2O. The diisobutylene acts as chain transfer agent and regulates the molar mass. The ethylene does not polymerize under these conditions on the other hand, it dissipates the heat of polymerization by volatilizing. 

Waterborne polyurethane resins are produced from maleinised monoglyceride (MMG) of sunflower oil, hydroxy-terminated polybutadiene, toluene diisocyanate and ethylene diamine. The carboxylic acid groups of MMG are neutralised by triethyl amine, making the resin water dispersible. The monoalkylated castor oil (MCO) or dehydrated castor oil (DCO) is treated with a polyether glycol at 120°C, followed by the addition of IPDI and DBTDL. To obtain a series of aqueous polyurethanes, butane diol and dimethylol propionic acids (DMPA) are added and the mixture heated to 70°C for two hours to produce a NCO-terminated pre-polymer which forms salt with triethylamine, giving a water-soluble polymer. The reaction mixture is dispersed in water and a chain extender, ethylene diamine, is added. Two aqueous polyurethanes, MCPU and DCPU, are finally obtained from MCO and DCO, respectively. 

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