The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Cleavage of cyclic acetals by acyl halides. Reaction mechanism》. Authors are Atavin, A. S.; Trofimov, B. A.; Orlova, S. E.; Keiko, V. V..The article about the compound:2-Chloroethyl acetatecas:542-58-5,SMILESS:CC(OCCCl)=O).Application of 542-58-5. Through the article, more information about this compound (cas:542-58-5) is conveyed.
A mixture of 25.5 g. 2,4-dimethyl-1,3-dioxolane (36% trans, 64% cis), 0.1 g. ZnCl2, and 19.6 g. AcC1 (I) was held at 50° 3 hrs. and distilled to yielding, in addition to starting materials, 2.2 g. resinous residue, and two fractions corresponding to β-chloroisopropyl acetate (II) and propylene glycol diacetate (III). To remove traces of an intermediate α-chloro ether, III was extracted with water, dried with Na2SO4, and redistilled The yield, b.p., n20D and d20 were resp.: II, 32.5%, b33 66-7°, 1.4223, 1.0914; III, 18.3%, b25 90-3°, 1.4170, 1.0559. Analogously, reaction of I with 2-methyl-1,3-dioxolane (IV) yielded β-chloroethyl acetate (V) and ethylene glycol diacetate (VI). Reaction of I with 2,4-dimethyl-1,3-dioxane yielded 1,3-butanediol diacetate (VII) and a mixture (VIII) of the acetates of 1-chloro-3-butanol and 3-chloro-1-butanol. The b.p., n20D and d20 were resp.: V, b10 41°, 1.4220, 1.1472; VI, b20 87°, 1.4170, 1.1063; VII, b7 82°, 1.4202, 1.0399; VIII b7, 57°, 1.4299, 1.0666. A mixture of 22 g. IV with 0.2 g. AlCl3 and 46.2 g. BzBr was agitated 11 hrs. at 70-100°, and vacuum distilled One fraction (b4 120-30°) afforded, after removal of BzOH crystals and redistillation, 14.5 g. β-bromoethyl benzoate (IX). A second fraction (b2 180-95°), after recrystallization from EtOH, afforded 13 g. of ethylene glycol dibenzoate, m. 69°, b2 180-3°. The tarry distillation residue weighed 8.9 g. Similarly, a mixture of 36.5 g. diisopropyl acetal, 19.6 g. I, and 0.15 g. ZnCl2 on fractionation yielded 8.2 g. of isopropyl acetate (X), along with iso-PrCl and a residue (13.7 g.). The b.p., n20D, and d20 of IX and X are, resp.: IX, b2 102-5°, 1.5478, 1.4308; X, b720 85-6°, 1.3760, 0.8689. To investigate proposed mechanisms involving chloro ether and ester intermediates, some of these possible intermediates were independently prepared Saturation of 10 g. vinyl acetate with HCl at 3-5°, and distillation of the product yielded 86% α-chloroethyl acetate, b718 115-18°, n20D 1.4055, d20 1.1016. I (39 g.) was added over 2.5 hrs. to an agitated mixture of 44 g. monovinyl ether of ethylene glycol in 100 ml. Et3N. After separation of the amine hydrochloride distillation yielded 70.4% vinyl β-acetoxyethyl ether (XI), b35 64-6°, n20D 1.4259, d20 1.0060. Saturation of XI with dry HCl at 0° and fractionation yielded 72% 1-(α-chloroethoxy)-2-acetoxyethane (XII), b15 84°, n20D 1.4348, d20 1.1281. When 16 g. XII was treated with 0.1 g. ZnCl2 and heated to 37°, the mixture evolved HCl and darkened. Fractionation yielded 6 g. V, 2.6 g. VI, and 1.9 g. tar. The decomposition of XII is consistent with the hypothesis that XII is a reaction intermediate in the reaction of I with IV. Since these reactions also proceed non-catalytically the catalyst role is regarded as accelerating the removal of the halogen from the acyl chloride (e.g. to form Ac+[ZnCl3-]), with subsequent nucleophilic attack by the acetal O on the pos. charged acylium carbon. If the resulting complex expels a proton, a vinyl ether is formed, whose polymerization explains the tars.
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