Liquid Phase Chlorination of Olefins with Cupric Chloride

Abstract

Summary:Cupric chloride reacts with gaseous and liquid olefins to form dichloroparaffins in various solvents under milder conditions. Acetic acid containing sodium acetate is the most convenient solvent for the reaction at lower temperatures. The reacting species in this system is found to be CuCl.OAc. NaCl. Acetonitrile containing lithium chloride and various alcohols can also be used as the solvent.Application of the reaction to butadiene in acetic acid containing sodium acetate has resulted in the formation of 1, 4-diacetoxy-2-butene and 3, 4-diacetoxy-1-butene.The kinetics of chlorination of styrene has been studied in acetonitrile-lithium chloride and in n-propyl alcohol. On the basis of the rate equation and the structure of the products, the chlorination mechanism and the retarding effect of cuprous chloride are discussed.

Catalytic, Stereoselective Dihalogenation of Alkenes: Challenges and Opportunities

“…215 The dichlorination of alkenes with CuCl 2 in organic solvents (AcOH or alcohols) was later studied by Uemura et al , including the reaction scope, 216 kinetics, 217 effect of additives (NaOAc, NaCl), 218 and the use of butadiene as a substrate, 219 all of which are summarized in a subsequent overview article. 220 Further detailed investigations by Koyano and co-workers, 221 including establishing the stereochemical course of the reaction, 222 the influence of additives (e.g., LiCl), 223 and the kinetics. 223 …”

“…220,221 The use of somewhat lower temperatures (70–80 °C) is possible in MeCN as the solvent, 224 but LiCl is usually added in these cases to solubilize the CuCl 2 and to further enhance the rate. 220,225 Chlorine has been deemed unlikely to be the active chlorinating agent in these reactions 221 as CuCl 2 is known not to decompose to CuCl and Cl 2 at these temperatures in the solvents employed 226 (albeit in the absence of olefins). Dichlorinations conducted in alcohol solvents are often complicated by competing chloroalkoxylation processes 220,221 although the addition of LiCl promotes the formation of dichloride products.…”

“…The reaction kinetics in alcohol solvents have been studied by the groups of Uemura 220 (with styrene in n -PrOH) and Koyano (with 1-octene in MeOH), 223 with both sets of authors arriving at a similar (initial) rate law of the form: ${\text{rate}}_0=k_{\text{obs}}{false[\text{alkene}false]}_0{false[{\text{CuCl}}_{2}false]}_0^n$ (where n = 1.8 for Uemura and n = 1.6 for Koyano). Additionally, a reactivity order (based on conversion of CuCl 2 in independent experiments) of ethylene > propylene > 1-butene > 2-butenes was also established.…”

“…In contrast, the RDS in MeCN is believed to be formation of either the alkene-CuCl 2 π-complex XXXVIII or the β-chlorocarbenium ion XXXIX , based on a first-order dependence on both alkene and CuCl 2 . 220 …”

“…Angewandte including the reaction scope, [216] kinetics, [217] effect of additives (NaOAc, NaCl), [218] and the use of butadiene as asubstrate, [219] all of which are summarized in as ubsequent overview article. [220] Further detailed investigations were performed by Koyano and co-workers, [221] including establishing the stereochemical course of the reaction, [222] the influence of additives (e.g.,LiCl), [223] and the kinetics. [223] In general, these dichlorination reactions are conducted using stoichiometric amounts of CuCl 2 ,typically in AcOH or alcohol solvents,a tt emperatures ranging from 70 to 150 8 8C (though often > 100 8 8C).…”