Chloroethyl radicals, reaction

The substitution reaction of CP with methyl chloride, 2-chloroethyl radical, and allyl chloride has been treated by several different ab initio theoretical models. Depending on the method, the intrinsic barrier for the 5ivr2 process in allyl chloride is 7-11 kcalmoP higher than the barrier for the 5ivr2 reaction of methyl chloride. The reaction of CP with the 2-chloroethyl radical involves an intermediate complex, which is best described as an ethylene fragment flanked by a resonating chloride anion-chloride radical pair. There are many other points of interest. 

Alkanes. The chlorination of ethane known to produce more 1,1-dichloroethane than 1,2-dichloroethane is explained by the so-called vicinal effect.115 One study revealed285 that this observation may be explained by the precursor 1,2-dichloroethane radical (the 11 2-chloroethyl radical) thermally dissociating into ethylene and a chlorine atom [Eq. (10.54)]. Indeed, this radical is the major source of ethylene under the conditions studied. At temperatures above 300°C, the dissociation dominates over the chlorination reaction [Eq. (10.55)], resulting in a high rate of ethylene formation with little 1,2-dichloroethane ... 

Fig. 23.13. The Srn2 and Skn2 mechanisms in the reactions between Cl and (3-chloroethyl radical. The mechanism is stepwise and the structure of the intermediate is shown at the bottom of the figure.

The rate coefficients of the metathetical reactions of chloroethyl radicals with HCl and Clj have been determined by kinetic analyses of photochlorination reactions in steady or intermittent light or by competitive techniques [68, 359]. 

Chlorine elimination reactions. Chloroethyl radicals CClEt) formed by Cl or Br transfer reactions in cyclohexane can subsequently eliminate a Cl atom by reaction 34 or abstract a H atom from the solvent by reaction 35. The rate constant ratio 34/ 35 el/ H related Arrhenius parameters can be... 

Oligomeric Vinylphosphonate. A water-soluble oligomer, Fyrol 76 [41222-33-7] is produced by reaction of bis(2-chloroethyl) vinylphosphonate and dimethyl methylphosphonate with elimination of all the chlorine as methyl chloride (127,128). This Hquid, containing 22.5% P, is curable by free-radical initiation, on cotton or other fabrics. Nitrogen components, such as A/-methylolacrylamide or methylolmelamines, are usually included in the finish, which can be durable to multiple launderings (129,130). 

A rate constant for the vapor phase reaction of bis(2-chloroethyl) ether with OH radicals in the atmosphere has been estimated to be 3.2 x 10 cm /molecule-sec at 25 °C. At an atmospheric concentration of 5 x 10 OH radicals/cm , the corresponding half-life is 5 d (Meylan and Howard, 1993). 

One embodiment of this general reaction led to a product which was commercially produced for several years by Stauffer as Fyrol 76 (9), a copolycondensation product of dimethyl methyl-phosphonate with bis(2-chloroethyl) vinylphosphonate. The features of Fyrol 76 were high phosphorus content (20%), water solubility, and ability to be polymerized by means of a radical initiator to a crosslinked polymer. A related polycondensation product was developed from tris(2-chloroethyl) phosphate and dimethyl methylphosphonate. By control of the reagents and procedure used for neutralization, these oligomeric products were produced with primary alcohol functional groups (7). 

Bis(2-chloroethyl)ether s former production and use in the textile industry and as solvent in natural and synthetic resins may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 1.55 mm Hg at 25°C indicates that bis(2-chloroethyl)ether will exist solely as vapor in the ambient atmosphere. Vapor-phase bis(2-chloroethyl)ether will be degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals the half-life for this reaction in air is estimated to be 5 days. If released into soil, bis(2-chloroethyl) ether has a high mobility. Many ethers are known to be resistant to biodegradation. Volatilization from moist soil surfaces is an important fate process. If released into water, bis(2-chloroethyl)ether is not adsorbed by suspended solids and sediment in water. Volatilization from water surfaces is an important fate process. The volatilization half-life from a model river and a model lake is estimated as approximately 40 h and 16 days. Bis(2-chloroethyl) ether is a marine pollutant and its release to the sea is prohibited by the International Convention since 1973. ... 

Several studies on the reactivities of small radicals with donor-acceptor monomer pairs have been carried out to provide insight into the mechanism of copolymerizations of donor-acceptor pairs. Tirrell and coworkers " reported on the reaction of n-butyl radicals with mixtures of N-phcnylmalcimidc and various donor monomers e.g. S, 2-chloroethyl vinyl ether),. lenkins and coworkers have examined the reaction of t-butoxy radicals with mixtures of AN and VAc. Both groups have examined the S-AN system (see also Section 7.3.1.2). In each of these donor-acceptor systems only simple (one monomer) adducts are observed. Incorporation of monomers as pairs is not an important pathway i.e. the complex participation model is not applicable). Furthermore, the product mixtures can be predicted on the basis of what is observed in single monomer experiments. The reactivity of the individual monomers (towards initiating radicals) is unaffected by the presence of the other monomer i.e. the complex dissociation model is not applicable). Unless propagating species are shown to behave differently, these results suggest that neither the complex participation nor complex dissociation models apply in these systems. 

Roualdes and co-workers have prepared phosphonated polymers by synthesizing fluorinated polymers via radical polymerization of fluorinated al-kenes such as chlorotrifluoroethylene and vinyl ethers such as 2-chloroethyl vinyl ether, followed by phosphonation via the Arbuzov reaction. The resulting polymers depicted in Scheme 13.3c had a phosphonic acid content ranging from 18 to 47 mol%. The level of conductivity was found to be in the range 0.02-20 mS cm, which was comparable with Nafion 115 at about 50 mS cm at 25 °C and 95% RH. 

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