Tertiary chlorine chloride

Primary alkyl chlorides are fairly stable to fluorine displacement. When fluorinated, 1-chloropropane is converted to 1-chloroheptafluoropropane and 1-chloto-2-methylbutane produces 39% l-chlorononafluoro-2-methylbutane and 19% perfluoro-2-methylbutane. Secondary and tertiary alkyl chlorides can undergo 1,2-chlorine shifts to afford perfluonnated primary alkyl chlorides 2-Chloro-2-methylpropane gives l-chlorononafluoro-2-methylpropane, and three products are obtained by the fluorination of 3-chloropentane [7] (equation 1). Aerosol fluorina-tion of dichloromethane produces dichlorodifluoromethane which is isolated in 98% purity [4 (equation 2). If the molecule contains only carbon and halogens, the picture is different. Molecular beam analysis has shown that the reaction of fluorine with carbon tetrachlonde, lodotrichloromethane, or bromotrichloromethane proceeds first by abstraction of halogen to form a trichloromethyl radical [5]... 

Perfluorination of tertiary alkyl chlorides gives products arising solely from rearrangement processes (Fig. 13) [60]. Rearrangement of the initially formed radical species 10 by a 1,2-chlorine shift to a more stable tertiary radical 11 in the early stages of the reaction (Fig. 14), accounts for these findings. In other... 

Earlier, tertiary chlorine was generally considered to be less reactive than internal double bonds. This was based on experiments with low molecular weight model substances, see e.g. ref. 45. However, using copolymers between vinyl chloride and 2-chloro-propene, Berens (46) stated that the presence of 1-2 tertiary chlorine per 1000 VC per se would account for the thermal lability observed in ordinary PVC. Furthermore, our previous investigation indicated that the thermal reactivity of internal allylic chlorine is of the same order as that of tertiary chlorine (8). We, therefore, consider it justifiable to use the total content of labile chlorine atoms. As shown in Figure 10, there is a very good relation between the rate of dehydrochlorination and the amount of labile chlorine obtained in this way. For comparison, it can be mentioned that the degradation rate of commercial samples is found in the interval 1.5-3.5 10 %... 

Systematic data on the relation between chemical structure or reactivity of chlorine compounds and lubricant additive performance are sparse. Table 11-11 gives some four-ball test data obtained by Mould, Silver and Syrett [35], with the additives listed in order of increasing effectiveness in terms of the wear/load index. The results show numerous departures from expectations based on chemical structure. For example, there is practically as much difference between the wear/load indices for the two primary chlorides, n-hexadecyl (16.2 kg) and n-hexyl (30.4 kg), as for n-hexyl chloride and t-butyl chloride (46.1 kg). A large difference would be expected on the basis of chemical reactivity between the additive effectiveness of primary and tertiary alkyl chlorides, but only a small difference for the two primary aliphatic chlorides. The overall trends are what would be expected in general, primary and aromatic chlorides are less efficacious than secondary chlorides, which in turn... 

These chlorine atoms were activated by addition of AgPF6 (in excess over the tertiary allylic chlorides) in the presence of THF this monomer was quantitatively grafted from the neoprene backbone ... 

Similarly, bromination of 2,2,5-trimethyUiexane gives an 82% yield of the product in which bromine replaces the tertiary hydrogen. Chlorination of the same alkane results in a 14% yield of the tertiary alkyl chloride (Section 9.3). 

PVC is not stable at temperatures of 220-230 °C at which the crystalline phase melts. As the crystallinity of PVC is only of the order of 10%, processing in the semisolid state is not an insuperable problem, but the apparent viscosity is much higher than for most other polymer melts. Tertiary chlorine atoms, which occur at long-chain branches in PVC, are weak points, where the elimination of a hydrogen chloride molecule can occur. 

From a purely kinetic point of view, the polymeiizatiai of vinyl chloride at reduced pressure may appear to be an attractive way of perfonning a rapid and controlled polymerization. In practice, however, it turns out that polymerization at reduced pressures reduces thermal stability due to the formation of tertiary chlorine atoms [62,64]. Therefore, polymerization is stopped and the remaining VC stripped off at a relativefy low conversion (90-95%). 

This is, in fact, an unusual way to carry out such reactions. The Friedel-Crafts alkylation, as this is known, usually involves treating benzene with a tertiary alkyl chloride and the Lewis acid AICI3. Rather in the manner of the reaction with bromine, AICI3 removes the chlorine atom from f-BuCl and releases the t-Bu cation for the alkylation reaction. 

Despite much investigation, the mechanism of thermal hydrogen chloride elimination is still disputed. It was originally assumed that the dehydrochlorination started at the tertiary chlorine atoms. But, according to recent evidence, PVC does not have any tertiary chlorine atoms. However, there are about 0.5-1.5 double bonds per 1 000 carbon atoms. The dehydrochlorination should start at these double bonds and proceed further by an unzipping reaction ... 

Cationic grafting from PVC often occurs at structural irregularities on the backbone. A similar uncertainty regarding the nature and concentration of the active centres in the grafting reaction surrounds the use of chlorinated and brominated butyl rubber backbones, chlorinated polycyclopentadiene, and chlorinated st rene-butadiene copolymers." The graft reaction of st3o ene into chlorosulphonated polyethylene appears to occur at tertiary chlorine sites and not at the sulphonyl chlorides. ... 

Trivinyl aluminium (AlVy,) has been employed as a cationic initiator for the preparation of ,co-dienepolyisobutylene. It also functions as a vinylating agent for tertiary alkyl, and secondary and tertiary allyl chlorides, and has been used, as in Scheme 10, for vinylating chlorinated ethylene-propylene rubber. ... 

Figure 10.2 Dehydrochlorination rate versus tertiary chlorine atoms + internal double bonds [72] fractionated commercial suspension PVC, polymerization temperature 55°C [73,74], OPVC polymerized at reduced monomer pressure, polymerization temperature 55 C, monomer pressure between 59-92% of the saturation pressure of vinyl chloride at 55 °C [73,74], bulk and suspension polymerization by lUPAC Sub-Group on Defects in the Molecular Structure of PVC and their relation to thermal stability. [Modified from [72].]...

As indicated previously, points of branching are also thought to feature in the degradation of poly(vinyl chloride). It was seen in Section 4.2.4. that branching which occurs during polymerization of vinyl chloride is likely to result in the formation of a tertiary chlorine atom. The high reactivity of tertiary chlorine in heterolytic reactions suggests that a branch point is a favourable site for unimolecular elimination. 

Polychloroprenes differ from other polydienes in that conventional sulphur vulcanization is not very effective. The double bonds are deactivated by the electronegative chlorine atoms and direct reaction with sulphur is limited. The vulcanization of polychloroprenes is normally achieved by heating at about 150°C with a mixture of zinc and magnesium oxides W type neoprenes also require an organic accelerator (commonly either a diamine or ethylene thiourea) but G types cure quite rapidly without acceleration. The mode of reaction has not been established with certainty, but it is generally supposed that cross-linking occurs at the tertiary allyUc chloride structures generated by 1,2-polymerization (see Section 18.8.3) and that a 1,3-allylic shift is the first step. The metal oxides may lead to ether cross-links as follows ... 

It was believed for a long time that head-to-head radical addition to monomers is a major route for formation of labile structures. Kinetic studies, in association with NMR measurements, reveal that formation of internal allylic and tertiary chlorine structures actually proceeds through an intramolecular or intermolecular chain-transfer reaction to polymer [Eqs. (31), (32) VC = vinyl chloride]. 

Later the same group demonstrated that the use of dialkyl- or diaryl-zinc compounds in dichloromethane enables a tertiary chlorine atom to be replaced by groups other than methyl. For example, the reaction of trityl chloride with diphenylzinc constitutes the best current synthesis of tetraphenylmethane (54% isolated yield). 

Other Oxidation and Chlorination Reactions. gem-Chloronitro compounds are prepared by treating nitronate anions with NCS in aqueous dioxane, or alternatively by reaction of ketoximes with NCS (eq 14). Oxidative decarboxylation of carboxylic acids with lead(IV) acetate and NCS has been used effectively for the synthesis of tertiary alkyl chlorides (eq 15). ... 

In the first step HCl is the main volatile product - the amount of the other products is very low, including quantities of benzene and some other hydrocarbons 883234. The main labile sites for dehydrochlorination are the allylic and tertiary chlorines 865099. Hydrogen chloride may be anticipated as a possible pyrolysis product from chlorine-containing polymeric materials, and, in any quantitative kinetic study of their thermal degradation, precise measurements of HCl yield will be required. Benzene formation (Scheme 7) is a relatively low-temperature process starting at 220-230 "C with parallel HCl elimination, and Scheme 8 shows the formation of other aromatic hydrocarbons [a.96j. 

As illustrated above, some side reactions occur in vinyl chloride polymerization due to rearrangement effects in the polymer chains, unsaturated structures in the polymer chains (1.5-3.0 double bonds per 1000 monomer units), and the tertiary chlorine structures formed by chain transfer to polymer. The chlorobutyl groups (2-3 per 1000 monomer units) formed by backbiting reactions contribute to the thermal instability of the polymer through the tertiary chlorine on the backbone [63]. 

Mioskowski s group employed the Johnson-Claisen rearrangement of dichloroalkene 81 with CH3C(OCH3)3 and TsOH under heating to construct tertiary chlorinated intermediate 82 in 55% yield (Scheme 43.11). Chloride 82 was transformed into bromohydrin 83 in nine steps (56% overall yield), which, upon treatment with Viehe s reagent (Af,Af-dimethylphosgeniminium chloride) 84, underwent unique bromine transposition to furnish halomon 67 in 75%... 

Phosphites. Tertiary phosphites are also commonly used and are particularly effective ia most mixed metal stabilizers at a use level of 0.25—1.0 phr. They can take part ia a number of different reactions duting PVC processing they can react with HCl, displace activated chlorine atoms on the polymer, provide antioxidant functionaHty, and coordinate with the metals to alter the Lewis acidity of the chloride salts. Typical examples of phosphites are triphenyl phosphite [101 -02-0], diphenyl decyl phosphite [3287-06-7], tridecyl phosphite [2929-86-4], and polyphosphites made by reaction of PCl with polyols and capping alcohols. The phosphites are often included in commercial stabilizer packages. 

Each isomer has its individual set of physical and chemical properties however, these properties are similar (Table 6). The fundamental chemical reactions for pentanes are sulfonation to form sulfonic acids, chlorination to form chlorides, nitration to form nitropentanes, oxidation to form various compounds, and cracking to form free radicals. Many of these reactions are used to produce intermediates for the manufacture of industrial chemicals. Generally the reactivity increases from a primary to a secondary to a tertiary hydrogen (37). Other properties available but not Hsted are given in equations for heat capacity and viscosity (34), and saturated Hquid density (36). 

Almost 40 years later the Lummus Co. patented an integrated process involving the addition of chlorine along with the sodium chloride and sodium hydroxide from the cathode side of an electrolytic cell to a tertiary alcohol such as tertiary butanol to produce the tertiary alkyl hypochlorite. The hypochlorite phase separates, and the aqueous brine solution is returned to the electrolytic cells. The alkyl hypochlorite reacts with an olefin in the presence of water to produce a chlorohydrin and the tertiary alcohol, which is returned to the chlorinator. With propylene, a selectivity to the chlorohydrin of better than 96% is reported (52). A series of other patents covering this technology appeared during the 1980s (53—56). 

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