Pentachlorophenyl acetate

Although perchloropheiiylacetylene with concentrated sulphuric acid gives acetophenone [98], as expected (Julia and Surzur, 1956), a substantial proportion of (pentachlorophenyl)acetic acid is also formed (Ballester et al., 1986b). The latter cannot result from [98], since, under the reaction conditions, it does not rearrange. An alternative reaction path involves an initial proton addition to acetylene a-carbon (path 2) instead of -carbon (path 1) (99). It is concluded that the electron attraction of the phenyl chlorines... 

Reaction of most enolates with MeOTf or Me0S02F is always likely to be kinetically controlled. There does not appear to have been a definitive study, but 0-alkylation is the normal outcome. O-Alkylation of a bicyclodecatrienone by Me0S02p is enhanced by the use of polar solvents like HMPA. O-Alkylation of enolates of appropriate cyclohexadienones by MeOTf has been used to generate various 3ai/-indenes. A ketene acetal is formed by exclusive 0-alkylation of the sodium enolate of isopropyl bis(pentachlorophenyl)acetate by MeOTf. ... 

A solution of pentachlorophenylmagnesium chloride" is prepared from hexachlorobenzene (66 g, 0.23 mol) and magnesium (8.44 g, 0.35 mol) in a mixture of THF (150 ml) and benzene (150 ml) (HAZARD toluene would be preferable). The solution is heated to reflux, and ethyl formate (40 ml, excess) is added by syringe at such a rate that the exothermic reaction maintains refluxing. The mixture is stirred as it is allowed to cool to room temperature during 1 h. Methanol (20 ml) is added, and the solvents are evaporated. The resulting dark-brown residue is washed with hydrochloric acid, methanol and ethyl acetate, and then recrystallized from 4 1 toluene-pyridine, to give bis(pentachlorophenyl)methanol (35 g, 29%). 

Thus, two types of active esters are of interest those formed from an acid and a substituted phenol (12-15) and those formed from an acid and a substituted hydroxylamine (16-19). Both types are reactive by virtue of the electron-withdrawing properties of the OR moiety in 2. The level of activation of the substituted phenyl esters varies directly with the electronic effect going from 4-nitrophenyl to 2,4,5-trichlorophenyl, pentachlorophenyl, and pentafluorophenyl, which corresponds with the increasing acidity of the phenols. A diminution in the rate of aminolysis is caused by the presence of a substituent in the ortho position of the ring.f l An additional phenomenon contributes to the reactivity of the esters formed from substituted hydroxylamines, namely anchimeric assistance. Since the anoinolysis of active esters is a bimolecular reaction, it is dependent on concentration and can be forced to completion by an excess of one of the reactants. Aminolysis is also characterized by a pronounced dependence on the polarity of the solvent in particular for the esters formed from substituted phenols, the half-life of a 2,4,5-trichlorophenyl ester in the presence of benzylamine being one hundred times less in dimethylformamide than in benzene. Furthermore, aminolysis is catalyzed by mild acid such as acetic acid. The rate of anoinolysis is slowed if the side chain of the active ester contains a P-methyl substituent. 

Pentachlorophenyl acrylate, (1), was terpolymerized with methyl methacrylate (MMA) and n-butyl acrylate (nBA) (Scheme III) to give a latex containing 537 solids and a pll of 4.7 which was adjusted to 6.8 by adding aqueous NaOH. The latex was stable up to pH =10. A small aliquot vzas coagulated and the resulting polymer purified. Its intrinsic viscosity was 3.1 /g and analysis indicated 2 mole percent (1), 587 CIA and 40" nBA. Similar terpolyner latices were prepared from acrylates (2) and (3) (Scheme III). Another terpolymer latex made from (3), vinyl acetate, and 2-ethylhexyl acrylate contained 547 solids. Tliese latices and their compositions are summarized in the Table 1 and a sample experimental procedure is given in the experimental section. 

In order to determine the reactivity of pentachlorophenyl acrylate, 8, in radical initiated copolymerizations, its relative reactivity ratios were obtained with vinyl acetate (M2), ri=1.44 and r2=0.04 using 31 copolymerization experiments, and with ethyl acrylate (M2), ri=0.21 and r2=0.88 using 20 experiments.The composition conversion data was computer-fitted to the integrated form of the copolymer equation using the nonlinear least-squares method of Tidwell and Mortimer,which had been adapted to a computerized format earlier. 

In this work,glass transition temperatures were studied as a function of copolymer composition. Poly(pentachlorophenyl acrylate) exhibited the high Tg value of 143°. Table 5 summarizes these Tg values versus Mj/M2 content of both vinyl acetate and ethyl acrylate copolymers.The Tg values for copolymers with higher mole fractions of 8 depended on their thermal history. Tg increases after heating above Tg the first time. For example a vinyl acetate copolymer (mole fraction of 8 = 0.67) exhibited Tg values of 77°, 99°, and 103°C in three successive heating cycles. 

Table 5-Glass Transition Temperatures For Pentachlorophenyl Acrylate (Mi) Copolymers With Vinyl Acetate or Ethyl Acrylate...

Peptide synthesis, N-protection Acetic-formic anhydride. Adamantyl chloroformate. Benzylthiocarbonyl chloride. /-Butoxycarbonyl-N-hydroxysuccinimide ester. /-Butyl azido-formate. /-Butylcarbonic diethylphosphoric anhydride. /-Butyl fluoroformate. /-Butyl oxycarbonyl fluoride. /-Butyl pentachlorophenyl carbonate. /-Butyl 2,4,5-trichlorophenyl carbonate. Carbobenzoxy chloride. 3,5-Dimethoxybenzyl p-nitrophenyl carbonate. [2-(Diphenyl)isopropyljphenyl carbonate. /-Pentyl chloroformate. 

B. Chemical Bonding with Polymerization. Two examples of this type are pesticide-isocyanate adducts with PVA and pentachlorophenyl acrylate with vinyl acetate (or ethyl acrylate). 

The other example, a polymer-bound fungicide, is found in the copolymerization of pentachlorophenyl acrylate with vinyl acetate and ethyl acrylate. This pentachlorophenol-based product could have use as an anti-fouling agent in marine coatings. In this case it was necessary to copolymerize with ethyl acrylate. The homopolymer was found to be too hydrophobic to allow decomposition of the polymer and allow release of the active agent in sufficiently high concentrations to have the appropriate biocide effect. 

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