Chloride,tert

Indeed, cumyl carbocations are known to be effective initiators of IB polymerization, while the p-substituted benzyl cation is expected to react effectively with IB (p-methylstyrene and IB form a nearly ideal copolymerization system ). Severe disparity between the reactivities of the vinyl and cumyl ether groups of the inimer would result in either linear polymers or branched polymers with much lower MW than predicted for an in/mcr-mediated living polymerization. Styrene was subsequently blocked from the tert-chloride chain ends of high-MW DIB, activated by excess TiCU (Scheme 7.2). 

Functionalization of quasi living PIB has been typically attempted through the use of functional initiators and through in situ functionalization by quenching. Most past efforts to produce functionality by quenching of quasi living chains have failed and led to tert-chloride terminal units (8). 

The reaction half-time for 4-chloro-2-pentene, the allylic chloride model, with dibutyltin -mercaptopropionate is about 1/20 that for 2-chloro-2-methylbutane, a tert-chloride model, with the same stabilizer. This result supports the choice of an allylic chloride as the most important unstable functionality of poly (vinyl chloride). 

Allylic Chloride vs. tert-Chloride Reactivity. There is some question in the literature as to whether the allylic chloride moiety or ferf-chloride group is more responsible for the thermal instability of poly (vinyl chloride) (I, 2). To shed some light on this problem we compared the relative reactivities at 100 °C. in chlorobenzene of 4-chloro-2-pentene and 2-chloro-2-methylbutane with dibutyltin -mercaptopropionate. Data are summarized in Table I. The half-time for the reaction of the allylic chloride with the stabilizer mercaptide group was less than 15 minutes, whereas the half-time for the tert-chloride was nearly 20 times longer. The greater reactivity of the allyl chloride suggests that it is the more important functionality in polymer degradation. However, these results on rates of chlorine substitution are not necessarily an exact measure of thermal instability. 

Reaction 10 depends on the selective removal of the tert-chloride ion and cationic polymerization of styrene in the first step. Subsequently and at higher temperatures the tert-bromide function is used to initiate the cationic polymerization of isobutylene (Reaction 11). 

Storey et al. [140] reported that the rate of depletion of tert-chloride end groups follows first-order kinetics with an apparent rate constant of 8 x 10 s The ratio of rate constants for propagation and rearrangement, p/ R was found by them to be 3 x 10 " ... 

Phosphorus pentachlorideJcalcium carbonate Tert chlorides from tert alcohols Retention of configuration... 

In an alternative procedure 26 g. of anhydrous ferric chloride replace the aluniiniuni chloride, the mixture is cooled to 10°, and the 50 g. of tert.-butyl chloride is added. The mixture is slowly warmed to 25° and maintained at this temperature until no more hydrogen chloride is evolved. The reaction mixture is then washed with dilute hydrochloric acid and with water, dried and fractionally distilled. The yield of tert.-butyl benzene, b.p. 167- 170°, is 60 g. 

Solutions of tert.-butylmagnesium chloride and cyclopentylmagnesium chloride in diethyl ether can be prepared in the same way. In these cases also the purity of the chlorides Is of great importance for a successful and smooth conversion into the Grignard reagent. 

Apparatus and procedure Closely similar to the preparation of tert.-Ci,H3MgCl, cyclohexyl-MgCl and cyclopentyl-MgCl (see Exp. 2). The yield (estimated from the results obtained from reactions with this reagent) is at least 90%. Here, too, it is essential to use M-butyl chloride which is free from butyl alcohol. 

In 400 ml of anhydrous liquid ammonia (note 1) (drawn from a cylinder) in the 3-1 flask were dissolved 25 g of K0-tert.-Ci,tig (see Exp. 4, note 2). 1,4-Dimethoxy--2-butyne (Chapter VIII-6, Exp. 8) (0.60 mol) was poured into the solution. The reaction mixture was allowed to stand (with occasional swirling) for 25 min, after which 50 g of powdered ammonium chloride were introduced in 5 min with manual swirling. The ammonia was driven off by placing the flask in a water bath at 40 C. 

To a solution of 0.40 mol of butyllithium in about 280 ml of hexane were added 300 ml of dry THF at -20 to -40 0. Subsequently 0.40 mol of freshly distilled tert.-butyl propargyl ether was added, keeping the temperature below -30°C. Freshly distilled acetaldehyde (0.40 mol) was then added at the same temperature during about 15 min. The cooling bath was removed and, after an additional 15 min, 200 ml of an aqueous solution of 30 g of ammonium chloride were introduced. After separation of the layers the aqueous layer was extracted twice with diethyl ether and the combined solutions were dried over magnesium sulfate and concentrated in... 

The rate of the reaction decreases with increasing number of substituents in the acetylenic halide, and it is higher with acetylenic bromides than with the corresponding chlorides. Methyl magnesium iodide gives equal amounts of 1,1- and 1,3--substitution products, whereas tert.-butylmagnesium bromide does not react. However, for some tert.-butyl substituted allenes there exists an attractive com-... 

The crude tosylate obtained after evaporation of the diethyl ether was dissolved In 150 ml of THF. After addition of 1 g of CuBr the solution was cooled to -10°C and a solution of tert.-butylmagnesium chloride in 250 ml of THF, prepared from 0.40 mol of -butyl chloride and magnesium (see Chapter II, Exp. 4) was added... 

Consider the reaction of tert butyl alcohol with hydrogen chloride... 

FIGURE 4 6 The mechanism of formation of tert butyl chloride from tert butyl al cohol and hydrogen chio ride... 

Step 3 Capture of tert butyl cation by chloride ion... 

---