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Dimethylallyl chloride, solvolysis

Allylic systems have also provided fertile ground for investigation of ion-pair phenomena. Young, Winstein, and Goering established the importance of ion pairs in solvolysis of these compounds. They showed that ion pairs are responsible for the rearrangement of a,a-dimethylallyl chloride to y,y-dimethyl-allyl chloride (Equation 5.8).24 Goering s labeling methods have subsequently supplied a number of details about allylic ion-pair structure.25... [Pg.220]

Young et reported in 1951 that the solvolysis of a,a-dimethylallyl chloride in acetic acid buffered with potassium or lithium acetate is accompanied by partial isomerization to 7,7-dimethylallyl chloride, which solvolyzes only about an eighth as fast as its tertiary isomer. It was possible to calculate from the titrirnetric data rate coefficients for the isomerization reaction as well as for the two solvolysis reactions. Since neither the reaction rates nor the product compositions were influenced by added potassium chloride, it was concluded that the isomerization is intramolecular. This is the first documented example of internal return from a carbonium ion-anion pair, viz ... [Pg.429]

The solvolysis and isomerization of a,a-dimethylallyl chloride in aqueous 75% ethanol is more complex In this solvent, the rate of isomerization at 25°C is doubled by the addition of molar LiCl. In the presence of 0.68 M Li Cl, about 63% of the chlorine incorporated into the primary chloride during rearrangement came from radioactive chloride in solution. Thus, under these conditions isomerization involves external return of chloride from solution as well as internal return from a tight ion pair intermediate. a-Phenylallyl chloride also undergoes simultaneous solvolysis and allylic... [Pg.429]

Early evidence for ion pairing was reported by Winstein from the reaction of a,a-dimethylallyl chloride (14) in acetic acid with added acetate. Although the major product of the reaction was the expected acetate, there was rapid isomerization of 14 to the isomeric Y,y-dimethylallyl chloride (15, equation 8.24). Formation of 15 can be explained by a mechanism in which the nucleofuge. Cl , competes as a nucleophile with solvent and rebonds to the allyl cation at the less hindered position. The rate of formation of 15 was found not to be a function of the concentration of added chloride ion, however. This finding is significant because the rate of the solvolysis should be decreased by addition of chloride ion if the mechanism involves dissociation of 14 to free ions (see equation 8.16). It appears, therefore, that the chloride ion in 15 must originate in the same molecule and not from the bulk medium. This process was characterized as internal return of a chloride ion held as part of intimate ion pair (16) within a solvent shell. Similar conclusions were obtained from... [Pg.482]


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Dimethylallyl chloride

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