The layers were separated, and the aqueous portion extracted several times with 5-ml. portions of methylene chloride. The combined methylene chloride extracts were washed with water, dried over magnesium sulfate and concentrated. The residual 2-chloro-2,3,3-trimethyIbutane was purified by sublimation under reduced pressure. The recovery was 0.60 g.The following procedures were used to convert the chloride samples to silver chloride for radioactive assay. A portion of the aqueous hydrochloric acid solution containing about 1-2 millimoles of chloride ion was diluted to 5 ml. with water containing 1 ml. of 6 IV nitric acid. The solution was warmed to about 50°and 10 ml. of 10% silver nitrate solution added rapidly with stirring. The precipitate of silver chloride was collected on a sintered-glass funnel, rinsed several times with acetone and dried in an evacuated desiccator over phosphorus pentoxide. The organic chloride (about 0.1-0.2 g.) was dissolved in 5 ml. of ethanol, warmed to 50-60°and a warm solution of 10 ml. of 10% silver nitrate containing 1 ml. of 6 At nitric acid was added with stirring. The precipitated silver chloride was collected and dried as above.The samples for counting were prepared by weighing out identical amounts of silver chloride on copper dishes previously checked for radioactive contamination. The samples were counted in a methane-filled proportional counter ("Nucleometer," Radiation Counter Laboratories).Trials indicated that the manner of spreading of the samples in the sample dish was not critical provided the samples were spread reasonably evenly. In the experiment described above, the measured activities for 29.0-mg. samples of silver chloride corrected for background with standard deviations were 1309 ± 44 and 15 ± 10 counts per minute for the silver chloride from the original aqueous solution and the organic chloride from the reaction mixture, respectively.In this experiment, the initial reaction mixture contained 98.5 millimoles of hydrochloric acid and 7.4 millimoles of organic chloride. If complete equilibration had occurred, the activity of the organic chloride would be (98.5/106) X 1310 ± 44 = 1220 ± 41 counts per minute. The extent of exchange was thus (15 ± 10/1220) X 100 or 1.2 ± 0.8%. Further experimental results regarding the exchanges are presented in Table II.Cambridge 39, Mass.
Alcohol Reaction conditions Product composition CHKHClCH=CHz SOCl2, no solvent 33% CHaCHClCH=CHs 6770 CH&H=CHCHICl CHaCH=CHCHzOH SOC12, no solvent 71% CHoCHClCH=CH* CHaCH=CHCHzOH SOC12 in Et20 99% CHsCHClCH=CHt CHaCHOHCH=CHz SOClz in Et20 100% CHsCH=CHCHzCl ( -)trans-CHsCH=CHCHOHCHa SOCl, in EtzO CHsCH=CHCHClCHs CsHsCH=CHCHzOH 0.1 M R O H + 0.1 MSOCl, in Et20 100% CeHsCHClCH=CHz CsHbCH=CHCH*OH 60% CsHrCHClCH=CHz 40% CeHsCH=CHCHzCl 29 7 0 CH,CH=CCH CHzCl 100% (-1 tram-show a-phenylallyl chloride is the product. This thermodynamically less stable secondary chloride is rearranged only very slowly in the reaction solution.Our present evidence is still insufficient to decide whether the SNi' mechanismZ involves a one-stage concerted process or ionization to an intimate, rigidly oriented carbonium chlorosulfinate ion pairI6 followed by internal returne of the chloride component of the chlorosulfinate anion to give rearranged chloride. It is very clear that the SNi' mechanisms does not involve a carbonium chloride ion pair of the type employed by Cram' in his preferred mechanism for the action of thionyl chloride on the 3-phenyl-2-butanols. A carbonium chloride ion pair in the a, y-dimethylallyl system would lead to a trans-chloride which is 100% racemic instead of the inverted chloride actually observed. Further, a carbonium chloride ion pair would not lead to the specific structural results obtained with the butenols and cinnamyl alcohol.The dominant role of the SNi' reaction is soinetimes difficult to preserve. In the case of cinnamyl alcohol, even the use of 1 M concentrations of reactants changes the polarity of the medium and results in the product ion of a mixture of 60% cinnamyl chloride and 40% a-phenylallyl chloride from the reaction itself since a-phenylallyl chloride is stable under the conditions used.
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