J. Hodge Markgraf and Mary F. Anton Williams College Williamstown. Massachusetts 01267
I 1
Solvolysis of I -Haloadamantanes A physical organic chemistry experiment
In the development of experiments for courses in physical organic chemistry it is customary to include correlations hetween structure and reactivity. Such exercises have usually necessitated a variety of instrumentation: pH meters, calorimeters, nmr spectrometers, ultraviolet and visible spectrophotometers (1%). A noticeable exception was an experiment on bridgehead reactivity in which the use of methyl orange as a p H indicator gave a visual demonstration of reactivity (9). That particular work, however, limited the structure-react i v i t y r e ~ a t i o n s h to i ~ a comparison between very rapid and very unreactive systems. We wish to report a related experiment in which a series of correlations among substrate structure, leaving group ability, and solvent ionizing power can he develoned. The solvolysis of l-haloadamantanes has received much attention recentlv. This tricvclic framework has proved to he a useful q+tem tor assessing such pnmmetrrs a5 inductive and sterit effecr.; (10. I I ). rarhun-carhun h w e r c o n i ~ t m t i mr 12, 13), ion pairinter&diates (14, 15), &cleoihik solvent Presented at the Pacific Conference on Chemistry and Spectroscopy, November 8-10.1916, in Phoenix, Arizona. 1 Since the boiling points of these three solvents span an eightdegree range, the reaction temperatures at reflux will differ slightly and, therefore, so will the relative rates. Such differences are a potential problem only for comparisons between trifluoroethanol and acetonitrile;the other two pairs involve only fnur-degreeranges. From the data in the tables, however, it can he seen that even a rate factor of two between runs in TFE and MeCN would not alter the overall conclusion. We do not feel that the use of a eonstant-temperaturebath is necessarv. althoueh it would enhance the orecision. With such aooaratus
Table 1. Reaction Times for Solvolysis of l-AdXa 1-AdX
TFE
MeCN
EtOH
Br
