"The brosylates and tosylates of cyclopentanol and its 1-d1, c̲i̲s̲-2-d1, t̲r̲a̲n̲s̲-2-d1, and 2,2,5,5-d4 analogs have been synthesized and their solvolysis rates measured at 25° in 70% vol. ethanol-water. The solvoylsis reactions were monitored by a conductance method. The isotope effects, k[subscript H]/k[subscript D], observed for the brosylates and tosylates of each of the isotopically substituted cyclopentyl alcohols are as follows: 1-d1-brosylate (1.1869) and 1-31-tosylate (1l1836); c̲i̲s̲-2-d1-brosylate (1.1533) and c̲i̲s̲-2-31-tosylate (1.1577); t̲r̲a̲n̲s̲-2-d1-brosylate (1.1803) and t̲r̲a̲n̲s̲-2-d1-tosylate (1.1765); 2,2,5,5-d4-brosylate (1.8881) and 2,2,5,5-d4-tosylate (1.8863). The closeness in magnitude of the isotope effects for the c̲i̲s̲- and t̲r̲a̲n̲s̲-isomers is important in that it shows the cyclopentyl system to be very nearly planer. If they had been greatly different it would have indicated that the ring was quite puckered. More important, however, is the fact that the t̲r̲a̲n̲s̲-isotope effect is greater than the c̲i̲s̲-isotope effect. this means that specific solvation of the [underscore Beta]-hydrogens, leading to an elimination driving force, is a possible explanation of secondary deuterium isotope effects. The isotope effects for the d4-compounsd were calculated by taking the products of the squares of the c̲i̲s̲- and t̲r̲a̲n̲s̲-isotope effects. The calculated isotope effect was 1.8530 for the d4-brosylate and 1.8552 for the d4-tosylate. These vales are very near the observed values of 1.8881 and 1.8863 for the brosylate and tosylate, respectively. Because of the great precision (~0.1-0.2%) of the technique used in obtaining these results, the difference between the calculated and the observed isotope effects for both the brosylate and tosylate is considered to be a true difference. However, the closeness of the calculated and observed values does indicate an almost cumulative isotope effects which supports the hyperconjugation postulate as a possible explanation of secondary deuterium isotope rate effects. There is a very close agreement between the isotope effects for the brosylate and tosylate of any one given isotopically substituted cyclopentyl alcohol, e.g., the greatest difference exhibited was that of 0.38% for the c̲i̲s̲-compounds. This close agreement tends to indicate that when changing from one leaving group to another structurally similar leaving group there is a negligible influence on the isotope effect. Attempts were made to synthesize 2,2-d2-cyclopentyl alcohol and c̲i̲s̲-2-d1-5,5-d2-cyclopentyl alcohol and the procedures are described in the Experimental section. Unfortunately, these synthetic procedures were unsuccessful"--Abstract, leaves iii-iv.