The infrared spectra of the OH groups of a hydrogen-Y-zeolite have been recorded in the presence of C2H4 at pressures up to 1 atm and in the temperature range 25 to 150 °C. From these data, the heat of formation of hydrogen-bonded C2H4 was estimated to be about 9 kcal mole-1 for interaction with the 3648 cm-1 groups. Isotopic exchange between C2D4 and the two principal types of OH groups was studied at temperatures between 200 and 350 °; both exchanged at about the same rate. Equilibration of C2D4 and C2H4 proceeded via exchange with the surface OH groups. C2D4 OH exchange took place 1.2 times faster than C2H4 OD exchange over zeolite samples pretreated in equivalent ways. The kinetics deviated slightly from a first order dependence on the distance from equilibrium. The apparent first order rate constants reached an apparent maximum for pretreatment at 290 °C. The apparent activation energy for exchange was 16 kcal mole-1 for samples pretreated at 290 °C and 19 kcal mole-1 for those heated at 475 °C in O2 and rehydrated at 350 °C. In both instances, the reaction was first order in C2D4 pressure.