catalyst: lithium tert-butoxide in neat (no solvent) Kinetics; soln. of lithium tert-butoxide in DMMA (according to the method described by Shapiro, I. O. et al., Izv. Akad. Nauk LatvSSR, Ser. Khim., 535 (1964)); isotope exchange react. with Cr-complex at 25°C in evacuated glass ampuls; stopping the react. by pouring into cold acidified H2O, filtration (glass filter), washing of pptn. with H2O, distn. in vac., detn. of deuterium content by cobustion of the substrate in a quartz tube under O2;