Photochemical reactions of molecules in solid orthodeuterium (o-D2) have been studied by high-resolution infrared spectroscopy and compared with previous results obtained in solid parahydrogen (p-H2). Ultraviolet photolysis of CD3I molecules in solid o-D2 yielded CD3 radicals and iodine atoms efficiently, which indicates a small cage effect in solid o-D2, as in the case of solid p-H2. The Fourier transform infrared spectrum of the nu3 vibrational band of CD3 showed a rotational structure with additional splitting due to crystal field interactions. The magnetic dipole transition (2P1/2<--2P3/2) of the I atom isolated in solid o-D2 was observed together with a strong rotational satellite of deuterium molecules through the electron-roton coupling in solid hydrogen. The tunneling reaction between CD3 and D2 was not observed in a time scale of a few days, which gives the upper limit of the tunneling reaction rate of 10(-8) s(-1) at 4.2 K.