Raman OD-stretching (first) overtone spectra, X(Z,X+Z)Y, X(ZZ)Y, and X(ZX)Y, from pure D2O between 22 and 98 degrees C yield an isosbestic frequency near 5130 cm(-1). This value corresponds to the X(ZX)Y fundamental isosbestic observed near 2624 cm(-1), but not to the X(ZZ)Y fundamental isosbestic near 2429 cm(-1), because the fundamental 2375 cm(-1) correlated deuteron OD stretch, nu(1), and its overtone, 2 nu(1), are weak in the X(ZX)Y spectra, compared to the three higher-frequency fundamentals, nu(2), nu(3), and nu(4), and their overtones. The 2375 and 2475 cm(-1) fundamentals and their overtones probably engage in coupling with a approximate to 175 cm(-1) LA phonon which is supported by H-bonded aggregates or patches, whereas the corresponding data for H2O provide clear and unequivocal evidence for this LA coupling. Deconvolution of the X(Z,+Z)Y overtone spectra, 22-152 degrees C, plus van’t Hoff treatment yields an enthalpy for H bond, O-D ... O, rupture of 2.8 +/- 0.2 kcal/mol O-D ... O, in good agreement with present values of 2.6 +/- 0.2 and 2.8 +/- 0.2 kcal/mol O-D ... O, obtained from the fundamental X(ZZ)Y and X(ZY)Y spectra. Raman overtone measurements are important because the spacing between the four-Gaussian components is large in the overtone OD- and OH-stretching contours compared to the fundamentals.