The most striking effect of increasing the amount of ethane is that the HCN 𝜈2 C-H stretching vibration is prominently red-shifted, indicating more pronounced hydrogen bond donation. The observation that polar compounds increase their mutual interaction as their surrounding becomes increasingly non-polar is expected (see e.g., ). This dependence of frequencies is linear and intersects the experimentally observed frequency shift when ethane mole fractions are in the range of 0.1-0.2. In other words, both our thermodynamic estimates and predicted trends in vibrational shifts are evidence in favor of approximately 10-20% of ethane intercalation or intermixing.