Yes. We can predict using gaussian.

Yes, there are several software tools and websites available that can predict the infrared (IR) spectra of unknown compounds. These tools utilize computational methods and databases to simulate and predict the IR spectra based on the compound's structure. Here are a few examples:

When using these tools, it's important to remember that the predicted IR spectra are based on computational models and assumptions, so they may not always perfectly match experimental results. However, they can provide valuable insights and aid in the interpretation and analysis of IR spectra for structural elucidation.

I have lost the plot here. How can you predict a spectrum if you don’t know the structure? Am I misunderstanding the word unknown ? Do you mean a not previously recorded structure?

there are several software and websites that can predict the IR spectra of unknown compounds:

Please note that the accuracy of the predictions can vary, and it’s always a good idea to confirm the results with experimental data if possible. Also, some of these services might require a subscription or purchase. It’s recommended to check their terms of use and pricing details.