As mentioned by Artur, a chemical mess necessitating starting again
The purpose of chlorform is to partition the initial Trizol (and also lipids) used to lyse cells and denature protein
If you were to add isopropanol directly to this Trizol lysate you would end up with a very impure fraction, high in salt and residual Trizol (as well as RNA) that would almost certainly inhibit any down stream applications
You need to remove Trizol, salt and genomic DNA from RNA by following the correct procedure in order to then manipluate the resulting RNA fraction by (say) reverse transcription: If you carried out RT directly on the isopropanol concentrated upper fraction, residual Trizol would denature reverse transcriptase and the high salt load would inhibit the RT reaction with any active transcriptase that still remained