[epapsiou]

You are right a chemical is a chemical. It is just that the smell Orris (or any other smelling flower) is made up of hundreds of chemicals each with its own volatility profile. No one has been able to get it right even with modern spectrography tools. Now the real kicker is even with the actual rose (or any other flower) oil, you can't recreate the smell of fresh rose. There is the whole field of headspace analysis that tries to cover that.