Final answer:
The frequency of a stretching vibration in an IR spec is influenced by the molecular structure and the strength of the bond being stretched.
Step-by-step explanation:
The frequency of a given stretching vibration in an IR spec can be related to two factors: the molecular structure and the strength of the bond being stretched.
Firstly, the molecular structure determines the natural frequency of vibration for a particular bond. Different types of bonds, such as carbon-carbon or carbon-oxygen, have characteristic frequencies at which they vibrate.
Secondly, the strength of the bond influences the frequency of vibration. Strong bonds require more energy to stretch, resulting in higher frequencies, while weaker bonds require less energy and have lower frequencies.