Can ir spectroscopy be used to distinguish 2-pentanone from 2-hexanone why or why not

No

Infrared (IR) Spectroscopy is a set of techniques that involves the analysis of the interaction between infrared light and a molecule. Infrared spectroscopy is mainly used to determine functional groups in molecules and it can also be employed to study and identify chemicals.  

IR spectroscopy cannot be used to distinguish 2-pentanone from 2-hexanone because the two structures have the same functional group. IR spectroscopy can only be used to distinguish molecules that have different functional groups.

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