# Distinguish 1-bromobutane and 2-bromobutane with IR

How can I distinguish 1-bromobutane and 2-bromobutane by their IR spectrums?

In the 1-bromobutane spectrum I think the $$\ce{-CH3}$$ peak is shorter, but I don't know if that is actually reasonable or just a fluke.

In the spectrum that I think is 2-bromobutane there is an additional peak at around $$1290$$. What might this be?

The only alkyl halide peaks we discussed in class was the $$\ce{C-Br}$$ stretch $$600-750$$. They both seem to have this (although they do look different). How can I distinguish?

• Meh, with NMR it would be crystal clear. – Mithoron Apr 7 '19 at 23:34
• Sure would! Unfortunately this is an IR problem set. – Noah Harris Apr 7 '19 at 23:49
• From NIST database 1-bromobutane and 2-bromobutane in the gas phase. – MaxW Apr 8 '19 at 1:07
• I did see the different spectrum on SDBS, but I'm more interested in given just the two spectrum and the two compounds, how can you tell which goes with which? – Noah Harris Apr 8 '19 at 14:50