# Distinguishing propan-2-ol from ethanol using IR spectroscopy

A question requires me to distinguish between propan-2-ol and ethanol from IR spectra. To me, they both look nearly identical, even though I know both of them contain the same functional group and that IR spectra are only capable of identifying functional groups.

My question is, how do you distinguish the two, without using a mass spectrometer?

• The isopropyl group shows characteristic coupled peaks around ~1350 cm-1 – Eashaan Godbole Mar 4 '18 at 19:49

Here are the tabulated peak positions ($\pu{cm^{-1}}$) and percent transmittance (%T) for the two. I've tried to match the appropriate peaks.
$$\begin{array}{cccc}% \hline% \text{ethanol position} & \text{ethanol %T} & \text{propan-2-ol position} & \text{propan-2-ol %T} \\ \hline% 3358 & 12 & 3346 & 9 \\ & & 3334 & 9 \\ 2974 & 13 & 2972 & 5 \\ 2927 & 38 & 2933 & 19 \\ & & 2907 & 23 \\ 2887 & 35 & 2884 & 20 \\ & & 2722 & 60 \\ & & 2669 & 60 \\ & & 2521 & 74 \\ & & 2408 & 79 \\ & & 2387 & 81 \\ & & 2198 & 84 \\ & & 1903 & 85 \\ & & 1766 & 84 \\ 1455 & 59 & 1467 & 24 \\ & & 1409 & 29 \\ 1381 & 54 & 1379 & 16 \\ & & 1368 & 17 \\ 1330 & 68 & 1341 & 28 \\ 1274 & 74 & 1309 & 23 \\ & & 1162 & 10 \\ 1090 & 22 & 1130 & 9 \\ 1050 & 7 & 1110 & 15 \\ & & \color{red}{954} & 4 \\ 881 & 37 & 818 & 13 \\ 669 & 67 & 660 & 37 \\ & & 654 & 37 \\ & & 490 & 66 \\ & & 436 & 68 \\ \hline% \end{array}%$$