→ When analysing organic substances, IR radiation of specific wavelengths will be absorbed by certain atoms of the organic molecules. The absorption is dependent on the length of the compound’s atomic bonds.

→ By utilising the complete IR spectrum, the particular bonds in a molecule can be identified. The degree of the absorption can be used to calculate the relative number of each specific bond.

→ The resulting absorption data can be used to create an absorption spectrum of the organic material. This spectrum can then be compared to published data and used to identify the organic material.

→ The absorbance shows an initial trough in the range 3100 – 3600 cm¯¹. This absorbance maximises at around 3350 cm¯¹. This data indicates the likely presence of a hydroxyl group within the compound.

→ The next trough occurs in the range 3100 – 3600 cm¯¹. Its intensity trough is not broad. This data is consistent with the presence of a  \(\ce{C-H}\)  bond.

→ There is little absorbance between 2500 – 1500 cm¯¹. This data indicates the absence of any  \(\ce{C=O}\)  group, discounting the possibility of the compound being carboxylic acid or a ketone.

→ An absorption peak between 1250 – 1050 cm¯¹ indicates the presence of a  \(\ce{C-O}\)  bond.

→ Propanol is a compound whose structure is consistent with the data above:

→ The molecular weight of propanol is 60.01 g mol ¯¹ which is also supported by the data.

→ Since the spectrum of isomers is similar, the two possible compounds that fit this are propan-1-ol or propan-2-ol.

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