Question

Select the IR spectrum that corresponds best to 3-hydroxy-2-butanone. (See the Hint for the structure. ) Key absorptions are marked on the spectra. Select the IR spectrum that corresponds best to 3-hydroxy-2-butanone. (See the Hint for the structure. ) Key absorptions are marked on the spectra. Wavenumber (cm-1) Select the IR spectrum that corresponds best to 3-hydroxy-2-butanone. (See the Hint for the structure. ) Key absorptions are marked on the spectra. Wavenumber (cm-1) Select the IR spectrum that corresponds best to 3-hydroxy-2-butanone. (See the Hint for the structure. ) Key absorptions are marked on the spectra. Wavenumber (cm-1)

Select the IR spectrum that corresponds best to 3-hydroxy-2-butanone. (See the Hint for the structure.) Key absorptions are marked on the spectra.

Answer 1

Concepts and reason

IR spectrum is an analysis of the interaction of molecule with infrared radiation. IR spectra help to identify the different functional groups present in a compound.

Fundamentals

Different functional group gives absorption band at different range and intensity in IR. By knowing the absorption range, predict the functional group present in the given molecule. The table shown below gives the IR absorption of the common functional groups.

These groups absorb the IR radiation since their bonds are polar which makes the bonds to vibrate at a wavenumber, and by using the wave numbers, different functional groups can be identified in the IR spectra.

Draw the structure of 3-hydroxy-2-butanone as shown below:

Identify the IR range for the functional group present in the compound as shown below:

Third spectrum showing the peaks at $3530\,{\rm{c}}{{\rm{m}}^{ - 1}}$ and $1740\,{\rm{c}}{{\rm{m}}^{ - 1}}$ is the best IR spectrum that corresponds to 3-hydroxy-2-butanone.

Ans:

Hence, the third spectrum showing the IR absorption at ${\bf{3530}}\,{\bf{c}}{{\bf{m}}^{{\bf{ - 1}}}}$ and ${\bf{1740}}\,{\bf{c}}{{\bf{m}}^{{\bf{ - 1}}}}$ corresponds best to ${\bf{3 - hydroxy - 2 - butanone}}$ .