IR spectroscopy is the most suitable technique for the purification of cyclohexanone from a mixture containing benzoic acid, isoamyl alcohol, cyclohexane, and cyclohexanone. IR spectroscopy stands for infrared spectroscopy, which is a powerful analytical technique that uses infrared light to identify and characterize chemical compounds based on their unique molecular vibrations.

- IR Spectroscopy Principle:
IR spectroscopy works on the principle that different chemical bonds in a molecule vibrate at specific frequencies when exposed to infrared radiation. Each functional group in a molecule has its characteristic set of vibrations, which can be detected and analyzed using an IR spectrometer.

- Selection of IR Spectroscopy for Purification:
In the given mixture, cyclohexanone is the desired compound to be purified. IR spectroscopy can be used to confirm the presence of cyclohexanone in the mixture by analyzing its characteristic vibrational frequencies. The other compounds in the mixture, such as benzoic acid, isoamyl alcohol, and cyclohexane, will have different functional groups and therefore different vibrational frequencies, allowing them to be distinguished from cyclohexanone.

- Steps Involved in IR Spectroscopy Purification:
1. Sample Preparation: The mixture containing cyclohexanone, benzoic acid, isoamyl alcohol, and cyclohexane is prepared for analysis by IR spectroscopy. This may involve extracting the desired compound or isolating it from the other compounds in the mixture.

2. IR Spectroscopy Analysis: The prepared sample is then subjected to IR spectroscopy analysis using an IR spectrometer. The sample is exposed to infrared radiation, and the resulting spectrum is obtained.

3. Interpretation of Spectrum: The obtained IR spectrum is analyzed to identify the characteristic vibrational frequencies of cyclohexanone. These frequencies correspond to specific functional groups present in cyclohexanone, such as the carbonyl group (C=O). By comparing the spectrum with reference spectra or databases, the presence of cyclohexanone can be confirmed.

4. Purification: Once the presence of cyclohexanone is confirmed, further purification techniques can be employed to separate it from the other compounds in the mixture. These techniques may include techniques such as distillation, extraction, or chromatography, depending on the specific requirements of the purification process.

In conclusion, IR spectroscopy is the most suitable technique for the purification of cyclohexanone from a mixture containing benzoic acid, isoamyl alcohol, cyclohexane, and cyclohexanone. It allows for the identification and confirmation of the presence of cyclohexanone based on its characteristic vibrational frequencies.