Nylon 6 fibers are produced by polymerization of caprolactam obtained after oximation and Beckmann rearrangement of cyclohexanone. For this reason, the purity of cyclohexanone used is an important parameter to control the quality of final nylon 6 products. The poor quality of cyclohexanone is related to the presence of some cyclic ketone impurities, such as 2-methylcyclopentanone, n-methylcyclohexanones (n = 2, 3, and 4), and 2-cyclohexen-1-one, which can remain after the purification process of cyclohexanone. In this study, the first step was to study the products promoted during the oximation of these cyclic impurities. The oximation of each impurity was carried out at T = 80 °C and pH = 5, and the reaction products were identified using gas chromatography−mass spectrometry (GC/MS) and NMR. Each cyclic oxime promoted a mixture of cis and trans stereoisomers, and the relative production ratio was determined. Additionally, the operating conditions that can affect the oximation step were studied. To do that, cyclohexanone was spiked with the mentioned cyclic impurities, and the oximation reaction was carried out using an aqueous solution of hydroxylammonium sulfate. The effects of experimental conditions, such as temperature (353.15−358.15 K) and pH (3.5−6), were studied. It was found that the higher the temperature, the higher the impurity conversion. However, when the pH was studied, the conversion of impurities presented a maximum due to the oximation mechanism. Additionally, a kinetic model of oximation reaction of cyclohexanone spiked with the cyclic impurities, based on an apparent constant to take into account that the reaction was carried out in two liquid phases, was proposed to explain the experimental results. The apparent kinetic constants obtained for 2-methylcyclohexanone and 2-cyclohexen-1-one were similar but lower than that for 2methylcyclopentanone. The study was completed promoting the Beckmann rearrangement of the oxime mixtures obtained from the oximation of pure cyclic impurities under mild conditions (sulfuric media at 100 °C). The amides produced were identified by gas chromatograph/mass selective detector (GC/MSD). Cis/trans oxime stereoisomers from n-methylcyclohexanones (n = 2 and 3) and 2-methylcyclopentanone presented the same reactivity to the corresponding amides, but only (Z)-2-cyclohexen-1one oxime reacts in the Beckmann rearrangement to produce its cyclic amide.