Synthesis of N ‐[4‐(dimethylalkylammoniomethyl) benzoyl]caprolactam chlorides as cationic bleach activators for low‐temperature bleaching of cotton fabric under near‐neutral pH conditions

Low‐temperature bleaching of cotton fabric can be achieved by incorporating a so‐called bleach activator into an aqueous solution of hydrogen peroxide. In this study, a series of N ‐[4‐(dimethylalkylammoniomethyl)benzoyl]caprolactam chlorides were synthesised for use as cationic bleach activators with various alkyl chain lengths. All these synthesised cationic bleach activators were confirmed by 1 H and 13 C nuclear magnetic resonance spectroscopy and mass spectroscopy. Bleaching experiments revealed that these synthesised bleach activators were effective for bleaching of cotton fabric at 50 °C under near‐neutral pH conditions, but the alkyl chain lengths had a great influence on their bleaching performance. Increasing the alkyl chain length from 2 to 6 carbon atoms could slightly enhance bleaching performance, while increasing the alkyl chain length from 8 to 16 carbon atoms markedly reduced bleaching performance.