The acylation reactions of alkylphenols is the one of the promising area in petroleum chemistry. They are used as the feedstock for the synthesis of high-performance thermal and photo stabilizers for polyolefin, additives to oils and fuels. This book is about the acylation reaction of p-cycloalkylphenol with acetic acid in the presence of KY-23 and zinc chloride catalysts and the affects of parameters ( temperature, duration, mol ratio, amount of catalyst) on the yield of 2-hydroxy-5-cycloalkylacetophenones.