PROBLEM TO BE SOLVED: To provide a method for producing a benzophenone derivative low in rhodamine-type dye content and having asymmetric alkyl groups.
SOLUTION: The method for producing the benzophenone derivative of the general formula(2) comprises the following process: A reaction is carried out between a compound of the general formula(1) and phthalic anhydride in the presence of an organic solvent, the resultant reaction liquid is charged with water to adjust the reaction liquid to pH4.0-7.0, an organic solvent layer obtained by separating the reaction liquid in two is charged with water to adjust the organic solvent layer to pH8.0-14.0, and an aqueous layer obtained by separating the organic solvent layer in two is mixed with a water-miscible organic solvent to deposit crystal, which is then separated by filtration. In the general formulas(1) and (2), R1 and R2 are each an alkyl, cycloalkyl, alkoxyalkyl, benzyl or (substituted) phenyl group, wherein R1 and R2 are not the same as each other.
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