METHOD FOR PRODUCING TERMINAL CARBOXY GROUP-CONTAINING POLYETHYLENE GLYCOL AND METHOD FOR PRODUCING ACTIVATED POLYETHYLENE GLYCOL

To provide a method for producing a polyethylene glycol (PEG) having high purity carboxy group in high yield from a PEG having a terminal hydroxy group.SOLUTION: There is provided a method for producing a polyethylene glycol (PEG) including: a step 1 of reacting a specific carboxylic acid ester compound having a functional group which is eliminated during an esterification reaction with a PEG having a hydroxy group in a solution containing an inorganic base of 0.5 to 4 mass times based on the PEG, an aprotic solvent and water, wherein the mass of the water is 5 to 20 meq based on the inorganic base and the mass of the water in the solution is 2000 ppm or less, to obtain a PEG ester; and a step 2 of hydrolyzing the PEG ester to obtain a terminal carboxy group-containing PEG.SELECTED DRAWING: None 【課題】末端水酸基のポリエチレングリコール（ＰＥＧ）から、収率良く、高いカルボキシル基純度のＰＥＧを製造する方法の提供。【解決手段】工程１：水酸基を有するＰＥＧ、前記ＰＥＧに対して０．５〜４質量倍の無機塩基、非プロトン性溶剤および水分を含有する溶液であって、水分の質量が前記無機塩基に対して５〜２０ｍｅｑであり、かつ前記溶液における前記水分の質量が２０００ｐｐｍ以下である溶液中で、エステル化反応時に脱離する官能基を有する特定のカルボン酸エステル化合物をＰＥＧと反応させてＰＥＧエステルを得る。工程２：ＰＥＧエステルを加水分解し、末端カルボキシル基含有ＰＥＧを得る。【選択図】なし