the solid on a sintered glass funnel by vacuum filtration the reaction flask is rinsed with cold ipa 6 3 l 6 3 ml per gram mpeg oh and this rinse is used to wash the isolated solid the solid is left under aspirator vacuum until no additional filtrate is evident the semi dry solid is dissolved in meoh and re precipitated from meoh ipa as described above two additional times the final wet cake is dried under high vacuum at 40 u00b0 c for 48 hours to give approximately 850 g of product as a white to light yellow solid the product is analyzed by high performance liquid chromatography under critical conditions and by proton nmr to a 20 l straight walled jacketed reactor with bottom drain and thermowell equipped with an overhead stirrer cold water condenser and nitrogen inlet is charged 700 grams of 10 000 gram per mole average molecular weight mpeg having a polydispersity of less than 1 1 and four liters of toluene the resulting solution stirred 250 rpm while heating to 60 u00b0 c before adding 100 milliliters of tripentylamine and 140 grams of p nitrophenylchloroformate an immediate yellow color forms but quickly dissipates the reaction is allowed to stir at 60 u00b0 c under an inert atmosphere until hplc analysis under critical conditions indicates an essentially complete reaction after approximately 18 24 hours of heating the reaction is cooled to 35 u00b0 c and methyl t butyl ether mtbe 7 l 10 ml per gram mpeg oh is added.