An amorphous copolyester comprising the reaction product of (a) a monomer of formula I wherein R1, R2, R3, and R5 are each independently a C1-3 alkyl group, a is 0-1, b is 0-4, c is 0-4 and d is 0-3, and each R4 is independently hydrogen or a C1-3 alkyl group; (b) a terephthalyl component selected from terephthalic acid, a di(C1-3 alkyl) terephthalate, and combinations thereof, derived from a terephthalyl-containing polyester; and (c) 1,4-cyclohexane dimethanol; wherein the monomer (a) units are present in an amount from 7 to less than 12 mole % of the copolyester based on the total moles of repeat units in the copolyester; and the copolyester has a glass transition temperature of at least 107° C., an intrinsic viscosity of at least 0.7 dl/g, and a molded sample has a Notched Izod value of at least 290 J/m determined in accordance with ASTM D256.