The present invention relates to a mixture comprising itaconic acid or an itaconic acid derivative and a primary amine of the formula (I) R—NH2  (I) where the molar ratio of primary amine to itaconic acid or the itaconic acid derivative is in the range from 0.5:1 to 20:1, wherein the mixture comprises 50 mole percent or less of 4-carboxypyrrolidones of the formula (II), derivatives of the 4-carboxypyrrolidones of the formula (II) and 4-carbamidopyrrolidones of the formula (III) based on the itaconic acid used or the itaconic acid derivative used and in which R is a linear or branched saturated aliphatic radical having 1 to 24 carbon atoms or a saturated cycloaliphatic radical having 3 to 24 carbon atoms.The invention further provides for the use of the inventive mixtures for preparing 1,3-alkylmethylpyrrolidones and/or 1,4-alkylmethylpyrrolidones, and also a process for preparing 1,3-alkylmethylpyrrolidones and/or 1,4-alkylmethylpyrrolidones.In addition, the present invention relates to mixtures comprising 1,3-alkylmethylpyrrolidones and/or 1,4-alkylmethylpyrrolidones and 1,3-alkylmethylpyrrolidines, where the proportion of 1,3-alkylmethylpyrrolidines is in the range from 10 to 10 000 ppm, and to mixtures comprising 1,3-alkylmethylpyrrolidone and 1,4-alkylmethylpyrrolidone, wherein the molar ratio of 1,3-alkylmethylpyrrolidone to 1,4-alkylmethylpyrrolidone is in the range from 1:1 to 10:1.