Abstract: Novel substituted derivatives of N-ethyl(meth)acrylamide complying with the general formula (I): ##STR1## wherein R=H or --CH.sub.3, R.sub.1 =C.sub.1 -C.sub.8 alkyl and R.sub.2 =H or C.sub.1 -C.sub.8 alkyl.They may be obtained by a method in which (meth)acrylamide is reacted with a dialkoxy-2,2 ethanal of the formula (II): ##STR2## wherein R.sub.1 has the meaning indicated above to provide a product of formula (I), in which R.sub.2 =H, and, if desired, by carrying out an etherification with a C.sub.1 -C.sub.8 alkanol.

Abstract: This process for the preparation of products of general formula (I): ##STR1## wherein either R.sub.1 and R.sub.2, which are identical, represent a --CHRR.sub.3 group, in which R and R.sub.3, which are identical or different, represent an alkyl, alkenyl or aralkyl group, or R.sub.1 and R.sub.2, which are identical, represent a --CH.sub.2 R group, in which R represents a hydrogen atom, an alkyl, alkenyl or aralkyl radical, or R.sub.1 and R.sub.2 together form a --CH.sub.2 --(CRR).sub.n --CHR-- radical, in which n represents 0 or 1 and R retains the meaning given previously, is characterized by reacting glyoxal in the presence of an acid catalyst with an excess of the corresponding alcohol of general formula (II) RR.sub.3 CHOH, (III) RCH.sub.2 OH or (IV) --(CRR).sub.n --CHROH, in which R, R.sub.3 and n retain the meaning given previously, then stopping the reaction as soon as the concentration of the desired monoacetal of general formula (I) decreases in the reaction medium in favor of bisacetal.