Process for preparing 1,1-disubstituted ethylene monomers of general formula wherein: A and D are independently selected from each other from the following functional groups CN, CO 2 R 1, COR 1, CONR 1 2, SO 2 R 1, SO 3 R 1, COPO(OR 1) 2, COPOR 1 2, NO 2, wherein R 1 means a linear or branched, saturated or unsaturated C 1 -C 20 alkyl, preferably linear, branched or alicyclic C 1 -C 3 alkyl, or linear, branched or alicyclic C 4 -C 20 alkyl, C 1 -C 20 halogenated alkyl, C 4 -C 20 alkyl silane, C 1 -C 20 acetoxy silane, C 2 -C 20 alkoxyalkyl, C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 2 -C 10 alkylene, C 3 -C 20 cycloalkyl, alkylcycloalkyl, C 3 -C 20 cycloalkenyl, alkylcycloalkenyl, aryl, substituted aryl, alkylaryl, substituted alkylaryl, aliphatic heterocyclic moiety, alkyl moiety linked to an aliphatic heterocycle, aromatic heterocycle moiety, alkyl moiety linked to an aromatic heterocycle, acrylic ester moiety, oxetane moiety, epoxy moiety, glycolate moiety, and carboxylic acid ester moiety; characterized in that it comprises the reaction of a compound of general formula wherein: E is (CH 2 X) m, m is comprised between 1 and 20, X is O or S, when n= 1, F is selected from the functional groups: when n= 2, F is selected from the functional groups: when n= 3, F is: G is selected from the functional groups: G and F are independently selected from each other, and R 2 and R 3 are independently selected from each other from the functional groups H, linear or branched C 1 -C 4 alkyl, linear or branched C 1 -C 4 halogenated alkyl, carboxy substituted C 1 -C 4 alkyl, C 3 -C 10 cycloalkyl, optionally substituted aryl, and a heterocyclic moiety, or when n = 1, F may be connected to G through one R 6 group selected from (CH 2) p, (CHR') p, (CR'R") p, where p is comprised between 1-6, preferably between 1 and 4, and more preferably is 1, and R' and R" may be the same or different C 1 -C 4 alkyl groups, with a compound of general formula in the presence of a catalytic amount of an ammonium or iminium salt, wherein this salt is in homogeneous phase or supported on a solid substrate. A and D are independently selected from each other from the following functional groups CN, CO 2 R 1, COR 1, CONR 1 2, SO 2 R 1, SO 3 R 1, COPO(OR 1) 2, COPOR 1 2, NO 2, wherein R 1 means a linear or branched, saturated or unsaturated C 1 -C 20 alkyl, preferably linear, branched or alicyclic C 1 -C 3 alkyl, or linear, branched or alicyclic C 4 -C 20 alkyl, C 1 -C 20 halogenated alkyl, C 4 -C 20 alkyl silane, C 1 -C 20 acetoxy silane, C 2 -C 20 alkoxyalkyl, C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 2 -C 10 alkylene, C 3 -C 20 cycloalkyl, alkylcycloalkyl, C 3 -C 20 cycloalkenyl, alkylcycloalkenyl, aryl, substituted aryl, alkylaryl, substituted alkylaryl, aliphatic heterocyclic moiety, alkyl moiety linked to an aliphatic heterocycle, aromatic heterocycle moiety, alkyl moiety linked to an aromatic heterocycle, acrylic ester moiety, oxetane moiety, epoxy moiety, glycolate moiety, and carboxylic acid ester moiety; E is (CH 2 X) m, m is comprised between 1 and 20, X is O or S, when n= 1, F is selected from the functional groups: when n= 2, F is selected from the functional groups: when n= 3, F is: G is selected from the functional groups: G and F are independently selected from each other, and R 2 and R 3 are independently selected from each other from the functional groups H, linear or branched C 1 -C 4 alkyl, linear or branched C 1 -C 4 halogenated alkyl, carboxy substituted C 1 -C 4 alkyl, C 3 -C 10 cycloalkyl, optionally substituted aryl, and a heterocyclic moiety, or when n = 1, F may be connected to G through one R 6 group selected from (CH 2) p, (CHR') p, (CR'R") p, where p is comprised between 1-6, preferably between 1 and 4, and more preferably is 1, and R' and R" may be the same or different C 1 -C 4 alkyl groups,