Herbicidally active phenoxy-.alpha.-phenoxy-alkanecarboxylic acid derivatives

A compound of the formula ##STR13## wherein the floating substituents Cl and CN are in the 2- and 4-positions,

• R.sub.1 is hydrogen or C.sub.1 -C.sub.4 alkyl, and
• R.sub.4 ' is C.sub.1 -C.sub.8 alkyl unsubstituted or substituted by halogen or cyano or interrupted by oxygen, sulfur, a carbonyl or a carboxyl oxy group;
• C.sub.2 -C.sub.8 alkenyl optionally substituted by halogen;
• C.sub.2 -C.sub.8 alkinyl optionally substituted by halogen;
• C.sub.3 -C.sub.8 cycloalkyl;
• C.sub.3 -C.sub.8 cycloalkenyl;
• phenyl unsubstituted or substituted by halogen, cyano, nitro, C.sub.2 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy or trifluoromethyl;
• or benzyl unsubstituted or substituted by halogen, cyano, nitro, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy or trifluoromethyl.