Thiobutyric acid derivatives

A 4-chloro-4,4-difluorothiobutyric acid derivative of the formula I ##STR42## in which R.sub.1 and R.sub.2 are, independently of one another, hydrogen, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 halogenoalkyl and

• R.sub.3 is hydrogen C.sub.1 -C.sub.20 alkyl, C.sub.3 -C.sub.6 cycloalkyl, C.sub.3 -C.sub.10 alkenyl, aryl,
• C.sub.3 -C.sub.10 halogenoalkenyl;
• C.sub.3 -C.sub.6 cycloalkyl substituted by halogen;
• aryl substituted by halogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 halogenoalkyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 halogenoalkoxy,
• C.sub.1 -C.sub.6 alkoxycarbonyl, C.sub.1 -C.sub.4 alkylthio or nitro;
• or
• C.sub.1 -C.sub.20 alkyl substituted by halogen, di-C.sub.1 -C.sub.4 alkylamino, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkylthio, C.sub.1 -C.sub.20 alkoxycarbonyl, C.sub.3 -C.sub.7 cycloalkoxycarbonyl, C.sub.1 -C.sub.4 alkylcarbonyloxy, C.sub.3 -C.sub.6 cycloalkyl, aryl, C.sub.1 -C.sub.10 alkylaminocarbonyl or anilinocarbonyl;
• where the aryl groups are in each instance selected from the group consisting of furyl, thienyl, phenyl and naphthyl and are unsubstituted or substituted by halogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 halogenoalkyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 halogenoalkoxy, C.sub.1 -C.sub.4 alkylthio or nitro.