isopropyl radical particularly well suited are those alkyl radicals r 1 where the branching point is the c 1 carbon atom examples of alkyl radicals r 1 in addition to hydrogen are the methyl ethyl n and iso propyl butyl hexyl octyl decyl 1 methyl octyl 2 ethyl octyl 1 methyl hexyl 1 1 dimethyl pentyl 1 3 3 trimethyl hexyl 1 ethyl pentyl 2 ethyl pentyl and preferably the cyclohexyl 1 methyl n propyl tertiary butyl 1 ethyl n propyl 1 methyl n butyl and 1 1 dimethyl n propyl radicals examples of alkyl substituted m phenylenediamines include 2 4 dimethyl 2 4 diethyl 2 4 diisopropyl 2 4 diethyl 6 methyl 2 methyl 4 6 diethyl 2 4 6 triethyl 2 4 dimethyl 6 cylohexyl 2 chlohexyl 4 6 diethyl 2 cyclohexyl 2 6 diisopropyl 2 4 dimethyl 6 1 ethyl n propyl 2 4 dimethyl 6 1 1 dimethyl n propyl and 2 1 methyl n butyl 4 6 dimethyl phenylenediamine 1 3 the compounds 3 3 39 di and 3 3 39 5 5 39 tetra n alkylsubstituted 4 4 39 diaminodiphenylmethanes such as 3 3 39 dimethyl 3 3 39 5 5 39 tetramethyl 3 3 39 diethyl 3 3 39 5 5 39 tetraethyl and 3 3 39 5 5 39 tetra n propyl 4 4 39 diaminodiphenylmethane have also proven to work well.