The invention relates to reaction products suitable as antioxidants which are substantially liquid at room temperature and which are obtained by the reaction of olefins with mixtures of diphenylamines and phenothiazines which may be alkylated. These products are obtainable by reacting an olefin of formulaR.sub.1 R.sub.2 C.dbd.CHR.sub.3 (I)with a mixture of compounds of formulae II and III ##STR1## in the presence of an acid catalyst, wherein R.sub.1 is hydrogen, C.sub.1 -C.sub.25 alkyl or phenyl,R.sub.2 is C.sub.1 -C.sub.25 alkyl, benzyl or phenyl,R.sub.3 is hydrogen or C.sub.1 -C.sub.12 alkyl,R.sub.4, R*.sub.4, R.sub.5 and R*.sub.5 are each independently of one another hydrogen, C.sub.1 -C.sub.25 alkyl, C.sub.5 -C.sub.12 cycloalkyl, benzyl, .alpha.-methylbenzyl or .alpha.,.alpha.-dimethylbenzyl, and R.sub.6 and R*.sub.6 are each independently of the other hydrogen, C.sub.1 -C.sub.18 alkyl, C.sub.1 -C.sub.4 alkenyl, benzyl or a radical of formula --CH(R.sub.9)--CH(R.sub.10)--S--R.sub.11, andR.sub.7 and R.sub.8 are hydrogen, or together form a divalent group ##STR2## R.sub.9 and R.sub.10 are each independently of the other hydrogen, phenyl or C.sub.1 -C.sub.12 alkyl,R.sub.11 is C.sub.4 -C.sub.18 alkyl, phenyl or --(CH.sub.2).sub.a --CO--OR.sub.12,a is 1 or 2, andR.sub.12 is C.sub.1 -C.sub.18 alkyl.