The reactions $\overline{p}n\to \overline{p}n{\pi }^{+}{\pi }^{-}$, $\overline{p}n\to \overline{p}p{\pi }^{-}{\pi }^0$, and $\overline{p}n\to \overline{n}p{\pi }^{-}{\pi }^{-}$ at $2.8-\frac{\mathrm{GeV}}{c}$ incident $\overline{p}$ laboratory momentum are analyzed with data from the Brookhaven National Laboratory 20-in. bubble chamber. $N^{*}\mathrm{}\left(1238\right)\mathrm{}$ isobar production in these channels is studied. It is found that the absorptive single-pion-exchange model cannot adequately explain all the features of simultaneous isobar production in these reactions. When the reactions $\overline{p}n\to ({\overline{N}}^{*--}{N}^{*+} or {\overline{N}}^{*0\mathrm{}}{N}^{*-})\to \overline{p}{\pi }^{-}n{\pi }^{+}$ are compared with their counterpart $\mathrm{pp}\to N^{*++}{N}^{*0\mathrm{}}\to \mathrm{pp}{\pi }^{+}{\pi }^{-}$, the former are found to be less peripheral than the latter, in sharp disagreement with a prediction of the model. A generalized single-pion-exchange model is discussed which gives better agreement with the nucleon-pion two-body mass and angular distributions. Some evidence for enhancements in the nucleon and antinucleon dipion systems at 1400 MeV is discussed.

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