  The nonleptonic decays of \Lambda_{b} that are dominated by W exchange are
studied. In particular, the decay modes
\varLambda_{b}\to\varDelta^{0}D^{0},\varDelta^{-}D^{+},\Sigma^{*-}D_{s}^{+},
\Lambda_{b}\to\Sigma_{c}^{*+}\pi^{-},\Sigma_{c}^{*0}\pi^{0},\Xi_{c}^{*0}K^{0}
and \varLambda_{b}\to\Sigma_{c}^{+}\pi^{-} are analyzed. In an another aspect,
the decay \Lambda_{b}\to\Lambda_{c}^{+}\pi^{-} in the factorization anstaz is
studied. It is shown that factorization contributes to parity-violating
(s-wave) amplitude A only. Hence factorization gives asymmetry parameter
\alpha=0. However, the dominant contribution to parity conserving (p-wave)
amplitude B comes from W exchange, i.e., from the baryon pole, giving asymmetry
parameter \alpha=-0.77.
