  In this paper, we propose a new phenomenological two parameter
parametrization of $q(z)$ to constrain barotropic dark energy models by
considering a spatially flat FRW universe, neglecting the radiation component,
and reconstructing the effective equation of state (EoS). This two
free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a
more general fitting for the scalar field models, like thawing and freezing
models. We constrain the $q(z)$ free parameters using the observational data of
the Hubble parameter obtained from cosmic chronometers, the
joint-light-analysis type Ia Supernovae sample and a joint analysis from these
data. We obtain a value of $q(z)$ today, $q_0=-0.48\substack{+0.10 -0.11}$, and
a transition redshift, $z_t=0.71\substack{+0.12 -0.12}$ (when the Universe
change from an decelerated phase to an accelerated one). The effective EoS
reconstruction and the $\omega'$-$\omega$ plane analysis pointed out a quintom
dark energy, which is consistent with a non parametric EoS reconstruction,
reported by other authors, and using the latest cosmological observations.
