  A detailed investigation of the low-energy chiral expansion is presented
within a model truncation of QCD. The truncation allows for a phenomenological
description of the quark-quark interaction in a framework which maintains the
global symmetries of QCD and permits a $1/N_c$ expansion. The model dependence
of the chiral coefficients is tested for several forms of the quark-quark
interaction by varying the form of the running coupling, $\alpha (q^2)$, in the
infrared region. The pattern in the coefficients that arises at tree level is
consistent with large $N_c$ QCD, and is related to the model truncation.
