  Binary stellar evolution calculations predict that Chandrasekhar-mass
carbon/oxygen white dwarfs (WDs) show a radially varying profile for the
composition with a carbon depleted core. Many recent multi-dimensional
simulations of Type Ia supernovae (SNe Ia), however, assume the progenitor WD
has a homogeneous chemical composition. In this work, we explore the impact of
different initial carbon profiles of the progenitor WD on the explosion phase
and on synthetic observables in the Chandrasekhar-mass delayed detonation
model. Spectra and light curves are compared to observations to judge the
validity of the model. The explosion phase is simulated using the finite volume
supernova code LEAFS, which is extended to treat different compositions of the
progenitor WD. The synthetic observables are computed with the Monte Carlo
radiative transfer code ARTIS. Differences in binding energies of carbon and
oxygen lead to a lower nuclear energy release for carbon depleted material;
thus, the burning fronts that develop are weaker and the total nuclear energy
release is smaller. For otherwise identical conditions, carbon depleted models
produce less Ni-56. Comparing different models with similar Ni-56 yields shows
lower kinetic energies in the ejecta for carbon depleted models, but only small
differences in velocity distributions and line velocities in spectra. The light
curve width-luminosity relation (WLR) obtained for models with differing carbon
depletion is roughly perpendicular to the observed WLR, hence the carbon mass
fraction is probably only a secondary parameter in the family of SNe Ia.
