  A high fraction of carbon bound in solid carbonaceous material is observed to
exist in bodies formed in the cold outskirts of the solar nebula, while bodies
in the terrestrial planets region contain nearly none. We study the fate of the
carbonaceous material during the spiral-in of matter as the sun accretes matter
from the solar nebula. From observational data on the composition of the dust
component in comets and interplanetary dust particles, and from data on
pyrolysis experiments, we construct a model for the composition of the pristine
carbonaceous material in the outer parts of the solar nebula. We study the
pyrolysis of the refractory and volatile organic component and the concomitant
release of high-molecular-weight hydrocarbons under quiescent conditions of
disk evolution where matter migrates inwards. We also study the decomposition
and oxidation of the carbonaceous material during violent flash heating events,
which are thought to be responsible for the formation of chondrules. It is
found that the complex hydrocarbon components are removed from the solid disk
matter at temperatures between 250 and 400 K, while the amorphous carbon
component survives up to 1200 K. Without efficient carbon destruction during
flash-heating associated with chondrule formation the carbon abundance of
terrestrial planets, except for Mercury, would be not as low as it is found in
cosmochemical studies. Chondrule formation seems to be a process that is
crucial for the carbon-poor composition of the material of terrestrial planets.
