A residue from
pyrolysis of organic material or tar distillation which is solid at room temperature, consisting
of a complex mixture of numerous, essentially aromatic
hydrocarbons and
heterocyclic compounds. It exhibits a broad softening range instead of a defined
melting temperature. When cooled from the melt, pitches solidify without
crystallization.
Note:
The ratio of aromatic to aliphatic hydrogen depends mainly on the source of the starting
material. The hydrogen
aromaticity (ratio of aromatic to total hydrogen atoms) varies between 0.3 and 0.9. The aliphatic
hydrogen in pitch is largely associated with alkyl side chains substituted on aromatic
rings. The content of
heterocyclic compounds in pitches varies depending on their origins. Also, the softening temperature can
vary in a broad range between about
and
depending on the
molecular weight (
relative molecular mass) and composition of the constituents.
Source:
PAC, 1995, 67, 473
(Recommended terminology for the description of carbon as a solid (IUPAC Recommendations
1995))
on page 500
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.
