PROPERTIES OF THE MAIN HIGH-MOLECULAR-WEIGHT HYDROCARBONS IN TITANS ATMOSPHERE

Titan's atmosphere contains some low and high molecular weight hydroca rbons, belonging to the Polyacetylene family (PA) CxH2 (x = 2n, n = 1, ...,N-1), Vinylacetylene family (VA) CxHx (x = 2n, n = 1,...,N-2), Pol yvinyl family (PV) CxHx+2 (x = 2n, n = 1,..., N-3) up to C-60 and a sm all amount of Allenes CxHx+4. (x =2 2n, n < 5). These species are form ed by primary CH4 photolysis and further conversion of the primary pro ducts. In this paper we derive the physico-chemical (density, temperat ure of phase transformation, surface tension, etc.) and thermodynamic (heat-capacity, enthalpy, entropy, etc.) properteis of these species b y a unified approach, based on their elemental and functional structur e. About 200 individual chemical hydrocarbons, both known and unknown (hypothetical), were kept under regular examination. The calculated da ta were compared, whenever possible, with available information and th e accuracy of estimation was found to be satisfactory (similar to 30%) . The values of recommended indices (more than 1000 items) can be foun d in three figures and a table in a condensed form. This information i s relevant both for the design of an Adequate Kinetic Model of the che mical pattern in Titan's atmosphere, possible condensation of hydrocar bons into aerosols, to describe the environments the Cassini-Huygens p robe will encounter during its descent through the atmosphere and land ing on Titan's surface or in the ocean. It may also be relevant for th e analysis of low-temperature conversion of acetylene and methane.