Synthesis of complex molecules in dense interstellar clouds via gas-phase chemistry: model update and sensitivity analysis

In an effort to update the work of Leung, Herbst & Huebner, a series of pseudo time-dependent model calculations of the gas-phase chemistry of dense interstellar clouds has been performed. In these calculations a revised list of 1958 reactions has been used which involves 206 species and includes a representative sample of complex molecules. The cloud chemistry has been studied as a function of visual extinction, cloud temperature, and carbon-to-oxygen abundance ratio. The changes in the calculated abundances of complex molecules under different physical conditions are emphasized. It is shown that these species can be synthesized under a variety of physical conditions. It is also shown that complex molecule development does not occur appreciably in the gas phase in interstellar clouds that are of low density ($$2\times10^3\text {cm}^{-3}$$) and of low visual extinction ($$A_V=2$$).