The Calculated Infrared Spectra of Functionalized Hexamethylenetetramine (HMT) Molecules

Numerous laboratory studies have shown that exposure of mixed ices of astrophysical interest to ionizing radiation leads to the production of large numbers of new, more complex compounds. A significant portion of these new species appear to belong to a family of molecules that consist of hexamethylenetetramine (HMT; C(6)H(12)N4) and hexamethylenetetramine to which different functional side groups have been added. In this paper, we present the computed harmonic vibational infrared spectra of a number of HMT variants that include HMT-OH, HMT-NH2, HMT-CH3, HMT-CN, HMT-OCN, HMT-OCH3 HMT-CH(OH)CHO, and HMT-NHCHO. Since all of the members of this family share the common HMT framework as a major part of their structure, they produce a number of infrared bands that fall at similar positions and have similar strengths, which will make them easier to detect in space as a family. However, each molecular HMT variant also produces additional unique bands due to its attached side group, so it is possible to distinguish between different variants.