- A proposal is made of a novel class of hydrocarbons CNH4 which may be viewed to extend from methane (N = 1) and tetrahedrane (N = 4) on up in an infinite sequence of tetrahedral-symmetry cages. The structures may typically be viewed to be symmetrically hydrogenated fullerene structures with no small rings (of size 5) belonging solely to the -network. Notably these CNH4 species avoid local antiaromatic structure and exhibit less curvature strain than the corresponding (nonhydrogenated) fullerenes. After a comprehensive structural characterization, a Hckel-theoretical investigation of the orbital structure is reported and analyzed, to suggest necessary and sufficient conditions for these CNH4 structures (and related fullerenes) to be (stable) closed-shell species. Furthermore, the resonance stabilities via Kekul-structure counts and conjugated-circuit calculations both for tetrahedral-symmetry fullerenes CN and their possible (hydrogenated) species CNH4 are presented. 1995 Elsevier Science B.V. All rights reserved.