Graphane is a two-dimensional hydrocarbon predicted to be stable, derived from a single graphene sheet with the formula CH. All carbon atoms are in sp³ hybridization, forming a hexagonal network, while hydrogen atoms are bonded to carbon on both sides of the plane in an alternating manner. Graphane is predicted to be stable with a binding energy comparable to other hydrocarbons such as benzene, cyclohexane, and polyethylene. It is a semiconductor with potential applications in hydrogen storage and two-dimensional electronics. The compound has a fully fluorinated analog, poly-(carbon monofluoride), which has been synthesized before. Graphane is also predicted to be more stable than mixtures of cyclohexene and graphite. First-principles total energy calculations show that graphane has a favorable formation energy, comparable to other hydrocarbons. The calculated binding energy of graphane in the chair conformation is 6.56 eV/atom, which is as stable as the analogous fluorinated compound CF. The electronic band structures of the two conformers are very similar, with a direct band gap at the Γ point. The chair conformer has a band gap of 3.5 eV, while the boat conformer has a band gap of 3.7 eV. The vibrational frequencies of the phonons at the Γ point are shown in Fig. 4. The highest frequency modes correspond to C-H bond stretching modes. Possible synthetic routes for graphane include hydrogenation of different forms of carbon and exchange of fluorine with hydrogen. Graphane has potential applications in hydrogen storage and two-dimensional electronics. It is a simple member of the hydrocarbon family that has been missing until now. If synthesized, it will be a noteworthy example of the predictive power of electronic structure methods and will open a new window into the world of low-dimensional materials.Graphane is a two-dimensional hydrocarbon predicted to be stable, derived from a single graphene sheet with the formula CH. All carbon atoms are in sp³ hybridization, forming a hexagonal network, while hydrogen atoms are bonded to carbon on both sides of the plane in an alternating manner. Graphane is predicted to be stable with a binding energy comparable to other hydrocarbons such as benzene, cyclohexane, and polyethylene. It is a semiconductor with potential applications in hydrogen storage and two-dimensional electronics. The compound has a fully fluorinated analog, poly-(carbon monofluoride), which has been synthesized before. Graphane is also predicted to be more stable than mixtures of cyclohexene and graphite. First-principles total energy calculations show that graphane has a favorable formation energy, comparable to other hydrocarbons. The calculated binding energy of graphane in the chair conformation is 6.56 eV/atom, which is as stable as the analogous fluorinated compound CF. The electronic band structures of the two conformers are very similar, with a direct band gap at the Γ point. The chair conformer has a band gap of 3.5 eV, while the boat conformer has a band gap of 3.7 eV. The vibrational frequencies of the phonons at the Γ point are shown in Fig. 4. The highest frequency modes correspond to C-H bond stretching modes. Possible synthetic routes for graphane include hydrogenation of different forms of carbon and exchange of fluorine with hydrogen. Graphane has potential applications in hydrogen storage and two-dimensional electronics. It is a simple member of the hydrocarbon family that has been missing until now. If synthesized, it will be a noteworthy example of the predictive power of electronic structure methods and will open a new window into the world of low-dimensional materials.