Jupiter is theorized to have a small, solid core or a gaseous core of dense materials.
http://en.wikipedia.org/wiki/Jupiter#Internal_structure

They just don't have all the info to know for sure yet, WW. The temperature near the core is believed to be 36,000 degrees Kelvin and under 3,000–4,500 GPa of pressure. I don't know enough about chemistry to formulate a real guess, but wouldn't the molecules be flying EVERYWHERE under the excitement generated by that insane amount of heat, or would the immense pressure cut down on some of that?