Chemistry happens in the electron cloud surrounding the atoms. Specifically the orbitals. While there may be some electrons in and around a neutron star, they a

Chemistry happens in the electron cloud surrounding the atoms. Specifically the orbitals. While there may be some electrons in and around a neutron star, they are not organized into orbitals. By definition, a neutron star cannot undergo chemical reactions. What happens in neutron stars is somewhere between nuclear reactions and quantum effects. Both of which are decidedly not "chemistry" in the way most people use that word. More generally, only normal atoms can undergo chemistry. All of chemistry depends on the arrangement of electron orbitals. Once you leave that domain, you're in an entirely different field of physics.