Consider the following premises. q. p <-> q_6. q -> q_6. Can we infer ~q_6 from them?
 From p <-> q_6 we can infer p -> q_6. From q we can infer q or p. Finally, from q -> q_6, p -> q_6, q or p we can infer q_6, which contradicts ~q_6. Therefore, the answer is no.