[Cryolite]

Here is my proposed compound (drawn at the bottom) for the following H-NMR, C-NMR and IR spectras. Is it reasonable/correct?

Why is there a triplet at 2.85ppm without another coupled protons? Why are the 4 protons at 2.5ppm shown as one single peak?

C11H16N2:

[fledarmus]

Piperazines have very complicated splitting patterns due to the combination of chair-flipping in cyclohexane rings and umbrella shifting on nitrogen atoms. Depending on the substitutuents it can range from sharp doublets of doublets of doublets to overlapped multiplets to broad singlets. What you're seeing is pretty typical.