@TheDragonOfFlame You were probably thinking of carbodydrates, and these may exist in an open chain conformation as aldoses or ketoses. The parent compound without OH is a ketone or aldehyde as orthocresol pointed out.

@Curio Late to the party, sorry :) It is common in such problems to assume p is constant unless told otherwise. BTW be careful, your derivation is incorrect. It is not generally true that Δ(pV) = VΔp + pΔV, only that d(pV) = Vdp + pdV