Tetracyanohydroquinone and its Dimorpholinium Salt: Hydrogen Bonds OH … N or O ⊖ H ⊕ N to Nitrogen Bases of Different Strengths

How a network of hydrogen bonds is influenced by the basicity of a proton acceptor center is demonstrated particularly clearly by the title compounds: tetracyanohydroquinone, a relatively acidic phenol, forms linear molecular strings by self‐association through hydrogen bonds between OH and CN groups—provided that addition of a stronger base such as morpholine does not cause hydrogen bonds to be formed preferentially between different molecules, with concomitant hydrogen transfer (see below).