DNA complementarity is expressed by way of three hydrogen bonds for a G:C base pair and two for A:T. As a result, careful control of the denaturation temperature of PCR allows selective amplification of AT-rich alleles. Yet for the same reason, the converse is not possible, selective amplification of GC-rich alleles. Inosine (I) hydrogen bonds to cytosine by two hydrogen bonds while diaminopuri...

In the title compound, C16H14O4, the benzene rings are inclined to one another by 4.91 (7)°. The conformation about the C=O and C=C bonds is trans and cis, respectively. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(14) ring motif. The dimers are linked via O-H⋯O and C-H⋯O hydrogen bonds, forming undulating two-dimensional networks lying...

In the title compound, C(16)H(16)N(2)O(2), the N'-acetyl-acetohydrazide group is approximately planar (r.m.s. deviation = 0.018 Å for the eight non-H atoms) and makes dihedral angles of 81.92 (6) and 65.19 (6)° with the terminal phenyl rings. The phenyl rings form a dihedral angle of 62.60 (7)°. In the crystal, mol-ecules are linked into sheets lying parallel to (001) by N-H⋯O and C-H⋯O hydroge...

In the crystal structure of the title compound, C(4)H(5)N(2) (+)·C(6)HCl(2)O(4) (-), there are three crystallographically independent 1,2-diazinium cations and hydrogen chloranilate anions. The anions are held together by pairs of O-H⋯O hydrogen bonds to form two types of dimers, one of which is centrosymmetric. The 1,2-diazinium cations are linked on both sides of each dimer via bifurcated N-H...

The structure of the title hybrid compound, (C6H16N2)[CrO4], has been determined from synchrotron data. The organic cation adopts a chair conformation. The inorganic CrO42- anion is slightly distorted owing to its involvement in N-H⋯O hydrogen-bonding inter-actions with neighbouring trans-cyclo-hexane-1,2-di-ammonium cations, whereby the two Cr-O bonds to the O atoms acting as acceptor atoms fo...

Block-localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance-assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between pi delocalization and hydrogen-bonding interactions. We examined the dimers of formic acid, formamide, 4-pyrimidinone, 2-pyridinone, 2-hydroxpyri...

The benzene ring in the title compound, C(10)H(10)O(4), makes an angle of 4.4 (1)° with the C-C-C-O linker. The hy-droxy groups are involved in both intra- and inter-molecular O-H⋯O hydrogen bonds. The crystal packing is stabilized by O-H⋯O hydrogen-bonding inter-actions. The mol-ecules of the caffeic acid ester form a dimeric structure in a head-to-head manner along the a axis through O-H⋯O hy...

In the title compound, C(4)H(9)N(2)O(3) (+)·NO(3) (-), alternatively called (1RS)-2-carbamoyl-1-carboxy-ethanaminium nitrate, the asymmetric unit comprises one asparaginium cation and one nitrate anion. The strongest cation-cation O-H⋯O hydrogen bond in the structure, together with other strong cation-cation N-H⋯O hydrogen bonds, generates a succession of infinite chains of R(2) (2)(8) rings al...