(+)‐3‐Oxo‐4‐pregnene‐20β‐carboxyl­ic acid: catemeric hydrogen bonding in a steroidal keto acid

The title keto acid, (+)‐23,24‐dinor‐3‐oxo­chol‐4‐en‐22‐oic acid, C₂₂H₃₂O₃, forms carboxyl‐to‐ketone hydrogen‐bonding catemers [O?O = 2.699 (4) Å and O—H?O = 173°], linking mol­ecules screw‐related in b. The four mol­ecules in the cell form two parallel counter‐directional chains, screw‐related in a. Intermolecular C—H?O=C close contacts to different neighboring mol­ecules were found for the ketone and the acid.     

Conformational preferences in 2‐­nitrophenylthiolates: S‐(2‐nitro­phenyl) 4‐toluenethiosulfonate

In the title compound, C₁₃H₁₁NO₄S₂, the nitro group is rotated by 44.1 (1)° out of the plane of the adjacent aryl ring and the toluene­thio­sulfonate group is almost orthogonal to the plane of the nitrated aryl ring. There are three types of C—H?O hydrogen bond in the structure [C?O range 3.324 (3)–3.503 (3) Å; C—H?O range 160–173°] and these link the mol­ecules into a three‐dimensional framework.     

2‐Formyl­benzonitrile

The title compound, C₈H₅NO, has an intra­molecular O⋯CN contact involving an O⋯C distance of 2.797 (2) Å and a C—C—N bond angle of 174.5 (2)°, both indicative of a weak nucleophilic attack of the aldehyde O atom on the electrophilic C atom in the nitrile group. Calculations at the B3LYP density functional level using the 6–31G* basis set support this inter­pretation; natural bond‐order analysis indicates an n_O1→π delocalization energy of 6.3 kJ mol⁻¹. Similar results were obtained from density functional calculations on three related mol­ecules. The 2‐formyl­benzonitrile mol­ecules pack in sheets as a consequence of C—H⋯N and C—H⋯O hydrogen bonds.     

N‐(o‐Chloro­phenyl)‐2,5‐di­methyl­pyrrole‐3‐carb­aldehyde

Crystal structure analysis of the title compound, C₁₃H₁₂ClNO, reveals three crystallographically independent mol­ecules in the asymmetric unit. The main conformational difference between these mol­ecules is the orientation of the phenyl rings with respect to the pyrrole rings. The coplanar arrangement of the aldehyde groups attached to the pyrrole rings influences the pyrrole‐ring geometry. The C2—C3 and N1—C5 bonds are noticeably longer than the C4—C5 and N1—C2 bonds. Two independent mol­ecules of the title compound form dimers via intermolecular C—H⃛O hydrogen bonds [D⃛A = 3.400 (3) Å and D—H⃛A = 157°]. The perpendicular orientation of the phenyl and pyrrole rings of one independent mol­ecule and its symmetry‐related mol­ecule allows C—H⃛π interactions, with an H⃛centroid distance of 2.85 Å and a C—H⃛π angle of 155°. The distances between the H atom and the pyrrole‐ring atoms indicate that the C—H bond points towards one of the bonds in the pyrrole ring.     

Hydro­gen bonding and C—H⃛O interactions in 4‐phenanthrenemethanol at 150 K

The title compound, C₁₅H₁₂O, crystallizes in the centrosymmetric space group I4₁/a with one mol­ecule in the asymmetric unit. In the single hydrogen bond, the H atom is ordered, the O_D?O_A distance is 2.788 (1) Å and the O—H?O angle is 176 (1)°. Each hydroxyl group forms hydrogen bonds with two other hydroxyl groups and the resulting chains of interactions, in four non‐linked subsets of mol­ecules, propagate along [001]. The single leading intermolecular C—H?O interaction has an H?O distance of 2.81 Å and a C—H?O angle of 140°; the single leading intramolecular C—H?O interaction has an H?O distance of 2.24 Å and a C—H?O angle of 152°. The phenanthrene core is less nearly planar in this structure than in the room temperature structure of phenanthrene‐4‐carboxylic acid.     

5‐Chloro‐N‐(2‐hydroxy‐5‐methyl­phenyl)­salicyl­ald­imine

The title compound, N‐(5‐chloro‐2‐oxido­benzyl­idene)‐2‐hydroxy‐5‐methyl­anilinium, C₁₄H₁₂ClNO₂, is a tridentate Schiff base with almost planar molecules. Each mol­ecule contains a strong intramolecular N—H?O hydrogen bond [2.576 (2) Å]. There is also an intermolecular O—H?O hydrogen bond [2.695 (2) Å] linking neighbouring mol­ecules into infinite chains along the [101] direction.     

7‐Phenyl‐1‐oxa‐4‐thiaspiro[4.5]decan‐7‐ol stereoisomers

The stereoisomers of 7‐phenyl‐1‐oxa‐4‐thia­spiro­[4.5]­decan‐7‐ol, C₁₄H₁₈O₂S, have the same stereochemistry at the C atom bearing an OH group, i.e. axial OH and equatorial phenyl groups. However, the acetal S and O atoms are axial and equatorial, respectively, in one isomer and reversed in the second. Furthermore, the crystals of one isomer are composed of hydrogen‐bonded mol­ecules involving the hydroxyl H atom and the O atom of the five‐membered heterocyclic ring, with an O?O distance of 2.962 (3) Å, forming a polymeric chain along the b axis. The asymmetric unit of the other isomer is composed of two mol­ecules, wherein hydroxyl H atoms and the O atoms of the five‐membered heterocyclic rings display intramolecular O—H?O hydrogen bonds with O?O separations of 2.820 (2) and 2.834 (2) Å.     

C[triple‐bond]C—H systems as hydrogen‐bond donors and acceptors: trans‐1,2‐diethynylcyclo­hexane‐1,2‐diol and trans‐1,4‐diprop‐2‐ynylcyclo­hexane‐1,4‐diol monohydrate

The title 1,2‐diol derivative, C₁₀H₁₂O₂, crystallizes with two independent but closely similar mol­ecules in the asymmetric unit. Only two of the four OH groups are involved in classical hydrogen bonding; the mol­ecules thereby associate to form chains parallel to the short c axis. The other two OH groups are involved in O—H⋯(C[triple‐bond]C) systems. Additionally, three of the four C[triple‐bond]C—H groups act as donors in C—H⋯O inter­actions. The 1,4‐diol derivative crystallizes with two independent half‐mol­ecules of the diol (each associated with an inversion centre) and one water mol­ecule in the asymmetric unit, C₁₂H₁₆O₂·H₂O. Both OH groups and one water H atom act as classical hydrogen‐bond donors, leading to layers parallel to the ac plane. The second water H atom is involved in a three‐centre contact to two C[triple‐bond]C bonds. One acetyl­enic H atom makes a very short `weak' hydrogen bond to a hydr­oxy O atom, and the other is part of a three‐centre system in which the acceptors are a hydroxy O atom and a C[triple‐bond]C bond.     

(1R,2S)‐2‐[N‐Methyl‐N‐(4‐toluene­sulfonyl)amino]‐1‐phenylpropan‐1‐ol

In the title compound, C₁₇H₂₁NO₃S, the S atom is in a distorted tetrahedral geometry and the N atom exhibits sp² character. The antiperiplanar conformation is observed for the N and hydroxyl‐O atoms and the torsion angle around the N—C linkage is ?136.3 (2)°. The mol­ecules are linked by O—H?O intermolecular hydrogen bonds to form an infinite one‐dimensional chains along the c axis.     

Coordinative NB bond formation and hydrogen‐bonded molecular ladders in 2,5‐bis[(N→B)‐(2‐aminoethoxy)phenylboryl]thiophene

The molecular structure of the title compound, C₂₀H₂₄B₂­N₂O₂S, is characterized by a twofold rotation axis passing through the S atom and the midpoint of the C—C single bond in the thio­phene ring. A coordinative NB bond is present in the boroxazolidine ring and a single N—H?O hydrogen bond [H?O 1.93 (3) Å, N?O 2.829 (3) Å and N—H?O 172 (2)°] links the mol­ecules into a molecular ladder.     

2‐Amino‐5‐nitro­thia­zole monoethanol solvate: triply‐interwoven hydrogen‐bonded sheets containing centrosymmetric R(8) and R(38) rings

2‐Amino‐5‐nitro­thia­zole crystallizes from solution in ethanol as a monosolvate, C₃H₃N₃O₂S·C₂H₆O, in which the thia­zole component has a strongly polarized molecular–electronic structure. The thia­zole mol­ecules are linked into centrosymmetric dimers by paired N—H⋯N hydrogen bonds [H⋯N = 2.09 Å, N⋯N = 2.960 (6) Å and N—H⋯N = 169°], and these dimers are linked by the ethanol mol­ecules, via a two‐centred N—H⋯O hydrogen bond [H⋯O = 1.98 Å, N⋯O = 2.838 (5) Å and N—H⋯O = 164°] and a planar asymmetric three‐centred O—H⋯(O)₂ hydrogen bond [H⋯O = 2.07 and 2.53 Å, O⋯O = 2.900 (5) and 3.188 (5) Å, O—H⋯O = 169 and 136°, and O⋯H⋯O = 55°], into sheets built from alternating (8) and (38) rings. These sheets are triply interwoven.     

(+)‐3,11‐Dioxoandrost‐4‐ene‐17β‐carboxyl­ic acid: catemeric hydrogen bonding in a steroidal keto acid

The title keto acid, C₂₀H₂₆O₄, forms carboxyl‐to‐ketone hydrogen‐bonding catemers [O?O = 2.653 (5) Å and O—H?O = 172 (5)°], linking translationally related mol­ecules via the A‐ring ketone. The two mol­ecules in the cell form two parallel counter‐directional chains, screw‐related in b. A total of four intermolecular C—H?O=C close contacts was found, involving both ketone functions.     

π‐Stacked hydrogen‐bonded dimers in 2‐(2‐nitro­phenyl­amino­carbonyl)­benzoic acid,and hydrogen‐bonded sheets in orthorhombic and monoclinic polymorphs of 2‐(4‐nitro­phenyl­amino­carbonyl)­benzoic acid

Molecules of 2‐(2‐nitrophenylaminocarbonyl)benzoic acid, C₁₄H₁₀N₂O₅, are linked into centrosymmetric R(8) dimers by a single O—H⋯O hydrogen bond [H⋯O = 1.78 Å, O⋯O = 2.623 (2) Å and O—H⋯O = 178°] and these dimers are linked into sheets by a single aromatic π–π stacking interaction. The isomeric compound 2‐(4‐nitrophenylaminocarbonyl)benzoic acid crystallizes in two polymorphic forms. In the orthorhombic form (space group P2₁2₁2₁ with Z′ = 1, crystallized from ethanol), the mol­ecules are linked into sheets of R(22) rings by a combination of one N—H⋯O hydrogen bond [H⋯O = 1.96 Å, N⋯O = 2.833 (3) Å and N—H⋯O = 171°] and one O—H⋯O hydrogen bond [H⋯O = 1.78 Å, O⋯O = 2.614 (3) Å and O—H⋯O = 173°]. In the monoclinic form (space group P2₁/n with Z′ = 2, crystallized from acetone), the mol­ecules are linked by a combination of two N—H⋯O hydrogen bonds [H⋯O = 2.09 and 2.16 Å, N⋯O = 2.873 (4) and 2.902 (3) Å, and N—H⋯O = 147 and 141°] and two O—H⋯O hydrogen bonds [H⋯O = 1.84 and 1.83 Å, O⋯O = 2.664 (3) and 2.666 (3) Å, and O—H⋯O = 166 and 174°] into sheets of some complexity. These sheets are linked into a three‐dimensional framework by a single C—H⋯O hydrogen bond [H⋯O = 2.45 Å, C⋯O = 3.355 (4) Å and C—­H⋯O = 160°].     

threo‐2‐(2,6‐Dimethoxy­phen­oxy)‐1‐(4‐hydr­oxy‐3,5‐dimethoxy­phenyl)­propane‐1,3‐diol: a conformational study

In the crystal structure of the title compound, C₁₉H₂₄O₈, the mol­ecules adopt a conformation in which the bulky 2,6‐dimethoxy­phen­oxy and 4‐hydr­oxy‐3,5‐dimethoxy­phen­yl groups are almost as far apart as possible. The C(aryl)·C(aryl) distance is 4.8766 (19) Å, which is close to the calculated maximum value (4.92 Å). The C(aryl)—C—C—O(aryloxy) torsion angle is 173.76 (11)° and the C(benzylic)—C—O—C(aryl) torsion angle is 149.09 (11)°. The conformation is compared with those of related lignin model compounds. The hydrogen‐bonding pattern is discussed in terms of graph‐set theory.     

(3R,4aS,5R)‐3‐Hydro­xy‐5‐isopropenyl‐3,8‐di­methyl‐4,4a,5,6‐tetra­hydro‐2(3H)‐naphthalenone

In the crystal structure of C₁₅H₂₀O₂, mol­ecules are associated by intermolecular hydrogen bonds between the hydroxy function and a keto group [O?O 2.770 (2) Å], forming chains along the [100] direction in the crystal. Both six‐membered rings in the decalin unit adopt envelope conformations; one section of the mol­ecule, encompassing the extended conjugation of a C=C double bond with an enone functionality [C=C—C=O = 175.6 (2)° and C=C—C=C = 176.6 (2)°], is flat, whilst the rest of the mol­ecule is folded relative to the constrained part. The stereochemistry was determined from the R‐(–)‐carvone starting material.     

Hydro­gen‐bonded molecular ladders in trans‐1,2‐bis(2‐nitro­anilino)­cyclo­hexane

Crystals of the title compound, C₁₈H₂₀N₄O₄, contain equal numbers of (R,R) and (S,S) mol­ecules, but these are not precise enantiomorphs, neither are they related by crystallographic symmetry; in addition, each mol­ecule exhibits approximate, but not exact, twofold rotational symmetry. There are intramolecular N—H?O hydrogen bonds [N?O 2.609 (4)–2.638 (5) Å; N—H?O 125–132°] and the mol­ecules are linked into molecular ladders by C—H?O hydrogen bonds [C?O 3.306 (6)–3.386 (6) Å; C—H?O 146–160°].     

Aquabromo(6‐carboxypyridine‐2‐carboxylato‐O,N,O′)mercury(II)

The title compound, [HgBr(C₇H₄NO₄)(H₂O)], was obtained by the reaction of an aqueous solution of mercury(II) bromide and pyridine‐2,6‐di­carboxylic acid (picolinic acid, dipicH₂). The shortest bond distances to Hg are Hg—Br 2.412 (1) Å and Hg—N 2.208 (5) Å; the corresponding N—Hg—Br angle of 169.6 (1)° corresponds to a slightly distorted linear coordination. There are also four longer Hg—O interactions, three from dipicH^? [2.425 (4) and 2.599 (4) Å within the asymmetric unit, and 2.837 (4) Å from a symmetry‐related mol­ecule] and one from the bonded water mol­ecule [2.634 (4) Å]. The effective coordination of Hg can thus be described as 2+4. The mol­ecules are connected to form double‐layer chains parallel to the y axis by strong O—H?O hydrogen bonds between carboxylic acid groups of neighbouring mol­ecules, and by weaker hydrogen bonds involving both H atoms of the water mol­ecule and the O atoms of the carboxylic acid groups.     

(2‐Amino­ethoxy)­bis(2‐thienyl)­boron

In the five‐membered ring in the title compound, (2‐amino­ethoxy)­bis(2‐thienyl)­boron, C₁₀H₁₂BNOS_2, the B atom is four‐coordinate with dimensions N—B 1.654 (3), O—B 1.479 (3), and C—B 1.606 (3) and 1.609 (3) Å. An intermolecular hydrogen bond between an amino H atom and the ethoxy O atom links the mol­ecules into infinite chains along the a axis. Only one of the two amino H atoms is involved in hydrogen bonding because there is only the one acceptor atom, the ethoxy O atom, and the molecular geometry precludes formation of a second hydrogen bond by the second amino H atom.     

Three N2‐benzoyl­oxybenz­amidines: sheet structures built from hard and soft hydrogen bonds and aromatic π–π stacking interactions

Molecules of the title compounds N²‐(benzoyl­oxy)­benz­ami­dine, C₁₄H₁₂N₂O₂, (I), N²‐(2‐hydroxy­benzoyl­oxy)­benz­ami­dine, C₁₄H₁₂N₂O₃, (II), and N²‐benzoyloxy‐2‐hydroxybenzamidine, C₁₄H₁₂N₂O₃, (III), all have extended chain conformations, with the aryl groups remote from one another. In (I), the mol­ecules are linked into chains by a single N—H⋯N hydrogen bond [H⋯N = 2.15 Å, N⋯N = 3.029 (2) Å and N—H⋯N = 153°] and these chains are linked into sheets by means of aromatic π–π stacking interactions. There is one intramolecular O—H⋯O hydrogen bond in (II), and a combination of one three‐centre N—H⋯(N,O) hydrogen bond [H⋯N = 2.46 Å, H⋯O = 2.31 Å, N⋯N = 3.190 (2) Å, N⋯O = 3.146 (2) Å, N—H⋯N = 138° and N—H⋯O = 154°] and one two‐centre C—H⋯O hydrogen bond [H⋯O = 2.46 Å, C⋯O = 3.405 (2) Å and C—H⋯O = 173°] links the mol­ecules into sheets. In (III), an intramolecular O—H⋯N hydrogen bond and two N—H⋯O hydrogen bonds [H⋯O = 2.26 and 2.10 Å, N⋯O = 2.975 (2) and 2.954 (2) Å, and N—H⋯O = 138 and 163°] link the molecules into sheets.     

trans‐4‐Bromo‐ONN‐azoxy­benzene at 100 K

The crystal structure of the α isomer of trans‐4‐bromo­azoxy­benzene [systematic name: trans‐1‐(bromophenyl)‐2‐phenyl­diazene 2‐oxide], C₁₂H₉BrN₂O, has been determined by X‐ray dif­frac­tion. The geometries of the two mol­ecules in the asymmetric unit are slightly different and are within ∼0.02 Å for bond lengths, ∼2° for angles and ∼3° for torsion angles. The azoxy bridges in both mol­ecules have the typical geometry observed for trans‐azoxy­benzenes. The crystal network contains two types of planar mol­ecules arranged in columns. The torsion angles along the Ar—N bonds are only 7 (2)°, on either side of the azoxy group.