2,4,6‐Trifluorobenzonitrile

The title compound, C₇H₂F₃N, contains three crystallographically independent molecules in the crystal structure; two of these molecules have symmetry m and the third has symmetry mm. Each independent molecule forms a planar or approximately planar layer with its own kind. There are three different types of interlayer contacts, two of which are similar to each other, while the third is distinctly different. The packing within the layers is similar to that found in 2,5‐ and 3,6‐difluorobenzonitrile, with weak C—H...N interactions holding the molecules in the layers. The remarkable feature of this structure is the presence of more than one type of interlayer interaction.     

15N NMR spectra and reactivity of 2,4,6‐triazidopyridines, 2,4,6‐triazidopyrimidine and 2,4,6‐triazido‐s‐triazine

2,4,6‐Triazido‐s‐triazine, 2,4,6‐triazidopyrimidine and six different 2,4,6‐triazidopyridines were studied by ¹⁵N NMR spectroscopy. The assignment of signals in the spectra was performed using the gauge‐independent atomic orbital (GIAO)–Tao‐Perdew‐Staroverov‐Scuseria exchange‐correlation functional (TPSS)h/6‐311+G(d,p) calculations on the M06‐2X/6‐311+G(d,p) optimized molecular geometries. The Truhlar and coworkers' continuum solvation model called SMD was applied to treat solvent effects. With this approach, the root mean square error in estimations of the ¹⁵N chemical shifts for the azido groups was just 1.9 ppm. It was shown that the different reactivity of the α‐ and γ‐azido groups in pyridines correlates well with the chemical shifts of the N_α signals of these groups. Of two nonequivalent azido groups of azines, the azido group with the most shielded N_α signal is the most electron‐deficient and reactive toward electron‐rich reagents. By contrast, the azido group of azines with the most deshielded N_α signal is the most reactive toward electron‐poor reagents. Copyright © 2013 John Wiley & Sons, Ltd.     

2,4,6‐Trimethylphenyl isocyanide

The title compound, C₁₀H₁₁N, displays a crystallographic mirror plane that incorporates all the non‐H atoms, as well as the H atoms attached to the aromatic ring. The iso­cyano group is almost linear and shows an N[triple‐bond]C bond distance of 1.158 (3) Å.     

2,4,6‐trichloropyrimidine. Reaction with anilines

The reaction of 2,4,6‐trichloropyrimidine 1 with a variety of 4‐substituted anilines 2 has been investigated. Monosubstitution occurs readily for all anilines except those containing strongly electron‐withdrawing groups. The yields of the isomeric products 3 and 4 parallel the Hammet constants of the ring substituents. The main product when ethanol was used as the solvent was the 4‐substituted‐2,6‐dichloropyrimidine 3. Spectral and X‐ray data confirmed this assignment. However, a solvent dependence on the 3:4 ratio was demonstrated. In some cases, excess aniline under forcing conditions led to 2,4‐disubstituted products.     

DFT Study of the Group Interactions in 1,3,5‐Triamino‐2,4,6‐Trinitrobenzene and 1,3,5‐Triamino‐2,4,6‐Tridifluoroaminobenzene

Density functional calculations on isodesmic disproportionation reactions of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) and 1,3,5‐triamino‐2,4,6‐tridifluoroaminobenzene (TATDB) indicate that the interaction between nitro groups on meta carbons of TATB, which brings about unstability to the molecule, is surprisingly larger than that between difluroamino groups in TATDB. The electron‐withdrawing and electron‐donating groups generate large positive and very small negative values of E_{disproportion}, respectively. When both electron‐withdrawing and electron‐donating groups are attached to the benzene skeleton at the same time, large negative disproportionation energy is produced, which stabilizes the derivatives. The values of E_{disproportion} for TATB and TATDB are predicted to be ‐48.03 kJ/mol and ‐63.54 kJ/mol, respectively, indicating that the total interaction among groups with stabilization effects in TATDB is larger than that in TATB. The large difference of the E_{disproportion} values between TATB and TATDB is derived from the large difference between the interactions of the meta‐nitro group and those of meta‐difluoroamino groups. The energy barriers for the C‐N internal rotation of NO₂ group and NF₂ groups are 74.7 kJ/mol and 185.8 kJ/mol for TATB and TATDB, respectively. The large energy barrier for the rotation of the NF₂ group is caused by its stabilization interaction with neighbor amino groups, instead of steric effects. When the number of pairs of amino‐nitro or amino‐difluoroamino groups increases, there are more negative charges on the NO₂/NF₂ groups and on the O/F atoms.     

2,4,6‐Trifluoropyrimidine. Reactions with nitrogen nucleophiles

In a continuation of our studies involving the nucleophilic displacement of one of the chlorines from 2,4,6‐trichloropyrimidine, we now report the initial displacement of one of the fluorine atoms from 2,4,6‐trifluoropyrimidine using both aliphatic and aromatic amines. The monosubstitution products favor 2‐substitution with ammonia and ethanolamine while aniline gave the 4‐substituted derivative as the preferred product.     

2,4,6‐Tri­methyl­phenol

Crystals of the title compound, C₉H₁₂O, were formed as an unexpected by‐product during the recrystallization of (2R,3R)‐α,α,α′,α′‐tetramesityl‐1,4‐dioxa­spiro­[4,5]­decane‐2,3‐di­methanol from hexane/ethyl acetate (7:3). Strong hydrogen bonds between hydroxide groups connect the mol­ecules around one set of four symmetry‐equivalent 2₁ axes.     

1,3,5‐Triiodo‐2,4,6‐trimethylbenzene at 293 K

In the structure of tri­iodo­mesityl­ene (1,3,5‐tri­iodo‐2,4,6‐tri­methyl­benzene), C₉H₉I₃, at 293 K, the benzene ring is found to be significantly distorted from ideal D_6h symmetry; the average endocyclic angles facing the I atoms and the methyl groups are 123.8 (3) and 116.2 (3)°, respectively. The angle between the normal to the molecular plane and the normal to the (100) plane is 5.1°. No disorder was detected at 293 K. The thermal motion was investigated by a rigid‐body motion tensor analysis. Intra‐ and intermolecular contacts are described and topological differences compared with the isomorphous compounds tri­chloro­mesityl­ene and tri­bromo­mesityl­ene are discussed.     

2,4,6‐Trimethyl‐N‐nitro­aniline

In 2,4,6‐trimethyl‐N‐nitro­aniline (alternatively called mesitylnitramine), C₉H₁₂N₂O₂, the primary nitramino group is planar with a short N—N bond and is nearly perpendicular to the aromatic ring. The methyl group located in the para position is disordered, each H atom having half‐occupancy. The mol­ecules are linked together along the [100] axis by inter­molecular N—H⋯O hydrogen bonds.     

Dimorphism of ethyl 1,4‐dihydro‐2,4,6‐triphenylpyridine‐3‐carboxylate

The title compound, C₂₆H₂₃NO₂, (Ia) and (Ib), shows polymorphism with crystals obtained from different solvents displaying different crystal structures. However, it is not the geometry of the single mol­ecules nor the hydrogen‐bond pattern that is different in (Ia) and (Ib), but the way in which the hydrogen‐bonded chains, running along the a‐axis direction, are arranged with respect to each other.     

2,4,6‐Tri­chloro­phenyl­iso­nitrile and 2,4,6‐tri­chloro­benzo­nitrile

The molecular structures of the title compounds, 2,4,6‐tri­chloro­phenyl­iso­nitrile (IUPAC name: 2,4,6‐tri­chloro­phenyl isocyanide), C₇H₂Cl₃N, and 2,4,6‐tri­chloro­benzo­nitrile, C₇H₂Cl₃N, are normal. The two structures are not isomorphous, but do contain similar two‐dimensional layers in which pairs of mol­ecules are held together by pairs of Cl?CN [3.245 (3) Å] or Cl?NC [3.153 (2) Å] interactions. The two‐dimensional isomorphism is lost through different layer‐stacking modes.     

5‐Amino‐2,4,6‐tribromoisophthalic acid: the MAD triangle for experimental phasing

The title compound, C₈H₄Br₃NO₄, shows an extensive hydrogen‐bond network. In the crystal structure, molecules are linked into chains by COO—H...O bonds, and pairs of chains are connected by additional COO—H...O bonds. This chain bundle shows stacking interactions and weak N—H...O hydrogen bonds with adjacent chain bundles. The three Br atoms present in the molecule form an equilateral triangle. This can be easily identified in the heavy‐atom substructure when this compound is used as a heavy‐atom derivative for experimental phasing of macromolecules. The title compound crystallizes as a nonmerohedral twin.     

1‐(2,4,6‐Tri­methyl­phenyl)‐1H‐1,2,3,4‐tetrazole

In the title compound, C₁₀H₁₂N₄, the tetrazole and phenyl rings are planar to within 0.001 (2) and 0.006 (2) Å, respectively. The two rings are not coplanar and have a dihedral angle of 69.07 (9)° between them. Each mol­ecule is connected with two adjacent ones by C—H?N bridges between atoms of tetrazole rings forming chains parallel with the y axis of the unit cell.     

Tris(1,10‐phenanthroline)sodium 2,4,6‐trimercapto‐1,3,5‐triazin‐1‐ide

The title compound, [Na(C₁₂H₈N₂)₃](C₃H₂N₃S₃), contains an Na⁺ centre which is ionicly bonded to three 1,10‐phenanthroline (phen) ligands and one tri­thio­cyanurate(1−) (ttcH₂) anion. In the crystal structure, the anions are linked via hydrogen bonds to form linear chains. The S and H atoms of the ttcH₂ anion participate in intermolecular N—H⋯S hydrogen bonding, with N⋯S distances of 3.298 (2) and 3.336 (2) Å. The phen ligands are almost parallel, with dihedral angles of 3.92 (5), 11.75 (5) and 15.45 (5)°; moreover, they are nearly perpendicular to the ttcH₂ chains, with angles of 81.94 (7), 85.86 (7) and 85.96 (7)°.     

2,4,6‐Tri­methyl­benz­amide

The crystal structure of the title compound, C₁₀H₁₃NO, displays an infinite one‐dimensional network composed of primary amide mol­ecules connected by N—H⋯Ozdbnd;C hydrogen bonds involving the anti NH amide H atoms, thus generating a C(4) motif. This network is additionally stabilized by a weak N—H⋯π interaction between the syn‐oriented amide H atom and the aromatic ring of a neighbouring mol­ecule. The distance between the H atom and the ring centroid is 2.50 Å. The amide group and the aryl moiety are nearly perpendicular, forming an intramolecular dihedral angle of 84.69 (6)°.     

Monitoring structural transformations in crystals. 13. On photocyclization in 2,3,4,5,6‐pentamethylbenzophenone, 1,3‐diphenylbutan‐1‐one and 2,4,6‐triisopropyl‐4′‐methoxybenzophenone

The geometrical parameters governing the potential for the photocyclization reaction occurring in crystals of 2,3,4,5,6‐pentamethylbenzophenone, C₁₈H₂₀O, (I), 1,3‐diphenylbutan‐1‐one, C₁₆H₁₆O, (II), and 2,4,6‐triisopropyl‐4′‐methoxybenzophenone, C₂₃H₃₀O₂, (IV), have been evaluated. Compound (IV) undergoes photocyclization but (I) and (II) do not, despite the fact that their geometrical parameters appear equally favourable for reaction. The structure of the partially reacted crystal of the photoactive compound, i.e. 2,4,6‐triisopropyl‐4′‐methoxybenzophenone–3,5‐diisopropyl‐7‐(4‐methoxyphenyl)‐8,8‐dimethylbicyclo[4.2.0]octa‐1,3,5‐trien‐7‐ol (9/1), 0.90C₂₃H₃₀O₂·0.10C₂₃H₃₀O₂, (III), was also determined, providing structural evidence for the reactivity of the compound. It has been found that the carbonyl group of the photoactive compound reacts with one of the two o‐isopropyl groups. The study has shown that the intramolecular geometrical parameters are not the only factors influencing the reactivity of compounds in crystals.     

Crystallographic report: tert‐Butyldifluoro(2,4,6‐tris‐iso‐propylphenyl)silane,t‐Bu(2,4,6‐i‐PrC6H2)SiF2

Owing to steric congestion within the title compound, the geometry at the silicon atom deviates slightly from ideal tetrahedral geometry with an increased C? Si? C angle of 115.97(12)° and an elongated Si? C_aryl bond distance. Copyright © 2004 John Wiley & Sons, Ltd.     

3,5‐Di­methyl‐1,3,5‐oxadi­azane‐2,4,6‐trione: short intermolecular contacts determining the crystal packing

In the title compound, C₅H₆N₂O₄, the mol­ecules lie across a crystallographic mirror plane. The compound lacks traditional hydrogen‐bond donors, and hence crystals are held together by unusual C=O⋯O, O⋯C and weak C—H⋯O interactions, forming layers. Adjacent layers are arranged in an antiparallel manner, yielding an ABA layer sequence. The intermolecular contacts are quite short; a topological analysis of charge density based on density‐functional‐theory calculations was used for consideration of these short contacts and indicated a strong attractive bonding closed‐shell interaction between these atoms in the crystal structure.