Abstract:ExperimentalA 1:1 adduct of hexamethylenetetramine oxide and hydroquinone, (CH2)6N40.C6H4(OH)2, has been prepared and subjected to crystal structure_analysis. The crystals are triclinic, space group P1, with a = 9.532(2), b = 6.521(1), c = 10.399(2) A, a= 102.13 (2), fl = 83.09 (2), y = 92.09 (2) °, and Z = 2. The structure was solved by a combination of direct phasing with packing considerations and refined to R = 0.053 for 2334 Mo Ka diffractometer data. The C6H4(OH)2 molecules occupy two non-equivalent site… Show more
“…62,63 It is a neutral molecule, though there is a formal charge separation between nitrogen and oxygen. The structure of several adducts of urotropine-N-oxide have also been reported; [64][65][66][67][68] we note that the molecular and crystal structure of 1 was first determined by Mak in 1978, from data accumulated at room temperature. 67,68 There is a potential coupling between the distribution of electron density associated with the hydrogen position and the structure of the formic acid residue in urotropine-N-oxide‚formic acid, and in a valence bond, atomistic description, this correla-tion automatically is present.…”
Section: [T]he Molecular Structure Hypothesissthat a Molecule Is A Co...mentioning
confidence: 80%
“…It is notable that the N−O bond length is particularly short at 1.3951(12) Å, where the normal range for the N−O distance in hydroxylammonium cations is 1.396−1.436 Å. , It is a neutral molecule, though there is a formal charge separation between nitrogen and oxygen. The structure of several adducts of urotropine- N -oxide have also been reported; − we note that the molecular and crystal structure of 1 was first determined by Mak in 1978, from data accumulated at room temperature. , 1 Molecular structure of urotropine- N -oxide.…”
The crystal structure of urotropine-N-oxide.formic acid, as determined from multiple temperature single-crystal X-ray diffraction experiments in the range 123-295 K and from neutron diffraction at 123 K, is reported. There is a strong hydrogen bonding interaction between the OH of formic acid and the N-oxide of urotropine, with the oxygen-oxygen distance ranging from 2.4300(10) to 2.4469(10) A. The electron density of the hydrogen atom associated with this interaction was located in the Fourier difference maps of the spherical atom refinement after all heavy atom positions were determined. The maximum of the electron density associated with the hydrogen bond is located approximately 1.16 A from the formate segment, though the distribution of electron density is very broad. The electron density associated with the H atom is thus shown by these accurate X-ray diffraction experiments to be approximately centered at all temperatures studied. This was conclusively confirmed by single-crystal neutron diffraction data obtained at 123 K, from which statistically equivalent O-H distances of 1.221(7) and 1.211(7) A were obtained.
“…62,63 It is a neutral molecule, though there is a formal charge separation between nitrogen and oxygen. The structure of several adducts of urotropine-N-oxide have also been reported; [64][65][66][67][68] we note that the molecular and crystal structure of 1 was first determined by Mak in 1978, from data accumulated at room temperature. 67,68 There is a potential coupling between the distribution of electron density associated with the hydrogen position and the structure of the formic acid residue in urotropine-N-oxide‚formic acid, and in a valence bond, atomistic description, this correla-tion automatically is present.…”
Section: [T]he Molecular Structure Hypothesissthat a Molecule Is A Co...mentioning
confidence: 80%
“…It is notable that the N−O bond length is particularly short at 1.3951(12) Å, where the normal range for the N−O distance in hydroxylammonium cations is 1.396−1.436 Å. , It is a neutral molecule, though there is a formal charge separation between nitrogen and oxygen. The structure of several adducts of urotropine- N -oxide have also been reported; − we note that the molecular and crystal structure of 1 was first determined by Mak in 1978, from data accumulated at room temperature. , 1 Molecular structure of urotropine- N -oxide.…”
The crystal structure of urotropine-N-oxide.formic acid, as determined from multiple temperature single-crystal X-ray diffraction experiments in the range 123-295 K and from neutron diffraction at 123 K, is reported. There is a strong hydrogen bonding interaction between the OH of formic acid and the N-oxide of urotropine, with the oxygen-oxygen distance ranging from 2.4300(10) to 2.4469(10) A. The electron density of the hydrogen atom associated with this interaction was located in the Fourier difference maps of the spherical atom refinement after all heavy atom positions were determined. The maximum of the electron density associated with the hydrogen bond is located approximately 1.16 A from the formate segment, though the distribution of electron density is very broad. The electron density associated with the H atom is thus shown by these accurate X-ray diffraction experiments to be approximately centered at all temperatures studied. This was conclusively confirmed by single-crystal neutron diffraction data obtained at 123 K, from which statistically equivalent O-H distances of 1.221(7) and 1.211(7) A were obtained.
“…A research program on the structural chemistry of polycyclic tertiary amine N-oxides has been pursued in our laboratory. A series of preparative and X-ray crystallographic studies on the adducts of hexamethylenetetramine N-oxide (HMTO) have shown that all these structures involve hydrogen bonding between the terminal 0 atom of the N + 0 dative bond and the proton donor molecule(s) (7)(8)(9)(10). We now report the synthesis and structural characterization of a series of heterocyclic tertiary amine N,N '-dioxide hydrates, namely N, N '-di(o-toly1)piperazine N,N '-dioxide tetrahydrate, I, N, N '-di(p-toly1)piperazine N, N '-dioxide tetrahydrate, 11, and N,N '-di(p-chloropheny1)piperazine N,Nr-dioxide tetrahydrate, 111.…”
The synthesis and X-ray structure determination of N,N′-di(o-tolyl)piperazine N,N′-dioxide tetrahydrate, I, N,N′-di(p-tolyl)piperazine N,N′-dioxide tetrahydrate, II, and N,N′-di(p-chlorophenyl)piperazine N,N′-dioxide tetrahydrate, III, are described. Compound I crystallizes in space group [Formula: see text] with a = 7.778(1), b = 7.915(2), c = 8.919(2) Å, α = 106.25(2), β = 99.56(1), γ = 108.80(2)°, and Z = 1. Compound II crystallizes in space group [Formula: see text] with a = 6.558(1), b = 7.134(2), c = 11.610(3) Å; α = 73.23(2), β = 78.08(2), γ = 72.67(2)°, and Z = 1. Compound III crystallizes in space group P21/c with a = 9.159(3), b = 12.390(4), c = 8.339(4) Å, β = 97.38(3)°, and Z = 2. The structures of I–III were solved by the direct method and refined to R = 0.049 (1749 observed MoKα reflections), 0.055 (2651 observed reflections), and 0.035 (1827 observed reflections), respectively. In each case, the N,N′-dioxide molecule occupies a site of symmetry [Formula: see text]. The piperazine ring takes the chair form, with two N—O bonds oriented axially in a trans configuration. The structures are characterized by strong hydrogen bonding between the water molecules, as well as between the N-oxide groups and water molecules, giving rise to puckered layers composed of various combinations of edge-sharing four-membered, six-membered, ten-membered, and twelve-membered rings. The aryl rings, which protrude on both sides of each puckered layer, constitute hydrophobic regions separating the hydrophilic layers in the crystal packing.
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