Biomedical subjects

R E Gerkin

Publications and source records attributed to R E Gerkin.

At least 55 records · Page 3Linked to original sources

PubMed1997

1,4,5,8-naphthalenetetracarboxylic acid cyclic 1,8-anhydride bis(dimethyl sulfoxide) solvate and 1,4,5,8-naphthalenetetracarboxylic 1,8:4,5-dianhydride.

1,4,5,8-Naphthalenetetracarboxylic acid cyclic 1,8-anhydride crystallized from dimethyl sulfoxide (DMSO) as the solvate, C14H6O7.2C2H6OS, in the centrosymmetric space group P1. Two O-H...O hydrogen bonds with O...O distances of 2.592 (3) and 2.598 (3) A are formed, with the two carboxylic acid OH groups as donors and the O atoms of the two inequivalent DMSO molecules as acceptors. The carboxylic H atoms are ordered, as are the carboxylic O atoms. In addition to the conventional hydrogen bonds, there are numerous C-H...O interactions consistent with the large number of potential CH donors and O-atom acceptors. 1,4,5,8-Naphthalenetetracarboxylic 1,8:4,5-dianhydride, C14H4O6, crystallized in the centrosymmetric space group P2(1)/c with half the molecule as the asymmetric unit. Each molecule is involved in four significant C-H...O interactions as a donor and in an additional four as an acceptor. These eight interactions link each molecule to six neighboring molecules, forming a three-dimensional network. Geometric parameters of both substances are in general agreement with analogous parameters for naphthalic anhydride, monosodium 1,4,5,8-naphthalenetetracarboxylic acid cyclic 1,8-anhydride monohydrate and 1,4,5,8-naphthalenetetracarboxylic 1,8:4,5-dianhydride, as reported previously.

Anhydrides↗

PubMed1997

2-Aminonicotinic acid.

2-Aminonicotinic acid, C6H6N2O2, crystallized in the centrosymmetric space group P2(1)/c in the zwitterionic form. Intermolecular N--H...O hydrogen bonds with N...O distances of 2.652 (2) and 2.807 (2) A link molecules into two sets of zigzag chains propagating along the b axis. The two sets of chains are crosslinked by C--H...O interactions. The dihedral angle between the planes of adjacent molecules in a chain is 9.77 (7) degrees. An intramolecular N--H...O hydrogen bond is also present.

Crystallography, X-Ray↗

PubMed1997

1,4-dimethoxy-2-naphthoic acid.

The title compound, C13H12O4, crystallized in the centrosymmetric space group P2(1)/c and exhibits cyclic dimer hydrogen bonding about a center of symmetry. The carboxylic H atom is modeled as disordered over two half-occupancy sites. Overall, the hydrogen bonding is little affected by the methoxyl groups and is very similar to that in 2-naphthoic acid.

Carboxylic Acids↗

PubMed1997

2-bromo-3-methyl-2-butenoic acid (2-bromosenecioic acid).

The title compound, C5H7BrO2, crystallized in space group P1. Molecules are linked to form normal centrosymmetric hydrogen-bonded dimers with O ... O 2.625(4)A. The carboxyl H and O atoms are ordered, But the H atoms of both methyl groups are disordered. The Br and C atoms lie very nearly in a plane which makes a dihedral angle of 30.0(1) degrees with the carboxyl group plane.

Crotonates↗

PubMed1997

Hydrogen bonding and ring asymmetry in a substituted cyclopropane: (+)-trans-(1S,2S)-2-phenylcyclopropanecarboxylic acid at 208 K.

The title compound, C10H10O2, crystallized in space group P2(1) with two molecules in the asymmetric unit. In this structure, hydrogen bonding of the cyclic dimer type [with O ... O 2.623(2)-2.637(2)A] links the two molecules of the asymmetric unit. The two carboxylic H atoms are ordered, as are the O atoms. Each of the two non-equivalent molecules exhibits an asymmetric cyclopropane ring; the values found for the asymmetry parameters are delta(COOH) = -0.034(4) and -0.025(4)A, and delta(phenyl) = -0.028(4) and -0.023(4)A.

Carboxylic Acids↗

PubMed1997

Phenanthrene-9-carboxylic acid.

The title compound, C15H10O2, crystallized in the centrosymmetric space group C2/c. Hydrogen bonding is of the cyclic dimer type about a center of symmetry. The carboxyl H and O atoms are ordered. The phenanthrene core is almost planar and the dihedral angle between the core plane and the carboxyl group plane is only 1.8(1) degrees. The bay H atoms, H4 and H5, lie close to the core plane and 2.02 (2) A from each other; the refinement places them on opposite sides of the core plane, but this result has little statistical significance.

Carboxylic Acids↗

PubMed1997

Benzophenone-3,3',4,4'-tetracarboxylic acid dihydrate.

The title compound, C17H10O9,2H2O, crystallizes in the centrosymmetric space group P2(1)/a but does not exhibit strong eight-membered cyclic dimer hydrogen bonds about centers of symmetry or otherwise. A richly three-dimensional hydrogen-bonding network is observed, however, which arises from 19 hydrogen bonds per asymmetric unit; it includes a 14-membered cyclic dimer about about a center of symmetry and hydrogen-bonding rings of 18 and 30 members involving the acid molecule and a water molecule, both also about centers of symmetry. The carboxyl H and O atoms are ordered in each of the carboxyl groups. The configuration of the benzophenone core is quite similar to that in benzophenone itself and the configuration of the adjacent carboxyl groups is quite similar to that in phthalic acid and naphthalene-2,3-dicarboxylic acid.

Benzophenones↗

PubMed1997

4-(3-phenanthryl)butanoic acid.

The title compound, C18H16O2, crystallized in the centrosymmetric space group P2(1)/a. The single type of carboxylic hydrogen bond forms cyclic dimers about centers of symmetry. The carboxylic H atom is ordered as are the carboxylic O atoms. This structure comprises double layers of aromatic rings in a herring-bone array separated by double layers of hydrogen-bonded aliphatic strings and is a very close analog of the structures of 4-(2-naphthyl)butanoic acid and other terminally arylsubstituted n-aliphatic carboxylic acids.

Butyrates↗

PubMed1997

Anthracene-1-carboxylic acid.

The title compound, C15H10O2, was found to crystallize in the centrosymmetric space group P2(1)/n. The hydrogen bonding is of the cyclic dimer type about a center of symmetry. The carboxyl O atoms are ordered as is the carboxyl H atom. The anthracene core, while less nearly planar, shows good agreement with the anthracene cores of anthracene-9-carboxylic acid and anthracene-1,6-dicarboxylic acid. The carboxyl group plane makes a dihedral angle of 12.4 (2) degrees with the best-fit anthracene core plane.

Anthracenes↗

PubMed1997

5,8-Dimethoxy-1-naphthoic acid and methyl 5,8-dimethoxy-1-naphthoate.

In 5,8-dimethoxy-1-naphthoic acid, C13H12O4, hydrogen bonding is of the cyclic dimer type. The acid H atom is modelled as being distributed equally over two sites. In addition to the conventional hydrogen bonds, there are three significantly attractive C-H...O interactions. The dihedral angle between the naphthalene core plane and the carboxyl plane is 80.0 (1) degrees. In methyl 5,8-dimethoxy-1-naphthoate, C14H14O4, there are no conventional hydrogen bonds but there are three significantly attractive C-H...O interactions. With the exception of the C-O distances in the carboxyl groups, the molecular geometries of the acid and the ester are quite similar.

Carboxylic Acids↗

PubMed1997

Interwoven hydrogen-bonding networks in benzene-1,3,5-triacetic acid.

The title compound, C12H12O6, crystallized in the centrosymmetric space group P21/n. Each molecule is hydrogen bonded to four others by ten hydrogen bonds forming a three-dimensional network. Two sets of such networks, which are not linked, comprise the structure. The carboxyl O atoms are ordered, as are the carboxyl H atoms. The best-fit acetic acid group planes make dihedral angles of 84.3 (1), 89.8 (2) and 58.0 (2) degrees with the best-fit benzene core plane.

Acetates↗

PubMed1997

1,8-bis(hydroxymethyl)anthracene.

Anthracene-1,8-dimethanol, C16H14O2, crystallized in the centrosymmetric space group P21/n. The anthracene core is nearly planar and shows good agreement with the anthracene core of anthracene-1,8-dicarboxylic acid. The geometric disposition of the hydroxymethyl groups and the values of the hydrogen-bond parameters are strikingly similar to those in the naphthalene analog. As in that structure, each hydroxyl group participates both as a donor and acceptor in an infinite zigzag chain of hydrogen bonds which propagates along the [010] direction. Moreover, the disposition of the entire molecule in the cell of the present compound is also strikingly similar to that of the naphthalene analog in its cell.

Anthracenes↗

PubMed1997

Alpha and beta phases of 4-aminoquinoline-2-carboxylic acid monohydrate.

The structures of two phases of the title compound, C10H8N2O2.H2O, are reported. While the organic molecule has very nearly the same molecular geometry in the two phases, the hydrogen-bonding patterns are quite different. In each case, however, a three-dimensional network of hydrogen bonds is formed. In the alpha phase, six N-H ... O hydrogen bonds have donor-acceptor distances ranging from 2.681 (2) to 3.206 (2) A, while three O-H...O hydrogen bonds range from 2.837 (2) to 3.173 (2) A, and in the beta phase, four N-H ... O hydrogen bonds range from 2.668 (2) to 3.038 (2) A, while two O-H...O hydrogen bonds are 2.951 (3) and 2.959 (3) A in length.

Aminoquinolines↗

PubMed1997

Anthracene-9-carboxylic acid.

Anthracene-9-carboxylic acid, C15H10O2, was found to crystallize in the centrosymmetric space group P2(1)/n. The hydrogen bonding is of the cyclic-dimer type about a center of symmetry. The carboxyl O atoms are ordered, as is the carboxyl H atom. The anthracene core is almost planar and shows good agreement with the anthracene core of anthracene-1, 8-dicarboxylic acid. The carboxyl group plane makes a dihedral angle of 54.87 (6) degrees with the best-fit anthracene core plane.

Anthracenes↗

PubMed1997

N-acetyl-L-glutamic acid.

In the structure of N-acetyl-L-glutamic acid, C7H11NO5, each molecule is directly hydrogen bonded to four others by a total of six hydrogen bonds. Two carboxylic O atoms and the N atom are donors, while all three acceptors are O atoms. There is also an intramolecular hydrogen bond with the N atom as donor and a carboxylic O atom as acceptor. The carboxyl O and H atoms are ordered. The conformation of the carbon chain with respect to the C3-C4 bond is trans as in L-glutamic acid hydrochloride, rather than gauche as in the beta form of L-glutamic acid.

Glutamates↗

PubMed1996

4-(2-Naphthyl)butanoic acid.

4-(2-Naphthyl)butanoic acid, C14H14O2, crystallizes in the centrosymmetric space group P2(1)/a. The single type of hydrogen bond forms cyclic dimers about inversion centers. The carboxylic-O atoms are ordered as is the acid-H atom. The structure comprises double layers of aromatic rings in a herringbone array separated by double layers of hydrogen-bonded aliphatic strings, a pattern seen previously in related substances.

Butyrates↗

PubMed1996

gamma-Aminobutyric acid: a novel tetragonal phase.

In the tetragonal phase of gamma-aminobutyric acid, C4H9NO2, the single type of molecule adopts a partially folded zwitterionic form. Whereas in the previously characterized monoclinic phase the partially folded zwitterionic molecules exhibit a gauche conformation with respect to the C2-C3 bond, in this phase the molecules exhibit a trans conformation. The altered pattern of intramolecular N...O distances may be of significance with respect to the neurotransmission behavior of this substance. In addition to three strong hydrogen bonds involving the three H atoms bound to the N atom, as in the monoclinic phase, there is a fourth weaker one which results in a two-center bifurcated bond. There is also evidence suggestive of an intramolecular bridging hydrogen bond involving the N atom, an O atom and a methylene H atom, as previously proposed as a stabilizing factor for the gauche conformation observed in the monoclinic phase.

Crystallography, X-Ray↗

PubMed1996

sym-Hexahydropyrene.

In 1,2,3,6,7,8-hexahydropyrene, C16H16, the unsaturated rings lie essentially in a plane, the r.m.s. deviation of the atoms defining this plane form the best-fit plane being 0.006 (2) A. The saturated rings are substantially non-planar, but the character of the non-planarity of the saturated rings is quite different from that observed in octahydrochrysene. The C-C bond distances in the saturated rings are quite uniform, ranging from 1.505 (2) to 1.520 (2) A. No intermolecular distance is less than the sum of the corresponding van der Waals radii; closest approaches involve both C...H and H...H interactions.

Crystallography, X-Ray↗