Complexes of N-methylxanthines with carboxylic acids

1968 ◽  
Vol 46 (19) ◽  
pp. 3055-3059 ◽  
Author(s):  
Denys Cook ◽  
Zephyr R. Regnier
Keyword(s):  
Hydrogen Bond ◽  
Acetic Acid ◽  
Salicylic Acid ◽  
Infrared Spectroscopy ◽  
Nitrogen Atom ◽  
Imidazole Ring ◽  
Intermolecular Forces ◽  
Strong Hydrogen Bond ◽  
Lipid Solubility ◽  
Aromatic Acids

Complexes of caffeine and theobromine, with acetic and salicylic acid, have been studied by means of infrared spectroscopy. In the complexes with aromatic acids a fairly strong hydrogen bond exists between the carboxylic OH group and the nitrogen atom N-9 in the imidazole ring. The acetic acid complexes involve no strong intermolecular forces and are probably weak lattice complexes.The complexes with aromatic acids are discussed in relation to theories of lipid solubility and gastrointestinal absorption.

Three metal(II) complexes constructed using the 2-(1H-benzo[d]imidazol-2-yl)quinoline ligand

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Feriel Aouatef Sahki ◽  
Mehdi Bouchouit ◽  
Sofiane Bouacida ◽  
Lyamine Messaadia ◽  
Elsa Caytan ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Acetic Acid ◽  
Coordination Compounds ◽  
Strong Hydrogen Bond ◽  
Acetate Anion ◽  
Coordination Geometry ◽  
Triclinic Space Group ◽  
Trigonal Bipyramidal ◽  
Tetrahedral Environment ◽  
Acetate Molecule

Abstract 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) as ligand and three coordination compounds of formula {Zn(BQ)Cl2} (1), {Pb(BQ)Cl2} n (2) and {[Cu(BQ)2(OC(O)CH3)]OC(O)CH3 · CH3COOH} (3) have been synthesized and fully characterized. The complexes crystallize in triclinic space group P 1 ‾ $P‾{1}$ . In complexes 1 and 2, the coordination geometry is a distorted tetrahedral environment around the zinc center and a distorted sixfold coordination geometry around the lead center, respectively. In complex 3 the central Cu(II) center is in a trigonal bipyramidal coordination geometry. The Cu(II) ion is surrounded by two bidentate 2-(2′-quinolyl)benzimidazole (BQ) ligands and one coordinated acetate molecule. One further acetate anion associated by a strong hydrogen bond with a molecule of acetic acid balances the charge of the compound.

The infrared spectra of theobromine salts

1967 ◽  
Vol 45 (23) ◽  
pp. 2899-2902 ◽  
Author(s):  
Denys Cook ◽  
Zephyr R. Regnier
Keyword(s):  
Hydrogen Bond ◽  
Nitrogen Atom ◽  
Infrared Spectra ◽  
Imidazole Ring ◽  
Free Base ◽  
Absorption Bands ◽  
Out Of Plane ◽  
Stretching Vibrations ◽  
Deformation Modes ◽  
Infrared Absorption Bands

From the infrared spectra of theobromine salts it is concluded that the salts are probably arranged in hydrogen-bonded centrosymmetric pairs involving [Formula: see text] interactions. [Formula: see text] anion− hydrogen bonds are formed by protonation of the free nitrogen atom (N9) in the imidazole ring. Infrared absorption bands arising from the former hydrogen bond constantly appear near 3 000 cm−1, whereas those from the latter shift from 2 580 to 3 300 cm−1, depending on the anion. In-plane NH and N+H deformation modes give bands near 1 485 and 1 160 cm−1, respectively. Out-of-plane NH modes have been located, but precise assignments are not possible.The assignments for some other bands which show deuteration shifts are detailed, and the carbonyl stretching vibrations which increase in frequency on protonation of the free base are identified.

Crystal structure of vardenafil hydrochloride trihydrate, C23H33N6O4SCl (H2O)3

2018 ◽  
Vol 33 (4) ◽  
pp. 319-326
Author(s):  
Austin M. Wheatley ◽  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Nitrogen Atom ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Strong Hydrogen Bond ◽  
Water Molecules ◽  
Ring Nitrogen ◽  
Intramolecular Hydrogen

The crystal structure of vardenafil hydrochloride trihydrate has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Vardenafil hydrochloride trihydrate crystallizes in space group C2/c (#15) with a = 34.78347(16), b = 11.56752(4), c = 14.69308(5) Å, β = 93.3410(4), V = 5901.839(30) Å3, and Z = 8. The fused ring system and the phenyl ring are nearly co-planar; the interplanar angle between them is 6.0°. Two intramolecular hydrogen bonds help determine this conformation. These planes stack along the c-axis. The side chains of these ring systems have a large Uiso and are neighbors in the stacks. Along the a-axis, these stacks are separated by hydrophilic layers of chloride, water molecules, and the positively charged nitrogen atoms of the vardenafil cation. Hydrogen bonds are prominent in the crystal structure. The protonated nitrogen atom forms a strong hydrogen bond to the chloride anion. The water molecules form a hexagon, making hydrogen bonds with themselves, as well as the C1 and a ring nitrogen atom. These discrete hydrogen bonds form a cluster, and there is no extended hydrogen bond network. There are many C–H⋯Cl, C–H⋯O, and C–H⋯N hydrogen bonds, which (although individually weak) contribute significantly to the crystal energy. The powder pattern is included in the Powder Diffraction File™ as entry 00-066-1620.

A mechanism for efficient proton-transfer catalysis. Intramolecular general acid catalysis of the hydrolysis of 1-arylethyl ethers of salicylic acid

1999 ◽  
Vol 77 (5-6) ◽  
pp. 792-801 ◽  
Author(s):  
Sarah E Barber ◽  
Kathryn ES Dean ◽  
Anthony J Kirby
Keyword(s):  
Hydrogen Bond ◽  
Salicylic Acid ◽  
Proton Transfer ◽  
Acid Catalysis ◽  
Enzyme Mechanism ◽  
Base Catalysis ◽  
Strong Hydrogen Bond ◽  
Cooh Group ◽  
Tert Butyl ◽  
General Acid

The tert-butyl (1) and 1-arylethyl ethers (2) of salicylic acid are hydrolyzed with efficient general acid catalysis by the ortho-COOH group. The half-life of the neutral COOH form of the tert-butyl ether is 15.2 min at 39°, and the estimated acceleration by the COOH group of 2, X = Me, Y = H is 2.13 × 105. The salicylate leaving group from 2 (X = Me, Y = H) has an effective pKa of 2.9, compared with a nominal pKa of 8.52. Analysis of substituent effects in both arylethyl and leaving groups provides the most detailed available mechanistic insight into a reaction involving efficient intramolecular proton-transfer catalysis. The mechanism is very different from classical general acid-base catalysis. Proton transfer takes place very rapidly within a developing strong hydrogen bond, and though an integral part of the C—O cleavage process is practically uncoupled from it. "Strategic delay" of the proton-transfer step, relative to C—O cleavage, makes a significant contribution to efficiency by setting up the conditions for the formation of the strong, intramolecular hydrogen bond.Key words: catalysis, carboxyl, hydrogen bond, proton transfer, enzyme mechanism.

scholarly journals Probing a strong hydrogen bond with infrared spectroscopy: Vibrational predissociation of BrHBr−⋅Ar

2003 ◽  
Vol 118 (12) ◽  
pp. 5275-5278 ◽  
Author(s):  
Nicholas L. Pivonka ◽  
Cristina Kaposta ◽  
Mathias Brümmer ◽  
Gert von Helden ◽  
Gerard Meijer ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Infrared Spectroscopy ◽  
Strong Hydrogen Bond ◽  
Vibrational Predissociation

Molecular Cocrystals of Carboxylic Acids. XXVIII. Nitro-Substituted Carboxylic Acids with Lewis Bases: the Crystal Structures of the Adducts of 3,5-Dinitrobenzoic Acid with N-Methylaniline (1 : 1), (4-Nitrophenyl)acetic Acid with Cyclohexane-1,4-diamine (2 : 1), and 5-Nitrosalicylic Acid with 2-Imidazolidone (2 : 1)

1998 ◽  
Vol 51 (2) ◽  
pp. 159 ◽  
Author(s):  
Graham Smith ◽  
Daniel E. Lynch ◽  
Raymond C. Bott
Keyword(s):  
Acetic Acid ◽  
Infrared Spectroscopy ◽  
Carboxylic Acid ◽  
Proton Transfer ◽  
Crystal Structures ◽  
Carboxylic Acids ◽  
Aromatic Acids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lewis Bases

A number of molecular adducts of nitro-substituted aromatic acids with Lewis bases have been prepared and characterized by infrared spectroscopy and in three cases by X-ray diffraction methods. These three compounds are the adducts of: 3,5-dinitrobenzoic acid (dnba) with N-methylaniline (nma), [(dnba)-(nma)+] (1); (4-nitrophenyl)acetic acid (4-npa) with cyclohexane-1,4-diamine (dach), [(4-npa)22-(dach)2+] (4); 5-nitrosalicylic acid (5-nsa) with 2-imidazolidone (idaz), [(5-nsa)2(idaz)] (5). Other compounds are the adducts of 3,5-dinitrobenzoic acid with 2,6-dimethylpyridine (dmp), [(dnba)(dnba)-(dmp)+] (2), and with 1-methylpyrrole-2-carboxylic acid (cmp), [(dnba)-(cmp)+] (3). Compounds (1) and (3) have 1 : 1 stoichiometry, while (2), (4) and (5) are 2 : 1 adducts. Proton transfer occurs in most examples [complex (5) is the exception].

Hydrogen bonds in N-(3-chloro-2-benzo[b]thienocarbonyl)- and N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thioureas

1987 ◽  
Vol 52 (11) ◽  
pp. 2673-2679 ◽  
Author(s):  
Oľga Hritzová ◽  
Peter Kutschy ◽  
Ján Imrich ◽  
Thomas Schöffmann
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Strong Hydrogen Bond ◽  
Cyclic Form ◽  
Thiourea Derivatives

N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocyclizations with lower yields than those obtained from analogous N',N'-disubstituted derivatives. This decreased reactivity is caused by the existence of a six-membered cyclic form with the very strong hydrogen bond NH···O=C. The possibility of formation of various conformers has been found with N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives as a consequence of the rotation around the C(2)-C(O) connecting line.

Crystal structure of tamsulosin hydrochloride, C20H29N2O5SCl

2021 ◽  
pp. 1-7
Author(s):  
Nilan V. Patel ◽  
Joseph T. Golab ◽  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Powder Diffraction ◽  
Density Functional ◽  
Carbon Chain ◽  
Strong Hydrogen Bond ◽  
Powder Diffraction File ◽  
Ether Oxygen ◽  
Sulfonamide Group

The crystal structure of tamsulosin hydrochloride has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Tamsulosin hydrochloride crystallizes in space group P21 (#4) with a = 7.62988(2), b = 9.27652(2), c = 31.84996(12) Å, β = 93.2221(2)°, V = 2250.734(7) Å3, and Z = 4. In the crystal structure, two arene rings are connected by a carbon chain oriented roughly parallel to the c-axis. The crystal structure is characterized by two slabs of tamsulosin hydrochloride molecules perpendicular to the c-axis. As expected, each of the hydrogens on the protonated nitrogen atoms makes a strong hydrogen bond to one of the chloride anions. The result is to link the cations and anions into columns along the b-axis. One hydrogen atom of each sulfonamide group also makes a hydrogen bond to a chloride anion. The other hydrogen atom of each sulfonamide group forms bifurcated hydrogen bonds to two ether oxygen atoms. The powder pattern is included in the Powder Diffraction File™ as entry 00-065-1415.

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