Molecular Association of Hydrogen Bonding Solutes, o-, m-, and p-Cresol, in Carbon Tetrachloride

1974 ◽  
Vol 52 (4) ◽  
pp. 653-660 ◽  
Author(s):  
Earl M. Woolley ◽  
Dennis S. Rushforth
Keyword(s):  
Hydrogen Bonding ◽  
Carbon Tetrachloride ◽  
Least Squares ◽  
Molecular Association ◽  
Intermolecular Hydrogen Bonding ◽  
Heats Of Dilution ◽  
Self Association

The intermolecular hydrogen-bonding self-association of the three cresols in CCl4 solutions at 25 °C has been investigated by calorimetric means. Calorimetrically determined heats of dilution of each of the cresols in anhydrous CCl4 are interpreted in terms of two different models: (i) dimerization and trimerization self-association reactions, and (ii) dimerization followed by stepwise polymerization self-association reactions. Values of K, ΔH0, and ΔS0 for these reactions are calculated using least-squares and other methods. Results show that o-cresol is clearly less associated in anhydrous CCl4 solution at 25 °C than either m- or p-cresol. Values of K2 and K3 (both based on molar concentrations of solutes) and ΔH20and ΔH30 (kcal) for the reactions [Formula: see text] respectively, are o-cresol: 0.7, 1.3,−3.4,−12.5; m-cresol: 0.8, 5.0,−5.0,−13.6; p-cresol: 0.35, 6.5,−5.5,−13.4. Values of K2 and Ks (both based on molar concentrations of solutes) and ΔH20 and ΔHs0 (kcal) for the reactions [Formula: see text] (all n > 2 with same Ks and ΔHS0), respectively, are o-cresol: 0.7, 1.6, −4.2, −4.5; m-cresol: 1.2, 4.0, −5.0, −4.3; p-cresol: 1.0, 7.0, −3.3, −3.5.

7α-Acetoxydihydronomilin: isolation, spectra, and crystal structure

1978 ◽  
Vol 56 (7) ◽  
pp. 1020-1025 ◽  
Author(s):  
Farid R. Ahmed ◽  
Angs Ng ◽  
Alex G. Fallis
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Least Squares ◽  
Furan Ring ◽  
Lactone Ring ◽  
Direct Method ◽  
Membered Ring ◽  
Intermolecular Hydrogen Bonding ◽  
X Ray ◽  
Twist Boat

Methanol extraction of the ground seeds of Uncaria Gambier Roxb. followed by chromatography afforded a crystalline C30H38O10 terpene. This has been shown by X-ray analysis to be 7α-acetoxydihydronomilin. The crystals are orthorhombic, P212121, a = 13.158(2), b = 17.092(2), c = 12.689(2) Å, Z = 4, dx = 1.300, do = 1.300 g cm−3. The structure has been determined by the direct method and Fourier syntheses, and refined by block-diagonal least-squares to R = 0.042 for 2621 observed reflexions. The molecule contains a seven-membered lactone ring A, three six-membered rings B, C, D, a three-membered ring E, a furan ring F, and two acetate groups. A and B are chair, C is twist-boat, D is 1,3-diplanar, while E and F are planar. The A/B, A/C, C/D junctions are trans, D/E is cis, and F is linked to D by an equatorial C—C bond. The two acetate groups are in axial positions on A and B and are cis to each other. The O atom forming the apex of the three-membered ring is wedged between two H atoms and their parent C atoms at short intramolecular distances O … H = 2.28(2) and 2.28(3), and O … C = 2.623(3) and 2.668(4) Å. No intermolecular hydrogen bonding is indicated.

NMR Study of Hydrogen Bonding Association of some Sterically Hindered Alcohols in Carbon Tetrachloride, Chloroform and Cyclohexane

2002 ◽  
Vol 216 (7) ◽  
Author(s):  
W.-C. Luo ◽  
J.-L. Lay ◽  
Jenn-Shing Chen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bonding ◽  
Carbon Tetrachloride ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
The Self ◽  
Resonance Spectroscopy ◽  
Nmr Study ◽  
Self Association

The self-association (dimerization) due to hydrogen bonding for some alcohols with bulky side chains was investigated by nuclear magnetic resonance spectroscopy. The systems studied include 2,4-dimethyl-3-pentanol or 3-methyl-3-pentanol in [

Crystal Structure and Chirality of the Ansamycin Antibiotic Actamycin

1991 ◽  
Vol 44 (5) ◽  
pp. 655 ◽  
Author(s):  
TW Hambley ◽  
V Parthasarathi ◽  
RW Rickards ◽  
GB Robertson
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Double Bond ◽  
Least Squares ◽  
Absolute Configuration ◽  
Torsion Angle ◽  
Title Compound ◽  
Intermolecular Hydrogen Bonding ◽  
Triclinic Space Group ◽  
Relative Stereochemistry

The structure of the title compound has been determined from diffractometer data recorded, initially, at 294 K and, subsequently, at 168 K. Crystals are triclinic, space group P1 with (168 K values in square brackets) a 16.080(2) [15.934(2)], b 15.958(2) [15.880(2)], c 8.443(2)Ǻ [8.233(1)Ǻ], α 85.55(1) [86.04(1)],β 82.65(1) [82.56(1)],γ 85.00(1)° [84.73(1)°], and contain two actamycin and two solvent ( tetrahydrofuran ) molecules in the asymmetric scattering unit. The structure was solved with DIRDIF and refined by block-diagonal least-squares analysis (of 168 K data) to R 0.049 ( wR 0.069) for 5640 reflections and 940 refined parameters. Molecules of actamycin (30-dechloro-2-demethyl-30-hydroxynaphthomycin A) exhibit the same relative stereochemistry (8S*,9S*,15S*,18S*,19S*,20S*) and double-bond configuration (2Z,4Z,6E,12E,16E,21E) as reported for crystalline 25-O-methylnaphthomycin A iminomethyl ether but are quite differently conformed. The two crystallographically inequivalent actamycin molecules in the present structure also exhibit substantial conformational (torsion angle) differences due, apparently, to the effects of intermolecular hydrogen bonding. Consideration of chiroptical data defines the absolute configuration of actamycin as 8S,9S,15S,18S,19S,20S and the helicity as P, as in naphthomycin A.

The interaction of dimethyl sulfoxide with N-benzoyl amino acids

1981 ◽  
Vol 34 (9) ◽  
pp. 1869 ◽  
Author(s):  
CW Fong ◽  
HG Grant
Keyword(s):  
Amino Acids ◽  
Hydrogen Bonding ◽  
Dimethyl Sulfoxide ◽  
Benzene Ring ◽  
Chemical Shifts ◽  
Side Chain ◽  
Torsional Angle ◽  
Intermolecular Hydrogen Bonding ◽  
Atom Increase ◽  
Self Association

The interaction of dimethyl sulfoxide with N-benzoyl amino acids in deuterochloroform has been investigated by 13C n.m.r. spectroscopy. Examination of the chemical shifts of the benzene ring reveals that intermolecular hydrogen bonding between dimethyl sulfoxide and the amido-hydrogen atom increase the effective steric size of the amino hydrogen, resulting in an increase in the torsional angle between the benzene ring and the C(O)NHCH(R)COOH side chain. Self-association of N- benzoyl amino acids in deuterochloroform occurs largely through two COOH...O=C hydrogen bonds and does not involve intermolecular hydrogen bonding to the N-H proton.

NMR study of hydrogen bonding in methanol – carbon tetrachloride solutions

2006 ◽  
Vol 84 (6) ◽  
pp. 886-892 ◽  
Author(s):  
J Q Deng ◽  
R H Lipson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bonding ◽  
Carbon Tetrachloride ◽  
Magnetic Resonance ◽  
Nonlinear Least Squares ◽  
Nmr Study ◽  
Liquid Solutions ◽  
Self Association ◽  
Hydroxyl Protons ◽  
Nuclear Magnetic

The nuclear magnetic resonance (NMR) frequencies of the hydroxyl protons of methanol clusters in carbon tetrachloride were measured as a function of concentration between 245.4 and 320.2 K. The size of the methanol cluster (n) and the enthalpy and entropy of methanol self-association were obtained from nonlinear least-squares fittings to a model that assumed that only one dominant cluster was in equilibrium with the monomer at each temperature. The chemical shift measurements at 273 and 299.1 K fit best to theoretical curves calculated for a monomer–tetramer equilibrium. However, at higher and lower temperatures, the analyses indicate that the most dominant clusters are smaller and larger, respectively.Key words: alcohol liquid solutions, structure, hydrogen bonding, thermodynamics of self-association, nuclear magnetic resonance.

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