Infrared Studies on Rotational Isomerism. V. 2-Nitroethanol

1971 ◽  
Vol 49 (23) ◽  
pp. 3815-3820 ◽  
Author(s):  
Paul A. Giguère ◽  
Tokiji Kawamura
Keyword(s):  
Hydrogen Bond ◽  
Crystalline Phase ◽  
Raman Effect ◽  
Rotational Isomerism ◽  
The Other ◽  
Trans Isomers ◽  
Definite Evidence ◽  
Pure Sample ◽  
Infrared Studies ◽  
Intramolecular Hydrogen

The i.r. spectra of 2-nitroethanol in the three physical states were measured between 4000 and 250 cm−1. The liquid and the crystal were also studied in Raman effect. In all three states the molecules exist as gauche and trans isomers, the former being stabilized by a weak intramolecular hydrogen bond. Definite evidence for a third isomer, previously reported in dilute CCl4 solutions, could not be ascertained from the vapor spectra as a function of temperature. On the other hand this study revealed appreciable decomposition of the vapor above 80 °C, with formation of nitroethylene and also some aldehyde. For that reason it was not possible to evaluate the enthalpy of isomerization. The difficulty of securing a pure sample of 2-nitroethanol is emphasized. Only one crystalline phase was obtained.

Infrared studies on rotational isomerism. IV. 2-Cyanoethanol

1969 ◽  
Vol 47 (24) ◽  
pp. 4685-4690 ◽  
Author(s):  
Michel Schneider ◽  
Paul A. Giguère
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
The Other ◽  
Trans Isomers ◽  
Kcal Mole ◽  
Infrared Studies ◽  
Enthalpy Difference ◽  
Temperature Deposition ◽  
Intramolecular Hydrogen

From the infrared spectra of the vapor measured between 4000 and 200 cm−1, 2-cyanoethanol was found to exist as gauche and trans isomers in roughly equal proportions around 100 °C. The gauche form is the more stable of the two, as in 2-chloro- and 2-bromo-ethanol, but the enthalpy difference is less than half as large; at most 0.7 kcal mole−1. This indicates some weak (about 1 kcal mole−1) intramolecular hydrogen bonding between the OH group and the π electrons of the C≡N bond.In the solid, two distinct crystalline phases have been observed. Crystal II, consisting of gauche molecules only, is normally obtained; for instance by annealing the vitreous solid from low temperature deposition of the vapor. Crystal I, which contains the two isomers, may be obtained irreversibly from the melt of crystal II under controlled conditions.On the other hand there was no indication in the spectra of a cyclic tautomer as suggested recently.

Infrared studies on rotational isomerism. III. 2-Chloro- and 2-bromo-ethanol

1969 ◽  
Vol 47 (6) ◽  
pp. 901-910 ◽  
Author(s):  
Paul Buckley ◽  
Paul A. Giguère ◽  
Michel Schneider
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Apparent Discrepancy ◽  
Trans Isomers ◽  
Kcal Mole ◽  
Infrared Studies ◽  
Isotopic Molecule ◽  
Intramolecular Hydrogen ◽  
Unambiguous Assignment

The relative intensities of the C—X stretching bands of the gauche and trans isomers in the vapor were measured as a function of temperature up to 165 °C for 2-chloroethanol, and up to 130 °C for 2-bromoethanol. From these the enthalpy differences between the two isomers were found to be 1.20 and 1.45 ± 0.1 kcal mole−1 respectively for the two halogenated ethanols. Similar measurements on the O—H stretching bands gave values higher than the above by 0.45 kcal mole−1 for both compounds. This apparent discrepancy is interpreted as due to a second gauche isomer, the OH group of which is not engaged in intramolecular hydrogen bonding, and which is less stable than the trans isomer.A study of the isotopic molecule ClCH2—CH2OD has led to unambiguous assignment of the OH bending and torsional frequencies. The spectra of the solid show that 2-chloroethanol can exist in two different crystalline phases: a stable one consisting of gauche molecules only, and a metastable one containing both isomers.

Infrared studies on rotational isomerism. II. 2-Fluoroethanol

1968 ◽  
Vol 46 (18) ◽  
pp. 2917-2923 ◽  
Author(s):  
Paul Buckley ◽  
Paul A. Giguère ◽  
Daijiro Yamamoto
Keyword(s):  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Condensed Phases ◽  
Frequency Range ◽  
Trans Isomers ◽  
Kcal Mole ◽  
Solid States ◽  
Infrared Studies ◽  
Free Molecules ◽  
Intramolecular Hydrogen

The infrared spectra of CH2FCH2OH were measured in the vapor, liquid, and solid states from 4000 to 200 cm−1. The Raman spectrum of the liquid was also measured over the same frequency range. From the results it appears that the free molecules exist almost entirely in the gauche configuration, which is stabilized by intramolecular hydrogen bonding. Only in the vapor at temperatures above 60 to 70 °C is there any indication of weak bands due to trans isomers. In the condensed phases the molecules are associated through strong hydrogen bonds (3–4 kcal/mole).

Intramolecular hydrogen bonds: common motifs, probabilities of formation and implications for supramolecular organization

2000 ◽  
Vol 56 (5) ◽  
pp. 849-856 ◽  
Author(s):  
Clair Bilton ◽  
Frank H. Allen ◽  
Gregory P. Shields ◽  
Judith A. K. Howard
Keyword(s):  
Hydrogen Bond ◽  
Bond Formation ◽  
Intermolecular Hydrogen Bond ◽  
The Other ◽  
Supramolecular Organization ◽  
Intermolecular Bond ◽  
Hydrogen Bond Formation ◽  
Ability To Act ◽  
Structural Database ◽  
Intramolecular Hydrogen

A systematic survey of the Cambridge Structural Database (CSD) has identified all intramolecular hydrogen-bonded ring motifs comprising less than 20 atoms with N and O donors and acceptors. The probabilities of formation Pm of the 50 most common motifs, which chiefly comprise five- and six-membered rings, have been derived by considering the number of intramolecular motifs which could possibly form. The most probable motifs (Pm > 85%) are planar conjugated six-membered rings with a propensity for resonance-assisted hydrogen bonding and these form the shortest contacts, whilst saturated six-membered rings typically have Pm < 10%. The influence of intramolecular-motif formation on intermolecular hydrogen-bond formation has been assessed for a planar conjugated model substructure, showing that a donor-H is considerably less likely to form an intermolecular bond if it forms an intramolecular one. On the other hand, the involvement of a carbonyl acceptor in an intramolecular bond does not significantly affect its ability to act as an intermolecular acceptor and thus carbonyl acceptors display a substantially higher inclination for bifurcation if one hydrogen bond is intramolecular.

A simple 1H nmr conformational study of some heterocyclic azomethines

1981 ◽  
Vol 59 (8) ◽  
pp. 1205-1207 ◽  
Author(s):  
Francesco A. Bottino ◽  
Maria L. Longo ◽  
Domenico Sciotto ◽  
Michele Torre
Keyword(s):  
Hydrogen Bond ◽  
Chemical Shift ◽  
Intramolecular Hydrogen Bond ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
Rotational Isomerism ◽  
Conformational Study ◽  
Pyrrole Derivatives ◽  
H Nmr ◽  
Intramolecular Hydrogen

The variable temperature 60 MHz 1H nmr spectra of some heterocyclic azomethines exclude the presence of rotational isomerism. Chemical shift values and stereospecific long-range couplings are used to establish that s-trans is the existing conformation. In the case of the pyrrole derivatives a chelated s-trans rotamer is indicated, depending on the presence of an intramolecular hydrogen bond.

Dipole moments of hydroxamic acids and N,O-diacylhydroxylamines

1981 ◽  
Vol 46 (3) ◽  
pp. 729-739 ◽  
Author(s):  
Aleksandr I. Artemenko ◽  
Inga V. Tikunova ◽  
Evgenii K. Anufriev ◽  
Václav Jehlička ◽  
Otto Exner
Keyword(s):  
Hydrogen Bond ◽  
Dipole Moment ◽  
Intramolecular Hydrogen Bond ◽  
Dipole Moments ◽  
Hydroxamic Acids ◽  
The Other ◽  
Total Dipole Moment ◽  
Statistical Population ◽  
Intramolecular Hydrogen ◽  
Peroxy Acids

Dipole moments of nine aromatic hydroxamic acids Ia-Ii and of nine N,O-diacylhydroxylamines IIa-IIi were measured in dioxan solution. The results for hydroxamic acids are interpreted in terms of the Zsp conformation (A) with an intramolecular hydrogen bond contributing considerably to the total dipole moment; the conformation is similar to that of peroxy acids but the hydrogen bond is weaker. A similar interpretation is possible for N-phenylbenzhydroxamic acids using the dipole moment data from the literature. New data for N,O-diacylhydroxylamine agree with the previously established nonplanar conformation (L). If axially unsymetrical aryl groups are present, they take one of the two coplanar positions independently of the other moiety; hence the effective dipole moments do not differ too much from the assumption of a statistical population of all conformations.

scholarly journals Crystal structure of (E)-9-({[4-(diethylamino)phenyl]imino}methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol

2017 ◽  
Vol 73 (1) ◽  
pp. 38-40 ◽  
Author(s):  
Md. Serajul Haque Faizi ◽  
Musheer Ahmad ◽  
Anatoly A. Kapshuk ◽  
Irina A. Golenya
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Title Compound ◽  
Condensation Reaction ◽  
The Other ◽  
Boat Conformation ◽  
Aromatic Rings ◽  
Compound C ◽  
Intramolecular Hydrogen ◽  
Ring Motif

The title compound, C23H29N3O, was synthesized from the condensation reaction of 8-hydroxyjulolidine-9-carbaldehyde andN,N-diethyl-p-phenylenediamine. The hydroxy group forms a intramolecular hydrogen bond to the imine N atom and generates anS(6) ring motif. The conformation about the C=N bond isE, and the aromatic ring of the julolidine moiety is inclined to the benzene ring by 3.74 (14)°. One of the fused non-aromatic rings of the julolidine moiety adopts an envelope conformation and the other has a screw-boat conformation. In the crystal, molecules are linked by C—H...π interactions involving the aromatic julolidine ring, forming slabs parallel to thebcplane. The tricyclic fragment of the julolidine ring and the azomethine C=N bond are disordered over two sets of sites with a refined occupancy ratio of 0.773 (3):0.227 (3).

scholarly journals Crystal structure of ethyl 2-(3-amino-5-oxo-2-tosyl-2,5-dihydro-1H-pyrazol-1-yl)acetate

2021 ◽  
Vol 77 (6) ◽  
pp. 615-617
Author(s):  
Nadia H. Metwally ◽  
Galal H. Elgemeie ◽  
Peter G. Jones
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Title Compound ◽  
Layer Structure ◽  
Membered Ring ◽  
The Other ◽  
Amino Group ◽  
Intermolecular Hydrogen Bonds ◽  
Compound C ◽  
Intramolecular Hydrogen

In the title compound, C14H17N3O5S, the five-membered ring is essentially planar. The substituents at the nitrogen atoms subtend a C—N—N—S torsion angle of −95.52 (6)°. The amino group forms an intramolecular hydrogen bond to a sulfonyl oxygen atom; two intermolecular hydrogen bonds from the amino group, to the other S=O group and to the oxo substituent, form a layer structure parallel to the ab plane. The structure determination confirms that the title compound is N- rather than O-alkylated.

scholarly journals Crystal structure of 1-amino-2-oxo-2,5,6,7,8,9-hexahydro-1H-cyclohepta[b]pyridine-3-carbonitrile

2016 ◽  
Vol 72 (9) ◽  
pp. 1239-1241 ◽  
Author(s):  
Galal H. Elgemeie ◽  
Peter G. Jones
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Title Compound ◽  
Intermolecular Hydrogen Bond ◽  
Membered Ring ◽  
The Other ◽  
Double Layers ◽  
Compound C ◽  
Intramolecular Hydrogen

In the title compound, C11H13N3O, the seven-membered ring adopts a conformation such that the three atoms not involved in the aromatic plane lie on the same side of that plane. One hydrazinic H atom forms an intramolecular hydrogen bond to the O atom; the other forms a classical intermolecular hydrogen bond N—H...O, which combines with a `weak' Har...O interaction to build up double layers of molecules parallel to thebcplane.

Conformational Terminology for Crystalline Cellulose

1972 ◽  
Vol 50 (6) ◽  
pp. 792-794 ◽  
Author(s):  
P. R. Sundararajan ◽  
R. H. Marchessault
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
The Other ◽  
Crystalline Cellulose ◽  
Chain Model ◽  
Glucose Residue ◽  
Straight Chain ◽  
A Value ◽  
Intramolecular Hydrogen ◽  
Mathematical Interpretation

Two different crystalline models of cellulose have received attention from crystallographers: the "straight chain" model of Meyer and Misch and the "bent chain" model of P. H. Hermans. We have examined these models and have given a mathematical interpretation of each in terms of the conformational angles [Formula: see text] and ψ and the glycosidic angle τ. For a given geometry of the glucose residue, the "straight chain" corresponds to a unique value of τ; for a value of τ greater than the unique value, two "bent chains" are possible, one allowing an intramolecular hydrogen bond (O-3 … O-5′) and the other not. It is suggested that the former only be referred to as the Hermans conformation.

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