NQR Study Research Articles

NQR study of hindered rotation in trans-1,2-dichloroethane under high pressure

The 35ClNQR frequency in trans-1,2-dichloroethane was studied at pressures up to 3 kbar and in the temperature range 77 to 230 K. The rotational barrier increases with increasing pressure and the pressure coefficient of the phase transition ϕT/ϕp is 10 deg/kbar. The pressure coefficient ϕp/ϕp was found to be negative at temperatures about 77 K and positive above the phase transition temperature. The activation volume was determined as ΔV ∗ = 6.0 cm 3/mole from the pressure dependence of the quadrupole spin-lattice relaxation time at 77 K. The effect of pressure on the various types of molecular motions existing in trans-1,2-dichloroethane is discussed.

35Cl NQR studies of irradiation defects in chlorates

Irradiation defects were produced in polycrystalline samples of KClO 3, NaCIO 3 and Ba(CIO 3) 2·H 2O at 300 K by γ irradiation. The frequency, the linewidth, and the intensity of the 35Cl NQR signal were investigated at 77 and 300 K as a function of the irradiation dose. In the irradiated crystals the resonance line is broadened, its intensity is reduced, and its center frequency is displaced to lower values. The perturbations of the NQR signal are less pronounced at lower temperatures. The observations can be explained satisfactorily if only elastic distortions of the chlorate lattice are taken into consideration.

75As NQR study of some hydrogen-bonded monohydrogen arsenates

The 75As Zeeman perturbed NQR spectra of (NH4)2HAsO4 as well as the 75As NQR spectra of Na2HAsO4, Na2HAsO4. 5H2O and Na2HAsO4. 7H2O were investigated. For comparison, the As NQR spectra of monoclinic TIH2AsO4 were as well measured in the ferroelectric phase.The results obtained show that the ordering of the protons in the O-H-··· hydrogen bonds in (NH4)2HAsO4 is of the antiferroelectric type so that the introduction of the NH4 group here too-similarly as in KH2PO4 type crystals-changes the structure of the ordered phase from a ferroelectric to an antiferroelectric one.A new phase transition is discovered at T = -30 °C in Na2HAsO4.

NMR and NQR study of orientational order in chiral and nonchiral biaxial smectics

NMR and NQR study of orientational order in chiral and nonchiral biaxial smectics

Double bonding in aminoheterocycles. An X-ray and NQR study

An examination of the molecular geometries of the three monoaminopyridines and several similar molecules shows that the CNH 2 bond lengths are linearly correlated both with the dihedral angle between the ring plane and the NH 2 plane and with the degree of pyramidality at the amino nitrogen. Using 14N NQR data and simple valence bond models corrected for the observed bond angles, it is shown that the π populations of the ring nitrogens and of the amino nitrogens are also linearly correlated with the CNH 2 bond lengths. Estimates of the charge transfer between the amino group and the ring are obtained as a function of bond length.

A Chlorine NQR Study of Trichloromethyl Derivatives. I

Abstract The chlorine NQR frequencies of several benzene derivatives with –CCl3 groups were measured at temperatures above 77 K. For all the compounds studied, the NQR signals of the –CCl3 groups were observed to fade out; the fade-out temperatures (Tf) were in the temperature range of 130–370 K. It was found that the most important factors involved in determining the Tf value are the intramolecular steric hindrance, hyper conjugation, and intermolecular interactions. In some compounds, an increase in the NQR frequency was found to be caused by the intramolecular steric hindrance.

ChemInform Abstract: NITROGEN‐14 NQR STUDY OF MOLECULAR REORIENTATION AND PHASE TRANSITION IN S‐TRIAZINE

Chemischer InformationsdienstVolume 8, Issue 21 Physical Organic Chemistry ChemInform Abstract: NITROGEN-14 NQR STUDY OF MOLECULAR REORIENTATION AND PHASE TRANSITION IN S-TRIAZINE A. ZUSSMAN, A. ZUSSMANSearch for more papers by this authorM. ORON, M. ORONSearch for more papers by this author A. ZUSSMAN, A. ZUSSMANSearch for more papers by this authorM. ORON, M. ORONSearch for more papers by this author First published: May 24, 1977 https://doi.org/10.1002/chin.197721046AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue21May 24, 1977 RelatedInformation

An X-ray and NQR study of 4-aminopyridine and related aromatic amines

An X-ray and NQR study of 4-aminopyridine and related aromatic amines

14N NQR study of molecular reorientation and phase transition in s-triazine

14N NQR frequencies, linewidth, and spin–lattice relaxation times were measured in s-triazine as a function of temperature between 77 and 280 °K. The second order phase transition from hexagonal to monoclinic which takes place at the critical temperature Tc=198.8 °K was studied in detail. The splittings of the NQR lines in the monoclinic phase, which are proportional to the order parameter, were found to vanish with the critical exponent β=1/2 on approaching Tc. Above 210 °K the temperature dependence of the linewidth and of the spin–lattice relaxation time indicates that the s-triazine molecule undergoes molecular reorientation around its threefold axis. The activation enthalpy for this motion was found to be ΔH=14.0 kcal/mole. These relaxation phenomena were analyzed using a density matrix formalism. Explicit expressions for the decay exponents and signal function were derived.

35Cl NQR studies on acid salts of chloroacetic acids

35Cl NQR spectroscopy has been used to provide information on the form of the potential energy curves governing the Hbonds in acid salts of chloroacetic acids.

Some remarks on the Raman spectra of selected menshutkin complexes

The Raman spectra of the solid complexes naphthalene·2SbCl 3, phenanthrene ·2SbCl 3 and diphenyl ·2SbCl 3 are presented. The differences found in their Raman spectra can be explained by comparing the results with those of NQR and X-ray structure studies given in the literature.

The Reactions of Halogenocyclophosphazenes with Nitrogenous Bases

The reactions of hexachlorocyclotriphosphazatriene, N3P3Cl6, and to a lesser extent octachlorocyclotetraphosphazatetraene, N4P4Cl8, and other halogenocyclophosphazenes with primary, secondary, and tertiary amines, are described. The effect on the substitution pattern of variables such as the structure of the amine, nature of the reaction solvent, etc., are discussed in some detail. Attention is drawn to the importance of steric effects. Isomerisation reactions are referred to. The physical properties of aminocyclophosphazenes and aminohalogenocyclophosphazenes are discussed in some detail. These include basicity studies, 1H and 31P NMR and 35Cl NQR studies, Faraday effect measurements, etc. Attempts are made to correlate the above properties with X-ray crystallographic studies and quantum chemical calculations. The distinction between ground state and perturbed state properties is emphasised. Synthesis, structure, and properties of phosphazenylcyclophosphazenes and related compounds are described and a novel conformational behaviour is discussed and rationalised.

NQR study of molecular crystals of solid solutions of chlorobenzene-bromobenzene

NQR study of molecular crystals of solid solutions of chlorobenzene-bromobenzene

ChemInform Abstract: CHLORINE‐35 NQR STUDY OF THE STRUCTURE OF CYCLIC PHOSPHADIAZINES

Chemischer InformationsdienstVolume 7, Issue 4 Organoelement Compounds ChemInform Abstract: CHLORINE-35 NQR STUDY OF THE STRUCTURE OF CYCLIC PHOSPHADIAZINES E. A. ROMANENKO, E. A. ROMANENKOSearch for more papers by this author E. A. ROMANENKO, E. A. ROMANENKOSearch for more papers by this author First published: January 27, 1976 https://doi.org/10.1002/chin.197604241AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume7, Issue4January 27, 1976 RelatedInformation

NQR study of molecular crystals of solid solution of methyl bromide-methyliodide

NQR study of molecular crystals of solid solution of methyl bromide-methyliodide

NMR and NQR study of ClF5 in its solid phases

The 19F NMR line shape and relaxation have been studied in solid ClF5 from the melting point down to liquid nitrogen temperature. The corresponding results, completed by relaxation data concerning 35Cl NMR and NQR, have yielded information about phase transitions and molecular motions. In particular, a new solid–solid transition was found at 117 °K. 35Cl wide-line and 19F high resolution NMR spectra were obtained in the high temperature phase SI, which is shown to be a plastic phase where molecular reorientations (τϑ=8×10−12 sec) are nearly as fast as in the liquid. In addition to the reorientation there is a much slower translational diffusion, the main characteristics of which are derived from 19F T1 and T1ρ measurements using Torrey’s theory. In the low temperature phases SII and SIII, the 19F T1 is due to rotations of the molecules by jumps around their C4 axis (τr=10−8 sec at 110 °K). In solid II the NQR relaxation time T1Q is due to another mechanism which is assumed to be jumps of the C4 axis between two equilibrium positions. The dipolar energy relaxation time TD was also measured; between 123 and 153 °K, the Cl–F dipolar coupling modulated by the chlorine relaxation appears to be the main TD mechanism, for which a theory is described.

Metal-carbon interactions in organogallium and organoindium compounds. A 13 C NMR and 69,71Ga and 115In NQR study

The interaction between variously substituted phenyl groups and gallium and indium has been examined by 69,71Ga and 115In NQR spectroscopy and 13C NMR spectroscopy. Four separate correlations involving either the 13C shieldings alone or the NMR and NQR data combined indicate the dominance of inductive transmission of substituent character to the metal via the σ-bond framework. This finding is to be contrasted with competitive inductive and resonance transmission mechanisms found to be present in the formally isoelectronic triphenylcarbonium ion, (C 6H 5) 3 C +. Reasons for the anomalous behavior of the methoxy substituent in both the NQR and the NMR spectra are discussed. The effects on the metal of a common substituent in the ortho, meta and para positions are in line with the trends found in the analogous arsenic and antimony compounds. The NQR spectrum of 35Cl as a function of its position on the ring is also in accordance with previous observations. The lack of strong resonance interaction between the phenyl ring and the group IIIB metal is in accord with the notion that p p π-interaction between second row elements and elements in lower rows is small. By the same token, the importance of p π-bonding must also be small in these compounds.

NQR study of hydrogen bonded trichloroacetic acid complexes

1. The35Cl NQR method was used to study 10 complexes of trichloroacetic acid with lactams, ketones, amides, and amines. 2. All of the studied compounds are complexes with a hydrogen bond. 3. The relation between the basicity of the donor and the average frequency shift is linear. 4. Employing the method of complete neglect of differential overlapping (second variation), it was shown by calculation that the relation between the negative charges on the chlorine atoms and the negative charge on the oxygen atom of the hydroxyl of the acceptor molecule is nonlinear.

The α effect in chlorinated organometallic compounds : I. 35Cl NQR studies of perchlorinated organomercurials

The 35Cl NQR spectra of mercurial- and organic-substituted pentachlorocyclopentadienes are analyzed to give equations relating the frequencies of the allylic chlorines, Cl(5), and the two types of vinylic chlorine, Cl(1,4) and Cl(2,3), as functions of the Taft constant σ for R in C 5Cl 5R. Cl(5) in mercuri derivatives shows higher frequencies than Cl(5) in organic derivatives, but the magnitude of this frequency difference, a type of “α effect”, decreases with increasing σ. This is best explained, not by previously-proposed theories of the α effect, but by hyperconjugation of the HgC σ bond with diene π orbitals. The unusual NQR properties of trichloromethylmercurials, previously rationalized as due to an α effect, are shown to be better explained by intermolecular coordination of Cl to Hg.

NQR study of the trichloride ion. Evidence for three-center four-electron bonding

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNQR study of the trichloride ion. Evidence for three-center four-electron bondingE. F. Riedel and R. D. WillettCite this: J. Am. Chem. Soc. 1975, 97, 4, 701–704Publication Date (Print):February 1, 1975Publication History Published online1 May 2002Published inissue 1 February 1975https://doi.org/10.1021/ja00837a003RIGHTS & PERMISSIONSArticle Views127Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (494 KB) Get e-Alerts Get e-Alerts