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Showing papers on "Intramolecular force published in 1973"



Journal ArticleDOI
TL;DR: In this article, the authors consider the problem of interpreting quenching kinetics in small molecules (e.g., CN, CH 2, NO 2 and SO 2 ) and argue the importance of analyzing these data in terms of collisional transitions between perturbed (mixed electronic parentage) as opposed to pure (non-spectroscopic) vibronic states.

132 citations



Journal ArticleDOI
TL;DR: Weak, broad, Raman bands have been observed from water and heavy water at shifts above and below those corresponding to the intramolecular bending and stretching vibrations of D2O and H2O molecules that are either partially, or fully hydrogen bonded.
Abstract: Weak, broad, Raman bands have been observed from water and heavy water at shifts above and below those corresponding to the intramolecular bending and stretching vibrations. Bands near Δv = 1190 cm−1 for D2O and Δv = 1625 cm−1 for H2O, in addition to relatively sharp bands at 1210 cm−1 for D2O and 1640 cm−1 for H2O are thought to arise from intramolecular bending vibrations of D2O and H2O molecules that are either partially, or fully hydrogen bonded. Other weak bands can be explained as combinations of known intra‐ and intermolecular vibrations, in particular, librations.

97 citations


Journal ArticleDOI
TL;DR: In this article, LCAO-SCF calculations with an extended basis set are used to predict the geometry and various vibrational properties of the hydrogen bonded complex between HCN and HF.

83 citations





Journal ArticleDOI
TL;DR: Evidence is presented that the interaction of the uncomplexed antibiotic with polar solvent molecules leads to conformational rearrangements which can be characterized by a step-wise opening of a closed structure stabilized by intramolecular hydrogen bond formation.
Abstract: The 13C nuclear magnetic resonance spectra of the membrane-active antibiotic valinomycin and its alkali-ion complexes are interpreted. From the 13C chemical shifts and infrared absorptions of the highly stable K+, Rb+ and Cs+ complexes in methanol it is concluded that the ligand conformations of these complexes must be similar. The essential features are the coordination of all ester carbonyl groups with the cation in addition to the formation of intramolecular hydrogen bonds between the amide groups. In contrast to these results the weaker Na+ complex of the antibiotic exhibits different spectral properties which are more similar to those of the uncomplexed antibiotic in polar solvents thus indicating the existence of a considerably different ligand conformation in this complex. The structure of the Na+ complex can be characterized by a reduced number of coordinated ester carbonyl groups and intramolecular hydrogen bonds between the amide groups as compared to the complexes with larger cations. The conformational rearrangements occurring during the complexation of cations are compared to those observed for the uncomplexed valinomycin in solvent systems of different polarities. Evidence is presented that the interaction of the uncomplexed antibiotic with polar solvent molecules leads to conformational rearrangements which can be characterized by a step-wise opening of a closed structure stabilized by intramolecular hydrogen bond formation.

69 citations


Journal ArticleDOI
TL;DR: In this paper, an iterative method is used to obtain, within the framework of the transition state theory, sets of force constants from experimental kinetic isotope effect data for the reaction system H2 + Cl → [H-H-Cl] → H+HCl.
Abstract: An iterative method is used to obtain, within the framework of the transition state theory, sets of force constants from experimental kinetic‐isotope‐effect data for the reaction system H2 + Cl → [H–H–Cl]‡ → H+HCl. Two sets of force constants, describing quite different transition‐state structures, are found to be equally compatible with all available rate data for the reactions of chlorine atoms with H2, HD, HT, DT, D2, and T2. These force fields are compared with force fields derived by semiempirical methods. Measurements of the intramolecular kinetic isotope effect, i.e., the relative rate of production of HCl/DCl in the reaction HD+Cl, are shown to be especially suited for selecting compatible transition‐state models.

67 citations


Journal ArticleDOI
TL;DR: Iodine-cyclohexa-amylose tetrahydrate (C6H10O5)6 ·I2·d4H2O] was solved by heavy-atom techniques and refined by least-squares methods to a conventional discrepancy index R  0.148 for the 2872 observed data as mentioned in this paper.







Journal ArticleDOI
TL;DR: In this article, the first example of intramolecular oxidative addition of an 'ortho' B-H bond of a coordinated phosphine to a transition metal was presented.
Abstract: : When (Ir(C8H14)2Cl)2 is allowed to react at room temperature with 6 moles of 1-(Me2P)-1,2-C2B10H11 in cyclohexane and then heated at reflux for two hours, IrHCl(C2B10H10P(CH3)2)(CH3)2)(C2B10H11P(CH3)2)2 is formed in nearly quantitative yield. This is the first example of intramolecular oxidative addition of an 'ortho' B-H bond of a coordinated phosphine to a transition metal. (Author)




Journal ArticleDOI
TL;DR: In this paper, a study of the i.r. spectra of dilute solutions of α, ω-dials in carbon tetrachloride has given information on the thermodynamics of formation of the intramolecular H bond by cyclisation.



Journal ArticleDOI
02 Oct 1973
TL;DR: In this article, the sum-and-difference bands of the OH stretch with other fundamentals, 14 summation modes were observed extending in frequency to over 5000 cm -1 and involving most of the fundamentals below 1500 cm −1.
Abstract: Infrared spectra are reported of methanol, ethanol, propan-2-ol, 2-methylpropan-2-ol, 2, 2, 2-trifluoroethanol, 2, 2, 3, 3-tetrafluoropropan-1-ol and 1, 1, 1, 3, 3, 3-hexafluoropropan-2-ol in the vapour phase in a 1 m path-length cell at pressures up to the s. v. p. of the alcohol. Also reported are 40 m path-length vapour and argon matrix spectra of trifluoroethanol. Dimer absorptions are identified for all the alkanols and for trifluoroethanol, and some estimates of ∆ H provided. Trifluoroethanol exhibits a striking series of sum-and-difference bands of the OH stretch with other fundamentals, 14 summation modes being observed extending in frequency to over 5000 cm -1 and involving most of the fundamentals below 1500 cm -1 . Other fluoroalcohols with fluorines substituted on β carbon atoms exhibit similar sum-and-difference modes. The alkanols exhibit only one such pair of bands due to the OH stretch plus or minus the OH torsion, and this provides a convenient method of measuring the torsional frequencies. The different behaviour of the fluoroalcohols is attributed to intramolecular hydrogen bonding.



Journal ArticleDOI
TL;DR: The photorearrangement of 3-hydroxyflavones to 3-aryl-3-hydroxyl H-bonded to the 4-carbonyl causes photoresistance in flavonoids.

Journal ArticleDOI
TL;DR: In this paper, a molecular orbital calculation in the CNDO/2 approximation has been used to discuss the tautomeric stability of pyridine and pyrimidine substituted by amino, mercapto and hydroxy groups, respectively.