Vibrational spectra of potassium hydrogen 2,3-furandicarboxylate and intramolecular H-bond

Infrared and Raman spectra of KHFur 2,3 and KDFur 2,3 are presented. An assignment of the bands is given which is in good agreement with previous results concerning acid salts possessing intramolecular hydrogen bonds. The ν_as OHO participation was observed at 670 and 520 cm⁻¹, absorption bands of medium intensity. The absence of a more pronounced broadening might be explained by assuming an anharmonic coupling between the ν_as OHO and the ν_s OHO modes, resulting in a combination band at 1000 cm⁻¹.     

Vibrational overtone spectra of chloroanilines--evidence for intramolecular hydrogen bonding in o-chloroaniline

The near infrared vibrational overtone absorption spectra of liquid phase aniline and chloroanilines are reported. The analysis of the observed CH and NH local mode mechanical frequency values shows that intramolecular hydrogen bonding occurs between NH2 group and chlorine atom in o-chloroaniline. This observation supports the conclusion drawn from microwave spectroscopic studies reported earlier.     

Vibrational overtone spectra of o-fluorophenol and the "anomalous" order of intramolecular hydrogen bonding strengths

The near infrared vibrational overtone absorption spectrum of liquid phase o-fluorophenol is examined in the region deltav=2, 3 and 4. The OH frequencies are compared with that of o-chlorophenol and phenol. Considering the relative electronegativities of all halogens, one might expect the order of intramolecular hydrogen bond strength for o-fluorophenol to be the greatest among all halogenophenols. It is evident that o-fluorophenol forms a weaker intramolecular hydrogen bond (an anomalous trend) contrary to that expected from relative electronegativities of halogens. The local mode mechanical frequency values and anharmonicity values obtained from fitting the overtones are analysed. Our observation is in agreement with the previous experimental as well as the recent theoretical vibrational analysis of halogenophenols using density functional theory (B3LYP). The overtone spectra of o-fluorophenol in carbon tetrachloride in different concentrations are also examined. It is noted that the OH-red shift which arises due to the intermolecular bond formation between the cis and trans conformers of o-fluorophenol (dimerization) increases with concentration.     

Vibrational spectra and quantum chemical calculations of 3,4-diaminobenzoic acid.

The Fourier Transform Raman and Fourier Transform infrared spectra of 3,4-diaminobenzoic acid (3,4-DABA) were recorded in the solid phase. Geometry optimizations were done without any constraint and harmonic-vibrational wave numbers and several thermodynamic parameters were calculated for the minimum energy conformer at ab initio and DFT levels invoking 6-311++G(d,p) basis set. The results were compared with the experimental values with the help of specific scaling procedures, the observed vibrational wavenumbers in FT-IR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range, the error obtained was in general very low. The appropriate theoretical spectrograms for the IR and Raman spectra of the title molecule were also constructed.     

Vibrational relaxation and coupling of two OH-stretch oscillators with an intramolecular hydrogen bond

We studied the vibrational dynamics of the OH-stretch oscillators of an alcohol with two vicinal OH groups using femtosecond midinfrared pump-probe spectroscopy. The absorption spectrum of pinacol (2,3-dimethyl-2,3-butanediol) in CDCl3 shows two OH-stretch peaks belonging to hydrogen bonded and free OH groups. The anharmonicities of the hydrogen-bonded and free OH-stretch vibrations are 180 and 160 cm(-1), respectively. The lifetime T1 of the OH-stretch vibration is found to be 3.5 +/- 0.4 ps for the hydrogen bonded and 7.4 +/- 0.5 ps for the free OH group. We observed sidebands in the transient spectra after excitation of the bonded OH group, which we attribute to a progression in a low-frequency hydrogen-bond mode. The sideband is redshifted 60 cm(-1) with respect to the 0 --> 1 transition. Due to the coupling between the two OH groups and the presence of the sidebands, simultaneous excitation of both OH-stretch vibrations leads to oscillations on the pump-probe signal with frequencies of 40 and 60 cm(-1).     

Vibrational spectra and intramolecular dynamics of six-membered azacycles in the ground and excited states

The geometrical structure, force fields, and parameters of vibrational-rotational interaction of six-membered azacyclic compounds in the ground and excited states are estimated using the structural dynamic model of a polyatomic molecule. Translated fromZhurnal Struktumoi Khimii, Vol. 38, No. 2, pp. 345–349, March–April, 1997.     

Vibrational spectra and structure of complexes containing the hydrogen dinitrate ion

Infrared and Raman spectra of solid hydrogen dinitrate complexes with K⁺, Rb⁺, Cs⁺, (CH₃)₄N⁺, trans-(Co py₄Cl₂)⁺, Ph₄As⁺, Ph₄P⁺, (C₂H₅)₄N⁺ and (C₄H₉)N⁺ have been recorded and analyzed. The assignments were assisted by deuteration and, in the case of the Cs⁺, (CH₃)₄N⁺, and Ph₄As⁺ complexes, by ¹⁵N substitution. Infrared spectra at 50 kbar of the (CH₃)₄N⁺ complex were also recorded. The salient features of the i.r. spectra are the lack of fundamental OH bands above 1800 cm⁻¹ and the appearance of a strong absorption centered at about 600 cm⁻¹, both indicating very strong hydrogen bonding. The i.r. and Raman spectra permit the differentiation between the planar and nonplanar types of the hydrogen dinitrate ion.     

Vibrational spectra of the potassium salt of methylnitramine and assignment of the frequencies

Conclusions From their study of the vibrational spectra of isotope-substituted analogs of the potassium salt of methylnitramine, the authors propose a new assignment of the vibrational frequencies of the methylnitramine anion.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2606–2608, November, 1969.     

Vibrational assignment, structure and intramolecular hydrogen bond of 4-methylamino-3-penten-2-one

The molecular structure, intramolecular hydrogen and vibrational frequencies of 4-methylamino-3-penten-2-one were investigated by a series of density functional theoretical (DFT) calculations and ab initio calculation at the post-Hartree-Fock (MP2) level. Fourier transform infrared and Fourier transform Raman spectra of this compound and its deuterated analogue were clearly assigned. The calculated geometrical parameters show a strong intramolecular hydrogen bond with a N...O distance of 2.622-2.670 A. This bond length is about 0.02 A shorter than that in its parent, 4-amino-3- penten-2-one which is in agreement with spectroscopic results. Furthermore, the conformations of methyl groups with respect to the plane of the molecule and with respect to each other were investigated.     

The influence of intramolecular H-bond on chromatographic behavior of phenylalkylamines

The thermodynamic characteristics of adsorption on the surface of graphitized thermal carbon black at 300 K were determined by the molecular statistical method for three phenylalklylamines. The influence of the intramolecular H-bond on the conformation of the molecules compared with structurally related n-alkyl-benzenes was considered. It was shown that the conformations of the molecules could influence chromatographic retention. Conformational isomers stabilized by intramolecular H-bonds were found to retain their structure in adsorption on graphitized thermal carbon black.     

Hydrogen bonds in fluorosubstituted dicarboxylic acids: vibrational spectra and crystal structure of potassium hydrogen difluorofumarate and potassium hydrogen difluoromaleate

The crystal structures of potassium hydrogen difluoromaleate (KHDFM) and potassium hydrogen difluorofumarate (KHDFF) have been determined by single crystal X-ray methods. The hydrogen difluoromaleate ion has a closed ring structure with a short intramolecular hydrogen bond. The O· O distance is 2.415(1) Å The hydrogen difluorofumarate ions form infinite chains via short intermolecular hydrogen bonds.The O· ;O distance is 2.450(5) Å. In both compounds the hydrogen bonds are across crystallographic symmetry elements. The vibrational spectra of both compounds and their deuterated derivatives have been recorded and assigned. The IR spectrum of KHDFF is of Speakman's A₂ type. The spectra of KHDFM and potassium hydrogen maleate are very similar.     

Vibrational spectra, structure and hydrogen bonding of 5-tert-butylpyrazole and its zinc complexes

New zinc complexes [L₂ZnX₂] with X=Cl (I), Br (II), I (III) and NO₃ (IV), [L₃Zn(OClO₃)]ClO₄ (V) and [L₄Zn](ClO₄)₂ (VI) with 5-tert-butylpyrazole as ligand L were synthesized and characterized by infrared-, Raman-, mass- and NMR-spectroscopy. The assignment of the vibrational frequencies for the complexes in the range of 4000–80 cm⁻¹ is proposed. Analysis of the IR spectra in the range of ν_NH frequencies shows that 5-tert-butylpyrazole forms cyclic associates in the solid using intermolecular NHN hydrogen bonds. This was proven by a crystal structure determination, which showed that L exists as tetramers in the solid state. In solution there is an equilibrium between tetramers and monomers and, probably, dimers or trimers. In the complexes, the NH-groups of L form intramolecular H-bonds with the X-group. The intramolecular H-bond in VI has interionic character and partially dissociates in solution at high dilution. Ligand vibrations that are sensitive to the coordination and the dependence of their frequencies on the anionic group X has been revealed.     

Vibrational spectra, co-operative intramolecular hydrogen bonding and conformations of calix[4]arene and thiacalix[4]arene molecules and their para-tert-butyl derivatives

The IR and Raman spectra and conformations of calix[4]arene, thiacalix[4]arene and their p-tert-butyl derivatives have been analysed within the framework of scaled quantum mechanics (SQM). It is shown that the introduction of four p-tert-Bu groups into the calixarene molecules influences the relative energies of their conformers and the enthalpy of the cooperative intramolecular H-bonding (DeltaH(intra)) almost negligibly. DeltaH(intra), evaluated from Iogansen's rule, amounts to approximately 26-28 kcal mol(-1) for the calixarenes and approximately 20-21 kcal mol(-1) for the thiacalixarenes, which essentially exceeds the enthalpies of non-cooperative H-bonds formed by related phenols. As a result of this strong bonding, bands of stretching, bending and torsion vibrations of an eight-membered cyclic system (OH...)4 arise, e.g., two delta(OH)4 bands are observed in the IR spectra of the most highly symmetric C4 cone conformations of calix[4]arene and thiacalix[4]arene. The "duplication" of the number of OH infrared bands is a good new indicator of cooperativity of intramolecular H-bonding of the calixarenes.     

Vibrational spectra and assignment for trans-3,4-dichlorocyclobutene. Revised assignment for the cis isomer

A complete assignment of the vibrational fundamentals of trans-3,4-dichlorocyclobutene has been derived from infrared and Raman spectra. These freq     

Vibrational spectra of alkali hydrogen selenites,selenous acid,and their deuterated analogs

The infrared and Raman spectra of alkali hydrogen selenites [(MHSeO₃), where M = Li, Na, K, or Cs], selenous acid (H₂Seo₃), and their deuterated analogs have been recorded and interpreted. The internal mode frequencies observed in sodium hydrogen selenite, selenous acid, and sodium trihydrogen selenite are used to generate general valence force constants for HSeO^?₃ and H₂SeO₃ under the assumption of C_s geometry for each species. Calculations of observed deuterium frequency shifts are made to aid in the assignments of the various internal modes. A low-temperature proton-triggered phase transition is observed in CsHSeO₃ and is confirmed in KHSeO₃. A discussion of the effects of proton order and disorder upon the selenite frequencies is also presented.     

Vibrational spectra of hexamethylcyclodisilazane

The synthesis and ring cleavage reactions of 2-alkyl-2-trimethylsilylmethyl-1.3-dithianes are described. The cleavage lead to 2-alkylthio-1-vinylsilanes and, via silicon migration, to 2-[3-alkylthio-3-(trimethylsilyl)propylthio]-1-alkenes.     

Vibrational spectra of mesitylene

Conclusions The Raman spectra of liquid mesitylene and the IR spectra (4000-100 cm^–1) of liquid and gaseous mesitylene were studied. An assignment of the frequencies according to the symmetry and the form of the vibrations is proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2265–2270, October, 1982.     

Vibrational spectra of diethylsulfoxide

FT IR and Raman spectroscopic studies of pure diethylsulfoxide (DESO) in the liquid and in the solid states and its solutions in various solvents have been performed. Analysis of SO- and CH-stretching regions in a wide range of concentration shows that the bands may be fitted satisfactorily by considering seven components. In addition, fundamental frequencies have been assigned using ab initio calculations at the RHF/3-21G* levels. The results obtained confirm a viewpoint on a self-associative structure of DESO, and support the hypothesis of the existence of different types of intermolecular associates including both dipole-dipole and hydrogen bonding mechanisms.     

Vibrational spectra of isocyanocyclopropane

Infra-red spectra of isocyanocyclopropane have been measured from 4000 to 400 cm⁻¹ in the vapour and to 200 cm⁻¹ in the liquid phase. The Raman spectrum of the liquid was obtained from 4000 to 50 cm⁻¹. A vibrational assignment of all fundamentals is proposed, which is in accord with those of structurally related molecules. Comparison with the vibrational spectra of cyanocyclopropane and cyclopropylacetylene shows the presence of a sizeable inductive effect of the nitrogen atom in isocyanocyclopropane.