Matrix isolation FTIR spectroscopical study of ethene secondary ozonide

A new method is used for the separation of ethene secondary ozonide (SOZ) from the other products of ethene ozonization reaction. The reaction was performed in the neat films of the reactants at 77 K. Ethene SOZ was separated from other products of the reaction by vacuum distillation at 190–210 K and analyzed by means of the matrix isolation IR absorption spectroscopy. Spectroscopic data from photolysis of the matrix isolated ozonide was used as an argument for assignment of the infrared spectral bands either to ethene SOZ or to other products of the reaction. The spectra of ethene SOZ isolated in the Ar matrix were analyzed by combining experimental results with the theoretical calculations performed at the MP2 6-311+G (3df, 3pd) level. A new assignment of some experimental fundamental bands is proposed taking in to account the Fermi resonance between CH stretch and the five membered ring vibrations. For the first time more than 30 weak infrared absorption bands were observed and assigned to various combination vibrations and overtones. By using new spectral information concerning the overtones and the combination bands it is concluded that the dissociation of unstable ethene SOZ involving breaking of any of the four CO bonds of the five membered ring of ethene SOZ has low probability. Dissociation of the ring starts from breaking of the OO bond.      

Evidence for new bands in the 3nu1 and 4nu1 regions of propyne

Vibrationally mediated photodissociation and room-temperature photoacoustic (PA) spectroscopy have been used for obtaining action (monitoring the yield of H photofragments) and absorption spectra of the second (3nu(1)) and third (4nu(1)) C-H acetylenic stretches overtone regions in propyne. The band contours appearing in these regions seem mostly regular even though they are perturbed, as expressed by the origin shifts in different K components, splitting of the K structure, and splitting due to resonances between neighboring states. Symmetric rotor simulations of the band contours of the PA and action spectra allowed extraction of the molecular parameters and rough estimates for the homogeneous broadening arising from energy flow to the bath vibrational states. We particularly benefited from the reduced congestion in the jet-cooled action spectra and their simulations, which enabled observation of yet unknown features in the vicinity of the 3nu(1) and 4nu(1) states. Particularly, the emergence of the new state in the 3nu(1) region was confirmed by the action spectra monitored at several differing jet temperatures, suggesting that it is a dark state in IR vibrational excitation that becomes brighter in UV excitation to the upper electronic state. The monitored and Gaussian-fitted Doppler profiles point to the release of H photofragments with low average translational energies, attributed to an indirect dissociation process occurring after internal conversion to the ground electronic state and isomerization to allene.     

Fermi interaction between the nu1 and the nu2+4 nu(s) bands of Ar...DN2(+)

Two rotationally fully resolved vibrational bands have been assigned unambiguously to the linear deuteron bound Ar...DN(2) (+) complex by using ground state combination differences. The ionic complex is formed in a supersonic planar plasma expansion optimized and controlled by a mass spectrometer and is detected in direct absorption using tunable diode lasers and applying production modulation spectroscopy. The band origins are located at 2436.272 cm(-1) and at 2435.932 cm(-1) and correspond to the nu(1) band (NN stretch) and to the nu(2)+4 nu(s) combination band (DN and intermolecular stretch), respectively. The two bands overlap strongly and the large intensity of the combination band is explained in terms of a Fermi interaction. This interaction perturbs the observed transitions, particularly for low J values. Least-squares fitting yields values for the Fermi interaction parameters of F(0)=0.332 cm(-1) and F(J)=-0.001 46 cm(-1) and results in accurate rotational constants. These are discussed both from an experimental and a theoretical point of view.     

High-resolution infrared study of vinyl fluoride in the 750-1050 cm(-1) region: rovibrational analysis and resonances involving the nu8, nu10, and nu11 fundamentals

The FTIR spectra of CH2[double bond]CHF have been investigated in the nu(8), nu(10), and nu(11) region between 750 and 1050 cm(-1) at a resolution of about 0.002 cm(-1). The nu(8) vibration of symmetry species A' gives rise to an a/b-type hybrid band, while the nu(10) and nu(11) modes of A' ' symmetry produce c-type absorptions. Due to the proximity of their band origins, the three vibrations perturb each other by Coriolis and high-order anharmonic resonances. In particular, the interactions between the nu(8) and nu(10) modes are very strong and widespread with band origins separated by only 1.37 cm(-1). Besides the expected c-type characteristics, the nu(10) band shows a very intense pseudo a-type component caused by the strong first-order Coriolis resonances with the nu(8) state. Furthermore, the 2nu(9) "dark state" was found to be involved in the interacting band systems. The spectral analysis resulted in the identification of 3144, 3235, and 3577 transitions of the nu(8), nu(10), and nu(11) vibrations, respectively. Almost all the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian in the Ir representation and the perturbation operators. The model employed includes nine types of resonances within the tetrad nu(8)/nu(10)/nu(11)/2nu(9) and a set of spectroscopic constants for the nu(8), nu(10), and nu(11) fundamentals as well as parameters for the "dark state" 2nu(9), and fourteen coupling terms have been determined.     

Observation of nu1+nu(n) combination bands of the HOOO and DOOO radicals using infrared action spectroscopy

Hydrogen trioxy (HOOO) and its deuterated analog (DOOO) have been generated in a supersonic free-jet expansion through association of photolytically generated OH or OD and molecular oxygen. The radicals were detected using infrared action spectroscopy, a highly sensitive double resonance technique. Rotationally resolved spectra of combination bands of HOOO and DOOO comprising one quantum of OH or OD stretch (nu(1)) and one quantum of a lower frequency mode (nu(1)+nu(n) where n=3-6), including HDOO bend (nu(3)), OOO bend (nu(4)), central OO stretch (nu(5)), and HDOOO torsion (nu(6)), have been observed and assigned to the trans conformer. All but one of these bands are accompanied by unstructured features which are tentatively assigned to the corresponding vibration of the cis conformer. In total, five additional bands of HOOO and four of DOOO have been recorded and assigned. These data represent the first gas-phase observation of the low-frequency modes of HOOO and DOOO and they are found to differ significantly from previous matrix studies and theoretical predictions. Accurate knowledge of the vibrational frequencies is crucial in assessing thermochemical properties of HOOO and present possible means of detection in the atmosphere.     

Contribution of the asymmetric stretch, nu3B1, to the fundamental Raman spectrum of water

The OD-stretching overtone from liquid D2O, 2nu, and the fundamental OD stretch from dilute HDO, both display high-frequency depolarization ratio minima, but the fundamental OD stretch from neat D2O displays a maximum, at the equivalent position. The rhoL minima arises from the decreased depolarization ratio produced by the absence of B1 modes. The fundamentals of HDO are of A species, and the 2nu overtone of D2O only involves A1 species, e.g., 2nu3B1 has A1 species via B1 x B1 = A1. A and A1 modes display small rhoL values which produce minima in rhoL near 2665 cm(-1) for HDO, and near 5250 cm(-1) for the D2O overtone. These minima give way to a depolarization ratio maximum when the depolarized, rhoL = 34, nu3B1 fundamental, makes its appearance in D2O at 2650 cm(-1). Fundamental and overtone depolarization ratios were used to determine the nu3B1 contribution to the depolarization ratio of the fundamental OD stretch; a value of approximately 28% resulted at 2655 cm(-1). Liquid H2O displays completely analogous features; a value of approximately 20% resulted for it at 3660 cm(-1). Nonhydrogen-bonded nu3B1, and more strongly hydrogen-bonded nu3B1, modes are also indicated for D2O and H2O. A rigorous test of the current results can be accomplished by measuring the depolarization ratio of the extraordinarily weak second Raman overtone, 3nu, recently detected for D2O.     

Structure of 7, 8, 17, 18-Tetrabromo-5,10,15, 20-Tetraphenylporphinatozinc(Ⅱ)

1mrnODUCTIONRecentlywereportedthestructureof7,8,17,18--tetrabromo--5,10,15,20--tetraphenylporphinatozinc(H,TPPBr.)ill.Inordertoobservetheeffectofthefoulelectron--withdrawingbromogroupsonthestructureofametalcomplexofthisPOrphyrin,thetitlecompoundwaspreparedbyanestablishedmethod[Ziandthecrysta:wasobtained,whichissuitableforstructureanalysisbylayeringasolutioninCHCI,withpetroleum(60--90C)--piperidine.2EXPERIMENTALThetitlecomplexwassynthesizedbyreactionofH,TPPBr.andZn(CH,COO):.ZH…     

Line strengths and transition dipole moment of the nu2 fundamental band of the methyl radical

The line strengths of nine Q-branch lines in the nu(2) fundamental band of the methyl radical in its ground electronic state have been measured by diode laser absorption spectroscopy. The vibration-rotation spectrum of methyl was recorded in a microwave discharge in ditertiary butyl peroxide heavily diluted in argon. The absolute concentration of the radical was determined by measuring its kinetic decay when the discharge was extinguished. The translational, rotational, and vibrational temperatures, also required to relate the line strengths to the transition dipole moment, were determined from relative integrated line intensities and from the Doppler widths of the lines after allowing for instrumental factors. The line strengths of the nine Q-branch lines were used to derive a more accurate value of the transition dipole moment of this band, mu(2)=0.215(25) D. Improved accuracy over earlier measurements of mu(2) (derived from line strengths of single lines) was obtained by integrating over the complete line profile instead of measuring the peak absorption and assuming a Doppler linewidth to deduce the concentration. In addition, a more precise value for the rate constant for methyl radical recombination than available earlier was employed. The new value of mu(2) is in very good agreement with high-quality ab initio calculations. Furthermore, the ratio of the transition dipole moments of the nu(2) and nu(3) fundamental bands in the gas phase is now in highly satisfactory agreement with the ratio determined for the condensed phase.     

FT-IR and FT-Raman study of hydrogen bonding in p-alkylcalix[8]arenes

The FTIR and FT Raman spectra of p-alkylcalix[8]arenes (alkyl = tert-butyl, isononyl) were recorded. Analysis of IR spectra showed that the cyclic cooperative intramolecular hydrogen bond is realized in calix[8]arene. It was found that the strength of the cyclic cooperative intramolecular hydrogen bond in the series of alkyl derivatives of calix[8]arenes depends very little on the replacement of the p-tert-butyl groups by the more bulky isononyl group. From our data follows that the orientation of aromatic fragments in calixarene molecules depends on the type of alkyl substituent.An analysis of the changes in the IR spectra with heating and dissolution shows that the conformation of the “pleated-loop” is retained in p-tert-butylcalix[8]arene. It turned out that the intramolecular hydrogen bond is a “probe” of the conformation of calixarene molecules and IR spectroscopy is a unique method that allows one to follow the slightest nuances of changes in the H-bound system of these supermolecules.     

Absolute band intensities in the nu19/nu23 (530 cm(-1)) and nu7 (777 cm(-1)) bands of acetone ((CH3)2CO) from 232 to 295 K

Absolute band intensities of acetone ((CH3)2CO) in the nu19/nu23 and nu7 band systems near 530 and 777 cm(-1), respectively, were measured at temperatures of 232, 262 and 295 K, using a Fourier transform infrared (FTIR) spectrometer. No evident temperature dependence for the band intensities was observed. The dipole moments and the fundamental band intensities were derived in the harmonic oscillator approximation. The results are useful for the spectroscopic retrieval of acetone concentrations in the upper atmosphere.     

High resolution infrared spectra and rovibrational analysis of the coupled nu2/nu5 bands of D3Si35Cl. Equilibrium rotational constants

The Fourier transform infrared spectrum of monoisotopic D3Si35Cl in the region of the nu2/nu5 band system was recorded with a resolution of 2.4x10(-3) cm-1. More than 9000 lines of the strongly Coriolis x,y-coupled bands, (nu2)0=701.936, and (nu5)0=688.898 cm-1, have been assigned, among them 276 forbidden but perturbation allowed transitions around avoided crossings according to Delta(k-l)=+/-3 mechanisms. Three different models taking into account redundancies in the framework of unitary equivalent reductions of the rovibrational Hamiltonian have been employed to fit the data. All three models reproduced consistently the full data set employing 28 refined parameters with an rms deviation of 0.31x10(-3) cm-1. The equivalence of the parameter sets was established by the agreement of parameter sums obtained with the different models. The analysis of the avoided crossings, together with the fit of the forbidden lines, allowed an independent determination of the ground state parameters A0 and D(K)0. Combined with existing data for nu1, nu3, nu4, and nu6, the present results allowed the determination of experimental values, Ae=1.4371895(94) and Be=0.19823049(59) cm-1. The experimental results are compared with those of previous ab initio calculations of the anharmonic force field.     

Total synthesis of optically active 7α,18- and 7β,18-dimethyl-19-nor-testosterone

A total synthesis of optically active 7α (β), 18-dimethyl-19-nor-testosterones 25 and 26 from the new common optically active synthon 5 obtained from acrolein 6 through the following sequence of reactions: 6→7→8→9→10→11→12→5, is described.     

A comparative study of the fundamental and overtone spectra of dioxane

Infrared, near infrared and visible (NIR) spectra were recorded for Dioxane, Tetrahydropyrane and Diethylether in the liquid. The study of the frequencies of the overtones in Dioxane provides parameters that can be used also for interpreting the fundamental spectrum between 2800–3000 cm⁻¹ as long as one takes into account the Fermi resonance. A characteristic trend for intensities of fundamental and overtones is observed and models for appropriate parametrization are discussed.