All-cis-retinal and 7-cis,9-cis,11-cis-retinal1

A modified 15 + 5 route led to 7-cis,9-cis,11-cis-retinonitrile in high selectivity and also a lesser amount of all-cis-retinonitrile. DIBAL reduction gave the corresponding retinal isomers. The absorption maximum 287nm of all-cis-retinal reveals the distorted nature of the chromophore.     

Synthesis of the 7-cis isomer of the natural leukotriene d4

Methyl 5(S), 6(S)-oxido-11-oxo-7-cis-9-trans-undecadienoate $\text{5}$ was prepared and used for the synthesis of the novel 7-cis-LTD₄ ($\text{9}$) as well as, after isomerization to the all-trans dienal ester $\text{3}$, for that of the natural leukotrienes.     

Raman spectrum of difluorodiazirine

The Raman spectrum of difluorodiazirine has been re-examined. Four well-defined bands have been found in the low frequency region, which lead to a definitive assignment for all nine vibrational fundamentals of this molecule. The fundamental frequences are (in cm⁻¹): (a₁) 1563, 1282, 805, 502; (a₂) 451; (b₁) 1248, 481; (b₂) 1091, 544.     

Raman spectrum of the phenoxy radical

The Raman spectrum of the phenoxy radical produced duing the course of oxidation of phenol by the Ce(IV) ion was measured by use of a stopped-flow method and a multichannel detection method. Five Raman bands were observed in the frequency region below 1700 cm^?1. The time dependence of the spectrum was also followed.     

A Facile Synthesis of the C-11 isomer of 5-epi-Kudtriol

Eudesmane derivatives contain a number of naturally occurring compounds. Amongthem many compounds possess intriguing biological properties"'.Kudtriol 1 and 5-epi-kudtriol 2 was first isolated from the aerial parts of Jasaniaglatinosa by Tereasa et al ', and their structures were determined as (-)-eudesm-4(14)-ensa,l 1,12-triol and ( )-eudesm-4(14)-en-50,l l,12-triol respectively by spectroscopicmethods.Although previous paper reported the synthesis of 2 from Q-santonin 4 in elevensteps#, an e…     

The Raman spectrum of propynal

The Raman spectrum of propynal as a vapour and dissolved in various solvents were recorded. These data and the observed polarization measurements were in accordance with the fundamental frequencies assigned to the ground state of this molecule. The vibrational modes of propynal were compared with those previously reported for the halopropynals.     

Raman spectrum of propylene carbonate

The Raman spectrum of propylene carbonate (4-methyl-1,3-dioxolan-2-one) has been recorded and analyzed. Vibrational assignments have been made for many of the observed frequencies on the basis of comparison with accepted assignments for certain vibrational modes in other compounds with close structural similarities.The spectra of propylene carbonate (PC)-water mixtures have been studied over the entire concentration range at 80° and there seems to be little or no interaction except for partial disruption of hydrogen bonding in water by PC. Raman spectra of solutions of LiClO₄ in PC and in PCH₂O mixtures indicate possible salvation of the Li⁺ ion.     

The resonance Raman spectrum of azulene

Excitation profiles have been measured for three Raman lines of azulene in CS₂ solution in the spectral range of the visible absorption system, viz. 665—570 nm. The results are unexpected in as much as the excitation profiles do not exhibit maxima at or near the absorption peaks. The results are interpreted on the basis of contributions to the A-term by other modes than the one studied in the Raman effect. These terms give rise to interferences which lower the excitation profile in some regions while causing maxima at other frequencies.     

Conformational energetics and excited state level ordering in 11-cis retinal.

Semiempirical molecular orbital theory and semiclassical solvent effect theory are used to analyze the conformational and electronic properties of the 12-s-cis and 12-s-trans conformers of 11-cis retinal. The goal is to examine the influence of solvent environment on the equilibrium geometries of these conformers as well as to provide a perspective on the electronic transitions that contribute to the four band systems that are observed in the 200-500 nm region of the optical spectrum. We conclude that the 12-s-cis isomer is more stable in vacuum, but that the 12-s-trans conformer is preferentially stabilized in both polar and nonpolar solvent environment due to dispersive as well as electrostatic interactions. This observation is in substantial agreement with previous literature results. In contrast, our analysis of the excited state manifold indicates that the spectral features observed in the absorption spectrum are associated with a complex set of overlapping transitions. A total of 18 pi*<--pi transitions contribute to the four bands, and in some cases, conformation changes the relative contribution of the individual transitions that define the overall band shape. This study provides the first definitive assignments for all four band systems.     

Theoretical IR and Raman spectra of diketene and its 3-methylene isomer

The IR and Raman spectra of diketene, 4-methylene-2-oxetanone, and its less stable isomer, 3-methylene-2-oxetanone, were calculated at the MP2, DFT B3PW91 and RHF levels using 6-311++G** basis set. The internal coordinates were defined for both isomers and used in potential energy distribution (PED) analysis. The PED analysis of the theoretical spectra forms the basis for a detection of the 3-methylene isomer traces in a reaction mixture as well as for elucidation of the future matrix isolation IR and/or Raman spectra.     

The resonance Raman spectrum of the aniline radical cation

The time-resolved resonance Raman spectrum of the aniline radical cation has been observed using pulse radiolysis methods. This radical exhibits a large inverse secondary isotope effect on deuteration of the NH₂ group on the CN stretching frequency. Various spectral features indicate that this radical is structurally similar to the phenoxyl radical.     

Qualitative features of the two-dimensional Raman spectrum in liquids

The theory presented earlier [J. Kim and T. Keyes, Phys. Rev. E 66, 051110 (2002)] is analyzed to determine the information available from the two-dimensional Raman spectrum R((5))(t(2),t(1)) in liquids. The known spectra are well represented by the sum of two products of ordinary time correlations predicted by the theory. The shape of R((5)) is related in general to the values of simple same-time averages and concepts amenable to physical intuition. Using standard models for the time correlations entering the theory, specific analytic expressions for the spectrum are obtained depending on two parameters and a time scale, and the behavior of the spectrum is mapped out in the parameter space.     

Raman spectrum and potential function of tetrachlorocyclopropene

The laser Raman spectrum of tetrachlorocyclopropene in the liquid and solid phases has been recorded and vibrational assignments are presented. These results together with root mean squared vibrational amplitudes from electron diffraction data have been employed in a normal coordinate analysis in which a 19 parameter potential function is refined. This potential function, originally expressed in terms of compliance constants, is then used to derive the corresponding conventional and relaxed force constants.     

The Raman spectrum of hexamethylbenzene single crystal

A set of polarized Raman spectra obtained from suitable hexamethylbenzene single crystals at room temperature is presented. All the observed frequencies are attributed to intramolecular vibrations or lattice modes on the basis of clear polarization data.     

The Raman spectrum of predissociating nitrogen dioxide

The Raman spectrum of NO₂ excited at 355 nm is found to be dominated by bands containing up to six quanta of the bending vibration and four quanta of the symmetric stretch, with an almost complete absence of bands containing asymmetric stretch quanta. These results are interpreted within a time-dependent view to provide insight into the predissociation dynamics of NO₂.     

The Raman and infrared spectrum of hexachloro-disilazane

The Raman and IR spectra of hexachlorodisilazane were measured, and the assignment carried out by comparison with those of the structurally related compounds, hexachlorodisiloxane, hexachlorodisilane and dimethylamine. The vibrational spectra of hexachlorodisilazane are very closely related to those of hexachlorodisiloxane, hexachlorodisilane and dimethylamine, and can be interpreted in terms of a non-rigid D_3d symmetry with an internal rotation.     

Raman spectrum of 1,5-hexadien-3-yne

Summary In the liquid phase, 1,5-hexadien-3-yne apparently exists as a mixture of two isomers, namely cis (I) and trans (II) forms with (I) predominating.