2612-46-6Relevant academic research and scientific papers
photochemical ring-opening reactions are complete in picoseconds: A time-resolved UV resonance raman study of 1,3-cyclohexadiene
Reid, Philip J.,Doig, Stephen J.,Wickham, Steven D.,Mathies, Richard A.
, p. 4754 - 4763 (1993)
Photoproduct formation, vibrational, and conformational relaxation kinetics in the photochemical ring-openings of 1,3-cyclohexadiene (CHD) and α-phellandrene (α-PHE) are determined by picosecond, time-resolved UV Stokes and anti-Stokes resonance Raman spectroscopy. The frequency-doubled output from an amplified, synchronously pumped dye laser system was used to perform transient, two-color resonance Raman Stokes experiments on the photoconversion of CHD to cis-hexatriene (c-HT) and of α-PHE to 3,7-dimcthyl-1,3,5-octatriene (OT). The appearance time of the Stokes scattering from ground-state c-HT is 6 ± 1 ps, while that of OT is 11 ± 2 ps. In both reactions, the photoproduct anti-Stokes ethylenic intensity appears with a time constant of 8 ± 2 ps and decays in 9 ± 2 ps. This similarity demonstrates that the photoproduct appearance and intermolecular vibrational relaxation kinetics are not dramatically affected by the presence of alkyl substituents. Analysis of the photoproduct spectral evolution in the Stokes and anti-Stokes data as well as the observation of Raman lines characteristic of the all-cis conformer in the anti-Stokes data demonstrates that all-cis-HT first appears on the ground-state surface and then undergoes conformational relaxation to produce mono-s-cis-HT with a time constant of 7 ps. The photoproduct anti-Stokes ethylenic and single-bond stretch intensities further demonstrate that the initial photoproduct temperature at 4 ps is 1500 plusmn; 500 K and that the cooling time is 15 ps. This is the first complete analysis of the photoproduct formation, vibrational, and conformational relaxation dynamics characteristic of photochemical pericyclic ring-opening reactions.
Resonance Raman and Absorption Spectroscopy of the Lowest Triplet State of 1,3,5-Hexatriene and Deuteriated Derivatives at 183 K: Molecular Structure in the T1 State
Langkilde, Frans W.,Wilbrandt, Robert,Moeller, Soeren,Brouwer, Albert M.,Negri, Fabrizia,Orlandi, Giorgio
, p. 6884 - 6894 (1991)
Time-resolved resonance Raman (RR) spectra of the lowest excited triplet state T1 of (E)-1,3,5-hexatriene, (E)-3-deuterio-1,3,5-hexatriene, and (E)-1,1-dideuterio-1,3,5-hexatriene are obtained at 183 K.The T1 potential energy surface (PES), determining energy minima, equilibrium geometries, frequencies, and normal modes of vibration, is calculated, and RR intensities are obtained on the basis of the Franck-Condon mechanism.By comparison with the calculated spectra, the observed RR spectra are assigned to an equilibrium mixture of planar E and Z species in the T1 state.The relative intensity of the E and Z bands at temperatures between 293 and 183 K gives an upper limit of 0.22 kcal/mol for the energy difference between the planar E and Z forms.Time-resolved triplet-triplet absorption measurements as a function of temperature between 296 and 183 K yield a frequency factor A of 1.6x107 s-1 and an apparent activation energy Ea of 0.7 kcal/mol for the decay of the T1 state.Consequently, an upper limit of 0.7 kcal/mol above the planar E and Z geometries is established for the possible local energy minimum at the twisted geometry.On the basis of these data, a PES is proposed for the T1 state of 1,3,5-hexatriene with respect to torsion around the central CC bond and the C2C3 and C4C5 bonds.
Cyclohexadiene ring opening observed with 13 fs resolution: Coherent oscillations confirm the reaction path
Kosma,Trushin,Fuss,Schmid
, p. 172 - 181 (2009)
The third harmonic (270 nm, 11 fs), produced in a short argon cell from Ti-sapphire laser pulses (810 nm, 12 fs), was used to excite 1,3-cyclohexadiene to its lowest ππ* state (1B). Probing was done by transient ionization by the 810 nm pulses, measuring the yields of the parent and a fragment ion. As previously found with 10 times longer pulses, the molecule leaves in two steps (time constants τ1, τ2) from the spectroscopic (1B) to a dark (2A) state and from there (within τ3) to the ground-state surface. In addition to slightly improved values for τ1-τ3, we found in all three locations (L1-L3) on the potentials coherent oscillations, which can be assigned to vibrations. They are stimulated by slopes (driving forces) of the potentials, and the vibrational coordinates indicate the slope directions. From them we can infer the path following the initial excitation: the molecule is first not only accelerated towards CC stretching in the π system but also along a symmetric C=C twist. The latter motion - after some excursion - also erects and stretches the CH2-CH2 bond, so that Woodward-Hoffmann interactions are activated after this delay (in L 2). On leaving L2 (the 1B minimum) around the lower cone of the 1B/2A conical intersection, the wave packet is rapidly accelerated along an antisymmetric coordinate, which breaks the C2 symmetry of the molecule and eventually leads in a ballistic path to (and through) the last (2A/1A) conical intersection. The ring opening begins already on the 1B surface; near the 2A minimum it is already far advanced, but is only completed on the ground-state surface. the Owner Societies.
Ultrafast Ring-Opening Reaction of 1,3-Cyclohexadiene: Identification of Nonadiabatic Pathway via Doubly Excited State
Horio, Takuya,Humeniuk, Alexander,Kanno, Manabu,Karashima, Shutaro,Mitri?, Roland,Nishitani, Junichi,Ohta, Tetsuro,Suzuki, Toshinori,Uenishi, Ryuta
, p. 8034 - 8045 (2021)
The photoinduced ring-opening reaction of 1,3-cyclohexadiene (CHD) to produce 1,3,5-hexatriene (HT) plays an essential role in the photobiological synthesis of vitamin D3 in the skin. This reaction follows the Woodward-Hoffmann rule, and C5-C6 bond rupture via an electronically excited state occurs with conrotatory motion of the end CH2 groups. However, it is noted that the photoexcited S1(π,π*) state of CHD is not electronically correlated with the ground state of HT, and the reaction must proceed via nonadiabatic transitions. In the present study, we have clearly observed the nonadiabatic reaction pathway via the doubly excited state of CHD using ultrafast extreme UV photoelectron spectroscopy. The results indicate that the reaction occurs in only 68 fs and creates product vibrational coherence. Extensive computational simulations support the interpretation of experimental results and provide further insights into the electronic dynamics in this paradigmatic electrocyclic ring-opening reaction.
Comparative matrix isolation infrared spectroscopy study of 1,3- and 1,4-diene monoterpenes (α-phellandrene and γ-terpinene)
Marzec,Reva,Fausto,Proniewicz
, p. 4342 - 4353 (2011)
In the present work, γ-terpinene (a 1,4-diene derivative) and α-phellandrene (1,3-diene derivative) were isolated in cryogenic argon matrices and their structures, vibrational spectra, and photochemistries were characterized with the aid of FTIR spectroscopy and quantum chemical calculations performed at the DFT/B3LYP/6-311++G(d,p) level of approximation. The molecules bear one conformationally relevant internal rotation axis, corresponding to the rotation of the isopropyl group. The calculations provide evidence of three minima on the potential energy surfaces of the studied molecules, where the isopropyl group assumes the trans, gauche+, and gauche conformations (T, G+, G- ). The signatures of all these conformers were identified in the experimental matrix infrared spectra, with the T forms dominating, in agreement with the theoretical predicted abundances in gas phase at room temperature. In situ UV (λ > 200 nm) irradiation of matrix-isolated α-phellandrene led to its isomerization into an open-ring species. The photoproduct was found to exhibit the ZE configuration of its backbone, which to be formed from the reactant molecule does not require extensive structural rearrangements of both the reagent and matrix. γ-Terpinene was photostable when subjected to irradiation under the same experimental conditions. In addition, the liquid compounds at room temperature were also investigated by FTIR-ATR and FT-Raman spectroscopies.
Ultrafast dynamics of the photochemical ring opening of 1,3-cyclohexadiene studied by multiphoton ionization
Fuss,Schikarski,Schmid,Trushin,Kompa
, p. 675 - 682 (1996)
Femtosecond time-resolved studies of the ring opening of 1,3-cyclohexadiene are presented. After absorption of a single UV photon in the region 250-270 nm (1A1 → 1B2 transition), the reaction is investigated using time-delayed single-and multiphoton ionization with probe pulses in the region 250-415 nm. Ions are detected by a time-of-flight mass spectrometer. The parent ion is only observed during the time when the pump and probe lasers overlap. The corresponding ionizable state, which we identify as 1B2, has a short lifetime which we estimate to be 60 fs. The only signal detected after a delay is due to C6H+7. It arises from dissociation of vibrationally hot parent ions which are produced by two-photon ionization of vibrationally excited products. The appearance rate constant of the product is as high as 1.7 ± 0.2 ps-1. It is assigned to the transition from the 2A1 to the 1A1 surface via a conical intersection, i.e. to the photochemical ring opening of 1,3-cyclohexadiene to Z-hexatriene. Measuring fragment ions generated by photoionization at suitable wavelengths may be a general method for monitoring vibrationally hot neutral molecules.
Time-resolved dissociative intense-laser field ionization for probing dynamics: Femtosecond photochemical ring opening of 1,3-cyclohexadiene
Fuss,Schmid,Trushin
, p. 8347 - 8362 (2000)
The concerted photochemical ring opening of 1,3-cyclohexadiene was investigated in the gas phase by low-intensity pumping at 267 nm and subsequent probing by high-intensity photoionization at 800 nm and mass-selective detection of the ion yields. We found five different time constants which can be assigned to traveling times along consecutive parts of the potential energy surfaces. The molecule is first accelerated in the spectroscopic state IB along Franck-Condon active coordinates, then alters direction before changing over to the dark state 2A. All constants including that for leaving the 2A surface are below 100 fs. These times are shorter than appropriate vibrational periods. Such a maximum speed is evidence that the pathway is continuous leading from surface to surface via real crossings (conical intersections) and that the molecule is accelerated right into the outlet of the 2A/1A funnel. On the ground state it arrives as a compact wave packet, indicating a certain degree of coherence. The experimental method promises a high potential for investigating dynamics, since many consecutive phases of the process can be detected. This is because the fragmentation pattern depends on the location on the potential energy surface, so that monitoring several different ions permits to conclude on the population flow through these locations. Ionization at the intensities used is normally considered to be an effect of the electric field of the radiation. But in our case it is enhanced by resonances in the neutral molecule and in particular in the singly positive ion, and it is not sensitive for the length of the molecule (different conformers of the product hexatriene). The ionic resonances explain why hexatriene has a much richer fragmentation pattern than cyclohexadiene. Coulomb explosion is observed from an excited state of a doubly positive ion. Its mechanism is discussed.
Preparation of (E)-1,3,5-Hexatriene and (3E,5E)-1,3,5,7-Octatetraene by the Palladium Catalyzed Elimination of Acetic Acid form Allylic Acetates
Yamamoto, Keiji,Suzuki, Shigeaki,Tsuji, Jiro
, p. 2541 - 2542 (1981)
Palladium complex-catalyzed elimination of acetic acid from (2E,4E)-2,4-hexadienyl acetate and (2E,4E,6E)-2,4,6-octatrienyl acetate afforded, respectively, the title conjugated polyenes stereoselectively.
Pyrolysis of tricyclic cyclobutane-fused sulfolanes as a route to cis-1,2-divinyl compounds and their Cope-derived products
Aitken, R. Alan,Cadogan, J. I. G.,Gosney, Ian,Humphries, Caroline M.,McLaughlin, Leo M.,Wyse, Stuart J.
, p. 605 - 614 (2007/10/03)
Functionalisation of the double bond of 3-thiabicyclohept-6-ene 3, readily formed by hydrolysis of the cycloadduct 1 of 3-sulfolene and maleic anhydride followed by oxidative bis-decarboxylation, gives tricyclic sulfones 5-7 and 9 with the bicyclo2,4> skeleton. FVP of 3 results in stereospecific extrusion of SO2 to give Z-hexa-1,3,5-triene which undergoes electrocylisation to give cyclohexa-1,3-diene while reaction of 3 with LiAlH4 results in non-stereospecific extrusion to give Z- and E-hexa-1,3,5-triene. Upon FVP the tricyclic sulfones 5-7 and 9 lose SO2 to give 7-membered ring products 16-19 by Cope rearrangement of the initially formed cis-1,2-divinyl intermediates 15. The 1,3-dipolar cycloaddition of nitrile oxides and a nitrone to the double bond of 3 gives tricyclic sulfones with the tricyclo2,6> skeleton and a wider variety of these can be prepared by conventional reactions of 1. Upon FVP these lose SO2 to give stable cis-1,2-divinyl compounds 23, 24, 37-40 and 41-44. The Diels-Alder adducts 48 and 49 have been prepared from 3 and these behave differently upon FVP, losing SO2 and butadiene to give tetrasubstituted benzenes, in the latter case by way of an unexpected tetracyclic intermediate.
1-Thia-3,4-diazolidine-2,5-dione Functionality: A Photochemical Synthon for the Azo Group
Squillacote, Michael,Felippis, James De
, p. 3564 - 3571 (2007/10/02)
The 1-thia-3,4-diazolidine-2,5-dione functional group was shown to yield azo compounds upon photolysis.This photoreaction when combined with the known ability of this group to react in a Diels-Alder fashion or as a dinucleophile toward alkylating agents greatly increases the utility of this functionality.The dual reactivity of this group was demonstrated in the synthesis of a number of 3,4-dialkyl-1-thia-3,4-diazolodone-2,5-diones.The photolysis of these compounds produced either thermally stable cyclic azo compounds or the decomposition products of thermally unstable azo compounds.
