scholarly journals Arresting doubly excited electronic state mediating lightning speed ring-opening reaction of 1,3-cyclohexadiene

2020 ◽  
Author(s):  
Shutaro Karashima ◽  
Ryuta Uenishi ◽  
Takuya Horio ◽  
Manabu Kanno ◽  
Alexander Humeniuk ◽  
...  
Keyword(s):  
Electronic State ◽  
Photoelectron Spectroscopy ◽  
Ring Opening ◽  
Excited Electronic State ◽  
High Harmonic ◽  
Spectroscopic Observation ◽  
Reaction Products ◽  
Orbital Symmetry ◽  
Ring Opening Reaction ◽  
Doubly Excited

Abstract The photoinduced ring-opening reaction of 1,3-cyclohexadiene to produce 1,3,5-hexatriene is a well-known example of the Woodward-Hoffmann rule for stereochemical reactions governed by molecular orbital symmetry, and it plays an essential role in photobiological synthesis of vitamin D3 in the skin. Since the photoexcited 11B state of 1,3-cyclohexadiene is not electronically correlated to the ground state of 1,3,5-hexatriene, the reaction is expected to proceed via non-adiabatic transitions through a doubly excited 21A electronic state. However, spectroscopic observation of this elusive state has been difficult. Here we present the results of a photoelectron spectroscopy study using table-top ultrafast deep and extreme UV lasers, based on filamentation four-wave mixing and high-harmonic generation, which enabled us to arrest the 21A state. It is shown that the ring-opening reaction takes only 60 fs to complete, which is a considerably shorter time than previous experimental and theoretical estimates. The ballistic reaction creates vibrational coherence in the reaction products.

scholarly journals Structural dynamics of photochemical reactions probed by time-resolved photoelectron spectroscopy using high harmonic pulses

2016 ◽  
Vol 194 ◽  
pp. 147-160 ◽  
Author(s):  
Ryo Iikubo ◽  
Taro Sekikawa ◽  
Yu Harabuchi ◽  
Tetsuya Taketsugu
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ring Opening ◽  
Potential Energy Surfaces ◽  
High Harmonic ◽  
Photochemical Reactions ◽  
Photoelectron Spectra ◽  
Time Resolved ◽  
Photon Excitation ◽  
Energy Surfaces ◽  
Sigma Bond

Femtosecond ring-opening dynamics of 1,3-cyclohexadiene (CHD) in gas phase upon two-photon excitation at 400 nm (=3.1 eV) was investigated by time-resolved photoelectron spectroscopy using 42 nm (=29.5 eV) high harmonic photons probing the dynamics of the lower-lying occupied molecular orbitals (MOs), which are the fingerprints of the molecular structure. After 500 fs, the photoelectron intensity of the MO constituting the CC sigma bond (σCC) of CHD was enhanced, while that of the MO forming the C–C sigma bond (σCC) of CHD was decreased. The changes in the photoelectron spectra suggest that the ring of CHD opens to form a 1,3,5-hexatriene (HT) after 500 fs. The dynamics of the σCC and σCC bands between 200 and 500 fs reflects the ring deformation to a conical intersection between the 21A and 11A potential energy surfaces prior to the ring-opening reaction.

scholarly journals Hydrophobic Modification of Nanocellulose via a Two-Step Silanation Method

Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1035 ◽  
Author(s):  
Wensheng Lin ◽  
Xiaoyong Hu ◽  
Xueqing You ◽  
Yingying Sun ◽  
Yueqin Wen ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Photoelectron Spectroscopy ◽  
Ring Opening ◽  
Chemical Characteristics ◽  
Surface Chemical ◽  
Hydrophobic Modification ◽  
Step Method ◽  
Water Contact ◽  
X Ray ◽  
Ring Opening Reaction

Dodecyltrimethoxysilane (DTMOS), which is a silanation modifier, was grafted onto nanocellulose crystals (NCC) through a two-step method using KH560 (ɤ-(2,3-epoxyproxy)propytrimethoxysilane) as a linker to improve the hydrophobicity of NCC. The reaction mechanism of NCC with KH560 and DTMOS and its surface chemical characteristics were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and HCl–acetone titration. These analyses confirmed that KH560 was grafted onto the surface of NCC through the ring-opening reaction, before DTMOS was covalently grafted onto the surface of NCC using KH560 as a linker. The grafting of NCC with DTMOS resulted in an improvement in its hydrophobicity due to an increase in its water contact angle from 0° to about 140°. In addition, the modified NCC also possessed enhanced thermal stability.

Observation and characterization of a doubly excited electronic state of 39K2

1988 ◽  
Vol 146 (3-4) ◽  
pp. 325-330 ◽  
Author(s):  
A. Katern ◽  
P. Kowalczyk ◽  
F. Engelke
Keyword(s):  
Electronic State ◽  
Excited Electronic State ◽  
Doubly Excited

Ultrafast Ring-Opening Reaction of 1,3-Cyclohexadiene: Identification of Nonadiabatic Pathway via Doubly Excited State

2021 ◽  
Author(s):  
Shutaro Karashima ◽  
Alexander Humeniuk ◽  
Ryuta Uenishi ◽  
Takuya Horio ◽  
Manabu Kanno ◽  
...  
Keyword(s):  
Excited State ◽  
Ring Opening ◽  
Ring Opening Reaction ◽  
Doubly Excited

scholarly journals Optimization of Reactions Opening Cyclic Ring of Pentose Sugar Derivatives through Dithioacetalisation Reactions

2017 ◽  
Vol 17 (2) ◽  
pp. 79
Author(s):  
Nuriman Nuriman
Keyword(s):  
Reaction Time ◽  
Ring Opening ◽  
Solvent Mixture ◽  
Reaction Products ◽  
Reaction Conditions ◽  
Ring Opening Reaction ◽  
Pentose Sugar ◽  
Sugar Derivatives ◽  
Derivatives Of ◽  
Better Than

Ring-opening reaction of cyclic pentose sugar derivatives of 2,3,4-Tri-O-benzyl- D-xylopyranoseto derivatives of acyclic 2,3,4-Tri-O-benzyl-D-xylose-Dipropyl dithioacetal been done andoptimized. The reaction was performed using a precursor propanathiol with concentrated HCl.Optimization of reaction conditions was conducted by varying propanathiol concentration,reaction time and optimization of the reaction temperature which the product ioslation conductedusing a variety of solvents. The results of this reaction was obtained 2,3,4-Tri-O-benzyl- Dxylose-Dipropyl dithioacetal with the highest randemen (97%), better than the previous reactionthrough propanathiol excessive concentration, reaction time of 2 hours and the temperature of thereaction at room temperature. Product Isolations using solvent dikloromathane more effectivethan the use of other organic solvents. Purification of reaction products is done through a columnchromatography using a solvent mixture of 20% ethyl acetate-hexane.Keywords: Optimization, Cyclic Ring, Dithioasetalisasi 

On the Conrotatory Ring Opening of 3-Carbomethoxycyclobutene Vis-À-Vis 3-Carbomethoxy-1,2-Benzocyclobutene and the Predominant Inward Opening of 3-Dimethylaminocarbonyl-1,2-Benzocyclobutene

2018 ◽  
Author(s):  
Veejendra Yadav ◽  
Dasari L V K Prasad ◽  
Arpita Yadav ◽  
Maddali L N Rao
Keyword(s):  
Transition State ◽  
Ring Opening ◽  
Electron Process ◽  
Ring Opening Reaction ◽  
Stable Species ◽  
Electron Event

<p>The torquoselectivity of conrotatory ring opening of 3-carbomethoxycyclobutene is controlled by p<sub>C1C2</sub>→s*<sub>C3C4</sub> and s<sub>C3C4</sub>→p*<sub>CO</sub> interactions in the transition state in a 4-electron process as opposed to only s<sub>C3C4</sub>→p*<sub>CO</sub> interaction in an apparently 8-electron event in 3-carbomethoxy-1,2-benzocyclobutene. The ring opening of 3-carbomethoxy-1,2-benzocyclobutene is sufficiently endothermic. We therefore argue that the reverse ring closing reaction is faster than the forward ring opening reaction and, thus, it establishes an equilibrium between the two and subsequently allows formation of the more stable species <i>via</i> outward ring opening reaction. Application of this argument to 3-dimethylaminocarbonyl-1,2-benzocyclobutene explains the predominantly observed inward opening.</p>

Variational Method for Estimating the Dipole Moment in the Second Excited State of Fluorescein Molecule from its Electronic UV Absorption Spectra

2019 ◽  
Vol 70 (10) ◽  
pp. 3538-3544
Author(s):  
Alina Costina Luca ◽  
Ana Cezarina Morosanu ◽  
Irina Macovei ◽  
Dan Gheorghe Dimitriu ◽  
Dana Ortansa Dorohoi ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Variational Method ◽  
Electronic State ◽  
Excited Electronic State ◽  
Spectral Band ◽  
Uv Absorption ◽  
Optical Parameters ◽  
Electrical Permittivity ◽  
Fluorescein Molecule

Electro-optical parameters of fluorescein molecule in the second excited electronic state and information on the interactions with solvents were obtained from a solvatochromic study. Parameters of the solvents such as the refractive index, electrical permittivity and Kamlet-Taft parameters (hydrogen bond acidity and basicity) were related with the experimentally recorded shifts of UV absorption spectral band of fluorescein dissolved in several solvents. Through a variational method, the electric dipole moment and polarizability in excited state of fluorescein molecule were estimated. The calculus requires some parameters of the fluorescein molecule in the ground electronic state, which were determined through a quantum-mechanical study.

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