The Photochemistry of a Dihydropyridazine

1973 ◽  
Vol 51 (11) ◽  
pp. 1729-1736 ◽  
Author(s):  
P. De Mayo ◽  
M. C. Usselman
Keyword(s):  
Triplet State ◽  
Ring Opening ◽  
Quantum Yields ◽  
Trans Isomers ◽  
Absorption Bands ◽  
Cis And Trans

Irradiation of a 5,6-dihydropyridazine in either the n → π* or π → π* absorption bands results in ring-opening to the two isomeric diazatrienes expected of a concerted, electrocyclic process. Population of the triplet state of the dihydropyridazine by sensitization also results in ring-opening, but much less efficiently. The quantum yields of the two processes were found to be 0.40 ± 0.04 and 0.07 ± 0.01, respectively. The primary photoproducts, cis,cis- and cis,trans-4,5-diazatriene, isomerize thermally at temperatures greater than 20° to the trans,cis and trans,trans isomers.

Cyclobutene photochemistry. Adiabatic photochemical ring opening of alkylcyclobutenes

1996 ◽  
Vol 74 (6) ◽  
pp. 951-964 ◽  
Author(s):  
William J. Leigh ◽  
J. Alberto Postigo ◽  
K.C. Zheng
Keyword(s):  
Ring Opening ◽  
Quantum Yields ◽  
Light Sources ◽  
Trans Isomers ◽  
Excited Singlet ◽  
Orbital Symmetry ◽  
Cis And Trans Isomers ◽  
Product Distributions ◽  
Reaction Proceeds ◽  
Cis And Trans

The photochemistry of the cis and trans isomers of a series of dimethylbicyclo[n 2.0]alk-(n + 2)-enes (n = 2–5) (bicyclic cyclobutene derivatives in which the C=C bond is shared by the two rings) in pentane solution is described. Irradiation of these compounds using monochromatic 193- or214-nm light sources results in ring opening to yield the corresponding 1,2-bis(1-ethylidene)cycloalkanes (C4–C7) in high chemical and quantum yields. In all cases, the reaction proceeds with a high (70–90%) degree of disrotatory stereoselectivity. Quantum yields for direct cis,trans photoisomerization of the isomeric E,E-and E,Z-1,2-bis(1-ethylidene)cycloalkanes have also been determined. The product distributions from irradiation of the cyclobutenes are wavelength dependent, but for 214-nm excitation the isomeric diene distributions obtained from cyclobutene ring opening agree fairly closely with those calculated from the quantum yields for cis,trans photoisomerization of the isomeric dienes on the assumption that the process involves purely disrotatory ring opening to yield a single diene isomer in the lowest excited singlet state. The results are consistent with an orbital-symmetry-controlled, adiabatic mechanism for ring opening. Key words: photochemistry, cyclobutene, electrocyclic, adiabatic, conical intersection, orbital symmetry.

Resonance Raman labels: spectroscopic studies on cis- and trans-4-benzylidene-2-phenyl-Δ2 -oxazolin-5-one and an isotopically substituted analog

1978 ◽  
Vol 56 (2) ◽  
pp. 232-239 ◽  
Author(s):  
K. Kumar ◽  
D. J. Phelps ◽  
P. R. Carey
Keyword(s):  
Raman Spectra ◽  
Electronic Transition ◽  
Raman Band ◽  
Resonance Raman ◽  
Spectroscopic Studies ◽  
Trans Isomers ◽  
Absorption Bands ◽  
Cis And Trans Isomers ◽  
Raman Excitation Profiles ◽  
Cis And Trans

The absorption and preresonance Raman spectra of cis- and trans-4-benzylidene-2-phenyl-Δ2-oxazoIin-5-one are reported. Although steric considerations suggest that the π electron pathway in the cis isomer is considerably distorted compared to the trans isomer, the Raman and absorption spectra of the two isomers are strikingly similar. Preresonance Raman excitation profiles for the cis and trans isomers indicate that the main features in the Raman spectra owe their intensity to coupling to the 360 nm absorption band present in both isomers. It is proposed that both the electronic dipole transition responsible for this absorption and the vibrational modes giving rise to the intense Raman bands are localized in the —C=C—N=C—Ph part of the molecule. Thus the main Raman and absorption bands are insensitive to isomerization in the benzylidene portion. Support for a localized electronic transition, polarized along the —C=C—N=C—Ph long axis, comes from Raman depolarization ratio (ρ) measurements which show that ail intense Raman features in both cis and trans isomers have ρ ∼ 0.33. Further support comes from ir and resonance Raman spectra of trans-4-(4-dimethylamino-3-nitrobenzylidene)-2-phenyloxazolin-5-one substituted either with 13C in the 4 position, or with 15N, in the oxazolinone ring. These spectra indicate that the main Raman feature seen in all 4-benzylidene-2-phenyloxazolinonesat 1561 cm−1 is a symmetric stretching mode associated with the —C=C—N=C— chain and that this feature has some C=N stretching character. The substitution experiments also show that the weak 1654 cm−1 Raman band has a high degree of C=C stretching character and may represent an essentially antisymmetric mode from the C=C—N=C moiety. The preresonance Raman excitation profiles show that the intensity enhancement follows an FB2 type dependence. The utility of the Raman spectrum as a probe for the chromophore responsible for the electronic transition in a highly conjugated system is discussed.

scholarly journals Identification of Anthocyanin Compounds in Butterfly Pea Flowers (Clitoria ternatea L.) by Ultra Performance Liquid Chromatography/Ultraviolet Coupled to Mass Spectrometry

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4539
Author(s):  
Nguyen Minh Thuy ◽  
Vo Minh ◽  
Tran Ben ◽  
My Tuyen Thi Nguyen ◽  
Ho Ha ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Ultra Performance Liquid Chromatography ◽  
Negative Ion ◽  
Trans Isomers ◽  
Clitoria Ternatea ◽  
Flower Extract ◽  
Cis And Trans Isomers ◽  
Butterfly Pea ◽  
Cis And Trans

Butterfly pea flower have great sensory attraction, but they have not yet been used widely in Vietnam. Extracts of butterfly pea flowers can be used conveniently as a natural blue colorant for food products. In this study, the identification of anthocyanin compounds in butterfly pea flowers was performed by UPLC coupled with a UV and Mass spectrometer instrument. Positive and negative ion electrospray MS/MS chromatograms and spectra of the anthocyanin compounds were determined. By analyzing the chromatograms and spectra for each ion, five anthocyanins were identified in the butterfly pea flower extract; these were delphinidin-3-(6”‐p-coumaroyl)-rutinoside, cyanidin 3-(6”-p-coumaroyl)-rutinoside, delphinidin-3-(p-coumaroyl) glucose in both cis- and trans- isomers, cyanidin-3-(p-coumaroyl-glucoside) and delphinidin-3-pyranoside. Additionally, based on their intensity, it was determined that cyanidin-3-(p-coumaroyl-glucoside) was the most abundant anthocyanin, followed by cyanidin 3-(6”-p-coumaroyl)-rutinoside, delphinidin-3-(p-coumaroyl-glucoside), delphinidin-3-(6”-p-coumaroyl)-rutinoside and delphinidin-3-pyranoside. In this study, cyanidin derivatives were discovered in butterfly pea flower extract, where these compounds had not been detected in previous studies.

Unveiling the coexistence of cis- and trans-isomers in the hydrolysis of ZrO2: A coupled DFT and high-resolution photoelectron spectroscopy study

2020 ◽  
Vol 153 (24) ◽  
pp. 244308
Author(s):  
Ali Abou Taka ◽  
Mark C. Babin ◽  
Xianghai Sheng ◽  
Jessalyn A. DeVine ◽  
Daniel M. Neumark ◽  
...  
Keyword(s):  
High Resolution ◽  
Photoelectron Spectroscopy ◽  
Spectroscopy Study ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Hydrolysis Of

PREPARATION OF ERUCIC AND NERVONIC ACIDS LABELLED WITH CARBON-14

1957 ◽  
Vol 35 (8) ◽  
pp. 757-760 ◽  
Author(s):  
K. K. Carroll
Keyword(s):  
Enoic Acid ◽  
Nervonic Acid ◽  
Malonic Ester ◽  
Ester Synthesis ◽  
Trans Isomers ◽  
Carbon 14 ◽  
Cis And Trans Isomers ◽  
Cis And Trans

The malonic ester synthesis of nervonic acid (tetracos-15-enoic acid) has been modified so that the product consists of pure cis rather than a mixture of cis and trans isomers. The modified synthesis has been used for the preparation of C14-labelled erucic and nervonic acids.

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