18409-46-6Relevant articles and documents
Kei Wei et al.
, p. 4225 (1967)
New 1,3-dithiol-2-ylidene donor-π-acceptor chromophores with intramolecular charge-transfer properties, and related donor-π-donor molecules: Synthesis, electrochemistry, X-ray crystal structures, non-linear optical properties and theoretical calculations
Moore, Adrian J.,Bryce, Martin R.,Batsanov, Andrei S.,Green, Andrew,Howard, Judith A. K.,McKervey, M. Anthony,McGuigan, Peter,Ledoux, Isabelle,Orti, Enrique,Viruela, Rafael,Viruela, Pedro M.,Tarbit, Brian
, p. 1173 - 1184 (1998)
New donor-π-acceptor chromophores 5a-c, 7a-c, 8a-c, 13a-c and 14b-c have been synthesised: substituted 1,3-dithiole derivatives span a range of donor abilities [viz. 4,5-dimethyl > 4,5-bis(methylsulfanyl) > 4,5-bis(methoxycarbonyl)], a conjugated ethylenic or oligoethylenic linker varies the central π-electron unit (one, two and four conjugated double bonds) and dicyanomethylene and N-cyanoimine groups are the acceptor units. Extended tetrathiafulvalene derivatives 15a-c have also been synthesised. The electronic absorption spectra of compounds 5,7,8 and 14 reveal a broad low-energy intramolecular charge-transfer band [λmax(MeCN) 354-533 nm] which shifts bathochromically with increasing donor strength of the dithiole ring, and with increasing length of the conjugative pathway. The solution redox properties of 5,7,8 and 14, studied by cyclic voltammetry, reveal a reversible one-electron oxidation wave, attributed to the formation of the radical cation of the 1,3-dithiol-2-ylidene moiety, and an irreversible one-electron reduction to form the radical anion located on the dicyanomethylene or N-cyanoimine groups. For the bis(dithiole) donors 15a-c a single two-electron redox wave is observed. The non-linear optical (NLO) properties of 7a-c and 14b have been determined using the EFISH technique: moderate NLO properties are observed for compounds 7a-c [μ.β(0) 85-112 × 10-48esu] whereas for the more extensively conjugated compound 14b, the value is increased to μ.β(0) 1170 × 10-48 esu. The molecular structure and electronic properties of the unsubstituted (R = H) compounds 7, 8, 14 and 15 have been calculated within the density functional theory approach. The minimum energy conformation corresponds to the trans orientation of the side chain for 7, and the cis orientation for 8, in agreement with X-ray crystal structures and solution NMR data. The redox properties and electronic spectra are discussed on the basis of molecular orbital energies and topologies. The X-ray crystal structures of compounds 7b, 8b and 15b are reported. In 7b the 1,3-dithiol-2-ylidene and dicyanopropene systems are planar and form an angle of 3° between each other; the 'butadiene' unit has a trans configuration. Molecule 8b is planar (with the exception of the methyl groups) and the imine nitrogen atom is in a syn orientation towards the dithiole group, forming a short intramolecular S ... N contact [2.719(6) A]. For both 7b and 8b π-delocalisation is observed within the central conjugated spacer unit. Molecule 15b has a predominantly planar structure, with the central tetraene unit in an all-trans configuration.
SIMPLE SYNTHESES OF ISOMERS OF MUCONALDEHYDE AND 2-METHYLMUCONALDEHYDE
Golding, Bernard T.,Kennedy, Gordon,Watson, William P.
, p. 5991 - 5994 (1988)
Periodate oxidation of cis-1,2-dihydrocatechol (3a) affords (Z,Z)-muconaldehyde (2b), wich can be readily converted (thermolysis and triethylamine catalysis, respectively) into its (E,Z)- (2c) and (E,E)-isomer (2a).Similarly, cis-1,2-dihydro-3-methylcatechol (3b) gives (Z,Z)-2-methylmuconaldehyde (2d) and thence (E,E)-2-methylmuconaldehyde (2c).
Evidence for the formation of Michael adducts from reactions of (E,E)-muconaldehyde with glutathione and other thiols
Henderson, Alistair P.,Bleasdale, Christine,Delaney, Kirsty,Lindstrom, Andrew B.,Rappaport, Stephen M.,Waidyanatha, Suramya,Watson, William P.,Golding, Bernard T.
, p. 363 - 373 (2008/02/04)
Glutathione induces the rapid isomerization of (Z,Z)-muconaldehyde to (E,E)-muconaldehyde via (E,Z)-muconaldehyde, probably via reversible Michael addition of the thiol to one of the enal moieties of the muconaldehyde. Reactions of (E,E)-muconaldehyde with glutathione (in the presence and absence of equine glutathione S-transferase), phenylmethanethiol, N-acetyl-l-cysteine, and N-acetyl-l-cysteine methyl ester were investigated using mass spectrometric techniques. In each case, evidence was obtained for the formation of Michael adducts, e.g., reaction between (E,E)-muconaldehyde and glutathione gave 4-glutathionyl-hex-2-enedial and 3,4-bis-glutathionyl-hexanedial. These experiments suggest that (Z,Z)-muconaldehyde, a putative metabolite of benzene, could lead to the long established urinary metabolite of benzene, (E,E)-muconic acid, via glutathione-mediated isomerization to (E,E)-muconaldehyde.
Gas-phase reaction of OH radicals with benzene: Products and mechanism
Berndt,Boege
, p. 4946 - 4956 (2007/10/03)
Benzene and a series of alkylated derivatives (toluene, xylenes, etc.) are predominantly emitted into the atmosphere by human activities (traffic, solvent use). The gas-phase reaction of OH radicals with benzene was studied in O2/He mixtures under flow conditions at 276-353 K and at 100 and 500 mbar using on-line FTIR spectroscopy and GC-MS measurements. Under conditions of a predominant reaction of the OH/benzene adduct with O2, the product formation was evaluated for variable NO concentrations. Identified products were the isomers of hexa-2,4-dienedial, phenol, nitrobenzene, p-benzoquinone and glyoxal. For increasing NO concentrations, there was a decrease of the phenol yield and the yields of trans,trans-hexa-2,4-dienedial and nitrobenzene increased. A reaction scheme was proposed describing the formation of phenol, nitrobenzene (upper limit), the hexa-2,4-dienedials and other products (unidentified carbonylic substances, etc.). The model allowed to predict formation of the different products in dependence on temperature and NOx concentration.
