Maurizio D’Auria

Photochemical degradation of crude oil: Comparison between direct irradiation, photocatalysis, and photocatalysis on zeolite.

Direct irradiation for 100h of crude oil from Basilicata (Southern Italy) gave in the case of linear and branched alkanes a reduction of 9 and 5%, respectively. On the contrary, cyclic alkanes decreased for 54% while aromatic hydrocarbons showed a reduction of 37%. These results are in agreement with a prevalent electron transfer mechanism. Photocatalysis (100h) gave extensive degradation of crude oil: linear alkanes were degraded for 98.66%, branched alkanes were reduced for 97.31%, cyclic alkanes for 96.04%, while aromatic compounds and alkenes were reduced for 99.54 and 98.38%, respectively. These results are in agreement with a prevalent hydrogen abstraction mechanism. When photocatalysis is performed in the presence of zeolite linear alkanes were degraded for 79.85%, branched alkanes were reduced for 45.38%, cyclic alkanes for 58.10%, while aromatic compounds were reduced for 91.85%. In this case, an increase of the relative amount of alkenes (42.05%) was observed.

On the origin of “Goût de Lumiere” in champagne

The flavour of champagne before and after UV irradiation was analysed by using SPME (solid phase microextraction). Fourteen components in the flavour were detected; some significant modifications in the composition of the flavour were observed: 1-propanol and 1-hexanol contents did not change during the irradiation, the amount of 2-methylpropanol increased, while 2,6-di-t-butylphenol disappeared after the irradiation. Furthermore, the presence of esters in the wine after the irradiation was completely modified. Ethyl acetate, ethyl butanoate, ethyl 2-hydroxypropanoate, 3-methyl-1-butanol acetate, ethyl hexanoate, and ethyl octanoate reduced their presence in the wine; ethyl decanoate disappeared in the flavour after the irradiation. In order to verify if riboflavin is responsible for the observed modifications in flavour composition, the irradiation of ethyl hexanoate in the presence of riboflavin in ethanol water with a 125 W mercury arc through Pyrex was carried out showing 9% decomposition of the ester.

Fine chemicals from singlet-oxygen-mediated degradation of lignin — a GC/MS study at different irradiation times on a steam-exploded lignin

One-hour irradiation of steam exploded lignin in the presence of singlet oxygen gave products showing high molecular weights. The irradiation at different times gave sinapyl alcohol, 4-hydroxy-3,5-dimethoxybenzaldehyde, and 2,4-dioctylphenol. It is interesting to note the isolation of a dehydroabietic acid derivative only after the treatment of lignin with singlet oxygen for 5 h. After 12 h irradiation of the same sample the presence of long chain hydrocarbons (octadecane), alkenes (1-octadecene) or alcohols (1-eicosanol) was detected.

Photochemical dimerisation of 2-vinylfuran and 2-vinylthiophene derivatives bearing electron-withdrawing groups

Abstract The photochemical dimerisation of 1,3-diheteroaryl-2-propen-1-one derivatives gave a mixture of dimers in agreement with the hypothesis that the reaction is under frontier orbitals control and preferential formation of only the more stable isomers. On the contrary, the reaction of 2-heteroaryl-nitroethylene derivatives were not observed to give cyclobutane dimers but only coupling products with the loss of one nitro group. This behaviour is in agreement with the nature of the HOMO–LUMO orbitals which do not allow the superimposition of the reagents. This result allows to formulate the hypothesis that the photochemical dimerisation of 1-heteroaryl-2-EWG-ethylenes must occur as a concerted reaction. Finally, 2-heteroaryl-1,1-dicyanoethylene derivatives gave the corresponding dimers. Also in this case, we obtained only the head-to-head dimer and the more stable one.

Composition of Volatile Fractions from Thymus, Origanum, Lavandula and Acinos Species

Abstract Three species of thyme (Thymus serpyllum, T. striatus and T. capitatus), Origanum vulgaris, Lavandula angustifolia and Acinos suaveolens were studied for their volatile components by using SPME technique. In Thymus serpyllum 69 compounds are observed. Out of the 51 volatile compounds observed in Thymus striatus, α - and γ-terpinene, thymol, p-cymene, and α-thujene seem to be the main components. Origanum vulgare showed the presence of 56 compounds, γ-terpinene, p-cymene, linalool and thymol were in large quantities. The analysis of Lavandula angustifolia gave 56 compounds, β-phellandrene, linalool and linalyl acetate were major components. Acinos suaveolens showed the presence of 9 monoterpenes and 3 sesquiterpenes.

FT–ICR–MS analysis of lignin

Fourier transform ion cyclotron resonance mass spectrometry (FT–ICR–MS) of a steam-exploded lignin from wheat straw showed that fragments with a mass higher than 4534 Da cannot be obtained. Furthermore, FT–ICR–MS showed that lignin is not a completely random polymer, but shows some regularity with a difference of 44.026 m/z (C2H4O) between the peaks. The distribution of Kendrick mass defect in the function of Kendrick nominal masses showed the same behaviour. FT–ICR–MS analysis of bagasse lignin (Granit) showed that the largest value of mass found was 4347 Da. The peaks show regularities with a difference of 44.026 m/z between the peaks. The organosolv lignin showed that the polymer with the largest mass value was 3699 Da in FT–ICR–MS. The analysis of the peaks did not show regularity; however, the Kendrick diagram for this lignin showed the same slope as in the other samples, in agreement with the C2H4O regular difference between peaks.

Volatile organic compounds of Schenella pityophilus

Volatile organic compounds of Schenella pityophilus have been identified via solid-phase microextraction-gas chromatography–mass spectrometry analysis. Ten compounds have been identified, in which 3-methylthio-1-propene was the most significant component. Some other components were previously identified in Tuber aestivum and Tuber melanosporum.

Frontier orbitals control in the reactivity of singlet oxygen with lignin model compounds. An ab initio study

Abstract The photochemical oxidation of lignin models in the presence of singlet oxygen was studied by using ab initio calculations. The treatment of the non-phenolic β- O -4-aryl ether derivatives 1 [4-ethoxy-3-methoxy-2-(2-methoxyphenoxy)-acetophenone], 2 [1-(4-ethoxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-3-hydroxy-1-propanone], and 3 [1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-3-hydroxy-1-propanol] gave products deriving from a formal β-CO cleavage formation. The reaction occurred in low yields when a 2,6-dimethoxyphenol derivative 2 is used. When the phenoxy part of the molecule showed a lower reactivity towards singlet oxygen [1-(4-hydroxy-3-methoxyphenyl)-2-(2,6-dimethoxyphenoxy)-3-hydroxy-1-propanol, 5 ], the oxidation of the phenol moiety can occur. These results can be interpreted assuming a frontier orbitals control between the HOMO of the lignin model and the LUMO of singlet oxygen. In fact, in the case of the compounds 1 , 2 , and 3 the HOMOs show almost the same value and it is localized mainly on the phenoxy part of the molecule. In the case of compound 4 the HOMO shows higher energy than in the other model compounds. In compound 5 the HOMO is mainly localized on the phenolic part of the molecule.

Photochemical substitution of halogenopyrrole derivatives

The photochemical behaviour of some iodo substituted pyrroles when they are irradiated in the presence of an aromatic compound is reported. N-Methyl-3,4-diiodopyrrole-2-carbaldehyde and 5-iodopyrrole-2-carbaldehyde are unreactive when they are irradiated in benzene solution. In contrast, ethyl 3,4-dimethyl-5-iodopyrrole-2-carboxylate gives a 1∶1 mixture of ethyl 3,4-dimethyl-5-phenylpyrrole-2-carboxylate and ethyl 3,4-dimethylpyrrole-2-carboxylate in quantitative yields. The same reaction when attempted with acetonitrile as solvent gives ethyl 3,4-dimethylpyrrole-2-carboxylate as the sole product in quantitative yield. Use of 4,5-diiodopyrrole-2-carbaldehyde as substrate and irradiation in benzene gives the corresponding 5-phenyl derivative. The same behaviour is observed with m-xylene, thiophene and 2-chlorothiophene as solvents. With acetonitrile as solvent, the reaction with benzene does not work. With 2-methylthiophene as solvent 2-(5-methyl-2-thienyl)-3-iodopyrrole is obtained as the sole product. The observed behaviour can be explained on the basis of the previously reported data on the mechanism of the photochemical arylation of halogenothiophene derivatives.

Fragrance components of Platanthera bifolia subsp. osca

Abstract SPME-GC-MS analysis of the scent of Platanthera bifolia subsp. osca collected during the night showed as main components lilac alcohols B, C and D and lilac aldehydes A, B and C. Other significant chemical components were linalool and caryophyllene. Some differences were found in comparison with previously reported analyses of the scent of P. bifolia and Platanthera chlorantha. The most important difference found was in the composition of the ester fraction.