Absence Of Benzophenone Research Articles

Studying the photodegradation of ethylcellulose and methylcellulose in the presence and absence of benzophenone (BPh)

ﺘﻀﻤن ﻫذا اﻟﺒﺤث د ارﺴﺔ اﻟﺘﺠزﺌﺔ اﻟﻀوﺌﻴﺔ اﻟﻤﺤﺘﺜﺔ ﻻﻓﻼم اﻻﺜﻴﻝ ﺴﻠﻴﻠوز واﻟﻤﺜﻴﻝ ﺴﻠﻴﻠوز ﻓﻲ اﻟﻬواء ﺒوﺠود وﻋدم وﺠود اﻟﻤﺘﺤﺴس اﻟﻀوﺌﻲ (اﻟﺒﻨزوﻓﻴﻨون) benzophenone (BPh) وﻗد ﺘم اﻟﺘﺸﻌﻴﻊ ﺒوﺴﺎطﺔ ﺠﻬﺎز اﻟﻤﻌﺠﻝ اﻟﺤﺎوي ﻋﻠﻰ ﻤﺼﺎﺒﻴﺢ ﻓﻠورﺴﻨت ﻟد ارﺴﺔ ﻋﻤﻠﻴﺔ اﻟﺘﺠزﺌﺔ اﻟﻀوﺌﻴﺔ ﻫذﻩ. ان اﻀﺎﻓﺔ (٠,٢ wt% ) ﻤن اﻟﺒﻨزوﻓﻴﻨون اﻟﻰ اﻓﻼم ﻤﺸﺘﻘﺔ اﻟﺴﻴﻠﻴﻠوز ﺒﺴﻤك ٢٥ ) ﻤﺎﻴﻛروﻤﻴﺘر) ﻴزﻴد اﻟﺘﺠزﺌﺔ اﻟﻀوﺌﻴﺔ ﻟﻼﺜﻴﻝ ﺴﻠﻴﻠوز و اﻟذي ﻴﺘﺠ أز اﺴرع ﻤن اﻟﻤﺜﻴﻝ ﺴﻠﻴﻠوز. ﺘم ﻗﻴﺎس اﻟﺘﺠزﺌﺔ اﻟﻀوﺌﻴﺔ ﺒوﺴﺎطﺔ اﻟزﻴﺎدة ﻓﻲ اﻤﺘﺼﺎص ﻤﺠﻤوﻋﺔ اﻟﻛﺎرﺒوﻨﻴﻝ وﺜﺎﺒت ﺴرﻋﺔ اﻟﺘﺠزﺌﺔ اﻟﻀوﺌﻴﺔ ( k d ) ﻟﻠﺒﻨزوﻓﻴﻨون ( BPh ) ﻓﻲ اﻟﺒوﻟﻴﻤر ﺒﺈﺴﺘﺨدام أطﻴﺎف اﻻﺸﻌﺔ ﺘﺤت اﻟﺤﻤ ارء و اﻻﺸﻌﺔ ﻓوق اﻟﺒﻨﻔﺴﺠﻴﺔ و اﻟﻤرﺌﻴﺔ. وﻤن اﻟﻨﺘﺎﺌﺞ اﻟﺤرﻛﻴﺔ واﻟطﻴﻔﻴﺔ ﺘم اﻗﺘ ارح ﻤﻴﻛﺎﻨﻴﻛﻴﺔ ﻟﻌﻤﻠﻴﺔ اﻟﺘﺠزﺌﺔ ﻟﻤﺸﺘﻘﺎت اﻟﺴﻴﻠﻴﻠوز وﺒﺎﺴﺘﺨدام ﻀوء ﺒطوﻝ ﻤوﺠﻲ ٣١٣ ﻨﺎﻨوﻤﻴﺘر وﺸدة اﻤﺘﺼﺎص ﻤﻘدارﻫﺎ 3.49*10 ­5 einsteins.dm ­3 .S ­1 و ﺒدرﺠﺔ ﺤ اررة ٤٥ م º .

An amperometric sensor for the determination of benzophenone in food packaging materials based on the electropolymerized molecularly imprinted poly-o-phenylenediamine film

Benzophenone is one of the most commonly used photoinitiators of UV-cured inks on food packaging materials and can migrate into foodstuffs. In this study, an amperometric benzophenone sensor based on molecularly imprinted polymer (MIP) was successfully constructed for the first time. The sensor was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode (GCE) in the presence of template benzophenone, and then removing the template by immersing the poly-o-phenylenediamine film-modified GCE in ethanol. The molecularly imprinted sensor was tested in the presence or absence of benzophenone by cyclic voltammetry and linear sweep voltammetry to verify the changes in the redox peak currents of potassium ferricyanide. The sensor responded sensitively to benzophenone over a linear range of 0.05–5μM with a detection limit of 10nM. The imprinted sensor showed high recognition ability for benzophenone and was successfully applied to the determination of benzophenone in food packaging material samples.

Lycopene control of benzophenone-sensitized lipid peroxidation

Lycopene antioxidant activity in the presence of two different mixtures of phospholipids in hexane solution, under continuous regime of UV-irradiation from three different ranges (UV-A, UV-B, and UV-C) has been evaluated in this work. Lycopene expected role was to control lipid peroxidation, by scavenging free radicals generated by UV-irradiation, in the presence and in the absence of selected photosensitizer, benzophenone. This work shows that lycopene undergoes to UV-induced destruction (bleaching), highly dependent on the incident photons energy input, more expressed in the presence than in the absence of benzophenone. The further increase (“excess”) of its bleaching is undoubtedly related to the further increase of its antioxidant activity in the presence of benzophenone, having the same cause: increase of (phospholipids peroxidation) chain-breaking activities.

UV-induced change in quercetin antioxidant activity toward benzophenone initiated lipid peroxidation

The aim of this work is to estimate the degradation and change in antioxidant activity of quercetin in the presence of two different mixtures of phospholipids in methanol solution, under continuous UV-irradiation from three different sub-ranges (UV-A, UV-B and UV-C), in the presence and in the absence of selected UV-absorbing photosensitizer, benzophenone. Quercetin is employed to control lipid peroxidation process generated by UV-irradiation, by absorbing part of the UV-incident light, or/and by scavenging the involved, created free radicals. The results show that quercetin undergoes to irreversible destruction, highly dependent on UV-photons energy input, more expressed in the presence than in the absence of benzophenone. In the same time quercetin expresses suppression effect on lipid peroxidation processes in UV-irradiated phospholipid mixtures in both cases - absence or presence of benzophenone (more or less effective, respectively). In UV-C-irradiated mixtures, benzophenone photosensitizing function is significantly reduced due to its strong absorption in the same UV-C spectral range, therefore affecting less antioxidant activity of the remained quercetin.

Beta-carotene suppression of benzophenone-sensitized lipid peroxidation in hexane through additional chain-breaking activities

The aim of this work is to estimate the antioxidant activity of β-carotene in the presence of two different mixtures of phospholipids in hexane solution, under continuous UV-irradiation from three different ranges (UV-A, UV-B, and UV-C). β-Carotene is employed to control lipid peroxidation process generated by UV-irradiation, in the presence and in the absence of selected photosensitizer, benzophenone, by scavenging the involved, created free radicals. The results show that β-carotene undergoes to a substantial, probably structural dependent destruction (bleaching), highly dependent on UV-photons energy input, more expressed in the presence than in the absence of benzophenone. The additional bleaching is synchronized with the further increase in β-carotene antioxidant activity in the presence of benzophenone, implying the same cause: increase in (phospholipids peroxidation) chain-breaking activities.

Photochemical Generation of Polymeric Alkyl-C60 Radicals: ESR Detection and Identification

Electron spin resonance (ESR) spectroscopy has been used to study various alkylfullerene radical adducts generated by UV-photoinitiated reactions between low-density polyethylene (LDPE) and C60 in the presence or absence of benzophenone (BP) as a photoinitiator under different conditions. Photolysis of LDPE/BP/C60 mixture in toluene at 323 K produced benzylfullerene (RC60) radical adducts, showing a strong ESR signal of g = 2.002 70 with several well-resolved pairs of 13C satellites. On the other hand, a well-resolved ESR spectrum characteristic of polymeric alkylfullerene (PC60) radical adducts was observed during UV irradiation of the LDPE/BP/C60 in benzene or in the molten state (413 K). Detailed analyses of hyperfine structures (hfs) revealed that the ESR spectrum for PC60 radical adducts consisted of three components: (1) a broad singlet at g = 2.002 50 arising from C60 radical anions; (2) an innermost pair of 13C satellites; and (3) a 12-line spectrum superimposed on the broad singlet. Spectroscopi...

Photo-oxidation of oxazolidones and hydantoins in the presence of benzophenone

Irradiation in the presence of benzophenone and oxygen of nitrogen-containing heterocycles having an NCO group yields products arising out of regioselective oxidation α to the nitrogen atom. Direct irradiation (in the absence of benzophenone and oxygen) of 5-methyl- and 5,5-dimethyl-hydantoins yields allophanates. The first step of this reaction involves the homolysis of the C(4)–C(5) bond of the hydantoin.

Photosensitized cyclodimerizations of 4‐vinylpyridine, 2‐vinylpyridine, and 2‐vinylquinoline

AbstractIrradiations of 4‐vinylpyridine and of 2‐vinylpyridine in either f‐butyl alcohol or benzene, with benzophenone, yielded a single photodimer, which, on the basis of the nmr and mass spectral data, was assigned the trans‐head‐to‐head structure (I). Upon irradiation in either t‐butyl alcohol or benzene, in the presence of benzophenone, 2‐vinylquinoline gave a single photodimer whose structure and stereochemistry were also determined from the nmr and mass spectral evidence as (V). Irradiation of 2‐vinylquinoline in benzene, in the absence of benzophenone, also gave rise to the same photodimer, but, when t‐butyl alcohol or methanol was used as a solvent, no dimer formation was observed.

Photoinitiation. III. Polymerization of acrylonitrile photoinitiated by benzophenone in the presence of naphthalene

AbstractThe polymerization of acrylonitrile photoinitiated by radiation of wavelengths 313 and 365 nm in the presence of benzophenone and naphthalene was studied. If radiation of wavelength λ = 313 nm which is absorbed by naphthalene as well as by benzophenone is used, a decrease of the acrylonitrile polymerization rate and of the molecular weight of the polymer is observed in comparison with the polymerization taking place in the absence of benzophenone. If a radiation of wavelength (λ = 365 nm) at which only benzophenone is excited is used, addition of naphthalene to the system acrylonitrile–benzophenone enhances the polymerization rate. The reaction mechanism which accounts for the observed behavior of the acrylonitrile polymerization is discussed.

Reactive polypeptides. II. Photochemistry of poly(γ‐cinnamyl L‐glutamate)

AbstractPoly(γ‐cinnamyl L‐glutamate) was irradiated in the presence and absence of benzophenone in dichloroethane. The irradiated polymers were analyzed by gas chromatography after hydrolysis. It was possible to assign the transformation in the presence of benzophenone to trans‐cis photoisomerization by comparing the effects with those observed for a model compound cinnamyl acetate. The equilibrium composition of cis and trans isomers in the photostationary state was similar for the model compound and the polypeptide. Photoisomerization was found to be accompanied by marked side reactions for the direct irradiation. Circular dichroism spectra were empolyed to study the structure, and no changes in the structure were found for the irradiated polymers.