Photoinitiator acetonitrile

A more efficient photoinitiator has been designed by combining the Eosin-MDEA system with diphenyliodonium salt. The quantum yield of photopolymerization of methyl methacrylate (7 M) in acetonitrile is 30 with MDEA (0.1 M) and diphenyliodonium (0.05 M). The molecular weight of the isolated polymer is 55,000. In the absence of quantum yield and molecular weight, respectively. Thus, the presence of diphenyliodonium decreases the quantum yield of initiation by approximately 40% and increases the value of k3/kt by a factor of 6. 

A notable improvement in halogenation procedures by polyhalomethanes has been introduced by the group of Makosza616 who utilize 50% sodium hydroxide solution in the presence of triethylbenzylammonium chloride (TEBA) as a PTC. With this system phenyl-acetonitrile, fluorene and trichloroethylene are chlorinated by tetrachloromethane. Another useful PTC is Bu4NOH617. Similar procedures are practiced for the chlorination of sulfones618 and ketones619,620. The latter would normally react in secondary reactions under the above conditions. This is utilized for the direct a-hydroxylation of alkyl aryl ketones which are useful photoinitiators (equation 73)621 ... 

TABLE 12.1 Photophysical Properties of Photoinitiators in Acetonitrile and Other Nonviscous Solvents"... 

Other Elements - Though most of the focus on photoinitiated SET processes remains on the mesolytic reactions of radical cations, organoselenium radical anions, produced by SET sensitisation by 1,5-dimethoxynaphthalene, show synthetic promise as intermediates leading to unimolecular group transfer radical sequences. Thus, irradiation of (525) in the presence of 1,5-dimethoxynaphthalene and ascorbic acid as sacrificial electron donor in aqueous acetonitrile... 

Laboratory studies have provided evidence that photochemical and photocatalytic (Section 6.8) steps might play an important role in the formation of amino acids or various heterocyclic compounds from very simple molecules. For example, UVC irradiation of acetonitrile ammonia water mixture produces hexamethylenetetramine, a potential precursor of amino acids, via two-step photoinitiated fragmentation of acetamide (formed by acetonitrile hydrolysis) to give carbon oxide, which undergoes further photochemical and dark reactions (Scheme 6.184).1183... 

If the photoinitiated autocatalytic chain decomposition outlined in Scheme 12 operates at all, it should be specially important in the photolysis of (4-nitro)phenyl azide where formation of the dehydroazepine is a minor path and the triplet nitrene is formed rapidly. Indeed, Waddell and co-workers [110] report that the quantum yield for disappearance of this azide is 434 when a 0.1 M solution in acetonitrile is irradiated. However, attempts to reproduce this experiment reveal a quantum yield for disappearance of (4-nitro)phenyl azide in acetonitrile solution of 0.7 that is independent of starting azide concentration from 0.001 to 0.1 M [45]. 

At comparable concentrations of photoinitiator, reaction temperature, and time, solvents such as dimethyl sulfoxide and tert-butanol enhance the conversion while ethyl acetate, hexane, dimethylformamide, isopropanol, acetone, acetonitrile, and hexamethylphosphoramide reduce the conversion. Sulfalone has no solvent effect. 

The dispersed phase was injected through a 35 pm hole drilled in the acetate sheet. The formulation for the MIP synthesis, containing the template [(J, S)-propranolol], the monomer (methacrylic acid, MAA), the crosslinker (trimethylolpropane trimethacrylate, TRIM), the photoinitiator (2,2-dimethoxy-2-phenylacetophenone, DMPAP) and a porogenic solvent (acetonitrile), was emulsified at the T-junction with a mineral oil (heavy white) and then photopolymerized by UV irradiation in the spiral-like channel. The resulting MIP particles were compared with those obtained with a conventional batch process. The continuous microsystem-assisted process led to near-monodisperse particles (CV <2%), whereas the conventional process gave particles having a broad range of sizes (CV >10%). The same conclusion holds for... 

Ionic conductivity of PSEG gel PSEG having pendent vinyl groups was mixed with tetrafunctional thiol, pentaerythritol tetrakis(2-mercaptopropionate) (4TP-5), and photoinitiator, 2,2-dimethoxy-2-phenylacetophenone (DMPA), in acetonitrile. Lithium perchlorate was dissolved to the mixture. The ratio for [Li] / [-0-] was in the range of 0.025 - 0.317. After the polymer was crosslinked by UV light (1.6 J/cm% the obtained sample was dried for 48 h at ambient temperature. 

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