Photochemistry bromine

Pyran-2-one, 5,6-dibromo-5,6-dihydro-reactions, 3, 735 Pyran-2-one, 5,6-dihydro-allylic bromination, 3, 799 dehydrogenation, 3, 724, 799 H NMR,3, 581 synthesis, 3, 841, 843 Pyran-2-one, 4,6-dimethyl-irradiation, 3, 677 photochemistry, 3, 678 Pyran-2-one, 5,6-dimethyl-chloromethylation, 3, 680 conformation, 3, 631 Pyran-2-one, 5-f ormyl-IR Spectra, 3, 595 Pyran-2-one, 6-formyl-IR spectra, 3, 595 Pyran-2-one, 5-halo-synthesis, 3, 799 Pyran-2-one, 3-hydroxy-IR spectra, 3, 595 Pyran-2-one, 4-hydroxy-methylation, 2, 57 3, 676 pyran-4-one synthesis from, 3, 816 reactions with phosphorus oxychloride, 2, 57 synthesis, 3, 792, 794, 795, 798 tautomerism, 2, 56 3, 642 Pyran-2-one, 4-hydroxy-6-methyl-methylation, 3, 692 reactions... 

One example of selective photochemistry with lasers is the gasphase photochemical addition of bromine to olefin molecules induced by the monochromatic light near 6940 A from a pulsed, tunable ruby laser, as studied by Tiffany... 

The photochemistry of bromine nitrate is expected to have similar reaction channels ... 

Finlayson-Pitts, B. J., F. E. Livingston, and H. N. Berko, Ozone Destruction and Bromine Photochemistry at Ground Level in the Arctic Spring, Nature, 343, 622-625 (1990). 

The reactions initiated by atoms do not belong in the realm of photochemistry since under a given set of experimental conditions these reactions will be the same no matter how the atoms are formed. The classical work on reactions initiated by chlorine after absorption of light has shown that chain reactions may be started38. The thermal and photochemical hydrogen-bromine reactions lead to the same products with the same mechanism, the one distinction being that bromine atoms... 

In principle, the photoreactions of CT s are able to offer a great number of photoinitiator systems for radical polymerization. But, so far, this subject has only received little attention, and the current knowledge relative to the photochemistry of such complexes is poor. In addition to the amine complexes mentioned above, chinoline-bromine [124-127], chinoline-chlorine [128], 2-methylpyridine-chlorine [129], pyridine-bromine [130], IV-vinylpyrrolidone-bromine [131], acridone-bro-mine [132], acridone-chlorine [133], benzophenone-S02 [134], isoquinoline-S02 [135, 136], and 2-methylquinoline-S02 [136] combinations are used for radical polymerization of AN, alkyl methacrylates, acrylic and methacrylic acid, and for... 

Changes in polar O3 column densities during springtime might influence the photochemistry during the time of the boundary layer ODEs, especially in the southern hemisphere. Increases in air temperatures will reduce the polar ice coverage (especially in the Arctic). This means the areas of fresh sea ice formation in winter will increase with time, and thereby the most important source for bromine in polar regions. 

Finlayson-Pitts B. J., Livingston F. E., and Berko H. N. (1990) Ozone destruction and bromine photochemistry at ground level in the Arctic spring. Nature 343, 622—625. 

Photochemistry of polyhaloalkanes results in a C—X bond fission of the weakest bond in the initial step. For example, irradiation of bromotrichloromethane affords trichloromethyl and bromine radicals, which add to styrene to obtain l-bromo-3,3,3-trichloropropylben-zene (477) in 78% chemical yield (Scheme 6.231).1338... 

It is reported that 1,4-dibromonaphthalene can be formed selectively and in 90% yield by irradiation of naphthalene and 1-bromonaphthalene with stoichiometric amounts of bromine and with the minimum amount of CH2CI2 as solvent at —30 to — SO C. In contrast, l,2,3,4,5-pentabromo-l,2,3,4-tetrahyd-ronaphthalenes result from irradiation of 1-bromonaphthalene in CCI4 at — 30°C, whereas at 77°C only 1,5-dibromonaphthalene is formed and in 80% yield. Two of the more unusual examples of the photoinduced introduction of groups into aromatic rings which have been described within the year are the formation of 1-cyanopyrene in a yield of up to 73% from irradiation at the interface of a solution of pyrene and 1,4-dicyanobenzene in propylene carbonate and an aqueous solution of NaCN in a polymer microchannel chip, and the addition of a variety of groups e.g. NH2, OMe, CN, and CO2H) to coronene by irradiation of arene-ice mixtures at low temperature and pressure." The latter work provides the first experimental evidence that such functionalized arenes, which are detected in primitive meteorites and interplanetary dust particles, may have arisen, at least in part, from photochemistry in ice. 

In the course of carrying out the benzophenone photochemistry described in the previous section, we noted that the use of CCI4 as solvent led to the formation of some chlorinated steroid products. Therefore we examined such halogenations further [36], and found that the simple free-radical chlorination of cholestanyl acetate with phenyliodine dichloride afforded the 9-chloro- and 14-chlorosteroids as the major products. Similar results were seen in bromination by bromotrichloromethane. We extended such selective radical halogenations to suppress reactions other than at C-9 and C-14 by appropriate substituent effects, but more significantly we used tethers to achieve essentially complete selectivity in the halogenations [36]. 

Seller, R., Nicovich, J.M., Wine, P.H. Bromine nitrate photochemistry quantum yields for O, Br, and BrO over the wavelength range 248-355 nm. J. Phys. Chem. A 106, 8378-8385 (2002) Stevens, C.G., Swagel, M.W., Wallace, R., Zare, R.N. Analysis of polyatomic spectra using tunable laser-induced fluorescence applications to the NO2 visible band system. Chem. Phys. Lett. 18,465 9 (1973)... 

Bromine is used to manufacture ethylene dibromide as an antiknock agent for gaso-iine. Bromine is used as an intermediate to make fumigants such as methyl bromide. It is commonly used to produce flame retardants for plastics and in photochemistry and dye synthesis. 

Photochemistry.—Benzo[b]thiophen-3-carbaldehydes and -carboxylic acid have been obtained uia light-catalysed N-bromosuccinimide bromination of 3-methylbenzo[b]thiophen. The photochemical behaviour of benzo[b]thiophen was found to differ from that of thiophen. It does not undergo photoisomerization and is not converted into an indole when irradiated in the presence of a primary amine. Its photochemical behaviour resembles that of naphthalene. Photolysis of various... 

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