Rayonet lamp

LAMPS HPM = high-pressure mercury lamp MPM = medium-pressure mercury lamp LPM = low-pressure mercury lamp RUL = Rayonet lamps. 

Photolysis at 254 nm can be much faster than is often supposed. Thus, irradiation of the herbicide analog iV-4-azidobenzoyl-3,4-dichloroaniline in methanol is half complete in 20 sec (70 ixM, 4 cm from the Rayonet lamp), and on irradiation in chloroplast membranes the half-life increases only to 45 sec (150 /nM, 3.4 cm from the lamp)... 

As with cyclohexanone, the observed rearrangement of nopinone to (A) could be initiated by the rupture of the —C(0)—CH2— bond (in this case, on the side with the fewer substituents) to form a diradical followed by transfer of an H-atom. Transformations of (A) to (B) could be the ultimate result of the occurrence of a Norrish type-11 reaction. In these cases, the abstraction of a y-H-atom would not lead to the formation of two molecules, but an opening of the 4-membered ring. In photolyses of nopinone in benzene solution using a 300 nm Rayonet lamp, Shaffer et al. determined the quantum yield of disappearance (i diss) of nopinone to be 0.32. 

Since poly(phosphazenes) have potential use in outdoor environments, an investigation of their photochemical stability is imperative. The UV absorption spectra of PMPP in air-saturated methylene chloride before and after irradiation with 300 nm Rayonet lamps are shown in Figure 7. The absorption band around 240 - 260 nm, due to the perturbed phenyl groups on the phosphazene backbone, decreases as the irradiation is carried out, whereas the band around 270 nm increases. The decrease in 240 - 260 nm absorption indicates loss of phenyl groups attached to the -P=N- backbone of the polymer, while the new absorption band appearing around 270 nm is due to the photoproducts. 

Figure 7. UV spectra of PMPP (0.1 mg/m() in air-saturated CH2Q2 before and after irradiation using 300 nm Rayonet lamps (a) 0 min (b) 30 min (c) 1 h (d) 3 h.

Preparative Photolysis. The preparative photolysis of an aqueous solution (pH=8.5) of AETSAPPE (2.5 M) was conducted in a 1-inch diameter quartz test tube in a Rayonet Reactor (Southern New England Radiation Co.) fitted with 254 nm lamps. Within two hours the solution gelled and the reaction was terminated. Upon acidification the solution cleared, and the product could be re-precipitated by addition of base. This indicates loss of the thiosulfate functionality. The product was dissolved in dilute HC1, precipitated with acetone, and filtered. This process was repeated three times, and the final precipitate was washed with water. The product (20 to 30 mg) was dried in vacuo for 24 hours and stored in a dessicator until use. Comparison of the13 C NMR spectrum of the product with the starting AETSAPPE 13C NMR spectrum clearly shows that the thiosulfate methylene peak shifted upfield, from 39 ppm to 35 ppm. The complete 13 C NMR and IR analysis of the product were consistent with the disulfide product. Further, elemental analysis of the product confirmed that the product was the desired disulfide product 2-amino (2-hydroxy 3-(phenyl ether) propyl) ethyl disulfide (AHPEPED) Expected C 58.39, H 7.08, N 6.20, S 14.18 actual C 58.26, H 7.22, N 6.06, S 14.28. 

Preparative photolysis of AETSAPPE (0.25 M aqueous solution) at 254 nm (Rayonet reactor) resulted in the formation of the disulfide product 2-amino(2-hydroxy-3-(phenyl ether) propyl) ether disulfide (AHPEPED) as the primary photoproduct Photolysis of AETSAPPE at 254 nm (isolated line of medium pressure mercury lamp) resulted in rapid initial loss of starting material accompanied by formation (analyzed by HPLC) of AHPEPED (Figure 12a and 12b) (Scheme IV). Similar results were obtained for photolysis- at 280 nm. Quantum yields for disappearance of AETSAPPE and formation of AHPEPED at 254 nm and 280 nm are given in Table I. The photolytic decomposition of AETSAPPE in water was also accomplished by sensitization ( x =366 nm) with (4-benzoylbenzyl) trimethylammonium chloride (BTC), a water soluble benzophenone type triplet sensitizer. The quantum yield for the sensitized disappearance (Table I) is comparable to the results for direct photolysis (unfortunately, due to experimental complications we did not measure the quantum yield for AHPEPED formation). These results indicate that direct photolysis of AETSAPPE probably proceeds from a triplet state. 

Peijnenburg et al. (1992) investigated the photodegradation of a variety of substituted aromatic halides using a Rayonet RPR-208 photoreactor equipped with 8 RUL 3,000-A lamps (250-350 nm). The reaction of 1,3-dichlorobenzene (initial concentration 10 M) was conducted in distilled water and maintained at 20 °C. Though no products were identified, the investigators reported photohydrolysis was the dominant transformation process. The measured pseudo-first-order reaction rate constant and corresponding half-life were 0.008/min and 92.3 min., respectively. 

Reaction of telluroglycosides with alkynes (typical procedure) A mixture of the teUuro-glycoside (R=Ac) and phenylacetylene (2.55 g, 25.0 nunol) in a sealed Pyrex tube was irradiated with a UV lamp (Rayonet RMR-600 equipped with RMR-3500 A lamp (4.5 W X 8)) at 120°C for 20 h. Purification of the crude mixture by silica gel chromatography afforded the addition product (R=Ph) in 93% yield (3.02 g, 4.65 mmol) as a 47 29 13 11 mixture of the a-E, a-Z, jS-E and j8-Z isomers. The reaction in the dark at 120°C also gave the adduct in good yield. By the addition of 10 mol% of AIBN, the reaction proceeded under milder conditions (80°C). 

Nonanone is added to a concentrated solution of urea in methanol, which leads to crystal formation of the urea inclusion complex. After irradiation (313 nm line from a mercury lamp, isolated with an interference filter similar results are obtained with a Rayonet RPR-3000 lamp), the residue is taken up in methanol, then purified by VPC yield 40% d.r. (cisjtrans) 97 3. 

The submitters used a Rayonet Model RPR-100 Photochemical Reactor, manufactured by the Southern New England Ultraviolet Company, Middletown, Connecticut, equipped with 16 Cat. No. RPR-3500A fluorescent lamps (ca. 24 W. each), rated to emit maximally at 350 nm. Equally good results were obtained with lamps rated to emit maximally at 300 nm. For reactions on a... 

The photochemical and thermal transformations of 5-methyldihydro-thiazolo[3,2-a]pyridinium-8-olate (515) have been investigated. Irradiation using a Hanovia mercury lamp and Pyrex filter gives the isomeric pyridone 516 (4%). When a Rayonet reactor was used, a product which appears to be the valence tautomer 517 (6%) was isolated. Further irradiation of 517 gave... 

An inexpensive commercial apparatus or equipment adapted from other uses usually makes a light source suitable for most experiments with photochemical reagents. I have found the Rayonet Model RMR-400 minireactor to be very useful. The apparatus comprises a single lamp (26 cm... 

Multilamp apparatus are commercially available where between eight and 12 lamps are arranged in a circular fashion (40-60 cm diameter), with room inside to accommodate the vessel in which the solution to be irradiated is contained. These were initially marketed by the Southern New England Ultraviolet Co. under the name of Rayonet, now the name is often used for similar devices by other companies. These units are fitted with a fan which maintains the temperature below 40 °C otherwise, this might increase in such a confined space (see Figure 1.2). 

In contrast, in the photolysis of3,6-diphenylpyridazine-N-oxide 28 (R1 = R2 = Ph), a mixture of 3-benzoyl-5-phenylpyrazole 31 and 2,5-diphenylfuran 32 is formed. Diazoketone 29 (R1 = R2 = Ph) undergoes two competing reactions (i) thermal internal cyclization into the pyrazole 31 or (ii) photoinduced formation of a carbene leading to the final furan 32 (Scheme 12.9) therefore, the product distribution depends heavily on the reaction conditions. Thus, the formation of pyrazole 31 (75%) is favored over that of furan 32 (3%) by irradiation in acetone in a Rayonet reactor equipped with lamps irradiating at 350 nm. On the other hand, by irradiation with a Hanovia immersion lamp the yield of 31 decreases to 27%, whereas the yield of 32 increases to 67%. Moreover, the exclusive formation of the furan derivative 32 (43%) was observed by irradiation in the Rayonet reactor at low temperatures (—65 °C) [27]. 

Moreover, 4(or 5)-heteroarylmethyl-imidazoles 67 can be obtained by a photo-induced ring-contraction of 4-heteroaryl-substituted l,4(or 3,4)-dihydropyrimi-dines 65 easily prepared by reaction of the corresponding pyrimidine with hetero-aryllithium (Scheme 12.19). The irradiations were performed in acetone in a Rayonet preparative photoreactor equipped with RUL 300 lamps, and the products isolated in 43-57% yields. The reaction was determined by the anion-stabilizing effect of the heteroaryl group R1, which affects the thermal development of the bicyclic intermediate 66 [44]. 

The photolysis of some tetraaryl- and pentaaryl-pyridine N-oxides 150 (in benzene solution, in a Rayonet photoreactor by using 3500, 3000, and 2537 A lamps) allows the isolation ofhigh yields of the corresponding 1,3-oxazepines 151, the structures of which have been confirmed using X-ray crystallography for 151f (Scheme 12.39) [95]. 

A solution of 10 g of the (S.y-unsauiratcd bicyclic ketone 55 (cf. Sch. 30) in lOOOmL of acetone was purged with argon and irradiated in a water-cooled quartz vessel placed in a Rayonet RPR-208 photochemical reactor equipped with RUL-3000 lamps (/. 300 nm). Irradiation was continued for 72 h and the reaction was monitored by tic. After 72 h of irradiation, the conversion was 98% and the only detectable compound was the ODPM rearrangement product, tricyclo[3.3.0.0.0]octane-3-one 57. The solvent was distilled off and the residue was chromatographed over silica gel using a benzene/ ether solvent mixture. The product which was eluted (8.6 g) was further distilled under vacuum (50 °C/1 mm) to get the pure ODPM rearrangement product (tricyclic ketone 57) in 81% yield with 99.5% purity. The quantum efficiency determined was found to be 4> = 1.0. 

The PET-reaction of 79 (150 mg, 0.92 mmol) with TEA (1.0 g) in acetonitrile (12 mL) was conducted using a Rayonet photoreactor fitted with 300 20 nm lamps. After roughly five days of irradiation, the solvent was evaporated and 40 mg of 80 were isolated (27%, purified by column chromatography). 

A detailed description of the excimer set-up is given in reference [63a], The potassium salt of 12 g (31.7 mmol) A-phthaloylanthranilic acid amide 81 was irradiated in ca. 2000 mL of water/acetone (40 1) for 3h. The crude reaction mixture was extracted with ethyl acetate, the combined organic layers were dried over MgS04 and evaporated to give 5.5 g of the pyrrolobenzodiazepine 82 (52%, 4 6 tran cis-mixture). Alternatively, a Rayonet photochemical reactor equipped with phosphor coated 300 lOnm lamps can be used for reactions on a smaller scale. 

A solution of 96 mg (65 mmol) of 85 in 60 mL of cyclohexane in a quartz tube is deoxygenated by argon bubbling. Irradiation is carried out by means of a Rayonet photochemical reactor using 254 nm irradiation lamps during 4 h. The solution is evaporated and the residue is separated by preparative HPLC (RSiL, 10 mm, 25 x 1 cm, 5mL/min) using hexane/ethyl acetate (30 1) as eluant. Compound 86 (30 mg) is obtained as colorless oil, while... 

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