Experimental procedure irradiation

Miriyala and Williamson have described the synthesis of /i-kctocarboxam idcs from primary and secondary amines and 2,2-dimethyl-2H,4H-l,3-dioxin-4-ones as reactive a-oxoketene precursors (Scheme 6.158) [304], The experimental procedure involved heating a mixture of the dioxinone with 2-3 equivalents of the amine at ca. 180 °C for 1-3 min under solvent-free conditions in a sealed vessel by microwave irradiation. A small collection of 18 /3-ketocarboxamides was prepared in very high yields using this protocol. 

A facile method for the oxidation of alcohols to carbonyl compounds has been reported by Varma et al. using montmorillonite K 10 clay-supported iron(III) nitrate (clayfen) under solvent-free conditions [100], This MW-expedited reaction presumably proceeds via the intermediacy of nitrosonium ions. Interestingly, no carboxylic acids are formed in the oxidation of primary alcohols. The simple solvent-free experimental procedure involves mixing of neat substrates with clayfen and a brief exposure of the reaction mixture to irradiation in a MW oven for 15-60 s. This rapid, ma-nipulatively simple, inexpensive and selective procedure avoids the use of excess solvents and toxic oxidants (Scheme 6.30) [100]. Solid state use of clayfen has afforded higher yields and the amounts used are half of that used by Laszlo et al. [17,19]. 

The. experimental procedure was to use a BeO-B sample to adjust the total system such that the 10B4+ beam was maximized and the accelerator voltage was well-stabilized on the 9Be4+ beam. The mass -10 Faraday cup was then replaced by an energy-telescope preceded by a 16 mg/cm2 absorber, which prevented any 10B and other, higher-mass adventitious ions from over-loading the detectors. (Since the mass-10 cup is rotated into position in front of the detectors, the switch can be done easily, and it is possible to easily check the system periodically.) The irradiated BeO sample with 10Be/9Be ratio of 10 9 was arbitrarily selected as a standard and measurements of all other samples were made with respect to this standard. 

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The experimental procedure adopted in the thermochemical study of reaction 10.17 was fairly simple. First, an electrical calibration was made. Then, after balancing the light input to the cells, 2.7 cm3 of a 7 x 10-3 mol dm-3 solution of hrms-azobenzene in heptane was added to the photochemical reactor. This solution was irradiated for a certain period (1.5-3.8 h) with 436 nm light, and the thermogram was recorded. The area of this thermogram multiplied by the calibration constant (e) gives A0b H. 

The performance and scalability of the various techniques is most easily compared in a side-by-side format. With respect to experimental procedures, it is now recognized that many chemical conversions (e.g., formation of C-N or C-C bonds) that were reported to require solid supports with catalytic activity and microwave irradiation (and thus introduced environmental concerns) do not require such auxiliaries or irradiation. They occur exothermally at low temperatures with quantitative yields and without solvent-consuming workups even on a large scale. 

In a convenient experimental procedure, nitrogen heterocycles 3 are alkylated by a mixture of a carboxylic acid 4 and [bis(trifluoroacetoxy)iodo]benzene in boiling benzene or under irradiation in dichloromethane at room temperature (Scheme 2) [11, 12]. A similar procedure has been used for the stereoselective synthesis of C-nucleosides and their analogs via photolysis of the gulonic acid derivatives, (diacetoxy)iodobenzene, and the appropriate heteroaromatic bases [13]. 

In contriving optimal photosplitting of water, it is desirable to irradiate two photoelectrodes. In considering photoanodes, it is difficult to achieve suitable properties with semiconducting oxides, which tend to be stable under oxygen evolution. On the other hand, arsenides and sulfides appear to have more suitable photoelectrochemical properties, but are clearly unstable when exposed to Oz evolution, (b) What experimental procedures could be used to overcome this difficulty (Bockris)... 

Bromination of 14 is achieved by reaction with three equiv of W-bromo-succinimide in boiling benzene under light irradiation. This reaction gives a mixture of the desired tribromide derivative 15a and also the dibromide and tetrabromide derivatives, 15b and 15c respectively (Scheme 9.12). The separation of these compounds is very difficult, and so the mixture is best used without purification for the next step. The experimental procedure is given in Protocol 10. 

Yen and co-workers [54] have reported an efficient one-pot procedure for the synthesis of 4,6-diaryl-2-pyridinones 3 based on a cyclocondensation reaction of iV-ethoxycarbonyl-methylpyridinium chloride or iV-carbamoylmethyl p3Tidinium chloride with an aromatic aldehyde and a substituted acetophenone. The MCR was performed under microwave irradiation (domestic oven) with NTUOAc/AcOH as the reaction medium. The nature of the substituents on the aromatic aldehyde and ketone seem to have little influence on the obtained yields. The highlights of this approach include a convenient and simple experimental procedure with easy product isolation (Scheme 3). 

Scientists in the United States and elsewhere quickly confirmed the idea of uranium fission, using other experimental procedures. For example, a cloud chamber is a device in which vapor trails of moving nuclear particles can be seen and photographed. In one experiment, a thin sheet of uranium was placed inside a cloud chamber. When it was irradiated by neutrons, photographs showed a pair of tracks going in opposite directions from a common starting point in the uranium. Clearly, a nucleus had been photographed in the act of fission. 

In addition, another irradiated methane hydrate (sample F) sample was annealed at 253 K for 3 hours (sample F ) were measured by Raman spectroscopy. A scheme of experimental procedure is shown in Figure 1. 

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