Chemical reaction in electric discharges. Part III. The meaning of Φ, the electrochemical analogue of the photo-chemical quantum yield, and the factors controlling Φ in the stationary state

1940 ◽  
Vol 36 (0) ◽  
pp. 1072-1087 ◽  
Author(s):  
R. Winstanley Lunt ◽  
G. E. Swindell
Keyword(s):  
Quantum Yield ◽  
Stationary State ◽  
Chemical Reaction ◽  
Electric Discharges

scholarly journals The photochemical Beckmann rearrangement

1969 ◽  
Vol 47 (1) ◽  
pp. 51-62 ◽  
Author(s):  
H. Izawa ◽  
P. De Mayo ◽  
T. Tabata
Keyword(s):  
Quantum Yield ◽  
Stationary State ◽  
Irradiation Time ◽  
Hydrogen Abstraction ◽  
High Energy ◽  
Beckmann Rearrangement ◽  
Direct Irradiation ◽  
Temperature Irradiation ◽  
Oxygen Migration ◽  
Favorable Conditions

The direct irradiation of aryl aldoximes gives the amide (the photochemical Beckmann rearrangement) by intramolecular oxygen migration. This has been shown by the rearrangement of 18O-labelled benzaldoxime in the presence of p-tolualdoxime: no exchange of label was observed.The rearrangement usually gives the amide, but in the case of the anisyl derivative the anilide was also obtained. The highest quantum yield for benzamide formation noted (in acetic acid) was 0.034, but the figure is dependent on irradiation time. The results of low-temperature irradiation suggest that an oxazirane is an intermediate. Phenyl-N-methyl oxazirane is converted into the amide on irradiation (though not thermally) and it seems likely that the reaction is induced, under the conditions of the reaction, by benzylic hydrogen abstraction by thermally produced small amounts of benzaldehyde; a fact which may explain the variation in quantum yield of amide formation with extent of irradiation. An additional route from oxazirane to amide may also be available.The activation of the oxime by high energy sensitizers under the most favorable conditions gives Φamide = 0.002, and so a singlet pathway for oxazirane formation is preferred. The main route for energy degradation appears to be by syn–anti isomerism. This can be induced by a variety of sensitizers and so can be a triplet process. The direct irradiation of benzaldoxime leads to isomerism with Φαβ = 0.40 and Φβα = 0.38. From these figures, together with the composition of the stationary state found, the composition of the sensitized stationary state can be calculated in fair agreement with the experimentally found value. This suggests that the isomerization following direct irradiation is also a triplet process.In a single example of an aralkyl ketoxime (p-anisylmethyl ketoxime) irradiation products of both aryl and alkyl migration, were found.

scholarly journals On chemical reaction in the electric discharge. I—The chemical effects of impulse discharges

1935 ◽  
Vol 152 (875) ◽  
pp. 158-171 ◽  
Keyword(s):  
Chemical Reaction ◽  
Electric Discharge ◽  
Discharge Tube ◽  
Atomic Hydrogen ◽  
Electric Discharges ◽  
Active Nitrogen ◽  
Atom Concentration ◽  
Chemical Effects ◽  
Spark Gap ◽  
In Series

Although a very large number of studies has been made upon the chemical reactions which can be induced by electric discharges, the effects of controlled condenser sparks appear to have been neglected, with one exception. Wrede has shown that if a large condenser (8 mfd) is charged to a high potential, and then allowed to discharge through a gas at low pressure, a spark gap being inserted in series with the discharge tube proper to increase the breakdown voltage, then hydrogen, oxygen, and nitrogen may be dissociated to the extent of 80, 60, and 40% respectively, the atom concentration being measured upon a most ingenious “diffusion gauge.” The Wrede discharge has been extensively employed by Steiner and his associates in a series of semi-spectroscopic investigations upon active nitrogen and atomic hydrogen, but its use as a means of effecting chemical reaction has not so far received attention.

Directional observation on lipid of male nectary of Lindera megaphylla hemsl. by the rapid embedding method with polyethylene glycol (PEG)

1990 ◽  
Vol 48 (3) ◽  
pp. 718-719
Author(s):  
Dai Dalin ◽  
Guo Jianmin
Keyword(s):  
Electron Microscope ◽  
Polyethylene Glycol ◽  
Chemical Reaction ◽  
Traditional Method ◽  
Osmium Tetroxide ◽  
Unsaturated Lipid ◽  
Embedding Method ◽  
Long Period ◽  
New Methods

Lipid cytochemistry has not yet advanced far at the EM level. A major problem has been the loss of lipid during dehydration and embedding. Although the adoption of glutaraldehyde and osmium tetroxide accelerate the chemical reaction of lipid and osmium tetroxide can react on the double bouds of unsaturated lipid to from the osmium black, osmium tetroxide can be reduced in saturated lipid and subsequently some of unsaturated lipid are lost during dehydration. In order to reduce the loss of lipid by traditional method, some researchers adopted a few new methods, such as the change of embedding procedure and the adoption of new embedding media, to solve the problem. In a sense, these new methods are effective. They, however, usually require a long period of preparation. In this paper, we do research on the fiora nectary strucure of lauraceae by the rapid-embedding method wwith PEG under electron microscope and attempt to find a better method to solve the problem mentioned above.

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