摘要:

AbstractThe spectrum of O2−ion was measured in several media. The absorption spectra of O2−in KCl discs, in acetonitrile and the reflection spectrum of KO2showed the maximum absorption in the range of 240 mμ.Solutions of KO2in liquid ammonia and ethylene diamine are characterized by an absorption band in the range of 370–380 mμ.It is shown that the latter absorption was misinterpreted and is due to the nitrite ion which is formed as a by‐product, rather than to t

ISSN:0021-2148    

DOI:10.1002/ijch.196700036

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY

摘要:

AbstractSolutions of o‐hydroxy or o‐methoxy azobenzene and phenylazonaphthalenes were studied spectroscopically and photochemically in a wide range of temperatures and solvents. All the hydroxy derivatives exist in solution in the azo form, except for (I) and (IV) which show an equilibrium between the azo and hydrazone forms. The latter predominates in (IV), and in (I) and (IV) is responsible for the so‐called luminescence of o‐hydroxy azo compounds. Luminescence was absent in the other compounds. All compounds except (IV) undergo distinct spectral changes when irradiated with ultraviolet or visible light at temperatures sufficiently low to prevent thermal reversion. In the methoxy derivatives the changes are due to cis‐trans isomerization, as shown also by the activation energy of 23 kcal/mole for the thermal reversion. The same explanation is assumed for the hydroxy compounds. The detailed involvement of the hydrazonic form of (I) in these spectral changes is not clear. In rigid media at −187°C, irradiation of (I) with visible light causes a different spectral change, tentatively ascribed to a “hydrazone” → “azo” conversion. Heating the solutions reverts the changes caused by irradiation. The kinetics of this reversion in the hydroxy compounds are complex, showing that the reactions are either catalyzed or else pass through a hydrazonic form, thereby proceeding with much smaller activation energies and frequency factors. It is suggested that several of the eight possible configurations of the “hydroxy” compounds serve as intermediates in the photochemical and thermal conversions, while others coex

ISSN:0021-2148    

DOI:10.1002/ijch.196700037

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY

摘要:

AbstractThe γ‐ray induced trans → cis isomerization of stilbene was investigated in solutions in the frozen organic solvents benzene, toluene, naphthalene, dibenzyl, and cyclohexane, and compared with fluid solutions in the same solvents, at appropriate temperatures. In dilute (up to 10−3M) solutions in benzene isomerization takes place in the frozen system at a higher rate than in the corresponding fluid system, with the ratio between these rates increasing with decreasing stilbene concentration. These results indicate that energy transfer in frozen benzene, and to stilbene embedded in it, takes place by a more efficient mechanism than the diffusional one operative in fluid solutions. It is suggested that singlet or triplet excitons are responsible for energy transfer within the microcrystals of the frozen benzene, and to stilbene molecules situated in specific (possibly surface) sites. At stilbene concentrations in the range 5 × 10−5to 10−1M G(trans → cis) in the frozen solutions is approximately constant (≃ 0.7), corresponding to G(excited stilbene) ≃ 1.4. This result is compatible with a mechanism involving efficient “harvesting” of all triplet benzene molecules in the solid under these conditions. Dilute solutions in toluene behave in a similar way, but no radiolytic isomerization takes place in solutions in solid naphthalene or dibenzyl, and also not in

ISSN:0021-2148    

DOI:10.1002/ijch.196700038

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY

摘要:

Abstract1‐Phenyl substituted cyclobutyl‐, cyclopentyl‐, and cyclohexylamines were obtained in the Hofmann reaction of 1‐phenylcycloalkanecarboxamides. 1‐Phenylcyclohexylamine was also prepared by the Ritter reaction of 1‐phenylc

ISSN:0021-2148    

DOI:10.1002/ijch.196700039

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY

摘要:

AbstractThe use of 2‐nitro‐4‐methoxy‐phenylsulfenyl‐(I) as an amino protecting group which is extremely sensitive towards electrophilic attack in the synthesis of amino penicillins (amino‐penicillin and DL‐α‐amino‐benzylpenicillin) is described. Synthesis of few protected dipeptides (2‐nitro‐4‐methoxyphenylsulfenyl‐L‐phenylalanyl‐L‐valine, 2‐nitro‐4‐methoxyphenylsulfenyl‐L‐phenylalanyl‐L‐phenylalanine and 2‐nitro‐4‐methoxyphenylsulfenyl‐L‐valyl‐L‐phenylalanine) demon

ISSN:0021-2148    

DOI:10.1002/ijch.196700040

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.196700041

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.196700042

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.196700035

出版商:WILEY‐VCH Verlag    

年代:1967

数据来源: WILEY