Olefins absorption, maxima

Electronic spectra of alcohols and olefins in strong proton acids (H2SO4) were obtained by Rosenbaum and Symons22. They observed, for a number of simple aliphatic alcohols and olefins, absorption maximums around 290 nanometers and ascribed this absorption to the corresponding alkyl cations. 

However, in the presence of NaN3, Br2 is rapidly transformed into a new species having an absorption maximum around 312 nm. This species is most likely BrN3, a material shown (75) originally by Hassner to be capable of ionic electrophilic addition to olefins. It has been demonstrated, (16) at least in neutral aqueous solutions, that BrN3 reacts with azide ions to give N2 and Br ... 

The initial excitation is of the carbonyl compound, rather than the olefin, since the reaction can be brought about by irradiation in a region where only the carbonyl compound absorbs. The simple olefins are essentially transparent at wavelengths longer than 250 m[x. The absorption maximum for the transition of simple olefins is shorter... 

A relatively sharp absorption in the UV region due to alkyl radicals is observed in electron-pulse irradiated alkanes [93]. It has an absorption maximum at 240 nm in n-dodecane and cyclohexane. (Mehnart et al. did not see this absorption maximum but found another short-lived absorption band peaking at 270 nm in n-hexane, n-heptane, and n-hexadecane containing 10 mmol dm-3 CC14. This absorption band was assigned to olefin monomer radical-cation... 

In a given series of olefins, the absorption intensity at the absorption maximum seems to increase with increasing symmetry of the molecule20. Thus, the intensity increases in the senes 4-methyl-f/my-2-pentene < tram-2-hexene = /ra w-2-pentene < toms-2-butene < ftm -3-hexene. The vibrational structure and the absorption intensity of the bands decrease in solution... 

Triplet Triplet Absorption Spectra. Triplet states of stilbenes and analogues with a fixed olefinic bond, which are unable to photoisomerize, were observed at low temperatures by flash photolysis (Tables 16a and b). T-T absorption spectra of a series of stilbenes were first reported by the group of Schulte-Frohlinde [16]. These findings were confirmed by Herkstroeter and McClure [96] and extended by others [412 415]. The properties of the "stiff stilbenes turned out to be quite consistent with those of the trans-stilbenes. cis-stilbene evaded spectral characterization even at — 196°C, probably because of rapid twisting, but an absorption maximum at 25.5 x 103cm 1 may be estimated on the basis of results with 5H-dibenzo[a,d]cycloheptane as model compound [96]. In EPA at — 196°C,... 

These were pyrolyzed directly in a 25-mL distillation flask fitted with a 3-in. Vigreux head. The sulfite was heated to 200°C under nitrogen at atmospheric pressure for 30 min. Vacuum (1 mmHg) was then applied, and the decomposition products were distilled slowly from the reaction mixture. The olefins were condensed in the air-cooled receiver, and the methanol and sulfur dioxide were allowed to pass into the dry ice trap. The yield of olefin was 86% from the cis isomer and 76% from the trans isomer.Analysis for the percentage of 1-substituted and 3-substituted cyclohexene was made by oxidation to the sulfones, and the position of the absorption maximum in the ultraviolet spectra was determined. The oxidized product from the cis isomer had an absorption maximum at 229 m u, corresponding to that of a mixture of 40% l-j -tolylsulfonyl-l-cyclohexene and 60% 3-p-tolylsulfonyl-i-cyclohexene. The oxidized product from the trans isomer had its absorption maximum at 232 m/z, corresponding to 80% of the 1-substituted isomer. 

A variety of compounds containing an olefinic bond, such as ethylene, allylisopropylacetamide (AlA), and secobaibital, can form covalent adducts on the nitrogen of the porphyrin group of the prosthetic heme leading to inactivation [382-385], Secobaibital has been shown to completely inactivate CYP2B1 with only partial loss of the heme chromophore [384, 386, 387], Isolation of the modified CYP2B1 protein and the A -alkylated porphyrins indicates that the reactive compound partitions between protein modifiea-tion, A -alkylation of the heme, and formation of an epoxide metabolite in the ratio of 0,2 0.8 59, respectively [387] (Fig, 5.17), The formation of a heme adduct in the active site of CYP2B1 was confirmed spectrally based on its typical absorption maximum at 445 nm, a characteristic fea-... 

A rectification zone in which the dissolved bntenes fraction is displaced from the solvent in countercurrent flow with butadiene t apdr, which is obtain by controlled reboiling of the extract. These butenes, which contain butadiene, are returned to the absorption zone. A sidestream is drawn off at a level where the olefin content is practically nil, the acenlene content low, and the 1,3-butadiene content a maximum. Separation takes place in a column with about 45 travs operatins at the bottom around 75 C at 0.7. 10 Pa. 

Table 6. Absorption characteristics of carbenium ions related to the cationic polymerisation of aromatic olefins, including model compounds. Only the longer wavelength maximum of each spectrum is given...

An indication of naphtha composition may also be obtained from the determination of aniline point (ASTM D-1012, IP 2), freezing point (ASTM D-852, ASTM D-1015, ASTM D-1493) (Fig. 4.2), cloud point (ASTM D-2500) (Fig. 4.3), and solidification point (ASTM D-1493). And, although refinery treatment should ensure no alkalinity and acidity (ASTM D-847, ASTM D-1093, ASTM D-1613, ASTM D-2896, IP 1) and no olefins present, the relevant tests using bromine number (ASTM D-875, ASTM D-1159, IP 130), bromine index (ASTM D-2710), and flame ionization absorption (ASTM D-1319, IP 156) are necessary to ensure low levels (at the maximum) of hydrogen sulfide (ASTM D-853) as well as the sulfur compounds in general (ASTM D-130, ASTM D-849, ASTM D-1266, ASTM D-2324, ASTM D-3120, ASTM D-4045, ASTM D-6212, IP 107, IP 154) and especially corrosive sulfur compounds such as are determined by the Doctor test method (ASTM D-4952, IP 30). 

The position of the absorption band is shifted slightly to the red with an increasing number of alkyl substituents. The maxima at 174-184.5 nm found for Z-l,2-disubstituted olefins are shifted to the red in E-isomers by 3-4nm and reach 186-189nm in 1,1-disubstituted olefins. Maxima of absorption bands are observed at 177-191 nm for trisubstituted and at 187-191 nm for tetrasubstituted olefins. The position of the maximum of the V - N band is further shifted to the red by a few nanometers in olefins with sterically demanding substituents like 66, 255b, and 263b. 

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