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Allylic absorptions

Figure 6.10 Relative allyl absorptions of EPM compounds cured with 2 phr of DCP and 3 phr of DATP, measured before and after acetone extraction [110]... Figure 6.10 Relative allyl absorptions of EPM compounds cured with 2 phr of DCP and 3 phr of DATP, measured before and after acetone extraction [110]...
Fig. 2.32. Time dependence of the allyl % absorption signal showing the approach to, and establishment of equilibrium in reaction (4,-4). T = 440 K, oxygen pressure = 5.44 Torr, hexadiene pressure = 166 mTorr, total pressure (argon) = 50 Torr. [Pg.204]

Two types of NMR absorptions are typically found in alkenes vinyl absorptions due to protons directly attached to the double bond (4.5-6.5 ppm) and allylic absorptions due to protons located on a carbon atom adjacent to the double bond (1.6-2.6 ppm). Both types of hydrogens are deshielded due to the anisotropic field of the r electrons in the double bond. The effect is smaller for the aUylic hydrogens because they are more distant from the double bond. A spectrum of 2-methyl-1-pentene is shown in Figure 3.38. Note the vinyl hydrogens at 4.7 ppm and the allylic methyl group at 1.7 ppm. [Pg.140]

One potentially important example of CIDNP in products resulting from a radical pair formed by electron transfer involves a quinone, anthraquinone j5-sulphonic acid (23). When irradiated in the presence of the cis-syn dimer of 1,3-dimethylthymine (24), enhanced absorption due to vinylic protons and emission from the allylic methyls of the monomer (25) produced can be observed (Roth and Lamola, 1972). The phase of the polarizations fits Kaptein s rules for intermediate X... [Pg.110]

In addition, a 532 (visible) or 355 (UV region) nm laser-induced photoisomerization of allylic alcohols to aldehydes catalyzed by [Fe3(CO)i2] or [Fe(CO)4PPh3] was developed by Fan [176]. In this reaction, key intermediates such as the 7i-allyl hydride species [FeH(CO)3(q -C3H3ROH)] (R = H, Me) were detected by pulsed laser FTIR absorption spectroscopy. These results strongly support the 7i-allyl mechanism of photoisomerization of allyl alcohols. [Pg.63]

In addition to the simple chemical methods for following these processes, infrared spectroscopy may also be used. In Fig. 9 is shown the spectrum of silica dried at 200°C before and after reaction with Zr(allyl)4- The characteristic absorption bands of the transition metal-allyl group are clearly displayed, also a significant reduction in the number of hydroxyl groups (3740 cm-1) is also clearly evident. [Pg.295]

It is more difficult to study equilibria between transition metal allyl compounds and bases, olefins, etc. In the case of Zr (allyl) 4 and pyridine, a valency change occurs as shown by Eq. (8), and the process is irreversible. The polymerization is considered to be preceded by displacement of one allyl group by the monomer (12) as shown in Eq. (1). In the methyl methacrylate/Cr(allyl)3 system it was not possible to detect any interaction between the olefin and catalyst with infrared radiation, even with equimolar concentrations because of the strong absorption by the allyl groups not involved in the displacement processes. Due to the latter, evidence for equilibrium between monomer and catalyst is less likely to be found with these compounds than with the transition metal benzyl compounds. [Pg.308]

Shida and Hamill23 found that the positive and negative molecular ions of 1,3-butadiene and its homologs have similar absorption spectra. Band maxima of the anions are not sensitive to substituent alkyl groups, whereas those of the cations are red-shifted as the number of substituent methyl groups increases. In alcoholic matrices the butadiene anions abstract the alcoholic proton to form an allylic radical (equation 23), as was proven by ESR spectroscopy. [Pg.335]

The infrared spectrum (neat) shows major absorptions at 2970, 2920, 2855, 1660, 1450, 1375, 1380, 1255, 835, and 660 cm.-1 The proton magnetic resonance spectrum (carbon tetrachloride solution, tetra-methylsilane reference) has a four-line multiplet in the 1.55-1.85 p.p.m. region characteristic of the olefinic methyl protons, two peaks in the 2.0-2.2 p.p.m. region due to the four allylic methylene protons, a doublet at 4.02 p.p.m. (,J = 7.0 Hz.) due to the allylic methylene protons adjacent to the chlorine, a very broad triplet at 5.09 p.p.m.,... [Pg.105]

A variety of alternating copolymers based on H-allyl- and N-(3-ethynylphenyl)maleimides, with substituted styrenes and vinyl ethers, have been prepared and their response to x-ray irradiation studied. Broadband and monochromatic x-ray exposures were conducted at the Stanford Synchrotron Radiation Laboratory. Sensitivities were observed to correlate with mass absorption coefficients of the copolymers and were found to be as high as 5-10 mJ/cm2. Preliminary fine line lithographic studies indicate 0.5 ion resolution capabilities. [Pg.172]

As expected, the incorporation of pendant unsaturation in the resists greatly enhances sensitivity as demonstrated by a comparison of the contrast curves for poly(N-aiiyl maleimide-VBC) and the structurally similar poiy(N-ethyl maleimide-VBC) (Figure 4). Both polymers have similar molecular weights and nearly identical mass absorption coefficients but the allyl-containing copolymer is 5X faster. [Pg.181]

The effect of increased x-ray absorption on sensitivity was explored by conducting monochromatic exposures of a bromine-containing resist, poly(N-allyl maleimide-vinyl benzyl bromide), at photon energies which bracket the bromine absorption edges between 1.6 and 1.8 keV contrast curves obtained for these monochromatic exposures are shown in Figure 7. The results are also plotted as l/D "5 vs absorption coefficient in Figure 8 the data accurately follow the predicted inverse relationship defined by Equation 1. [Pg.181]

In 1993, Blatter and Frei [34] extended the Aronovitch and Mazur [28] photo-oxidation into zeolitic media, which resulted in several distinctive advantages as described below. Irradiation in the visible region (633 nm) of zeolite NaY loaded with 2,3-dimethyl-2-butene, 16, and oxygen resulted in formation of allylic hydroperoxide, 17, and a small amount of acetone. The reaction was followed by in situ Fourier-transform infrared (FTlR) spectroscopy and the products were identified by comparison to authentic samples. The allylic hydroperoxide was stable at - 50°C but decomposed when the zeolite sample was warmed to 20°C [35]. In order to rationalize these observations, it was suggested that absorption of light by an alkene/Oi charge-transfer complex resulted in electron transfer to give an alkene radical cation-superoxide ion pair which collapses... [Pg.291]

Figure 7. EPR absorption derivative spectra of photoreduced active aconitase. Enzyme ( 5 mg/ml) in 100 mM Hepes, pH 7.5, plus 5 pM deazaflavin and 10 mM potassium oxalate was photoreduced in the presence of either A) 10 mM tricarb-allylate, B) 1 mM citrate, or C) 10 mM rrans-aconitate. The numbers above each spectrum are the g-values of prominent features. Experimental conditions for obtaining EPR spectra were 13 K, 1 milliwatt microwave power, 0.8 mT modulation amplitude, and 9.24 GHz microwave frequency. Figure 7. EPR absorption derivative spectra of photoreduced active aconitase. Enzyme ( 5 mg/ml) in 100 mM Hepes, pH 7.5, plus 5 pM deazaflavin and 10 mM potassium oxalate was photoreduced in the presence of either A) 10 mM tricarb-allylate, B) 1 mM citrate, or C) 10 mM rrans-aconitate. The numbers above each spectrum are the g-values of prominent features. Experimental conditions for obtaining EPR spectra were 13 K, 1 milliwatt microwave power, 0.8 mT modulation amplitude, and 9.24 GHz microwave frequency.
The corresponding lanthanide allyl, Sm(C5H5)2(allyl), has recently been reported and preliminary indications, based upon the absence of infrared absorptions in 1610—1640 cm i region, are consistent with a jr-bonded structure 149). Since the jr-bonded structure would be formally eight coordinate and the a-bonded structure only six coordinate, this would be the predicted ground state. [Pg.59]

Deuteration of one end of the allyl moiety in these compounds removes the equivalence of the two positions and in place of the single line for the terminal position, two separate absorptions should appear (W). One, in the normal decoupled spectrum, is a singlet for the hydrogen substituted carbon, and the other a weak quintet for the deuterated end which would be difficult to observe. These two signals would bracket the normal singlet. If a mixture of deuterated and undeuterated allyl compound is used, therefore, two easily observable peaks should appear, one in the normal position, the other shifted. In the spectra of allyllithium and allylsodium the line from the deuterated compound appeared I and 11 Hz upfield respectively, at 0°C, of the normal lines. The potassium compound only showed a somewhat broadened line. At -80°C the separation for allyllithium was 22 Hz. [Pg.90]

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for allyl alcohol is 2 ppm (4.8mg/m ) with a short-term excursion limit of 4ppm (9.5mg/m ) and a notation for skin absorption. [Pg.32]


See other pages where Allylic absorptions is mentioned: [Pg.156]    [Pg.230]    [Pg.232]    [Pg.156]    [Pg.230]    [Pg.232]    [Pg.28]    [Pg.634]    [Pg.268]    [Pg.212]    [Pg.424]    [Pg.879]    [Pg.27]    [Pg.49]    [Pg.248]    [Pg.368]    [Pg.132]    [Pg.28]    [Pg.110]    [Pg.24]    [Pg.253]    [Pg.568]    [Pg.175]    [Pg.184]    [Pg.325]    [Pg.338]    [Pg.232]    [Pg.66]    [Pg.83]    [Pg.9]   
See also in sourсe #XX -- [ Pg.254 ]




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