Spectroscopic Analysis of Ethers

FIGURE 16.7 Nucleophilic substitution at the primary carbon of adenosine triphosphate (ATP) by the sulfur atom of methionine yields S-adenosylmethionine (SAM). The reaction is catalyzed by an enzyme. 

NMR The chemical shift of the proton in the H—C—O—C nnit of an ether is very similar to that of the proton in the H—C—OH unit of an alcohol. A range 8 3.3-4.0 ppm is typical. In the NMR spectrum of dipropyl ether, shown in Fignre 16.9, the assignment of signals to the varions protons in the molecnle is 

FIGURE 16.8 The infrared spectrum of dipropyl ether (CH3CH2CH2OCH2CH2CH3). The strong peak near 1100 cm Ms due to C—O—C stretching. 

NMR The carbons of an ether function (C—O—C) are about 10 ppm less shielded than those of an alcohol and appear in the range 8 57-87 ppm. The chemical shifts in tetrahydrofuran offer a comparison of C—O—C and C—C—C units. 

UV-VIS Simple ethers have their absorption maximum at about 185 nm and are transparent to ultraviolet radiation above about 220 nm. 

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The most characteristic feature in the spectroscopic analysis of ethers is the strong band of C-0 stretching. It occurs in the 1060-1300 cm range. In this region, many bands are present, but this alone does not establish the presence of an ether. For note, alcohols, carboxylic acids, and esters also show C-0 stretching. They can be eliminated as possibilities, however, by the fact alcohols would also show the strong and broad 0-H stretch in the 3200-3600 cm , car-... 

Although many organic chemists still use 3,4-dihydro-2H-pyran [214,215] for the protection of OH groups, protection with ethyl vinyl ether has distinct advantages. Ethyl vinyl ether [216] is much cheaper than the cyclic ether, but chemists working in a university will perhaps find the advantage of the easier protection and deprotection more important Furthermore, H NMR-spectroscopic analysis of the adducts from ethyl vinyl ether in many cases will be easier. 

The materials analyzed were blends of polystyrene (PS) and poly(vinyl methyl ether) (PVME) in various ratios. The two components are miscible in all proportions at ambient temperature. The photooxidation mechanisms of the homo-polymers PS and PVME have been studied previously [4,7,8]. PVME has been shown to be much more sensitive to oxidation than PS and the rate of photooxidation of PVME was found to be approximately 10 times higher than that of PS. The photoproducts formed were identified by spectroscopy combined with chemical and physical treatments. The rate of oxidation of each component in the blend has been compared with the oxidation rate of the homopolymers studied separately. Because photooxidative aging induces modifications of the surface aspect of the material, the spectroscopic analysis of the photochemical behavior of the blend has been completed by an analysis of the surface of the samples by atomic force microscopy (AFM). A tentative correlation between the evolution of the roughness measured by AFM and the chemical changes occurring in the PVME-PS samples throughout irradiation is presented. 

The oligomers of methyl vinyl ether were synthesized by the successive addition of methyl vinyl ether to the corresponding dimethyl acetal in the presence of BF3OEt2 in toluene the steric course of each addition step was studied by H NMR spectroscopic analysis of the oligomers from dimer to pentamer.248 The meso-diad probability of each addition step was found to be almost constant, indicating that the stereoregulation obeys Bernoullian statistics. 

Synthesis and Characterization of Poly(isobutylene-b-mcthyl vinyl ether) Light-Scattering Studies of Poly(ethylene-co-butylene) Polystyrcne-Moc -poly(2-cinnamoylethyl methacrylate) Adsorption IR Spectroscopic Analysis of Poly(l/f,l/f-fluoroalkyl Ot-fluoroacrylate)... 

The general synthesis procedure of heterocyclylmethylphosphonates IG-U is introduced in Sect. 9.1.7. IG-U were soluble in a variety of organic solvents such as benzene, diethyl ether, ethyl acetate, and so on. They were stable to hght and air at room temperature but easily decomposed under the acidic or basic conditions. Their structures were characterized by H NMR, NMR, 1R and MS, and confirmed by elementary analysis. Spectroscopic analysis of some representative IG-U are given in the next section. 

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