Spectroscopic Analysis of Ethers, Epoxides, and Sulfides

Infrared The infrared spectra of ethers are characterized by a strong, rather broad band due to antisymmetric C—O—C stretching between 1070 and 1150 cm Dialkyl ethers exhibit this band consistently at 1120 cm as shown in the IR spectmm of dipropyl ether. 

The analogous band in alkyl aryl ethers (ROAr) appears at 1200-1275 cm (Section 22.15). 

Epoxides typically exhibit three bands. Two bands, one at 810-950 cm and the other near 1250 cm correspond to asymmetric and symmetric stretching of the ring, respectively. The third band appears in the range 750-840 cm  

NMR The chemical shift of the proton in the H—C—O—C unit of an ether is very similar to that of the proton in the H—C—OH unit of an alcohol. A range of 8 3.2. 0 is typical. The proton in the H—C—S—C unit of a sulfide appears at higher field than the corresponding proton of an ether because sulfur is less electronegative than oxygen. 

Oxidation of a sulfide to a sulfoxide or sulfone is accompanied by a decrease in shielding of the H—C—S—C proton by about 0.3-0.5 ppm for each oxidation. 

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