Special Topic Thiols Mercaptans and Thioethers Sulfides

8c Structure The carbon-oxygen bond length in ethers is similar to that in alcohols, and the opening of the angle as we go from H—O—H (104.5°) to R—O—H ( 109°) to R—O—R ( 112°) continues. As the angle in ethers is approximately 112°, the oxygen is hybridized approximately sp.  

8d Acidity and Basicity Of course, ethers lack the OH group of their relatives water and the alcohols and so are not Bronsted acids. The oxygen atom has two pairs of nonbonding electrons, however, and they make ethers weak Bronsted and Lewis bases. Ethers can be protonated, and the protonated form has a pAj in the same range as those of the protonated alcohols, which means that ethers and alcohols are strong bases of similar strength (Fig. 6.52). 

FIGURE 6.52 Ethers are weak Br0nsted bases and can be protonated. Protonated ethers (and protonated alcohols) are strong acids. 

We have already seen one instance in which the ability of ethers to donate electrons, that is, to act as a Lewis base, was a critical property. Recall from p. 228 that an ether solvent is vital to success in the formation of the Grignard reagent (Fig. 6.53). Ethers are stabilizing to Lewis acidic species. Boron trifluoride etherate is a commercially available complex of BF3 and ether that can even be distilled. 

It is commonly used as a source of BF3. For similar reasons, the cyclic ether THF (Fig. 6.51) is used to stabilize the highly reactive molecule BH3. 

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Special Topic Thiols [Mercaptans] and Thioethers (Sulfides]... 

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