ABSTRACT
Ethers are chemical compounds with an oxygen bridge between two organic (alkyl or aryl) residues. The word ether originates from Greek and means “higher air” or “air of fire.” These compounds are very common in natural products, e.g., they can be found in the glycosidic linkages of polysaccharides but also in other natural materials and drugs. The ether bond is relatively stable and inert, which renders these materials interesting, e.g., as solvents. The C-O-C bond is angulated (ca. 112°) and polar, while the length of the C-O bond spans ca. 143 pm (Figure 7.1). The solubility in water decreases with increasing length of the alkyl chain due to the increasing sterical hindrance resulting in polarity. The physical properties strongly vary from the corresponding alcohols, and the ethers show lower melting and boiling points due to the loss of active hydrogen bonding. As ethers can accept hydrogen bonds from water, they interact also with water and are found to be hygroscopic and often rather “wet” solvents (diethylether can dissolve up to ca. 8% of water).
