ether

Examples of ether in the following topics:

• Nomenclature

  • Examples of ether nomenclature are provided on the left.
  • Simple ethers are given common names in which the alkyl groups bonded to the oxygen are named in alphabetical order followed by the word "ether".
  • These are named as "dialkyl ethers".
  • Examples are: CH3CH2OCH2CH3, diethyl ether (sometimes referred to as ether), and CH3OCH2CH2OCH3, ethylene glycol dimethyl ether (glyme).
  • Sulfur analogs of ethers (R–S–R') are called sulfides.

• Ethers

  • Ethers are a class of organic compounds that contain an ether group.
  • There are two ways to name ethers.
  • If the two alkyl groups are identical, the ether is called di[alkyl] ether.
  • For example, diethyl ether is the ether with an ethyl group on each side of the oxygen atom.
  • The general structure of an ether.

• Preparation of Ethers

  • Ethers are usually prepared from alcohols or their conjugate bases.
  • When applied to an unsymmetrical ether, as in this case, there are two different combinations of reactants are possible.
  • A second general ether synthesis, alkoxymercuration, is patterned after the oxymercuration reaction.
  • Acid-catalyzed dehydration of small 1º-alcohols constitutes a specialized method of preparing symmetrical ethers.
  • At 110º to 130 ºC an SN2 reaction of the alcohol conjugate acid leads to an ether product.

• Reactions of Ethers

  • Ethers are widely used as solvents for a variety of organic compounds and reactions, suggesting that they are relatively unreactive themselves.
  • The inert nature of the ethers relative to the alcohols is undoubtedly due to the absence of the reactive O–H bond.
  • The most common reaction of ethers is cleavage of the C–O bond by strong acids.
  • The reaction shown here (#4) is the reverse of the tert-butyl ether preparation described earlier.
  • Because of their chemical stability, ethers may be used to protect hydroxyl functions from undergoing unwanted reactions.

• Reactions of Epoxides

  • Epoxides (oxiranes) are three-membered cyclic ethers that are easily prepared from alkenes by reaction with peracids.
  • Because of the large angle strain in this small ring, epoxides undergo acid and base-catalyzed C–O bond cleavage more easily than do larger ring ethers.
  • Among the following examples, the first is unexceptional except for the fact that it occurs under milder conditions and more rapidly than other ether cleavages.
  • The second and third examples clearly show the exceptional reactivity of epoxides, since unstrained ethers present in the same reactant or as solvent do not react.

• Nucleophilicity of Sulfur Compounds

  • Sulfur analogs of alcohols are called thiols or mercaptans, and ether analogs are called sulfides.
  • The chemical behavior of thiols and sulfides contrasts with that of alcohols and ethers in some important ways.
  • Although the basicity of ethers is roughly a hundred times greater than that of equivalent sulfides, the nucleophilicity of sulfur is much greater than that of oxygen, leading to a number of interesting and useful electrophilic substitutions of sulfur that are not normally observed for oxygen.
  • Although equivalent oxonium salts of ethers are known, they are only prepared under extreme conditions, and are exceptionally reactive.

• Boiling Point and Water Solubility

  • It is instructive to compare the boiling points and water solubility of amines with those of corresponding alcohols and ethers.
  • Indeed, 3º-amines have boiling points similar to equivalent sized ethers; and in all but the smallest compounds, corresponding ethers, 3º-amines and alkanes have similar boiling points.
  • As expected, the water solubility of 3º-amines and ethers is also similar.

• Other Sigmatropic Shifts

  • Base catalyzed reactions of allylic ethers and amines may take different paths depending on substitution and conditions.
  • A general example involving diallyl ethers is shown in the following diagram.

• Main Group Organometallic Compounds

  • For example, simple alkyl lithiums are largely hexameric clusters in hydrocarbon solvents, but change to tetrameric and dimeric forms in various ether solvents.
  • Grignard reagents require an ether solvent for their formation, and have been crystallized as monomeric and dimeric ether complexes.
  • The following equilibrating species, called the Schlenk equilibrium, have been identified in ether solution.

• Organometallic Reagents from Geminal Dihalides

  • For example, 1,4-dibromobutane and para-dibromobenzene react with excess magnesium in ether to generate di-Grignard reagents that may be used in the same manner as any simple Grignard reagent.
  • This ether soluble substance is thought to be an equilibrium mixture of the compounds written in the blue brackets.
  • Also, enol ether products may be obtained from esters (example (iii).