Ethers Ethers are compounds with the general formula: R-O-R’ symmetrical ethers: R = R’ unsymmetrical ethers: R = R’ two lone pairs of electrons on oxygen sp3 hybrid oxygen atom bent molecular geometry

Ethers Ethers are commonly used as solvents in organic reactions. Polar molecules no hydrogen bonding between ether molecules lower BP than comparable alcohols serves as hydrogen bond acceptor in the presence of alcohols, amines, or carboxylic acids

Nomenclature of Ethers Common Names: Name the two alkyl groups and add the word ether alphabetical order in order of increasing complexity use prefix “di” to indicate both alkyl groups are identical if only one alkyl group is described in name, it implies the ether is symmetrical OR

Nomenclature of Ethers Examples of Common Names CH3CH2OCH3 methyl ethyl ether CH3CH2OCH2CH3 diethyl ether or ethyl ether

Ethers IUPAC Names (Alkoxy alkane) : Ethers names as alkoxy alkanes Use the more complex alkyl group as the base name The other alkyl group is named as an alkoxyl group Examples CH3CH2OCH3 methoxyethane CH3CH2OCH2CH3 ethoxyethane

Ethers Example: Name the following ethers.

Ethers Example: Draw the following compounds. Methoxycyclopentane Ethyl t-butyl ether Chloromethyl methyl ether (1R, 2R)-2-methoxycyclohexanol

Nomenclature of Ethers Cyclic ethers are heterocyclic compounds: compounds containing a ring in which one or more ring atoms is an element other than carbon Epoxide (oxirane): three membered cyclic ether Ethylene oxide oxirane epichlorohydrin cyclohexene oxide

Nomenclature of Ethers Furan : a five-membered aromatic cyclic ether Tetrahydrofuran (oxolane): saturated, five-membered cyclic ether

Nomenclature of Ethers Pyran (Oxane): an unsaturated, six-membered cyclic ether Dioxane: heterocyclic ether with two oxygen atoms in a six-membered ring 1,4-dioxane

Synthesis of Ethers Williamson Ether Synthesis SN2 attack of an alkoxide ion on an unhindered methyl or primary alkyl halide or tosylate

Synthesis of Ethers Alkoxymercuration-Demercuration: formation of Markovnikov ether from an alkene “anti” addition to the double bond Reagents: (1) Hg(OAc)2, ROH (2) NaBH4 R

Synthesis of Ethers Examples:

Synthesis of Ethers Epoxidation of Alkenes formation of an epoxide from an alkene using a peroxyacid Reagents: MCPBA CH3CO3H Retains stereochemistry of C=C

Synthesis of Ethers Example:

Synthesis of Ethers Base-Promoted Cyclization of Halohydrins formation of epoxides from halohydrin via internal SN2 attack of an alkoxide ion on an adjacent carbon containing a halogen Reagents: NaOH (aq)

Synthesis of Ethers Example:

Reactions of Ethers Autoxidation of Ethers: spontaneous oxidation of ethers to hydroperoxides and dialkyl peroxides in the presence of atmospheric oxygen Hydroperoxides and dialkyl peroxides are highly explosive do not distill to dryness use ether promptly test old cans of ether before use

Reactions of Ethers Acid-Catalyzed Ring Opening of Epoxides SN2 attack of water or alcohol molecule on a protonated epoxide ring Using H+/H2O: anti stereochemistry Water attacks at the more substituted carbon

Reactions of Ethers Using H+/ROH: anti stereochemistry ROH attacks at the more substituted carbon

Reactions of Ethers Base-Catalyzed Ring Opening of Epoxides: SN2 attack of OH- or RO- on an epoxide ring Anti stereochemistry OH- and RO- attack at the least hindered (least substituted) carbon in the epoxide ring

Reactions of Ethers Examples:

Reactions of Ethers Reactions of Epoxides with Grignard and Organolithium Reagents Attack of RMgX or RLi on the least hindered carbon in the epoxide ring forming an alcohol

Reactions of Ethers Example:

Ethers Examples: Predict the product of each of the following reactions.

Ethers Examples:

Ethers Example: How would you prepare the following compounds from the reactant given?