Ethers & Epoxides

Ether Nomenclature Compounds that contain two organic groups attached to an oxygen atom General formula is 1. Common Names – Name both groups attached to the oxygen in alphabetical order – Add the word ether

Ether Nomenclature Examples

4. 5.

2. IUPAC Names In the IUPAC system, ethers are named as alkoxy substituents Ex.: CH 3 —CH—CH 2 —CH 2 —CH 3 O—CH 3

Epoxide Nomenclature Also known as oxiranes Three-membered, saturated cyclic ring with one oxygen atom Much more reactive than ordinary ethers (due to the abnormally small bond angles) General formula

1. Common names – Number the alkyl chain indicating the two carbons to which the oxygen is attached – Use the prefix epoxy- – Ex. 1 – Ex.2.

Ex IUPAC Names – Number the ring with oxygen as #1 – Use the ending oxirane Ex. 1

Ex. 2.

Reactions of Ethers Ethers are relatively stable, especially to dilute acids or alkalis & many oxidizing & reducing agents Do not react with sodium (this property distinguishes them from alcohols) Are weak bases which dissolve in concentrated sulfuric acid (this property distinguishes them from saturated hydrocarbons) React with oxygen in the air to form dangerous explosive peroxides

Preparation of Ethers 1. Intermolecular Dehydration of Alcohols Used to make symmetrical ethers Reagent is H 2 SO 4 at 140°C Ex. Dehydrate two moles of ethanol Ex. Dehydrate tertbutanol

2. Williamson Synthesis Reaction of an alkyl halide with an alcohol (or an alkoxide ion) Can be used to make either symmetrical or unsymmetrical ethers The alkyl halide must be primary or secondary Ex. React methanol with ethyl chloride.

Alkyl sulfates, in the presence of NaOH, are used to prepare ethers of phenols Ex. React phenol with dimethylsulfate

Preparation of Epoxides 1. Oxidation of Ethylene Uses silver as the catalyst at 250°C Ex: 2. Intramolecular Williamson Synthesis Uses hypochloric acid (HClO) and hydroxide Ex:

Reactions of Epoxides the three membered ring is highly strained and opens easily 1. Acid Catalyzed Addition – A. Hydrolysis of epoxyethane Uses dilute acid; used to make trans diols Ex.; Hydrolyze 1,2-epoxycyclohexane with dilute acid – B. Treatment with concentrated acid Ex. React oxirane with concentrated HCl.

– C. In alcoholic solutions – Ex. React oxirane with methanol – D. with ethylene glycol – Ex. React oxirane with ethylene glycol

2. Base Catalyzed Addition Uses ammonia 3. Reaction with a Grignard Reagent Extends the chain of the Grignard reagent by two carbons Product is a primary alcohol Ex. React oxirane with phenylmagnesium bromide