Ethers CHEM 2030 - 01
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CHEM 2030 - 01
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This 3 page Class Notes was uploaded by Shannon Z. on Sunday November 1, 2015. The Class Notes belongs to CHEM 2030 - 01 at University of Missouri - Columbia taught by Rainer Glaser in Fall 2015. Since its upload, it has received 17 views. For similar materials see Survey of Organic Chemistry in Chemistry at University of Missouri - Columbia.
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Date Created: 11/01/15
1. Ethers a. Contain two organic groups, designated R and R’, connected by an oxygen atom. 2. Nomenclature a. Give the name of each alkyl or aryl group, in alphabetical order, followed by the word there. b. For complex or cyclic ethers, name the smallest OR group as an alkoxy group (name+ suffix –oxy). c. 3. Properties of ethers. a. Colorsless b. Have a lower boiling point than alcohols containing and equal number of carbon atoms. i. Ethers have no OH bonds. ii. The lack of OH bonds prevent ethers from forming hydrogen bonds with one another. iii. The inability to bond together via hydrogen bonding contributes to the lower boiling point. c. Ethers do not form hydrogen bonds with one another, but, they can form hydrogen bonds with alcohols. i. ii. This results in ethers being mutally soluble. d. Ethers with a low molecular weight are soluble in water. e. Water is denser than ethers. 4. Ethers as Solvents a. Solvent: a substance that will dissolve a solute. b. Ethers are frequently used as a solvent i. They are relatively inert, not reacting much with dilute acids, dilute bases, or common oxidizing and reducing agents. ii. Most organic compounds are ether soluble. iii. This combination makes ethers a good solvent. iv. But, if an ether has been exposed to air over time, it may accumulate organic peroxides, which makes the ether become highly explosive. c. Grignard Reagent – a common example of an ether used as a solvent. i. When magnesium and an alkyl or aryl halide are mixed together in an ether solution, the magnesium will be inserted between the halogen and alkyl group. The resulting structure is called a Grignard Reagent. 1. ii. The ether solvent in this reaction further stabilizes the Grignard reagent using the lone pairs on their oxygen atom. 1. iii. The two ethers most commonly used to prepare Grignard reagents are diethylether and tetrahydrofuron (THF) iv. Grignard reagents will not form if there is any trace of water or alcohol in the ether used. The would-be Grignard reagent will react with either the H20 or OH. 1. However, reactions between Grignard reagents and heavy water, represented as D, can be useful. v. Nomenclature 1. Divide into two pieces at the magnesium atom. 2. Give the R name (no space), magnesium (space), the halogen name 3. vi. Grignard reagents usually end up with a partially (-) R group and partially (+) MgX group. vii. Grignard reagents are carboanions. 1. Carboanion: an alkyl or aryl group with a (-) carbon atom. Tend to be strong bases. viii. Grignard reagents are organometallic compounds; they contain a carbon-metal bond. 5. Preparation of Ethers a. Two alcohols combine at the OH groups. A water molecule is removed. b. See equation 8.8 from the text. c. Williamson Synthesis. i. Two steps 1. Step 1 a. An alcohol is converted into an alkoxide. 2. Step 2 a. SN2 reaction between the alkoxide and an alkyl halide. 6. Cleavage of Ethers a. Due to the one pairs on the oxygen atom in an ether, they are Lewis bases and will react will with proton acids and Lewis acids in a similar way as alcohols reacting to strong acids. b. You can break the bond to the oxygen atom if the attached alkyl groups are primary or secondary via SN2 with a strong nucleophile.