8.1 NAMES AND PHYSICAL PROPERTIES OF ETHERS, Summaries of Organic Chemistry

Download 8.1 NAMES AND PHYSICAL PROPERTIES OF ETHERS and more Summaries Organic Chemistry in PDF only on Docsity! CHM-134 ORGANIC CHEMISTRY CHAPTER-8: ETHERS Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 8.1 NAMES AND PHYSICAL PROPERTIES OF ETHERS In the IUPAC system, ethers are alkoxyalkanes. IUPAC: Ethers are alkanes bearing an alkoxy substituent. The larger substituent is the stem and the smaller substituent is the alkoxy group (methoxyethane). Common Names: The names of the two alkyl groups are followed by the word “ether” (ethyl methyl ether). • Except for strained cyclical derivatives, ethers are fairly unreactive and are often used as solvents in organic reactions. • Cyclic ethers are members of the class of cycloalkanes called heterocycles, in which one or more carbon atoms have been replaced by a heteroatom. Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 Cyclic polyethers based on the 1,2-ethanediol unit are called crown ethers. The crown ether 18-crown-6 contains 18 total atoms and 6 oxygen atoms. Note that the inside of the ring is electron rich. The absence of hydrogen bonding affects the physical properties of ethers. 8.1 NAMES AND PHYSICAL PROPERTIES OF ETHERS The smaller alkoxyalkanes are water soluble, however solubility decreases with increasing hydrocarbon size. Methoxymethane → completely water soluble Ethoxyethane →10% aqueous solution Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 8.2 SYNTHESIS OF ETHERS Williamson Ether Synthesis Ethers are prepared by SN2 reactions. Ethers can be prepared by the reaction of an alkoxide with a primary haloalkane or sulfonate ester under SN2 conditions. The parent alcohol of the alkoxide can be used as the solvent, however other polar solvents are often better, such as DMSO (dimethyl sulfoxide) or HMPA (hexamethylphosphoric triamide). Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 8.2 SYNTHESIS OF ETHERS Cyclic ethers can be prepared by intramolecular Williamson synthesis. Haloalcohols serve as the starting point for the Williamson synthesis of cyclic ethers. The intramolecular reaction is usually much faster than the intermolecular reaction. If necessary, the intermolecular reaction can be suppressed by using a high dilution of the haloalcohol. Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 8.2 SYNTHESIS OF ETHERS Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 8.2 REACTIONS OF ETHERS ❖ Hydride and organometallic reagents convert strained ethers into alcohols. ❖ LiAlH4 can open the rings of oxacyclopropanes to yield alcohols. (Ordinary ethers do not react.) ❖ In asymmetrical systems, the hydride attacks the less substituted side. Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 8.2 REACTIONS OF ETHERS Ring opening of oxacyclopropane by acid catalysis proceeds through an initial cyclic alkyloxonium ion. This acid catalyzed ring opening is both regioselective and stereospecific. Asst. Prof. Gülbin KURTAY For more details please study: Organic Chemistry: Structure and Function Eighth Edition K. Peter C. Vollhardt (Author), Neil E. Schore (Author) ISBN-10: 1319079458 8.3 SULFUR ANALOGS OF ALCOHOLS AND ETHERS The sulfur analogs of alcohols and ethers are thiols and sulfides. The IUPAC system calls the sulfur analogs of alcohols, R-SH, “thiols.” The –SH group in more complicated compounds is referred to as “mercapto”. The sulfur analogs of ethers are called “sulfides” (common name, thioethers). The RS group is called “alkylthio,” and the RS- group is called “alkanethiolate.”