8. Alcohols, Ethers, and Thiols

8. Alcohols, Ethers, and Thiols - 2010 Department of...

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© 2010 Department of Chemistry, The University of Western Ontario 8.1 8. Alcohols, Ethers, and Thiols (text 8.1 – 8.6) A. Structure and Nomenclature: Alcohols and Thiols Alcohols have the general formula R–OH, while thiols have the general formula R–SH. The O atom has a valence of 2, and one of these is taken by the H. Thus, the OH group substitutes an H atom in general formulas. So, the O atom is always ignored in unsaturation calcs. CH 3 CH 2 OH C 2 H 6 O C 6 H 6 O 0 units unsat. 4 units unsat. OH In nomenclature, the OH or SH group is given the lowest possible number in the carbon chain. These groups take priority over bonds. However, in complex molecules, OH can be treated as a simple hydroxy substituent. OH OH trans -cyclopentane-1,2-diol trans -1,2-dihydroxycyclopentane or OH 3-buten-2-ol
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8.2 Like alkyl halides, alcohols are classified as 1°, 2°, or 3° depending on the carbon atom that the OH is bonded to. OH OH Me secondary tertiary B. Physical Properties of Alcohols and Thiols The properties of alcohols stem from the high electronegativity of O, resulting in polar bonds. Effect is less in thiols (S less electronegative). Due to hydrogen bonding, alcohols have very high boiling points for their molar mass. C 5 H 12 36° C 5 H 11 Cl 108° CH 4 –136° C 5 H 11 OH 136° H 2 O 100° + - R O H +
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8.3 C. Spectroscopy of Alcohols and Ethers Both ethers and alcohols contain a C–O bond, but only alcohols contain an O H bond.
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8.4 The 13 C-NMR spectrum of 1-pentanol shows the five signals, with the ones furthest downfield closest to the OH. The carbon NMR of diethyl ether shows two signals.
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8.5 D. Reactions of Alcohols and Thiols Alcohols and thiols undergo a series of common reactions: acid-base reactions, conversion to alkyl halides, dehydrations to alkenes, and oxidations. 1. Acid-base reactions Like water, alcohols/thiols are amphiprotic. They can function as acids (in the presence of strong bases), and also as bases (in the presence of strong acids).
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This note was uploaded on 05/01/2011 for the course CHEMISTRY Chemistry taught by Professor Dr.felixlee during the Fall '11 term at UWO.

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8. Alcohols, Ethers, and Thiols - 2010 Department of...

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