lecture 17 - Chapter 17 Alcohols and Phenols Based on...

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Chapter 17: Alcohols and Phenols Based on McMurry’s Organic Chemistry , 7 th edition
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2 Alcohols and Phenols Alcohols contain an OH group connected to a a saturated C (sp 3 ) They are important solvents and synthesis intermediates Phenols contain an OH group connected to a carbon in a benzene ring Methanol, CH 3 OH, called methyl alcohol, is a common solvent, a fuel additive, produced in large quantities Ethanol, CH 3 CH 2 OH, called ethyl alcohol, is a solvent, fuel, beverage Phenol, C 6 H 5 OH (“phenyl alcohol”) has diverse uses - it gives its name to the general class of compounds OH groups bonded to vinylic, sp 2 -hybridized carbons are called enols
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3 Why this Chapter? To begin to study oxygen-containing functional groups These groups lie at the heart of biological chemistry
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4 17.1 Naming Alcohols and Phenols General classifications of alcohols based on substitution on C to which OH is attached Methyl (C has 3 H’s), Primary (1°) (C has two H’s, one R), secondary (2°) (C has one H, two R’s), tertiary (3°) (C has no H, 3 R’s),
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5 IUPAC Rules for Naming Alcohols Select the longest carbon chain containing the hydroxyl group, and derive the parent name by replacing the - e ending of the corresponding alkane with - ol Number the chain from the end nearer the hydroxyl group Number substituents according to position on chain, listing the substituents in alphabetical order
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6 Naming Phenols Use “phenol” (the French name for benzene) as the parent hydrocarbon name, not benzene Name substituents on aromatic ring by their position from OH
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7 17.2 Properties of Alcohols and Phenols The structure around O of the alcohol or phenol is similar to that in water, sp 3 hybridized Alcohols and phenols have much higher boiling points than similar alkanes and alkyl halides A positively polarized OH hydrogen atom from one molecule is attracted to a lone pair of electrons on a negatively polarized oxygen atom of another molecule This produces a force that holds the two molecules together These intermolecular attractions are present in solution but not in the gas phase, thus elevating the boiling point of the solution
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8 Properties of Alcohols and Phenols: Acidity and Basicity Weakly basic and weakly acidic Alcohols are weak Brønsted bases Protonated by strong acids to yield oxonium ions, ROH 2 +
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9 Alcohols and Phenols are Weak Brønsted Acids Can transfer a proton to water to a very small extent Produces H 3 O + and an alkoxide ion, RO - , or a phenoxide ion, ArO -
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10 Acidity Measurements The acidity constant, K a , measures the extent to which a Brønsted acid transfers a proton to water [A - ] [H 3 O + ] K a = ————— and p K a = - log K a [HA] Relative acidities are more conveniently presented on
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This note was uploaded on 09/06/2009 for the course CHEM chem 12 AB taught by Professor Adamczeski during the Spring '09 term at San Jose City College.

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lecture 17 - Chapter 17 Alcohols and Phenols Based on...

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