Ch20Su08

Ch20Su08 - Carboxylic Acids When a carbonyl carbon also...

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Carboxylic Acids When a carbonyl carbon also bears a hydroxyl group, then these compounds are appreciably acidic, and are called carboxylic acids. Carboxylic acids are classified according to the substituent that is bonded to the carboxyl carbon: Aliphatic acids have an alkyl group bound to the carboxyl group. An aromatic acid has an aryl group bound to the carboxyl group. The simplest acid is formic acid. A carboxylic acid donates protons by the heterocyclic cleavage of the O-H bond, generating a carboxylate ion. 1197f6d9f64ffd8db2cdd5b4a1056e7b88da4b95.doc Page 1 R C O O-H RCOOH RCO 2 H H C O O-H CH 3 CH 2 C O O-H C O O-H H C O O-H H C O O - H +
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Nomenclature IUPAC formulation The root name is based on the longest continuos chain of carbon atoms bearing the carboxyl group. The -e is replaced by -oic acid. The chain is numbered starting with the carboxyl carbon atom . The carboxyl group takes priority over any other functional groups previously discussed. E.g. Unsaturated acids are named using the name of the alkene with -e replaced with -oic acid. The chain is numbered starting with the carboxyl group, and a number designates the location of the multiple bond (and use Z or E). E.g. 1197f6d9f64ffd8db2cdd5b4a1056e7b88da4b95.doc Page 2 H 3 C C O O-H CH C O O-H H 3 C O-H o H 2 N ethanoic acid 2-cyclohexylpropanoic acid 4-aminobutanoic acid CH 2 -CO 2 H CH 3 CH 2 H 3 C H (E)-4-methyl-3-hexenoic acid
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Cycloalkanes with carboxyl substituents are named as cycloalkanecarboxylic acids. E.g. (Notice that -CO 2 H as a substituent makes the carbon it is bound to C-1, not itself). Aromatic acids of the form Ar-CO 2 H are named as derivatives of benzoic acids, with ortho, meta and para indicating the location relative to the carboxyl group. 1197f6d9f64ffd8db2cdd5b4a1056e7b88da4b95.doc Page 3 CO 2 H CH 3 CH 3 3,3-dimethylcyclohexanecarboxylic acid CO 2 H CO 2 H CO 2 H benzoic acid p-aminobenzoic acid o-hydroxybenzoic acid NH 2 OH
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Dicarboxylic Acids Aliphatic dicarboxylic acids are named by simply adding the suffix -dioic acid to the root name. The root name comes from the longest carbon chain containing both carboxyl groups. Numbering starts at the end closest to a substituent. E.g. The older numbering system is with greek letters, starting at the second carbon. The omega term, ϖ is given to the last carbon atom in long chain carboxylic acids. 1197f6d9f64ffd8db2cdd5b4a1056e7b88da4b95.doc Page 4 H-O O-H O Br O 3-bromohexanedioc acid
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The most stable conformation of formic acid is an almost planar arrangement of the molecule. The carbon is sp 2 hybridized , and the O-H bond lies in the plane described by the sp 2 carbon, eclipsing the C=O double bond. This unexpected geometric arrangement can be explained by resonance (or
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This note was uploaded on 02/23/2010 for the course CHEM 202 taught by Professor Smith during the Spring '10 term at Duke.

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Ch20Su08 - Carboxylic Acids When a carbonyl carbon also...

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