Ch 19 textbook

Ch 19 textbook - CHAPTER 19 Carboxylic Acids 19-1 Naming...

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HAPTER 19 CHAPTER 19 Carboxylic Acids
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Naming the Carboxylic Acids 19-1 hemical Abstracts retains the common names for the two Chemical Abstracts retains the common names for the two simplest carboxylic acids, formic acid and acetic acid. The IUPAC system derives the name of carboxylic acids by replacing the ending –e in the parent alkane by the ending –oic acid .
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The alkanoic acid stem is numbered by assigning 1 to the carbonyl carbon and labeling any substituents along the longest chain incorporating the CO 2 H group accordingly. The carbonyl group and the functional groups of its derivatives take precedence in naming over any other groups discussed so far:
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When other functional groups are present, the main chain is chosen to include other functional groups as much as possible. Saturated cyclic acids are named as cycloalkanecarboxylic acids . romatic acids are named enzoic acids Aromatic acids are named benzoic acids . Dicarboxylic acids are referred to as dioic acids .
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Structural and Physical Properties of Carboxylic Acids 19-2 Formic acid is planar. he molecular structure of formic acid is roughly planar, which is The molecular structure of formic acid is roughly planar, which is characteristic of carboxylic acids in general.
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The carboxy group is polar and forms hydrogen- onded dimers. bonded dimers. The carboxy function is strongly polar and forms hydrogen bonds to other polarized molecules such as water, alcohols and other carboxylic acids. Carboxylic acids up to butanoic acid are completely soluble in water. As neat liquids, and even in fairly dilute solutions, carboxylic acids form hydrogen-bonded dimers (6–8 kcal mol -1 ).
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Carboxylic acids have relatively high melting and boiling points due to hydrogen bonding in both the solid and liquid states.
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Volatile carboxylic acids (low MW) exhibit characteristically strong odors (butanoic acid, cheese; (E)-3-methyl-2-hexenoic acid, human sweat).
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NMR and IR Spectroscopy of Carboxylic Acids 19-3 he carboxy hydrogen and carbon are deshielded The carboxy hydrogen and carbon are deshielded. Hydrogens on a carbon next to a carbonyl group are slightly deshielded. The effect diminishes rapidly with increasing distance from the carbonyl. The hydroxyl proton resonates at very low field ( = 10-13 ppm). Its chemical shift varies strongly with concentration, solvent and temperature because of its involvement in hydrogen bonding.
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The 13 C NMR chemical shifts of carboxylic acids are similar to those of aldehydes and ketones. The amount of deshielding is maller because of the presence of the extra OH group smaller because of the presence of the extra OH group. The smaller deshielding can be attributed to the extra resonance form present in carboxylic acids:
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The carboxy group shows two important IR bands.
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This note was uploaded on 08/04/2009 for the course CHEM CHEM 140C taught by Professor Finn during the Spring '08 term at UCSD.

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Ch 19 textbook - CHAPTER 19 Carboxylic Acids 19-1 Naming...

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