MCAT Organic Chemistry - Carboxylic Acids

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carboxylic acid

contains both a carbonyl group and a hydroxyl group, bonded to the same carbon; always terminal groups

IUPAC: parent root + -ioc acid or cycloalkane + carboxylic acid

common names: formic (methanoic) acid, acetic (ethanoic) acid, proionic (propanoic) acid

carboxylic salts

carboxylic acid anions

IUPAC: parent root + -oate

dicarboxylic acids

have a carboxylic acid group on each end of the molecule

IUPAC: parent alkane + -dioc acid

common names: oxalic (ethanedioic) acid, malonic, succinic, glutaric, adipic, pimelic

dimers

pairs of molecules connected by two hydrogen bonds

β-dicarboxylic acids

dicarboxylic acids in which each carboxylic acid is positioned on the β-carbon of the other; notable for the high acidity of the α-hydrogens located on the carbon between the two carboxyl groups (pKa ≈ 9−14).

Synthesis of Carboxylic Acids

prepared via oxidation of aldehydes and primary alcohols

oxidants: dichromate salt (Na2Cr2O7 or K2Cr2O7), chromium trioxide (CrO3), or potassium permanganate (KMnO4)

Nucleophilic Acyl Substitution

similar to nucleophilic addition to an aldehyde or ketone; after opening the carbonyl via nucleophilic attack and forming a tetrahedral intermediate, the carbonyl can reform, thereby kicking off the leaving group; favored by a good leaving group.

Acyl derivatives

all molecules with a carboxylic acid-derived carbonyl, including carboxylic acids, amides, esters, anhydrides, and others.

Amides

a derivative of a carboxylic acid (R−C(=O)−OH) with the hydroxyl group (−OH) replaced by an amino group (−NR′R″); exist in a resonance state where delocalization of electrons occurs between the oxygen and nitrogen atoms

IUPAC: parent carboxylic acid - -oic acid + amide

alkyl groups on the nitrogen are placed at the beginning of the name with the prefix N−

lactams

cyclic amides

IUPAC: parent carboxylic acid - -oic acid + -lactam / named by indicating the specific carbon that is bonded during cyclization

Esters

hybrid between a carboxylic acid and an ether (ROR′),

IUPAC: non-carbonyl containing chain + parent carboxylic acid root + -oate

Esterification

condensation reaction using carboxylic acid to make ester with water as a side product;

amide synthesis

amide formed from carboxylic acid via nucleophlic substitution of carboxylic acid under acidic or basic conditions

lactones

cyclic esters

IUPAC: parent carboxylic acid - -oic acid + -lactone / named by indicating the specific carbon that is bonded during cyclization

Anhydrides

combination of two carboxylic acids at the hydroxyl site

IUPAC: parent carboxylic acid - acid + anhydride

anhydride synthesis

Carboxylic Acid Condensation; nucleophilic acyl substitution

Reduction

Carboxylic acids can be reduced to primary alcohols by the use of lithium aluminum hydride (LiAlH4) but NOT NaBH4

Decarboxylation

complete loss of the carboxyl group as carbon dioxide

1,3-Dicarboxylic acids and other β-keto acids spontaneously decarboxylate when heated

saponification

carboxylic acids react with sodium or potassium hydroxide and a salt is formed;

soap

mixing fatty acids with lye (sodium or potassium hydroxide) resulting in the formation of a salt; solvate nonpolar organic compounds in aqueous solutions because they contain both a nonpolar tail and a polar carboxylate head

micelles

spherical structures of soap; polar heads face outward, where they can be solvated by water, and the nonpolar hydrocarbon chains are oriented toward the inside of the sphere, protected from the solvent