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Flashcards in Carboxylic Acids Deck (16):
1

Carboxylic Acid

-always terminal groups
-oic acid
-with three bonds to oxygen, one of the most oxidized functional groups

2

Salts of Carboxylic Acids

-named beginning with the cation followed by the name with the ending -oate instead of -oic acid

3


Dicarboxylic Acids

-smallest- oxalic acid
-named by adding -dioic acid
carboxylic acid on either end of the molecule

4

Hydrogen Bonding in Carboxylic Acids

-strong intermolecular attractions because both hydroxyl oxygen and carbonyl oxygen can participate in H bonding so they tend to form dimers
-multiple H bonds elevate the boiling points and melting points past those of corresponding alcohols
-can H bond because they contain a hydrogen bonded to a very electronegative atom

5

Acidity in Carboxylic Acids

-resonance stabilization occurs between both of the electronegative oxygen atoms
-delocalization of negative charge results in a very stable carboxylate anion
-the more stable the conjugate base, the easier it is for the proton to leave and thus the stronger the acid
-hydroxyl hydrogen is very acidic resulting in a negative charge that remains after the H is removed

6

Substituents Affecting Acidity of Carboxylic Acid

-electron donating groups destabilize the negative charge, and decrease stability (-NH2, -OCH3)
-closer the substituent to the carboxyl, the greater the effect will be
-electron withdrawing groups increase acidity (-NO2 or halides)

7

Dicarboxylic vs Monocarboxylic Acid Acidities

-BUT when one proton is removed from dicarboxylic acid, the carboxylate anion forms resulting in a decrease in acidity of the remaining carboxylic acid
-due to instability, the second proton is less acidic and harder to remove than the analogous proton of a monocarboxylic acid
-carboxylic acids are electron withdrawing so dicarboxylic acids are more acidic than the mono

8

β-dicarboxylic Acids

-there are 2 carboxylic acids separated by a single carbon
-high acidity of the α-hydrogens
-loss of the acidic hydrogen produces a carbanion which is stabilized by the electron withdrawing effect of both carboxyl groups
-dicarboxylic acids in which each carboxylic acid is positioned on the β-carbon of the other

9

Synthesis of Carboxylic Acids

-oxidant is usually a dichromate salt --(Na2Cr2O7 or K2Cr2O7), chromium trioxide (CrO3), or potassium permanganate (KMnO4)
-secondary and tertiary alcohols cannot be oxidized to carboxylic acids
-oxidation of primary alcohols and aldehydes

10

Nucleophilic Acyl Substitutions

-after opening the carbonyl through nucleophilic attack and forming tetrahedral intermediate, the carbonyl can reform, kicking off the leaving group
-nucleophilic molecule replaces the leaving group of an acyl derivative
-nucleophilic molecule replaces the leaving group of an acyl derivative
-acyl derivative - all molecules with a carboxylic acid derived carbonyl including carboxylic acids, amides, esters, anhydrides, and others
-favored by a good leaving group
-favored in acidic or basic conditions
-focuses on the existence of a leaving group in carboxylic acids and their derivcatives

11

Amide

-can be in acidic or basic conditions
-named by replacing -oic acid with -amide
-cyclic called lactams (add -lactam instead of -oic acid)

-carboxylic acids can be converted into amides if incoming nucleophile is ammonia (NH3) or an amine

12

Ester

-esterification - condensation reaction with water as a side product
-in acidic solutions, carbonyl oxygen can be protonated enhancing the polarity of the bond thereby placing additional positive charge on the carbonyl carbon and increasing its susceptibility to nucleophilic attack
-occurs most rapidly with primary alcohols
cyclic lactones
-hybrid between a carboxylic acid and an ether which can be made by reacting carboxylic acids with alcohols under acidic conditions

13

Anhydrides

-named by replacing acid with anhydride whether cyclic or linear
-ex- condensation of two molecules of ethanoic acid to form ethanoic anhydride
-formed by the condensation of 2 carboxylic acids

14

Reduction of Carboxylic Acids

-aldehyde intermediates may be formed but they too will be reduced to -OH
-reaction is through nucleophilic addition of hydride to the carbonyl group
-a gentler reducing agent- NaBH4, is not strong enough to reduce carboxylic acids
with LiALH4, carboxylic acids can be reduced to primary alcohols

15

Decarboxylation

-common way of getting rid of a carbon from the parent chain
-1,3-dicarboxylic acids and other β-keto acids may spontaneously decarboxylate when heated where the carboxyl group is lost and replaced with hydrogen
-electrophile and nucleophile are in the same molecule, so reaction proceeds through a 6 membered ring in its transition state
enol that is initially formed tautomerizes to the more stable keto form
-complete loss of the carboxyl group as a carbon dioxide

16

Sopanification

-mixing fatty acids with lye (sodium or potassium hydroxide) resulting in the formation of a salt called soap
-contain both a nonpolar tail and polar carboxylate head so when placed in aqueous solution, soap molecules will rearrange themselves into micelles
-nonpolar molecules dissolve in the hydrocarbon interior of the spherical micelle
-micelle as a whole dissolves in water due to the polarity of the exterior
-long chain carboxylic acids react with sodium or potassium hydroxide and a salt is formed