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Carboxylic Acids

Carboxylic Acids. −. Carboxyl group: -CO 2 H, -COOH. H-bond acceptor. +. −. +. H-bond donor. Intermolecular forces: dipole-dipole, H-bonding. Pure carboxylic acids form hydrogen bonded dimers very high boiling points (higher than alcohols). Carboxylic Acid Nomenclature.

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Carboxylic Acids

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  1. Carboxylic Acids − Carboxyl group: -CO2H, -COOH H-bond acceptor + − + H-bond donor Intermolecular forces: dipole-dipole, H-bonding • Pure carboxylic acids form hydrogen bonded dimers • very high boiling points (higher than alcohols)

  2. Carboxylic Acid Nomenclature • Parent chain: longest containing carboxyl group (COOH) • Name of parent: replace “–e” with “–oic acid” • Numbering starts at carboxyl carbon • Priority: Carboxylic acid > aldehydes > ketones > alcohols  “hydroxy” substituent “oxo” substituents 3-oxobutanoic acid (diabetes) trans-3-methyl-2-hexenoic acid (human armpits) propanedioic acid (apples)

  3. aspirin Tylenol Can irritate your stomach Gentle on the stomach A carboxylic acid Just an alcohol

  4. Carboxylic Acid Reactions • Acid-Base reactions (formation of carboxylate salts) + + NaOH H2O  + + carboxylic acid strong base carboxylate salt water Naming: cation, then anion (regular ionic compound) Anion name: replace “–oic acid” with “–oate” sodium hexanoate • Reduction to 1° alcohols • Only LiAlH4 reduces carboxylic acids (not NaBH4 or H2/Pt) LiAlH4 butanoic acid 1-butanol

  5. What are the products? 3-oxo-4-pentenoic acid H2/Pt NaBH4 LiAlH4 3-hydroxypentanoic acid 3-hydroxy-4-pentenoic acid 4-pentene-1,3-diol

  6. Carboxylic Acid Reactions H-OR′ H-NH2 • Certain molecules can attack the carboxyl carbon and replace the –OH group H H−Nu + + H2O OH H−Nu Product Alcohol Ester Amine Amide

  7. What do these flavors/smells have in common? apricot grape rum banana pear orange apple raspberry pineapple wintergreen Made from a carboxylic acid and an alcohol Esters

  8. Esters from Carboxylic Acids & Alcohols • Nucleophilic substitution – a condensation reaction H+  + + H2O  + + carboxylic acid alcohol ester water • Reverse reaction = hydrolysis (“water-splitting”) H+  + H2O +  + + ester water carboxylic acid alcohol

  9. Esters O R – C – O – R’ from propanoic acid methyl group H O H H C C C CH3 O H H an ester H O H H C C C H O H H a carboxylic acid propanoic acid An ester is similar to a carboxylic acid, but the acidic hydrogen has been replaced by an alkyl group (R) methyl propanoate

  10. Naming Esters • Named as “alkyl alkanoates” • Alkyl group first (from alcohol) • Acid name: “-oic acid” changed to “-oate” ethyl butanoate (pineapple) pentyl butanoate (apricot) 3-methylbutyl ethanoate 1 3 (banana) 4 2

  11. Naming Esters O R – C – O – R’ O Name the following ester: CH3CH2CH2C-O-CH2CH3 ethyl Step 1) the ester alkyl group (R’) = butanoic acid Step 2) the acid (R) = ethyl butanoate Step 3) the name =

  12. Formation of an Ester O H H H H H H C C C C C C H O H H H H H O H H H H H H C C C C + HO HO C C H OH H D H H H H H ethyl alcohol butyric acid (butanoic acid) + water ethyl butanoate or ethyl butyrate (tastes and smells like pineapple)

  13. O O CH3 R C R' O H C C CH3 O H H O C C H CH2 (CH2)6 CH3 O H Ester Raspberry H O CH3 C C H CH2 CH2 CH CH3 O H CH3 Banana Orange

  14. O R C R' O H O C C H CH2 CH2 CH3 O H Ester Pear H H C C H O C C H CH2 H O C C H C C Peach H H

  15. Structural Isomers • Draw all possible isomers of C3H6O2 Two oxygen's → carboxylic acids and esters

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