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Carboxylic acids: R-COOH, R-CO 2 H, Common names : HCO 2 H formic acid

Carboxylic acids: R-COOH, R-CO 2 H, Common names : HCO 2 H formic acid CH 3 CO 2 H acetic acid CH 3 CH 2 CO 2 H propionic acid CH 3 CH 2 CH 2 CO 2 H butyric acid CH 3 CH 2 CH 2 CH 2 CO 2 H valeric acid . 5 4 3 2 1 C—C—C—C—C=O

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Carboxylic acids: R-COOH, R-CO 2 H, Common names : HCO 2 H formic acid

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  1. Carboxylic acids: R-COOH, R-CO2H, Common names: HCO2H formic acid CH3CO2H acetic acid CH3CH2CO2H propionic acid CH3CH2CH2CO2H butyric acid CH3CH2CH2CH2CO2H valeric acid 5 4 3 2 1 C—C—C—C—C=O δ γ β α used in common names

  2. IUPAC nomenclature for carboxylic acids: parent chain = longest, continuous carbon chain that contains the carboxyl group  alkane, drop –e, add –oic acid HCOOH methanoic acid CH3CO2H ethanoic acid CH3CH2CO2H propanoic acid CH3 CH3CHCOOH 2-methylpropanoic acid Br CH3CH2CHCO2H 2-bromobutanoic acid dicarboxylic acids: HOOC-COOH oxalic acid HO2C-CH2-CO2H malonic acid HO2C-CH2CH2-CO2H succinic acid HO2C-CH2CH2CH2-CO2H glutaric acid HOOC-(CH2)4-COOH adipic acid HOOC-(CH2)5-COOH pimelic acid

  3. salts of carboxylic acids: name of cation + name of acid: drop –ic acid, add –ate CH3CO2Na sodium ethanoate CH3CH2CH2CO2NH4 ammonium butanoate (CH3CH2COO)2Mg magnesium propanoate physical properties: polar + hydrogen bond  relatively high mp/ bp water insoluble exceptions: four carbons or less acidic soluble in 5% NaOH RCO2H + NaOH  RCO2-Na+ + H2O stronger stronger weaker weaker acid base base acid

  4. Carboxylic acids, syntheses: • oxidation of primary alcohols • RCH2OH + K2Cr2O7 RCOOH • 2. oxidation of alkylbenzenes (arenes) • ArR + KMnO4, heat  ArCOOH • 3. carbonation of Grignard reagents • RMgX + CO2 RCO2MgX + H+  RCOOH • 4. hydrolysis of nitriles • RCN + H2O, H+, heat  RCOOH

  5. oxidation of 1o alcohols: • CH3CH2CH2CH2-OH + CrO3 CH3CH2CH2CO2H • 1-butanol butanoic acid • CH3 CH3 • CH3CHCH2-OH + KMnO4  CH3CHCOOH • 2-methyl-1-propanol` 2-methylpropanoic acid • oxidation of alkylbenzenes (arenes):

  6. carbonation of Grignard reagent: • R-X RMgX RCO2MgX RCOOH • Increases the carbon chain by one carbon. • Mg CO2 H+ • CH3CH2CH2-Br CH3CH2CH2MgBr CH3CH2CH2COOH • n-propyl bromide butyric acid Mg CO2 H+ • Hydrolysis of a nitrile: • H2O, H+ • R-CN R-CO2H • heat • H2O, OH- • R-CN R-CO2- + H+ R-CO2H • heat • R-X + NaCN  R-CN + H+, H2O, heat  RCOOH • 1o alkyl halide • Adds one more carbon to the chain. • R-X must be 1o or CH3!

  7. carboxylic acids, reactions: • as acids • conversion into functional derivatives • a)  acid chlorides • b)  esters • c)  amides • reduction • alpha-halogenation

  8. as acids: • with active metals • RCO2H + Na  RCO2-Na+ + H2(g) • with bases • RCO2H + NaOH RCO2-Na+ + H2O • relative acid strength? • ROH < HOH < RCO2H • ionization in water • HA + H2O  H3O+ + A- • Ka for carboxylic acids  10-5 • Effect of substituent groups on acid strength? • Ka • CH3COOH 1.75 x 10-5 • ClCH2COOH 136 x 10-5 • Cl2CHCOOH 5,530 x 10-5 • Cl3CCOOH 23,200 x 10-5

  9. Nucleophilic Acyl Substitution of Carboxylic Acids • Nucleophilic acyl substitution converts carboxylic acids into carboxylic acid derivatives, i.e., acid chlorides, anhydrides, esters and amides. NH3, D, -H2O SOCl2 amide ROH H+ acid chloride D -H2O acidanhydride ester

  10. acid chlorides

  11. esters • “direct” esterification: H+ • RCOOH + R´OH  RCO2R´ + H2O • -reversible and often does not favor the ester • “indirect” esterification: • RCOOH + PCl3 RCOCl + R´OH  RCO2R´ • -convert the acid into the acid chloride first; not reversible • amides • “indirect” only! • RCOOH + SOCl2 RCOCl + NH3  RCONH2 • amide

  12. Reduction: • RCO2H + LiAlH4; then H+ RCH2OH • 1o alcohol • Alpha-halogenation: (Hell-Volhard-Zelinsky reaction) • RCH2COOH + X2, P  RCHCOOH + HX • X • α-haloacid • X2 = Cl2, Br2

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