Carboxylic Acids: Properties, Spectroscopy, Synthesis, and Uses - Prof. Thomas Albright, Study notes of Organic Chemistry

Download Carboxylic Acids: Properties, Spectroscopy, Synthesis, and Uses - Prof. Thomas Albright and more Study notes Organic Chemistry in PDF only on Docsity! Chapter 29. Carboxylic Acids A. Properties 1; Acidic!! sO: 10: :0: h base Vi f R—c Pa R—c —~_—s R—cC + BH \ 9B \ \ 2 20: 10: Resonance-stabilized carboxylate anion T oy = Gescee af 7 CH,CH,CHi~ OH Cl) LH C _ Ro “oe Ro SS pK, = 4.81 <B Butyric acid => + HB 70: 6: iO: I L 4 H,CCHCH~ “OH ATO ROTO: He _ £2 ry pK, = 4.06 3-Chlorobutyric acid t C CH,CH;CH7 OH Cl: pK, = 4.52 4-Chlorobutyric acid :0: | C. CH,CH,CH~ CH Cl: pK, = 2.84 2-Chlorobutyric acid Chapter 20 2 2. Addition to carbonyl group 3. Protonation - two possibilities Always favored!! (why?) Chapter 20 5 C. Nomenclature 1. Common names - very prevalent - -C(O)OH carboxyl group acid common name derivation HCO2H formic acid formica - Lt. ant CH3CO2H acetic acid acetum - Lt. vinegar CH3CH2CO2H propionic acid protos pion - Gk. dairy fat CH3(CH2)2CO2H butyric acid butyrum- Lt. rancid butter CH3(CH2)3CO2H valeric acid valerian - Lt. smelly root CH3(CH2)4CO2H caproic acid caper - Lt. goat oder C C C C C O OH abgd CH2 CH2 CH2 C O OHPh Br a-bromo-g-phenylbutyric acid Chapter 20 6 other common names: CO2H benzoic acid CO2H CO2H phthalic acid CH3 CH OH CO2H lactic acid CH3 C O CO2H pyruvic acid HO2C CO2H oxalic acid malonic acid HO2C CH2 CO2H 2. IUPAC names - drop “e” in alkane name, replace with “oic acid”. Number starting from carboxyl carbon H3C C Br Ph CH Br C O OH 2,3-dibromo-3-phenylbutanoic acid (common name: a,b-dibromo-b-phenylbutyric acid) CH3 CH CH3 C C H CH2 C O OH (E)-4-cyclopropyl-5-methyl-3-hexenoic acid Chapter 20 7 3. IUPAC for cycloalkanecarboxylic acids: CO2H Br CH3 trans-2-bromo-trans-4-methylcyclohexanecarboxyl acid 4. IUPAC for dicarboxylic acids - just add dioic acid to end of parent alkane name. HO C O CH2 C CH3 CH2CH3 CH2CH2 C O OH 1 2 3 4 5 6 3-ethyl-3-methylhexanedioic acid Chapter 20 10 DIRT!! Chapter 20 11 E. Synthesis of carboxylic acids: 1. Oxidation of primary alcohols- RCH2 OH Na2Cr2O7 H2SO4 R C O H R C O OH (chpt. 11-2) 2. Oxidation of alkynes with permanganate 33. KMnO4 heat, OH- (9-10) O O - O O - + 34. (9-10) O OH O HO +1) O3 2) H2O 3. Oxidation of alkynes with ozone Chapter 20 12 4. Benzylic oxidation R KMnO4/ H2O or Na2Cr2O7/ H2SO4 CO2H (chpt 17-14) 5. Carboxylation of Grignard reagents a. overall rxn. R MgX 1) CO2 2) H3O + R CO2H R MgX O C O + O C OR - H3O + O C OHR b. mechanism: b. mechanism :0: :0H :0H GOH . :6H | =|) | {|e Ll se —_—— I- C—O + Aw OH R~ OH R~* GH OOH | -y Q Q e by OR Acid = + D B + H,OR wae 76H Fie R—o—8R :0H Q < i we = H.-H oa oa ‘a ‘a 4 KK. = Gu x, CG .. + _ = R—c—OR RO Sp aw OH RO? SH SSH l Ester E *OH + oe +H,0: + H,0: c Chapter 20 15 Chapter 20 16 c. To get a reasonable yield of ester we need to: • use excess alcohol • distill ester off as soon as it is formed Chapter 20 17 d. formation of lactones - must be 5 or 6 membered rings G. Synthesis and uses of acid chlorides 1. synthesis a. SOCl2 and PCl5 Chapter 20 20 b. general mechanism R C O Cl + :N R C O N + ClR C O Cl N Another example… Chapter 20 21 H. Esterification with diazomethane 1. overall reaction R C O OH + CH2N2 R C O OCH3 2. mechanism 3. example Chapter 20 22 I. Direct condensation of carboxylic acids with amines We can make this a much better reaction by: 2. DCC - dicyclohexylcarbodiimide 1. general reaction Chapter 20 25 K. Reduction of carboxylic acids 1. general reaction 2. mechanism Chapter 20 26 3. alternatives - we can stop at the aldehyde stage by using bulky aluminum hydrides R C O Cl + LiHAl[OC(CH3)3] R C O H L. Alkylation of carboxylic acids 1. general reaction Recall: R X + 2 Li R Li + LiX 2. mechanism 10: :0: O: Li | H RLi RH + 4 addition R I rut ; ‘ pe “™g-" deprotonation “PBT it a R 5 R 7 OF Li | R—Li a A dianion wey +. 703 Li :OH Or +: oe . | sot OL l si, te I = Li c oe . oe = | H,0% | a “R R R Hydrate Ketone _ali* O02 te He IF ea — A—c—ér —-G = Uc! +R I~ R~ ~O! | 5 Q : Leaving groups? Lit No! ‘ ui? - Ve R—c—o: OS Cc. + 30: ks R~ “SR R bie 20: 10: el, — I #05 ; i RR 27 R This reaction is fine, as long as L is a good leaving group