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Unformatted text preview: Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series CH 310/318 M LECTURE 8 Textbook Assignment: Chapter 4-Contd Todays Topics: pKa pKa; ; Thermochemistry Thermochemistry-Mechanisms Mechanisms 1 Notice & Announcements: Exam 1: Grading in progress Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series pK pK a- Some Organic & Inorganic Acids Some Organic & Inorganic Acids CH 3 NH 2 CH 3 NH 3 + H 2 O HO- CH 3 CH 2 OH CH 3 CH 2 O- HC CH HC C- H 2 H- NH 3 NH 2- CH 2 = CH 2 CH 2 = CH- CH 3 CH 3 CH 3 CH 2- Acid Fo rm ula p K a Co nju gate Bas e Ethan e Am mo nia Ethan ol W ater 35 25 51 38 15.7 15.9 S tro ng er co nju gate base W eaker acid M ethy lamm on ium ion 10.64 Acety lene H yd ro gen Ethy lene 44 2 HI I- HBr Br- HCl Cl- H 2 SO 4 HSO 4- H 2 O H 3 O + H 3 PO 4 H 2 PO 4- C 6 H 5 COOH C 6 H 5 COO- CH 3 COOH CH 3 COO- H 2 CO 3 HCO 3- H 2 S HS- NH 3 NH 4 + C 6 H 5 OH C 6 H 5 O- HCO 3- CO 3 2 - 3 2 3 3 Bicarbo nate io n Phen ol Am mo niu m io n Carbo nic acid Acetic acid Benzo ic acid Pho sp ho ric acid Sulfuric acid H yd ro gen ch loride H yd ro gen brom ide H yd ro gen iod ide 10.33 4.76 6.36 9.24 9.95-5.2-7-9-8 4.19 2.1-1.74 H yd ro niu m io n Weaker co nju gate base Stron ger acid H yd ro gen su lfid e 7.04 Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series Acid Acid-Base Equilibria Base Equilibria Equilibrium favors reaction of the stronger acid and stronger base to give the weaker acid and weaker base. CH 3 COOH NH 3 CH 3 COO- NH 4 + + + 3 Ammonia (stronger base ) Acetate ion (weaker base) Acetic acid p K a 4.76 (stronger acid) Ammonium ion p K a 9.24 (weaker acid) Favors the side with the highest pKa Favors the side with the highest pKa (i.e weaker acid) (i.e weaker acid) Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series Consider the reaction between acetic acid and sodium bicarbonate. s write the equilibrium as a net ionic equation. s omit Na + because it does not undergo any chemical change in the reaction. Acid Acid-Base Equilibria Base Equilibria 4 s Equilibrium lies to the right. s Carbonic acid forms, which then decomposes to carbon dioxide and water....
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- Spring '08