Chapter 2 - Polar Covalent Bonds; Acids and Bases For questions 1-10 give the letter of the term that best matches the given definition. a. Brønsted-Lowry Acid f. Ionic Bond b. Brønsted-Lowry Base g. Covalent Bond c. Lewis Acid h. Polar-Covalent Bond d. Lewis Base i. ydrophobic e. Electronegativity j. ydrophilic 1. Any species that can accept electrons. c 2. A bond between two atoms differing in electronegativity by 0.5 2. h 3. A term used to describe a water loving species. j 4. A compound that can donate a proton. a 5. The ability of an atom to attract the shared electrons in a covalent bond. e 6. A term used to describe a water fearing species. i 7. Any species that can donate electrons. d 8. A bond between two atoms differing in electronegativity by < 0.5 g 9. A compound that can accept a proton. b 10. A bond between two atoms differing in electronegativity by > 2. f 4 Chapter 2: Polar Covalent Bonds; Acids and Bases
Calculate the formal charges on the indicated atoms in each compound below. : Cl : : P : Cl : 6. Cl: 5. 7. : C : 8. 11. The formal charge on phosphorous is. 1 12. The formal charge on oxygen is. 1 13. The formal charge on carbon is. 1 14. The formal charge on oxygen is. 1 Phenylalanine is an amino acid that is essential to human nutrition. The representation below shows the structure of phenylalanine at physiological p. Consider this structure to answer the following questions. A. * C 2 CC 3 15. Assign any formal charges to atoms in this representation of phenylalanine. B. phenylalanine C 2 CC 3 16. The oxygen atom labeled A. has non-bonding electrons. four 17. The oxygen atom labeled B. has bonding electrons. two Test Items for McMurry s rganic Chemistry, Seventh Edition 5
Use the δ / δ convention and the crossed arrow ( ) to show the direction of the expected polarity of the indicated bonds in the following compounds. 18. The C F bond in fluorobenzene, F δ δ F 19. The C-Si bond in tetramethylsilane, (C 3 ) 4 Si 3 C C 3 δ δ Si C 3 C 3 20. The C bond in furan, δ δ Label the acid, conjugate acid, base, and conjugate base in each reaction below. 21. 22. C 3 a C 3 - a 2 C 3 a C 3 - a 2 acid base conjugate base conjugate acid - C 3 C 3 B 3 3 C B 3 C 3 C 3 C 3 B 3 3 C - B 3 base acid C 3 6 Chapter 2: Polar Covalent Bonds; Acids and Bases
Refer to the following equation to answer the questions below. Place the letter corresponding to the correct answer in the blank. pka = 18 pka = 15.7 (C 3 ) 3 C K (C 3 ) 3 C K 2 A. B. C. D. 23. The strongest Brønsted-Lowry acid in the equation is. D 24. The strongest Brønsted-Lowry base in the equation is. C 25. Will this reaction take place as written? Explain. o, the reaction will not take place as written because the strongest acid reacts with the strongest base to give the weakest conjugate acid and the weakest conjugate base. D (pk a = 15.7) is a stronger acid than A (pk a = 18). 26. An acid with a low pk a : a. is a weak acid b. is a strong acid c. has a weak conjugate base d. both b and c d 27. Circle all the Lewis bases in the group of compounds below. C 3 Cl BCl 3 FeBr 3 C 3 Cl BCl 3 FeBr 3 Test Items for McMurry s rganic Chemistry, Seventh Edition 7
28. Put a box around all the Lewis acids in the group of compounds below. C 3 Cl BCl 3 FeBr 3 C 3 Cl BCl 3 FeBr 3 29. Draw two resonance structures for the species below. C 3 C 3 C 3 C 3 30. Draw two resonance structures for the species below. : : C 2 : : : : : : C 2 C 2 C 2 31. Draw two resonance structures for the species below. : Ọ :. : Ȯ. : : Ọ. 8 Chapter 2: Polar Covalent Bonds; Acids and Bases
Consider the acidity constants below to answer the following questions. ACID STRUCTURE pk a phenol 10.00 ethanol water C 3 C 2 16.00 15.74 32. Which acid above will be almost completely deprotonated by a? phenol 33. Which acid has the strongest conjugate base? Ethanol is the weakest acid (largest pk a ) so its conjugate base, ethoxide, C3C2, will be the strongest base. 34. Explain why phenol has a much lower pk a than ethanol. Phenol is more acidic (has a lower pk a ) than ethanol because the phenoxide anion is resonance stabilized by the pi electrons in the ring. Ethoxide anion has no resonance stabilization. The negative charge is borne fully by oxygen. C 3 C 2 - : C 3 C 2 - : Ọ :. : : Test Items for McMurry s rganic Chemistry, Seventh Edition 9
Consider the reaction below to answer the following questions. : 35. Using the curved arrow formalism, show the flow of electrons for this reaction. : 36. Label the acid and the base in the reaction. : base acid Indole is pleasant smelling in highly dilute solutions and had been used in perfumery. Use the structure of indole, below, to answer the following questions. indole 37. Indole can function as a Bronsted-Lowry acid in the presence of strong bases. Formulate a reaction, showing electron flow with arrows, that demonstrates this reactivity of indole. B B 10 Chapter 2: Polar Covalent Bonds; Acids and Bases
38. Indole can function as a Lewis base in the presence of strong acid. Formulate a reaction, showing electron flow with arrows, that demonstrates this reactivity of indole. A A 39. The condensed structure for dimethyl ether looks symmetrical. owever, dimethyl ether has a dipole moment. Draw a structure that explains this and indicate the expected direction of the molecular dipole moment. C 3 C 3 dimethyl ether net dipole 3 C C 3 Consider the acid-base reaction below to answer the following questions. C 3 C C 3 base acid 40. Using the curved arrow formalism, show the flow of electrons for this reaction. C 3 C C 3 base acid 41. Write the products of this Lewis acid - base reaction. C 3 C C 3 C C 3 base acid C 3 Test Items for McMurry s rganic Chemistry, Seventh Edition 11