1. 1.3 Covalent Bonding - Electrons Shared 1.2-1.3 Bonding 1.2 Ionic Bonding - Electrons Transferred type of bond that is formed is dictated by the relative electronegativities of the elements involved Atoms trying to attain the stable configuration of a noble (inert) gas - often referred to as the octet rule YSU

2. Electronegativity the attraction of an atom for electronsYSU

3. 1.2 Ionic bonding Electrons Transferred Big differences in E.N. values Metals reacting with non-metals YSU

4. Important Electronegativity Values H 2.1 LiBeBCNOF 1.02.02.53.03.54.0 Cl 3.0 Br 2.8 I 2.5YSU

5. 1.3 Covalent Bonding - Similar electronegativities H. + H. H : H Hydrogen atomsHydrogen molecule B.D.E +104 kcal/mol B.D.E +104 kcal/mol B.D.E. = bond dissociation energy YSU

6. 1.3 Lewis Dot Structures of MoleculesYSU

7. 1.4 Double bonds and triple bonds Double bonds - alkenes Triple bonds - alkynesYSU

8. 1.5 Polar covalent bonds and electronegativity H 2 HFH 2 O CH 4 CH 3 Cl Based on electronegativity YSU

9. 1.6 Structural Formula - Shorthand in Organic ChemistryYSU

10. 1.6 Constitutional Isomers Same molecular formula, completely different chemical and physical properties YSU

11. 1.7 Formal Charge Formal charge = group number - number of bonds -number of unshared electrons YSU

12. 1.8 Resonance Structures - Electron Delocalization Table 1.6 – formal rules for resonanceYSU

13. 1.9 Shapes of Molecules Shapes of molecules are predicted using VSEPR theory YSU

14. 1.9 Shape of a molecule in terms of its atoms Figure 1.9 Table 1.7 – VSEPR and molecular geometry YSU

15. YSU

16. Trigonal planar geometry of bonds to carbon in H 2 C=O Linear geometry of carbon dioxide YSU

17. 1.10 Molecular dipole momentsYSU Figure 1.7

18. Curved arrows used to track flow of electrons in chemical reactions. Consider reaction shown below which shows the dissociation of AB: 1.11 Curved Arrows – Extremely ImportantYSU

19. Many reactions involve both bond breaking and bond formation. More than one arrow may be required. Curved Arrows to Describe a ReactionYSU

20. 1.12 Acids and Bases - Definitions Arrhenius An acid ionizes in water to give protons. A base ionizes in water to give hydroxide ions. Brønsted-Lowry An acid is a proton donor. A base is a proton acceptor. Lewis An acid is an electron pair acceptor. A base is an electron pair donor. YSU

21. HAB : B H : A – + 1.13 A Brønsted-Lowry Acid-Base Reaction A proton is transferred from the acid to the base. + + Base acid conjugate acid conjugate base YSU

22. Proton Transfer from HBr to Water YSU

23. Equilibrium Constant for Proton Transfer YSU

24. Acids and Bases: Arrow PushingYSU

25. YSU

26. YSU

27. Need to know by next class: pKa = -log 10 Ka STRONG ACID = LOW pKa WEAK ACID = HIGH pKa HI, HCl, HNO 3, H 3 PO 4 pKa -10 to -5 Super strong acids H 3 O + pKa – 1.7 RCO 2 HpKa ~ 5acids PhOHpKa ~ 10get H 2 O, ROHpKa ~ 16weaker RCCH (alkynes)pKa ~ 26 RNH 2 pKa ~ 36Extremely weak acid RCH 3 pKa ~ 60Not acidic at allYSU

28. 1.14 What happened to pK b ? A separate “basicity constant” K b is not necessary. Because of the conjugate relationships in the Brønsted- Lowry approach, we can examine acid-base reactions by relying exclusively on pK a values. pKa ~60 Essentially not acidic Corresponding base Extremely strong YSU

29. 1.15 How Structure Affects Acid/Base Strength Bond Strength Acidity of HX increases (HI>HBr>HCl>HF) down the periodic table as H-X bond strength decreases and conjugate base (X: - anion) size increases. HFHClHBr HI pKapKapKapKa3.1-3.9-5.8-10.4 weakest acid strongest acid strongest H—X bond weakest H—X bondYSU

30. Electronegativity Acidity increases across periodic table as the atom attached to H gets more electronegative (HF>H 2 O>H 2 N>CH 4 ). pKapKapKapKa 6060606036 16 163.1 weakest acid strongest acid least electronegative most electronegative CH 4 NH 3 H2OH2OH2OH2O HFYSU

31. Inductive Effects Electronegative groups/atoms remote from the acidic H can effect the pKa of the acid. pKa = 16 pKa = 11.3 O – H bond in CF 3 CH 2 OH is more polarized CF 3 CH 2 O- is stabilized by EW fluorine atomsYSU

32. Resonance Stabilization in Anion Delocalization of charge in anion (resonance) makes the anion more stable and thus the conjugate acid more acidic e.g. (CH 3 CO 2 H > CH 3 CH 2 OH). pKa ~16 pKa ~5YSU

33. 1.16 Acid-base reactions - equilibria The equilibrium will lie to the side of the weaker conjugate baseYSU

34. 1.17 Lewis acids and Lewis bases Product is a stable substance. It is a liquid with a boiling point of 126°C. Of the two reactants, BF 3 is a gas and CH 3 CH 2 OCH 2 CH 3 has a boiling point of 34°C.YSU