StructurepKaHybridizations characterLecture 6Outline of Last Lecture I. Dispersion ForcesII. Trends in Physical PropertiesA. Small vs. larger moleculesB. Boiling pointsC. SolubilitiesCHEM 333 1st EditionI. Hydrophobic vs. hydrophilicII. Reactions mechanismsIII. Homolytic vs. heterolytic cleavageIV. Acid/BaseA. Bronsted acidB. Bronsted baseC. ExampleD. How to tell if it is a strong or a weak acidE. TrendsF. pKa numbers to memorizeG. How equilibrium lies toward the weaker acidOutline of Current LectureI. How to determine acidityA. ElectronegativityB. Larger sizeC. ResonanceD. InductionE. HybridizationII. How to determine strongest baseIII. Lewis acid/baseIV. Alkanes vs. CycloalkanesCurrent LectureI. How to determine acidityA. Electronegativity:a. Example: Acidity: O > N > C (this method of determining acidity onlyworks when you are looking at elements on the same row of the periodic table). Oxygen is happier to have the negative charge over the carbon because electrons are held closer to the nucleus.B. Larger size: Bigger is better for negative charge (look for atoms in the same column)a. Example:Size: F < Cl < Br < IAcidity: F < Cl < Br < IC. Resonance: If there is no resonance available, it is not as stable. If there is resonance available, it is more stable. a. Example:D. Induction: bond polarization due to presence of electronegative atom �(distance dependent)a. Example: Stabalization falls off rapidly with distance pKa = 4.76 pKa = 2.86b. Example:E. Hybridization: More s character = more acidica. Example: is most acidic compared to the others in the table below. The negative charge is located closer to the nucleus when there is more s character.Structure pKa Hybridization s characterC2H650 sp325%44 sp233%25 sp 50%b.II. How to determine strongest baseA. Look at stability. Least stable = best base.B. Look at pKa of its conjugate acid. Weakest conjugate acid = strongest/best base.C. Example: What is the strongest/best base?III. Lewis acid/baseA. Lewis acid: electron acceptorB. Lewis base: electron donorC. Example:Lewis Acid Lewis BaseIV. Alkanes and CycloalkanesA. Alkane: saturated hydrocarbon (maximum number of hydrogens possible)B. Cycloalkane: carbons are connected in a ringC. Carbons in alkanes are sp3, bond angles are
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