CHEM 2211 1st Edition Lecture 2 Outline of Last LectureI. Molecular Orbital Theory (MO)II. Linear Conservation of Atomic Orbitals (LCAO)Outline of Current LectureI. Brᴓnsted-Lowry Acid Base TheoryII. Ka valueIII. Factors that affect KaIV. Conjugate Acids and BasesV. Resonance StructuresChapter 3I. IUPACII. Line Angle StructureIII. AlkanesVocabularyBrᴓnsted-Lowry Acid Base TheoryKa valueDepronatepKaHydrogen bondsLondon Dispersion ForcesElectronegativityConjugate Acids and BasesEquilibriumResonance StructuresDelocalization of electronsIUPACLine Angle StructureHeteroatomsAlkanesCurrent LectureI. Brᴓnsted-Lowry Acid Base TheoryA. Acids are defined as anything that releases an H+B. Bases are defined as H+ acceptorsi. They form OH- in waterII. Ka valueA. Ka values define the likelihood of a chemical to depronate in a specific solventB. The higher the Ka value the stronger the Acidi. String Acids are defined as chemicals which readily depronate and have strong conjugate basesC. Ka is found using the following equation:+¿H3O¿¿−¿A¿¿¿Ka=¿D. However, since Ka is generally a very, very small number, we use the pKa instead. It is found using the following equation:p Ka=−log KaE. The lower the pKa number the stronger the AcidIII. Factors that effect pKaA. Nature of Groupi. H-O-H vs. H-F (pKa = 15.5 vs. pKa = 3-5)ii. Because water is held together by hydrogen bonds instead of only London dispersion forces like in hydrofluoric acid, the H+ ion is easier to remove from HF. This means HF is a stronger acid than water.B. Sizei. Example: HI > HBr > HCl > HFii. HI is the strongest Acid because the large size of Iodine and the small size of Hydrogen causes poor orbital overlap. This phenomenon is comparableto bonding a marble (H+) with a basketball (I-).C. Electronegativity IV. Conjugate Acids and Bases−¿+ BH−¿ ↔ A¿HA+ B¿A. HA is the acid, A- is the conjugate base.B. B- is the base. BH is conjugate acid.C. Equilibrium shifts to the side with the lowest pKa value.i. Example:D. The equilibrium shifts to the left because the pKa of the Acid is higher than the pKa of the conjugate Acid. This means the conjugate acid is more likely to dissociate in the solution than the Acid.V. Resonance Structures: Brief OverviewA. Resonance is the average of two or more structures which differ only in the placement of electronsB. It adds stability to a moleculei. Example #1:ii. The Resonance structure (number 3) is more stable than numbers 1 and 2because the electrons are shared across the Oxygens.iii. Example #2:iv. As seen by the mechanism above, the phenol is more stable because the electrons are shared around the aromatic ring as opposed to staying on one atom. This delocalization of electrons makes phenol less likely to react with other molecules.Chapter 3I. IUPAC: International Union of Pure and Applied ChemistryA. Created the nomenclature for organic chemistryi. Prefix (specifies number of carbons) + suffix (specifies the type of molecule)ii. KNOW the first thirteen prefixes1. Meth-2. Eth-3. Prop-4. But-5. Pent-6. Hex-7. Hept-8. Oct-9. Non-10. Dec-11. Undec-12. Dodec-13. Tridec-II. Line Angle Structure (for drawing molecules)A. Rulesi. Lines are bondsii. Vertices and end points are carbonsiii. The Hydrogens are implicitiv. Heteroatoms get Hydrogens drawn in1. Heteroatom- atom other than carbonB. ExampleC. Example of HeteroatomIII. Alkanes (suffix –ane)A. Singly bonded carbonsB. NonpolarC. Held together by London Dispersion ForcesD.
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