Lecture 5Outline of Last Lecture I. HydrocarbonsA. AlkanesB. AlkenesC. AlkynesCHEM 333 1st EditionII. Functional GroupsA. Alkyl HalidesB. AlcoholsC. EthersD. AminesE. AldehydesF. KetonesG. Carboxylic AcidsH. EstersI. AmidesJ. NitrilesIII. Physical PropertiesOutline of Current Lecture I. Dispersion ForcesII. Trends in Physical PropertiesA. Small vs. larger moleculesB. Boiling pointsC. SolubilitiesI. 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 acidCurrent LectureI. Dispersion Forces: very weak intermolecular forces of attraction resulting from the interaction between temporary induced dipolesA. Happen at any time where there can be polarization of electron desnisty because electrons moveB. Gives a temporary dipole moment that can induce a temporary dipole in a molecule next to itC. The attractive force is temporaryII. Trends in Physical PropertiesA. Small vs. larger moleculesa. Small molecules: less surface area = less interaction = weaker attractionb. Larger molecules: more surface area = more interaction = stronger attractionB. Boiling points: stronger intermolecular interactions increase the boiling pointC. Solubilities: “Like dissolves like.” For example, oil dissolves in oil and water dissolves in water.a. Polar and ionic solids usually dissolve in polar solventsb. Polar liquids are miscible, meaning they can mix togetherc. Nonpolar solids are soluble in nonpolar solventsd. Nonpolar solvents are miscible, meaning they can mix togetherIII. Hydrophobic vs. hydrophilicA. Hydrophobic: incompatible with waterB. Hydrophilic: water lovingC. Example: H3C - OHa. The OH is hydrophylic.D. Example: Which is hydrophilic?E.The second structure is hydrophylic because it would dissolve in H2OV. Reactions mechanisms: a description of molecular events as reactants become products. Watch the flow of electrons and atoms.VI. Homolytic vs. heterolytic cleavageA. Homolytic: bond breaks and one electron goes to each atoma. Example: (red line shows where electrons go)B. Heterolytic: bond breaks and one atom gets both electrons, the other gets nonea. Example: (red lines show where electron goes)VII. Acid/BaseA. Bronsted acid: substance that gives up a proton (proton donor)Acid-H H2O ⇌ Acid- H3O+B. Bronsted base: substance that can accept a proton (proton acceptor)Base H2O ⇌ Base-H OHC. Example: (red line shows where electrons move to)a. HCl H2O ⇌ Cl- H3O+ C⇌D. How to tell if it is a strong or a weak acid: measure acidity and get a pKa valuea. HA H2O ⇌ A- H3O+ (determine concentration of each component)b. Keq = [products]/[reactants] = [A-][H3O+]/[HA][H2O]c. Keq[H2O] = Ka = [A-][H3O+]/[HA]d. Generally express Ka as -logKa = pKaE. Trends:a. Larger pKa = weaker acidb. Small pKa = stronger acidc. Weak acid = stronger conjugate based. Strong acid = weaker conjugate baseF. pKa numbers to memorizea. C2H6, pKa = 50b. , pKa = 44c. NH2 - H, pKa = 38d. , pKa = 25e. , pKa = 16f. HO - H, pKa = 15.7g. , pKa = 10h. H3N+ - H, pKa = 9i. H2CO3, pKa = 6j. , pKa = 5k. H3O+, pKa = -1.7l. HCl, pKa = -7m. H2SO4, pKa = -9n. HI, pKa = -10G. How equilibrium lies toward the weaker acida. Example: H-Cl H2O ⇌ Cl- H3O+ pKa -7 15.7 -1.7Equilibrium lies towards the right side of the equation because H3O+ is weaker than HCl. This can be seen by the pKa of -7 < -1.7, and the lower the pKa, the stronger the acid. Since we are looking for the weaker acid as the side which the equilibrium lies, H3O+ with the pKa of -1.7 would be the weaker acid where the equilibrium will shift