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Property Relationships Acid-Base Chemistry W 109, Structure & Properties, Acid-Base CHEM 109, Lecture 1 Structure – Property Relationships Acid-Base Chemistry McMurry & Begley (M&B) Chapter 1.1-1.2 (posted on CHEM 109 website) CONCEPT MAP: CHEMICAL STRUCTURE & PROPERTY RELATIONSHIPS WHAT DO WE KNOW WELL & WHAT COULD WE KNOW BETTER? The intention of this exercise is to figure out your current knowledge of the relationship between chemical structures and properties. Perhaps more importantly, we want to identify misconceptions or gaps in knowledge. Learning that you don’t understand something as well as you thought is actually a good thing! This will be based on your knowledge and, eventually, that of your peers. No outside resources such as cell phones, notebooks, textbooks, etc. are necessary. Before Class: Cut out each term on page E1-3 to create a set of cards. Begin to categorize and relate the fundamental general chemistry terms to each other by moving the term cards around. Brainstorm your current understanding of each term on a separate sheet of paper. Draw structures and/or figures to exemplify the term where appropriate (this is appropriate for most terms). Create a concept map (example on next page) with these terms – use the cards, write the terms by hand, or use a digital format such as ThinkSpace or Mindmeister. Add terms and links as necessary to complete your map. There are many, many ways to organize and describe these terms. Do what make sense to you! I can’t stop you from looking up terms on your own, but I’d recommend avoiding this as much as possible. Searching for and reproducing someone else’s definition is not nearly as useful as creating your own. If there’s anything you don’t know – that’s ok! Leave the card blank. Maybe you’ll remember it tomorrow or when you get to class. In Class: Instructors will facilitate rotations for you to discuss parts of your concept map and collaborate with your peers to build a new one. Think about how you’ll share your ideas to your classmates on the first day of class. Quick reference to the terms: Intramolecular Lewis structure Boiling Polar Forces Skeletal structure Ionic Bond Melting Non-polar Hybridization Covalent Bond Dissolve Nucleophile Intermolecular Molecular Geometry Dissociate Electrophile Forces Bond Polarity Hydrogen bond Salt Mechanism Molecular Polarity London Dispersion Hydrocarbon Arrow Pushing Dipole Dipole-Dipole Solubility Chemical Reaction Electronegativity Ion-Dipole Alcohol Physical Change L1-1 109, Structure & Properties, Acid-Base L1-2 109, Structure & Properties, Acid-Base Pre-class assignment: Color each column (see title), cut into cards, make concept map Column 1 - Blue Column 2 - Red Column 3 – Green Column 4 - Yellow Intramolecular Lewis structure Boiling Polar Forces Skeletal Ionic Bond Melting Non-polar structure Hybridization Covalent Bond Dissolve Nucleophile Molecular Intermolecular Dissociate Electrophile Geometry Forces Bond Polarity Hydrogen bond Salt Mechanism Molecular London Hydrocarbon Arrow Pushing Polarity Dispersion Chemical Dipole Dipole-Dipole Solubility Reaction Electronegativity Ion-Dipole Alcohol Physical Change L1-3 109, Structure & Properties, Acid-Base L1-4 109, Structure & Properties, Acid-Base ACID-BASE CHEMISTRY Rulz to Live By Bronsted-Lowry Lewis (BL) Acid Base pKa = - log Ka = AFFINITY OF AN ACID FOR ITS PROTON eqm favors the weaker acid Acid Dissociation Equation: HA Ka = pKa = What does it mean if Ka > 1? If Ka < 1? If Ka = 1? ARROW-PUSHING = the language / symbology of this class! What do arrows push? What are the possible outcomes of arrow pushing? ELECTRON RICH TO ELECTRON POOR Identify the acid, base, conjugate base, conj. acid, and direction of equilibrium (eqm) Draw proper Lewis structures & mechanism for the reaction above L1-5 109, Structure & Properties, Acid-Base Organic Acid-Base Reactions Amino acid residues = acids & bases in enzyme active sites: pKa’s to Memorize Approximating pKa’s: Into which pKa family does each compound belong? OH HO NH2 HO Norepinephrine L1 & L2 HW “due” in discussion next week (quiz directly from HW) – assignment online Next time: Electrophilic Add’n & Substitution Reaction Mechanisms L1-6 109, Binder E-philic Add’n / SN1 & SN2 CHEM 109, Lecture 2 Mechanism Review 1. Electrophilic Addition (E-philic Add’n) 2. Nucleophilic Substitution (SN1 & SN2) * Given starting materials and either product(s) or name of mechanism, you should be able to complete the mechanism and/or draw the product(s). MECHANISM REVIEW 1. Electrophilic Addition to Alkenes E-philic Add’n in Synthesis: Acid-Catalyzed Hydration of Alkenes E-philic Add’n in Biology: Biosynthesis of -terpineol OP O 3- 2 6 PP i Intramolecular Electrophilic Addition Linalyl diphosphate Carbocation Rearrangement H2O H2O O H H OH -Terpineol L2-1 109, Binder E-philic Add’n / SN1 & SN2 2. Nucleophilic Substitution SN1 or SN2 2A. Unimolecular Nucleophilic Substitution (SN1) Mechanism SN1 in Synthesis (8L Lab Practical): SN1 in Biology: Biosynthesis of geraniol, rose oil component L2-2 109, Binder E-philic Add’n / SN1 & SN2 2B. Bimolecular Nucleophilic Substitution (SN2) Mechanism SN2 in Williamson ether synthesis (McMurry Chapter 18) SN2 in Biology: Synthesis of Adrenaline Hint: the most basic atom is also the best nucleophile! Next time… Carbonyl Mechanisms: McMurry & Begley (M&B) Chapter 1.5-1.7 Next week in discussion… Open notebook quiz directly from week 1 HW (posted online) o Take a few days or at least sleep on it before checking the solutions online! L2-3 109, Binder E-philic Add’n / SN1 & SN2 L2-4 109, Binder Nuc Add’n to Ald / Ket CHEM 109, Lecture 3 3. Nucleophilic Addition Reactions to Aldehydes & Ketones (Nuc Add’n) A. Alcohol Formation B. Imine (Schiff Base) Formation C. Acetal Formation D. Conjugate (Michael) Addition * Given starting materials and either product(s) or name of mechanism, you should be able to complete the mechanism and/or draw the product(s). CARBONYL MECHANISM REVIEW The New Guy: Michael Addition (AKA conjugate addition, AAKA 1,4-addition) Another new guy: Claisen condensation (lecture 4) L3-1 109, Binder Nuc Add’n to Ald / Ket 3. Nuc Add’n Rxns to Aldehydes & Ketones 3A. Alcohol Formation… Synthesis: Sodium borohydride reduction of acetone 1. NaBH + O 4 2. H2O, H alkoxide Synthesis: Grignard addition to acetone + O 1. CH3MgBr 2. H2O, H alkoxide Nuc Add’n in Biology: Fatty acid synthesis 3B. Imine (Schiff Base) Formation Synthesis: Treatment of acetone with ammonia L3-2 109, Binder Nuc Add’n to Ald / Ket 3B. Imine (Schiff Base) Formation (cont’d) Biosynthesis of Amino Acids: 2- O3PO - N CO2 HN OH 3C. (Hemi)Acetal Formation Synthesis: Treatment of acetone with ethanol + H+ H H O O :B H2O hemiacetal H O O O :B Hemiacetals in Nature: Carbohydrates L3-3 109, Binder Nuc Add’n to Ald / Ket 3D. Conjugate 1,4 (Michael) Addition Synthesis O R2CuLi O R enolate Biology: Citric Acid Cycle Apply the template mechanism from page 1 and keep track of those protons! Next time… Nucleophilic Acyl Substitution & Carbonyl Condensation Reactions (aldol & Claisen) - M&B Chapter 1.6-1.7 L3-4 109, Binder Nuc Add’n to Ald / Ket L3-5 109, Binder NAS / aldol & Claisen Condensation CHEM 109, Lecture 4 4. Nucleophilic Acyl Substitution (NAS) 5. Carbonyl Condensation A. Aldol Condensation B. Claisen Condensation * Given starting materials and either product(s) or name of mechanism, you should be able to complete the mechanism and/or draw the product(s). 4. Nucleophilic Acyl Substitution (NAS) Synthesis: Fischer Esterification – Fruity Fragrances BIOREACTIVITY SERIES toward NAS NAS in Biology: Glycolysis (first step) CHO H OH HO H H OH ADP H OH 2- CH2OPO3 Glucose-6-phosphate L4-1 109, Binder NAS / aldol & Claisen Condensation 5. Carbonyl Condensation Reactions Enolate Ions 5A. Aldol Condensation Draw that mechanism in one step: Retro-aldol Reaction H O O + NaOH H O H O enolate Retro-aldol: Glycolysis 2- CH2OPO3 C O 2- CH2OPO3 CHO HO H aldolase C O + H OH H OH CH OH CH OPO 2- H OH 2 2 3 Dihydroxyacetone Glyceraldehyde- CH OPO 2- 2 3 phosphate 3-phosphate Fructose-1,6- (DHAP) (GAP) bisphosphate (F1,6P) Re-draw F1,6P below and propose a one-step mechanism… L4-2 109, Binder NAS / aldol & Claisen Condensation 5B. Claisen Condensation Draw that mechanism in two steps! Claisen Condensation in Biology: Lipid Biosynthesis Retro-Claisen Reaction: L4-3 109, Binder NAS / aldol & Claisen Condensation Carbonyl Reaction Overview Nucleophilic Addition Nucleophilic Acyl Substitution (NAS) to Aldehydes & Ketones with Esters, Thioesters, Carboxylic Acids, Amides Aldol Condensation Claisen Condensation Next time…Elimination, Redox, pKa and Amino Acids L4-4 109, Binder Elimination, Redox, Acids & pKa’s CHEM 109, Lecture 5 Mechanism Review 6. Elimination Reactions 7. Oxidation & Reduction Reactions Polyprotic Acids & pKa o Relationship between (pKa of acid) and (pH of solution) o Titration of amino acids ** Know the full structures & abbreviations of the 20 common amino acids (p 7) ** 6. Elimination Reactions What is eliminated? E2 E1 E1cB Elimination in synthesis… strong base E2 Br weak base E1 - Br Br carbocation H strong base E1cB O Br Br- enolate Elimination in Biology – Fatty Acid Synthesis L5-1 109, Binder Elimination, Redox, Acids & pKa’s 7. Oxidation and Reduction (Redox) Reactions Reduction in Synthesis Redox in Biology… REDUCING AGENTS: NADH & NADPH OXIDIZING AGENTS: NAD+ & NADP+ L5-2 109, Binder Elimination, Redox, Acids & pKa’s Polyprotic Acids & pKa How does an acid’s pKa relate to the pH of a solution of that acid? HA H+ + A- pH = pKa + log [A-] [HA] pH < pKa pH = pKa
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