CHEM 3153 1st EditionExam# 3 Study Guide Lectures: 19 - 29Lecture 19 (March 2)Synthesis Involving Addition to C==OYou need to know the following reactions learned from organic chemistry 1:1. Adding OH2. Making C==O3. Adding to C==OYou don’t need to know the mechanism, just how to apply the mechanisms1. Adding OH to Alkenes- Markovnikov- Anti-Markovnikov- Dihydroxylation (syn only)2. Making C==O- Oxidationo PCC/DCM to primary alcohols results in aldehydeso Na2Cr2O7/H2SO4 H2O to secondary alcohols results in carboxylic acids- Ozonolysis3. Adding to C==O- Reduction- GrignardOther reactions to know:- Acetal/thioacetal formation- Imine/enamie formation- Cynohydrin formation- Witting reactionTwo Types of Reaction Problems1. Synthesize the product from a specific starting materialEx:You must show aretrosynthesis to solve and get credit. You must use disconnection arrows.Synthesis:Lecture 20 (March 9)2. Synthesize the product from restricted starting materialsEx: Synthesize this from starting materials of 3 carbons or lessRetrosynthesis:Synthesis:It is very important to remember to list reagents in steps when necessary! For example, the Grignard reagent must be in a separate step from the acid because an acidic environment woulddestroy the Grignard reagent and the reaction wouldn’t proceed.Chapter 21: Carboxylic Acid and DerivativesCarboxylic Acid: Carboxylic Acid Derivative:X = heteroatomEx: halogen, OR, NR2, OAc- Total of 3 bonds to heteroatomsExamples of Carboxylic Acid Derivatives- Carboxylic acid derivatives are electrophilesEx: - Can add nucleophiles to carboxylic acids and derivativesReactivity of Carboxylic Acid DerivativesIntegrated Question:1. Which one of the following statements is correct?A) Molecule A is a betterelectrophile,becauseitscarbon2hasalargerδ+thanmoleculeB’scarbon2.B) Molecule A is a better electrophile, because its carbon 2 has a smaller δ+ than molecule B’s carbon 2.C) Molecule B is a better electrophile, because its carbon 2hasalargerδ+thanmolecule A’scarbon2.D) Molecule B is a better electrophile, because its carbon 2 has a smaller δ+ than molecule A’s carbon 2.Draw the resonance structures for both molecules.With molecule B, there is more competition with the other carbonyl the oxygen is attached to. Oxygen’s ed is split between both carbonyls, so it donates less. The lesser donation, the larger the δ+. C is correct.2. Which one of the following statements is correct?A) Molecule A is a betterelectrophile,becauseitscarbon2hasalargerδ+thanmolecule C’scarbon2.B) Molecule A is a better electrophile, because its carbon 2 has a smaller δ+ than molecule C’s carbon 2.C) Molecule C is a better electrophile, because its carbon 2hasalargerδ+thanmolecule A’scarbon2.D) Molecule C is a better electrophile, because its carbon 2 has a smaller δ+ than molecule A’s carbon 2.Draw the resonance structures for both molecules.There molecules are practically the same except for oxygen and nitrogen. These two elements are located in the same row of the periodic table. So, the positive charge on nitrogen is more favorable since it is less EN than oxygen (oxygen is closer to the upper right of the periodic table). Thus, nitrogen’s double bond is more prevalent in the molecule. The positive charge on oxygen is less favorable, so that resonance structure appears less. With the double bond being less prevalent, there is less ed at carbon 2 and thus a larger δ+ on molecule A. A is correct.3. Which one of the following statements is correct?A) Molecule A is a betterelectrophile,becauseitscarbon2hasalargerδ+thanmolecule D’scarbon2.B) Molecule A is a better electrophile, because its carbon 2 has a smaller δ+ than molecule D’s carbon 2.C) Molecule D is a better electrophile, because its carbon 2hasalargerδ+thanmolecule A’scarbon2.D) Molecule D is a better electrophile, because its carbon 2 has a smaller δ+ than molecule A’s carbon 2.Chlorine can’t donate ed since it uses its 3p orbital and carbon uses its 2p orbital. Like with the S==O, there isn’t good overlap. The resonance chlorine doesn’t contribute much, making its carbon very electron poor. C is correct.4. Rank the molecules from most to least electrophilic.D > B > A > CChlorine can’t donate anything, so its carbon 2 is very electron poor; then B because the two carbonyls are in competition so carbon 2 can’t get as much donation as A and C can; A because its double bond resonance structure is much less common than C’s.March 11 (Lecture 21)Which of the following two compounds do you expect to be a better electrophile and why?- Look for the carbonyl carbon, where we would find the δ+- Draw out resonance structures- How much do they contribute to the resonance hybrid?o In this example, O and S are in the same column of the period table, so we need to look at their size next.o S uses its 3p orbital which isn’t good overlap with C’s 2p orbital Therefore, the structure on the right for the S molecule doesn’t contribute as much to the resonance hybrid There is a larger δ+ on the C of C==S since it can’t receive any ed from So Molecule B is the better electrophileTypes of Mechanisms that Occur for Carboxylic Acid DerivativesCarboxylic Acid Derivatives as Electrophiles1. Acidic conditions – look for a strong acid (H2SO4, HCl, TsOH)Mechanism:- Kick off the X group when collapsing tetrahedral intermediate- For any reaction under acidic conditions, you cannot have any strong basesEx: OCH3- is a strong base and can’t exist in acidic conditionsIntegrated Question:1. Show the mechanism for the first step of the reaction.2. Show the mechanism for the next step of the reaction.3. Show the mechanism for the next step of the reaction.4. Show the mechanism for the next step of the reaction.5. Show the mechanism for the next step of the reaction.6. Show the mechanism for the last step of the reaction.March 13 (Lecture 22)Consider the following reaction:A. Draw the mechanism for the reaction and show the product.B. Give two ways we could push the equilibrium toward the products.Mechanism:Note: this is in the textbook as Fisher EsterificationWe can push toward equilibrium by either removing water or adding EtOH.2. Neutral conditions – No strong acid or strong base (no positive charges)Here’s a specific example:Mechanism:3. Basic conditions – Look for a strong base (NaOH, NaOR, a negatively charged nuc)- If the nuc is OH, depotonate the product then