CHEM3410 Exam 1 Study GuideOutline of Chapter 14 I. Conjugated Dienes A. Conjugated vs NonconjugatedB. Definition of a Conjugated DieneC. Relative StabilityII. Synthesis of Conjugated DienesIII. Electrophilic Addition to Conjugated DienesA. 1,2 & 1,4 productsIV. Kinetic vs Thermodynamic ControlV. Diels-Alder CycloadditionsA. StereochemistryB. Endo/ExoOutline of Chapter 15VI. Benzene and AromaticityA. Definition of AromaticityB. Physical characteristicsC. Ortho, Para, MetaVII. Common Names of Aromatic Rings/ Benzene derivativesVIII. Rules of AromaticityA. Anti-aromaticsB. Aromaticity and acidityC. HeterocyclesOutline of Chapter 16I. Molecular Orbital TheoryII.Benzene ReactionsChapter 14I. Conjugated DienesA. Nonconjugated These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Recall from last semester that the presence of a single pi bond (a double bond) means that the carbons of the alkene are sp2 hybridized (containing s and p orbitals), and without pi bonds, thecarbon is sp3 hybridized (containing only s orbitals). The p orbitals in this diene do not overlap because they are separated by a central sp3 hybridized carbon; therefore, the molecule is a nonconjugated diene. The electrons are localized and unable to flow freely. B.1 Conjugated (Trans/E)In a conjugated diene, there will be four sp2 hybridized carbons in a row. A conjugated diene contains overlapping p orbitals from two alkenes that are connected to each other. The p orbitals line up, allowing for this overlap, thus they are in conjugation. Furthermore, there are is a delocalization of electrons because of the overlap of p orbitals, allowing the electrons to move freely. Delocalization increases stability. Conjugated dienes are more stable than nonconjugated dienes.B.2. Conjugated (Cis/Z)Again, note the four sp2 carbons in a row. This is a conjugated diene. However, note the stereochemistry. Is it more stable than the previous conjugated diene? No. Cis is less stable than Trans due to reduced steric strain. When the molecules eclipse in a cis molecule, there is steric strain. That strain is reduced in the trans relationship because the largest groups are not eclipsing. Recall the rules of stability from last semester:> >C. Relative Stability (Cis/Trans Conjugated vs Nonconjugated)> >Again, Nonconjugated is less stable than Conjugated, and Cis is less stable than Trans. The increase of stability between nonconjugated and conjugated is due to the delocalization of electrons due to the overlap of p orbitals. The relative stability of tans vs cis is due to the decreased steric strain. II. Synthesis of a Conjugated DieneRecall that last semester, we learned two manners in which to create alkenes from alkyl halides: dehydration of water and dehydrohalogenation.In the example above, we note that the first step of the reaction occurs in a single, concerted step, similar to an E2 reaction (notice the strong, bulky nucleophile). The strong, bulky nucleophile attacks the Hydrogen, causing the electrons from the bond formed between it and the carbon of the cyclohexane to return to the system, creating a double bond. That overloads the carbon attached to the bromine, kicking the bromine off. Next, we react the substance with NBS and uv light to create a radical (the radical symbol is faint and hard to see.) The radical thenattracts a radical Bromine from the NBS, creating an alkyl halide. We then repeat the E2 elimination like step to create a conjugated diene. Remember that the conjugated diene is morestable, thus more favored than its less stable, nonconjugated counterpart. Recall dehydration. In this example, we reduced the single alkene to an anti-diol with the addition of OsO4 and pyridine. We take that a step further via dehydration with Al2O3 in heat,and get the conjugated diene AND the alkyne. The conjugated diene will be slightly more prevalent in your final product due its stability.III. Electrophilic Addition to Conjugated DienesResonance gives us a second intermediate and a second product. The products are named “1,2 addition product” and “1,4 addition product” because of where we add things on the molecule. Hydrogen attaches to carbon one of the alkene as it is pulled on by the electrons from the double bond. Recall Markovnikov again – The carbocation forms that is more stable – that is why the Hydrogen attaches to “carbon 1.” The addition to 2 or 4 depends on resonance. The electrophile will attach to carbon 2 of the original alkene (the more stable, available carbon of the alkene from which we began), in the resonance structure, the electrophile will attach to carbon 4. For clarification, the resonance of the figures is displayed below with arrows of electron flow. Note that the arrow is coming from the double bond of the second alkene to carbon 2 or the carbon that shared a double bond with CH3 before electrophilic addition.Finally, in any conjugated diene system, our first intermediate should be the allylic that has resonance!! The only carbocation observed is the one with resonance (due to resonance stabilization)Only the bottom figure will form.IV. Kinetic vs Thermodynamic Controls Temperature Amount 1,2 Produced Amount 1,4 produced Major Product of Reaction Reason“Cold” (0°C)71 % 29% Kinetic Product (always 1,2)Fastest forming (before resonance rearrangement)Added Heat (40 °C and higher)15% 85% Thermodynamic Product(can be 1,2 or 1,4) It will most often be the 1,4, but you must always check!Most stableThe numerical values are specific to the reaction of this example.Temperature can affect reactivity. What the means is that if you want one product over the other, you can control the reaction with temperature: Kinetic vs Thermodynamic Control. When drawing these diagrams, remember than all your transition states will be higher than the energy of your starting materials. Furthermore, no other peaks will be higher than your first transition state (B) because, as you may recall from last semester, the first transition step is the rate determining step or RDS. The slowest part is breaking the double bonds to form the intermediates. Interacting one charged species (intermediates) with another charged species (your halide ion) will be very fast. Also, remember to mark these transition state peaks (B, D) with the double dagger symbol (‡). Your intermediates will be indicated at point