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Organic Chem Exam 2
| Term | Definition |
|---|---|
| Alkenes | Carbon-carbon double bonds - Have two less H than alkanes - General formula for alkene is Cn H2n |
| Iupac Nomenclature Alkenes | 1. Identify the longest chain containing C=C 2. Give alkane name but change ending "ene" 3. Give double bond lowest number -Use substituents to break tie 4. Alphabetize substituents Rest of naming rules remain the same |
| The structure of alkenes | Each carbon of the double bond is: -SP2 -120 degree bond angle -Trigonal planar shape -Note: Double bond structure (does not rotate) |
| E/Z nomenclature | - A system used to describe the spatial arrangement of substituents around a double bond in organic chemistry -E: entgegen: opposite -Z: zusammen: together |
| E (E/Z nomenclature) | "Opposite" - Higher-priority groups are on opposite sides of the double bond |
| Z (E/Z nomenclature) | "Together" - Designates a double bond where the higher-priority groups are on the same side |
| Reactions | - Electron rich molecules are attracted to electron deficient molecules - Nucleophile: Electron rich - Electrophile: Electron deficient |
| Common electrophiles | - H+, proton - Carbocations |
| Common nucleophiles | - Br- - C=C pi bond - H2O |
| Intermediates | - Have full bonds and full charges - Are drawn in mechanisms |
| Transition states | - The hills on the graph (reaction coordinate diagram) - Have partial bonds and partial charges |
| Tail arrow (curved arrows) | Starts at the electrons (lone pairs/bonds) |
| Head of arrow (curved arrows) | Points at electron deficient atom |
| Reaction Coordinate diagram | Picture of the energy changes that take place in a reaction - Plot energy vs progress |
| First step (RCD) | - Alkene is converted into a carbocation that is less stable and higher in energy -Endothermic reaction |
| Endothermic reaction | - Consumes energy - Unfavorable - (+)delta H |
| Second step (RCD) | - The carbocation reacts to form the product that is more stable and lower in energy - Exothermic reaction |
| Exothermic reaction | - Releases energy - Favorable - (-) delta H |
| Rate determining step (RDS) | - Slowest step in reaction - Greatest energy of activation (Ea) - Highest hill on the graph |
| Thermodynamics | - Measure of stability at equilibrium - What our reaction coordinate diagram measures - The more stable the compound, the greater its concentration at equilibrium |
| Kinetics | - Measure of how fast the reaction occurs - Number of collisions with sufficient energy *Enough energy to allow for a reaction to occur - Number of collisions with "proper" orientation |
| Increase Rate of Reaction | - Add a catalyst - Increase temperature, pressure, surface area, etc. - Increase concentration of reaction *La Chatelier's principle |
| Reactions of Alkenes | Addition via a carbocation intermediate |
| Major product | The product formed in the greatest concentration or highest yield |
| By-product | A secondary substance produced during a chemical reaction alongside the main product, often unintentionally |
| Regioselective | - Two products are possible, but one predominates - A chemical reaction where one particular site on a molecule is preferentially targeted over others, leading to the favored formation of one constitutional isomer over other possible regioisomers |
| Highly regioselective | 1° VS 3° carbocation |
| Moderately regioselective | 1° VS 2° regioselective |
| Markovnikov's rule | Hydrogen adds to the carbon that is already bonded to the greater number of hydrogens |
| Methods of rearrangement (carbocations) | - Ring expansion - Hydride shift - Methyl shift |
| Hydride shift | - A hydrogen moves next door with its bonding electrons - A carbocation rearrangement where a hydrogen atom with its electrons (a hydride ion) migrates from one carbon atom to an adjacent carbon atom to form a more stable, more substituted carbocation |
| Methyl shift | - Methyl moves with its bonding electrons to neighboring carbon - A type of carbocation rearrangement in organic chemistry where a methyl group moves to an adjacent, positively charged carbon atom to form a more stable carbocation |
| Ring Expansion | - Carbocations can also expand via ________________ *Up to a 6 membered ring *Need a C+ next to a small ring to become more stable *3->4, 4->5, 5->6 |
| Hydration of water | - Requires acid catalyst *Increase rate of reaction by lowering activation energy *Regenerated in reaction - Markovnikov addition - Carbocation intermediate (rearrangements possible) - Product is alcohol (-OH) |
| Halogenation | - Addition of a halogen to an alkene - Markovnikov additon - No carbocation intermediate (no rearrangements possible) - Product is vicinal dihalide |
Created by:
lavonj12