Course Goals for CHEM 202 Students will use their understanding of chemical bonding and energetics to predict and explain changes in enthalpy, entropy, and free energy for a variety of processes and reactions. Students will use their understanding of collision theory, temperature, and average kinetic energy of the system to make predictions about reaction rate and explain in the context of a reaction coordinate diagram. Students will be able to demonstrate their understanding of chemical equilibrium and acid base chemistry through two different approaches: quantitative (mathematical calculations) and qualitative (structural analysis). Students will apply their understanding of acids and bases, thermodynamics, and kinetics to predict and explain simple organic reactions: substitution, elimination, and nucleophilic acyl substitution. Students will illustrate their understanding of reaction mechanisms by using curved arrow formalisms and proposing reaction coordinate diagrams. Students will interpret experimental kinetic data to distinguish between unimolecular and bimolecular substitution and elimination mechanisms and explain the differences in mechanisms from a structural perspective.
Class 1 2 3 4 5 6 Topics and Demos/Applications Introduction to Free Energy Free Energy Continued Collision Theory Intro to Equilibrium LeChatelier Connecting equilibrium and free energy Learning Objectives 1. Calculate the enthalpy of a reaction ( H ) from bonds broken and bonds formed. 2. Describe the difference between endothermic and exothermic reactions. 3. Define enthalpy and explain how it relates to free energy. 4. Describe the difference between spontaneous and non-spontaneous processes. 1. Define enthalpy, entropy, and free energy as well as describe the relationship between them. 2. Explain the difference between spontaneous and non-spontaneous processes and how this connects to G. 3. Predict changes in enthalpy and entropy for a given 4. Develop criteria for determining whether a reaction will be spontaneous or not at high or low temperatures 5. Apply the concept of temperature dependence of spontaneity and describe what is meant by entropy- or enthalpy-driven reactions. 6. Describe how enthalpy changes with protein folding (considering both the interactions along the protein chain and those with the solvent). 7. Explain the hydrophobic effect and draw simple diagrams to back up your explanation. 1. Describe what interactions are involved in a physical vs. a chemical change. 2. Write reactions to illustrate changes of state. 3. Define temperature and describe how it relates to kinetic energy. 4. Define activation energy and explain how changing temperature affects particle collisions and the rate of 5. Describe how particle orientation affects whether or not a reaction will occur. 6. Explain how some particles can react even when the avg. kinetic energy of the system is less than the activation energy for the 7. Describe how concentration influences rates within a gas-phase reaction 8. Interpret and draw thermal energy distribution graphs. 1. Define dynamic equilibrium and the law of mass action. 2. Use the law of mass action to write an equilibrium constant expression for any reaction and calculate the value from provided data. 3. Calculate the reaction quotient (Q) and use it to determine the direction of the 4. Calculate equilibrium concentrations or the equilibrium constant depending on the information provided. 1. Predict how changes in concentration, temperature, and the presence of a catalyst affect equilibrium. 2. Calculate new equilibrium concentrations from any of the above changes. 3. Describe how certain changes cause the equilibrium to shift in one direction or the other and propose an explanation for why this happens (rates of reactions and collisions). 4. Graphically represent how changes in concentration or temperature affect concentrations. 1. Describe what is meant by the standard state. Give examples of elements and compounds in their standard states. 2. Write and apply the mathematical relationship between G and K. Be able to represent G on a graph of free energy as a function of the ratio between reactants and products. 3. Explain, from a free energy perspective, why reactions proceed to a lower energy state when they reach equilibrium.
7 Conformations of Cyclohexanes 4. Explain the difference between G and G. 1. Draw chair and boat conformations as well as ring flipped conformations for cyclohexane 2. Identify the most stable conformation of mono- and di-substituted cyclohexanes and explain why these conformations are the most stable. 3. Draw reaction coordinate diagrams for the ring flip of cyclohexanes. 8 9 10-11 12 Intro to acid base chemistry Weak acids and bases Combining quantitative and qualitative Predicting acid strength Qualitative Salt Hydrolysis 1. Define and identify acids and bases using the Lewis definition. 2. Describe how the Lewis definition of acids and bases includes all Arrhenius and Bronsted-Lowry acids and bases. 3. Use curved arrow notation to show the flow of electrons in acid-base reactions. 4. Memorize the six strong acids. 5. Describe the autoionization of water and the relationship between K a, K b, and K w. 1. Write a Ka expression in a chemical equation, its equilibrium ratio, and draw the curved arrows to show the proton transfer. 2. Write a Kb expression in a chemical equation, its equilibrium ratio, and draw the curved arrows to show the proton transfer. 3. Calculate equilibrium concentrations of all species for a weak acid or weak base hydrolysis in water. 4. Understand the 5% rule and explain why it is a valid approximation. 5. Interconvert the Ka value of a weak acid and the Kb value of its weak conjugate base. Understand the inverse relationship between these two values. 6. Apply the concept of conjugate base stability and how it relates to acid strength 7. Define and identify a strong electrolyte (no equilibrium here). 1. Predict relative acidity of one acid compared to another based on the stability of their conjugate bases. 2. Predict which side of an acid-base equilibrium will be favored based on which side has the weaker conjugate acid-base pair. 3. Use curved arrows to convert one resonance structure to another. 4. Use the following to predict stability: a) Element effects b) Resonance effects c) Inductive effects d) Hybridization effects 1. Predict whether a salt dissolved in water will be acidic, basic, or neutral. Be able to recognize garbage ions that have no effect on ph. 2. Write out any appropriate reactions with curved arrow notation to support your prediction of the acidity or basicity of various salts. 3. Calculate the ph of a solution containing a non-neutral salt. 4. Predict shifts in equilibrium due to the common ion effect and calculate the resulting changes in ph. 13 Buffers 1. Predict shifts in equilibrium due to the common ion effect and calculate the resulting changes in ph.
14 15 16 17 Introduction to Carbonyl Compounds Carbonyl Reactivity Continued Acid-catalyzed Hydrolysis of esters: Proposing mechanisms Driving reactions uphill : base-promotion and SOCl 2 2. Identify the major species in a buffer solution the ones with the highest concentration will affect the ph. 3. Write the uni-directional reaction or equilibrium reactions needed to calculate the final ph of a buffer or the ph after acid or base has been added. 4. Predict acid-base reactions and determine whether or not a buffer has been formed. 5. Explain what a buffer is and why it s important 6. Explain two ways of making a buffer from a conceptual standpoint. 7. Calculate the final ph of a buffer solution that is formed from one of the two ways in #6. 8. Calculate the final ph of a buffer solution after strong acid or base has been added. 1. Predict the relative order of Lewis acidity or electrophilicity based on the carbonyl compound s structure. 2. Explain why a carbonyl compound can be electrophilic using Lewis structures. 3. Draw an energy diagram for a one- or two-step mechanism showing how free energy changes as a function of reaction progress. 4. Draw an energy diagram to show the free energy change of a reaction based on equilibrium position. 5. Use your newly gained vocabulary, structures, and curved arrows in the context of reactions: mechanisms, reaction pathway, and transition state. 6. Apply pka data as a method to predict the position of equilibrium in a nucleophilic acyl substitution 1. Use your knowledge of electrophiles, nucleophiles, and Bronsted-Lowry acid base reactions to propose mechanistic pathways with curved arrows for acid catalyzed NAS reactions. 2. Explain how basicity and nucleophilic strength are correlated. 3. Apply the concept of LeChatelier to drive equilibrium towards the products. 4. Draw a reaction coordinate diagram for multi-step mechanisms 5. Define what is meant by a leaving group. 1. Identify all steps of a mechanism as Bronsted-Lowry acid-base, nucleophilic addition, or elimination steps. 2. Use the pka of the conjugate acid to predict which substituent will be the best leaving group. 3. Illustrate, with a mechanism and arrows, how protonating an ester, amide, or carboxylic acid increases the electrophilicity of the carbonyl carbon and also affects the exophilicity of a leaving group. 4. Draw an energy diagram to show how the addition of a catalyst speeds up the reaction by making the carbonyl a better electrophile. (Be aware that catalysts affect the rate of the reaction, not the equilibrium.) 1. Apply your knowledge of pka to illustrate how a reaction could be defined as uphill. 2. Recognize the concept of kinetic vs. thermodynamic products and the conditions that lead to each. 3. Apply your knowledge of nucleophilicity and electrophilicity to new nucleophiles and electrophiles. 4. Explain the difference between an acid-catalyzed reaction and a base-promoted 5. Draw mechanisms for base-promoted reactions that result in a carboxylate anion. 6. Predict the products of a NAS Also be able to predict when a reaction will not occur. 7. Explain why the reaction between a carboxylic acid and SOCl 2 is considered entropy-driven. Draw the mechanism for this
18 19 20-21 22 23 24 Intro to reaction rates through S N 1 reactions Rate Laws, Initial Rates, and Mechanism The S N 2 Reaction and how kinetics can help determine reaction mechanism Factors affecting S N 1 reaction mechanisms Predicting S N 1 vs S N 2 mechanism and carbocation rearrangements. Biological Applications of carbonyl chemistry 1. List all of the factors that may affect the rate of a chemical 2. Explain how increasing concentration, temperature, and adding a catalyst can all increase the rate of the 3. Define rate, rate law, average rate, instantaneous rate, and initial rate. 4. Interpret graphical data to determine average rate, instantaneous rate, and initial rate. 5. Determine the rate of formation or disappearance of any reactant or product knowing only one rate. 1. Predict the units of a rate constant based on the order of a reaction or vice versa. 2. Apply the method of initial rates using a given set of experimental data to determine rate laws and calculate a rate constant. 3. Make a hypothesis about the order of a reaction based on the structure of an alkyl halid and the strength of a nucleophile. 4. Interpret and explain a given table of experimental data correlating structure with rate constants. 1. Use pka data to predict leaving group ability. 2. Know the relative rates of common leaving groups: Halides, OTf, OMes, OH 3. Explain the typical correlation between nucleophilicity and basicity 4. Make predictions about what substitution reactions will follow an S N 2 pathway based on leaving group ability, alkyl halide structure, and the strength of the incoming nucleophile. 1. Compare the rates of S N 1 reactions of alkyl halides in common protic and aprotic solvents and explain any differences using your knowledge of intermolecular forces. 2. Propose a substitution mechanism based on the relative stability of a carbocation intermediate. 3. Explain, using appropriate diagrams, how hyperconjugation stabilizes carbocations 4. Use your knowledge of relative rates of S N 1 reactions, proton transfer, and nucleophilic attack to predict the mechanistic pathway(s) of a reaction 1. Summarize the major factors for S N 1 and S N 2 reactions. 2. Predict if a reaction will proceed through an S N 1 or S N 2 mechanism and draw a supporting energy diagram. 3. In reactions with carbocation intermediates, make a prediction about when a hydride or alkyl shift will likely occur. 4. Predict the products of an S N 1 reaction that undergoes hydride or alkyl shifts and draw the mechanism, transition state, and energy diagrams for the reaction 1. Identify acyl derivatives in biological molecules. 2. Explain how entropy and intermolecular forces drive reactivity in biological systems. 3. Explain reaction rate acceleration when enzymes are involved. 4. Explain how enzymes accelerate a reaction rate by chemical complementarity (spatial orientation and the formation of non-covalent interactions).