Chapter 6 orgchem (wiley)

86
Chapter 6 Chemical Reactivity and Mechanisms Organic Chemistry Second Edition David Klein Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e

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orgchem

Transcript of Chapter 6 orgchem (wiley)

Page 1: Chapter 6 orgchem (wiley)

Chapter 6Chemical Reactivity and Mechanisms

Organic ChemistrySecond Edition

David Klein

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e

Page 2: Chapter 6 orgchem (wiley)

6.1 Enthalpy• Enthalpy (ΔH or q) is the heat energy exchange between

the reaction and its surroundings at constant pressure• Breaking a bond requires the system to absorb energy.

WHY?• Show on Figure 6.1 how much energy is needed

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Page 3: Chapter 6 orgchem (wiley)

6.1 Enthalpy• Bonds can break homolytically or heterolytically

• Bond dissociation energy (BDE) or ΔH for bond breaking generally represents the energy associated with HOMOlytic cleavage

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• More BDEs in table 6.1

6.1 Bond Dissociation Energies

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Page 5: Chapter 6 orgchem (wiley)

6.1 BDEs• Explain how heat energy is exchanged between the

reaction (system) and the solution (surroundings) for each scenario below1. H• and F• free radicals come together to form bonds

2. A C–Br bond is broken

3. A strong bond is broken and a weak bond is formed

4. A weak bond is broken and a strong bond is formed

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Page 6: Chapter 6 orgchem (wiley)

6.1 BDEs• Most reactions involve multiple bonds breaking and

forming. The energy associated with each bond that breaks and forms must be considered

• If during a chemical reaction the temperature of the reaction solution DECREASES, what can be said about the relative potential energies, stabilities, and bond strengths for the reactants and products

• If during a chemical reaction, the temperature of the reaction solution INCREASES, what can be said about the relative potential energies, stabilities, and bond strengths for the reactants and products

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Page 7: Chapter 6 orgchem (wiley)

6.1 Enthalpy ΔH• Match the reaction coordinate diagrams below with the

statements below– The reaction causes the surrounding temp. to DECREASE– The reaction causes the surrounding temp. to INCREASE

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Page 8: Chapter 6 orgchem (wiley)

6.1 Enthalpy ΔH• For a chemical reaction, why is the sign (+/-) for ΔH

important?• If you were performing a chemical reaction in a lab,

what experimental considerations might you make if you knew ΔH = +

• If you were performing a chemical reaction in a lab, what experimental considerations might you make if you knew ΔH = -

• Practice with SkillBuilder 6.1

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Page 9: Chapter 6 orgchem (wiley)

6.2 Entropy ΔS• Although most reactions are EXOthermic, there are

many ENDOthermic reactions that occur• Enthalphy and entropy must BOTH be considered when

predicting whether a reaction will occur• ENTROPY (ΔS) can be though of as molecular disorder,

randomness, or freedom• Entropy may most accurately be thought of as the

number of states that a molecule’s energy can be distributed over

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Page 10: Chapter 6 orgchem (wiley)

6.2 Entropy ΔS• If the energy of molecules can be distributed in a higher

number of vibrational, rotational, and translational states, the sample will have a greater entropy.

• Molecules exhibit vibrational, rotational, and translational motion. Explain HOW

• Which of the two molecules below should have greater entropy, and WHY?

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Page 11: Chapter 6 orgchem (wiley)

6.2 Entropy ΔS• Consider the ENTROPY and ENTHALPY change for the

following process

• The number of possible translational distributions for the molecules increases with increasing volume. HOW?

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Page 12: Chapter 6 orgchem (wiley)

6.2 Entropy ΔS• The total entropy change will determine whether a

process is spontaneous (favors the forward direction)

• If ΔStot is positive, the process is spontaneous. What if ΔStot is negative?

• When the volume of a gas expands to fill a container, what should ΔSsurr be?

• For chemical reactions, we must consider the entropy change for both the system (the reaction) and the surroundings (the solvent usually)

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Page 13: Chapter 6 orgchem (wiley)

6.2 Entropy ΔS

• For each of the reactions below, predict the sign for ΔSsys

• Consider how a change in a molecule’s structure affects the number of possible translational, rotational, and/or vibrational distributions for the molecules?

• Why does ΔSsurr depend on ΔHsys?

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Page 14: Chapter 6 orgchem (wiley)

6.2 Entropy ΔS

• How would the following conditions affect spontaneity (the degree to which the reaction is product favored)?1. The reactions are exothermic2. The reactions are highly endothermic3. The reactions are slightly endothermic

• Practice with conceptual checkpoint 6.3

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Page 15: Chapter 6 orgchem (wiley)

6.3 Gibbs Free Energy ΔG• We know that the spontaneity of a process depends

only on ΔStot

• ΔSsys can be measured or estimated

• ΔSsurr depends on ΔHsys

• Plug in

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Page 16: Chapter 6 orgchem (wiley)

6.3 Gibbs Free Energy ΔG

• Multiply both sides by Temperature

» or

• How will the sign (+ or -) for ΔG affect spontaneity?

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Page 17: Chapter 6 orgchem (wiley)

6.3 Gibbs Free Energy ΔG• Consider the example reaction

• Predict the sign (+ or -) for ΔSsys

• In the reaction, two pi bonds are converted into two sigma bonds. Predict the sign (+ or -) for ΔHsys

• Predict the sign (+ or -) for ΔSsurr

• Predict the sign (+ or -) for ΔG• How will the spontaneity of the reaction depend on

temperature?

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Page 18: Chapter 6 orgchem (wiley)

6.3 Gibbs Free Energy ΔG• If a process at a given temperature is calculated to have

a (-) ΔG, the process is exergonic• • It will be spontaneous

and favor the products

• Note that G is plotted rather than H

• Does the value for ΔG tell us about the rate of the reaction?

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Page 19: Chapter 6 orgchem (wiley)

6.3 Gibbs Free Energy ΔG• If a process at a given temperature is calculated to have

a (+) ΔG, the process is endergonic• It will be

NONspontaneous and favors the reactants

• What does it mean exactly to favor the reactants?

• Practice with conceptual checkpoint 6.4

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Page 20: Chapter 6 orgchem (wiley)

6.4 Equilibria• Consider an exergonic process with a (-) ΔG. Will every

molecule of A and B be converted into products?– No, an equilibrium will

eventually be reached– A spontaneous process

will simply favor the products meaning there will be more products than reactants

– The greater the magnitude of a (-)ΔG, the greater the equilibrium concentration of products

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Page 21: Chapter 6 orgchem (wiley)

6.4 Equilibria• Why doesn’t an exergonic process react 100% to give

products? Why will some reactants remain?– The diagram shows

one unit of A react with one unit of B

– In reality, moles of reactants are present

– How will concentrations of A, B, C, and D change as the reaction progresses?

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Page 22: Chapter 6 orgchem (wiley)

6.4 Equilibria• In any reaction, collisions are necessary• As [A] and [B] decrease collisions between A and B will

occur less often• As [C] and [D] increase, collisions between C and D will

occur more often– The more often C and D collide, the more often collisions will

occur with enough free energy for the reverse reaction to take place

• Recall that equilibrium is dynamic and occurs when the forward and reverse reaction rates are equal

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Page 23: Chapter 6 orgchem (wiley)

6.4 Equilibria• Equilibrium is also the state with the lowest free energy

overall• Why does the

equilibrium mixture have the least G?

• How would Stot

compare for a mixture of all reactants and products versus only products?

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Page 24: Chapter 6 orgchem (wiley)

6.4 Equilibria• An equilibrium constant (Keq) is used to show the degree

to which a reaction is product or reactant favored

• Keq, ΔG, ΔH, and ΔS are thermodynamic terms. They do not describe reaction kinetics. What is the difference?

• Practice with checkpoint 6.6

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Page 25: Chapter 6 orgchem (wiley)

6.4 Equilibria• What trends do you notice in table 6.2?

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Page 26: Chapter 6 orgchem (wiley)

6.5 Kinetics• Recall that a (-) sign for ΔG tells us a process is product

favored (spontaneous) • That does NOT tell us anything about the RATE or

kinetics for the process• Some spontaneous processes are fast such as

explosions. Can you think of other examples?

• Some spontaneous processes are slow such as C (diamond) C (graphite). Can you think of other examples?

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Page 27: Chapter 6 orgchem (wiley)

6.5 Kinetics• The rate of a reaction tells us how many molecules are

reacting in a given period of time• Give some examples for typical reaction rate units

• Recall that for reactions to take place, reactants must collide with sufficient force. WHY?

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Page 28: Chapter 6 orgchem (wiley)

6.5 Kinetics• The reaction rate (the number of collisions that will

result in product production in a given period of time) is affected by multiple factors1. The concentrations of the reactants2. The Activation Energy3. The Temperature4. Geometry and Sterics5. The presence of a catalyst

• How will an increase in [reactant] generally affect the reaction rate? WHY?

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Page 29: Chapter 6 orgchem (wiley)

6.5 Rate Law Equations• To quantify how much the reactant concentration affects

the rate of reaction, the Rate Law equation is used

• The degree to which a change in [reactant] will affect the Rate is known as the order.

• The order is represented by x and y in the Rate Law equation

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Page 30: Chapter 6 orgchem (wiley)

6.5 Rate Law Equations

• Consider a generic reaction that is known to be first order with respect to A and zero order with respect to B: A + B C + D– Write the appropriate Rate Law– How should he rate change if [A] were doubled?– How should he rate change if [B] were doubled?

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Page 31: Chapter 6 orgchem (wiley)

6.5 Rate Law Equations

• Consider a generic reaction that is known to be first order with respect to A and first order with respect to B: A + B C + D– Write the appropriate Rate Law– How should he rate change if [A] were doubled?– How should he rate change if [B] were doubled?

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Page 32: Chapter 6 orgchem (wiley)

6.5 Rate Law Equations

• Consider a generic reaction that is known to be second order with respect to A and first order with respect to B: A + B C + D– Write the appropriate Rate Law– How should he rate change if [A] were doubled?– How should he rate change if [B] were doubled?

• How are the orders (exponents) determined for a Rate Law?

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Page 33: Chapter 6 orgchem (wiley)

6.5 Factors that Affect Rates• Locate the Activation

Energy in figure 6.13?

• Why must the free energy (G) increase before the products can be formed?

• Why would Eact be different for different reactions?

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Freeenergy

(G)

Page 34: Chapter 6 orgchem (wiley)

6.5 Factors that Affect Rates• Temperature is a measure

of a system’s average kinetic energy

• Would you expect there to be a temperature below which the reaction rate is zero and above which the reaction rate instantaneous for all molecules? WHY or WHY NOT?

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Freeenergy

(G)

Page 35: Chapter 6 orgchem (wiley)

6.5 R Factors that Affect Rates• Why does a lower Eact result in a greater reaction rate?

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-35

Freeenergy

(G)

Freeenergy

(G)

Page 36: Chapter 6 orgchem (wiley)

6.5 Factors that Affect Rates• Why does increasing the temperature increase the rate

of reaction?

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Page 37: Chapter 6 orgchem (wiley)

6.5 Factors that Affect Rates• How might geometry and sterics affect the reaction

rate?

• How might the presence of a catalyst affect the reaction rate?

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Freeenergy

(G)

Page 38: Chapter 6 orgchem (wiley)

6.6 Energy Diagrams• Distinguish between kinetics and thermodynamics

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Freeenergy

(G)

Freeenergy

(G)

Page 39: Chapter 6 orgchem (wiley)

• For the energy diagram below, which pathway do you think is favored? WHY?

6.6 Kinetics vs Thermodynamics

• Will a decrease in temperature affect which pathway is favored?

• Will an increase in temperature affect which pathway is favored?

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Freeenergy

(G)

Page 40: Chapter 6 orgchem (wiley)

6.6 Kinetics vs Thermodynamics• For the energy diagram below, which pathway is

kinetically favored?• Which pathway is

thermodynamically favored?

• How can temperature be used to control which set of products predominate?

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Freeenergy

(G)

Page 41: Chapter 6 orgchem (wiley)

6.6 Transition States vs Intermediates

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Freeenergy

(G)

Page 42: Chapter 6 orgchem (wiley)

6.6 Transition States• A transition state

occurs at an energy maxima

• Transition states exist for a fleeting moment; they cannot be isolated or directly observed

• Why are transition states so unstable?

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Freeenergy

(G)

Page 43: Chapter 6 orgchem (wiley)

6.6 Intermediates• An intermediate occurs at an energy minima• Intermediates often exist long enough to observe

because bonds are NOT in the process of breaking or forming

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Freeenergy

(G)

Page 44: Chapter 6 orgchem (wiley)

6.6 The Hammond Postulate• Two points on an energy diagram that are close in

energy should be similar in structure

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Freeenergy

(G)

Page 45: Chapter 6 orgchem (wiley)

• For each of the diagrams below, will the transition state structure look more like the reactants or the products?

6.6 The Hammond Postulate

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Freeenergy

(G)

Freeenergy

(G)

Page 46: Chapter 6 orgchem (wiley)

6.6 The Hammond Postulate• Draw a reaction coordinate diagram for the generic

exergonic reaction sequence below. Label the axes, reactants, products, intermediates, and transition states

A B + CC + D E

Net reaction: A + D B + E• How would the diagram look different if it were

endergonic?• Practice with conceptual checkpoint 6.7

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Page 47: Chapter 6 orgchem (wiley)

6.7 Nucleophiles and Electrophiles• A major focus in this course is on predicting reaction

products for ionic reactions and explaining HOW such reactions work

• Ionic or polar reactions result from the force of attraction between opposite charges

• Ionic reactions are also guided by the octet rule• Consider how methyl chloride and methyl lithium might

react

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Page 48: Chapter 6 orgchem (wiley)

6.7 Nucleophiles• When an atom carries a formal or partial negative

charge and an available pair of electrons, it is considered a nucleophile

• It will love to attack a nucleus. WHY?• Explain how the molecules below are nucleophiles

• What is the difference between a nucleophile and a Lewis Base? NOTHING!

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Page 49: Chapter 6 orgchem (wiley)

6.7 Electrophiles• When an atom carries a formal or partial positive

charge and can accept a pair of electrons, it is considered a electrophile

• It will love available electrons. WHY?

• Explain how the molecules above are electrophiles• What is the difference between an electrophile and a

Lewis Acid? NOTHING!• Practice with SkillBuilder 6.2

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Page 50: Chapter 6 orgchem (wiley)

6.7 Electrophiles• Label all of the nucleophilic and electrophilic sites on

the following molecule

O

O

O

NH2

HO

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Page 51: Chapter 6 orgchem (wiley)

6.8 Mechanisms and Arrow Pushing• We use arrows to show how electrons move when

bonds break and form• It will be a huge benefit in this course to master the

skill of arrow pushing• There are four main ways that electrons move in ionic

reactions1. Nucleophilic Attack2. Loss of a Leaving Group3. Proton Transfers (Acid/Base)4. Rearrangements

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Page 52: Chapter 6 orgchem (wiley)

6.8 Nucleophilic Attack• When you identify a nucleophilic site and an

electrophilic site, the arrow shows the nucleophile attacking

• The tail of the arrow starts on the electrons (- charge)• The head of the arrow ends on a nucleus (+ charge)• The electrons end up being sharing rather than

transferred

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Page 53: Chapter 6 orgchem (wiley)

6.8 Nucleophilic Attack• Nucleophilic attack may appear to occur in two steps

• The alcohol is the nucleophile in this example. It attacks a carbon with a δ+ charge

• The second arrow shows the flow of negative charge. WHY is it necessary?

• The second arrow could be thought of as a resonance arrow. HOW?

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Page 54: Chapter 6 orgchem (wiley)

6.8 Loss of a Leaving Group• Loss of a leaving group occurs when a bond breaks and

one atom from the bond takes BOTH electrons

• For the molecule below, draw the structure that will result after the leaving group is gone

• Which arrow shows the loss of a leaving group?

• What is the purpose of the other arrows?

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Page 55: Chapter 6 orgchem (wiley)

6.8 Proton Transfers• Recall from Chapter 3 that a base is protonated when it

uses a pair of electrons to take an H+ from the acid. • The acid retains its electron pair

• A group can also be deprotonated (sometimes shown by writing –H+ over the reaction arrow)

or

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Page 56: Chapter 6 orgchem (wiley)

6.8 Proton Transfers• Multiple arrows may be

necessary to show the complete electron flow when a proton is exchanged

• Such electron flow can also be thought of as a proton transfer combined with resonance

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Page 57: Chapter 6 orgchem (wiley)

• Carbocations can be stabilized by neighboring groups through slight orbital overlapping called hyperconjugation

6.8 Carbocation Rearrangements

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Page 58: Chapter 6 orgchem (wiley)

6.8 Carbocation Rearrangements• Hyperconjugation and induction can both be invoked

to explain the stability trend below. HOW?

• If a carbocation can INTRAmolecularly rearrange to become more stable, it will likely do so before reacting with a nucleophile. WHY?

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Page 59: Chapter 6 orgchem (wiley)

6.8 Carbocation Rearrangements• Two types of carbocation rearrangement are common

– Hydride shift

– Methyl shift

• Shifts can only occur from an adjacent carbon. WHY?• Do the shifts above make the carbocation more stable?• Practice with SkillBuilder 6.3

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Page 60: Chapter 6 orgchem (wiley)

6.9 Combining Arrow Pushing Patterns• Classify each step in the following mechanism

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Page 61: Chapter 6 orgchem (wiley)

6.9 Combining Arrow Pushing Patterns• Many times a single step in a mechanism will include

more than one arrow pushing pattern• Identify the patterns below

• There are hundreds of mechanisms that involve these key patterns

• Practice with SkillBuilder 6.4

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Page 62: Chapter 6 orgchem (wiley)

6.10 Arrow Pushing Rules• To draw reasonable mechanisms, a few key rules

should be followed1. The arrow starts ON A PAIR OF ELECTRONS (a bonded

pair or a lone pair)

– Don’t make the mistake of starting an arrow on a nucleus! Both arrows below are incorrect. WHY?

ClO

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Page 63: Chapter 6 orgchem (wiley)

6.10 Arrow Pushing Rules• A few key rules should be followed2. The arrow ends ON A NUCLEUS (electrons become a

lone pair) or between two NUCLEI (electrons move into position to become a bond)

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Page 64: Chapter 6 orgchem (wiley)

6.10 Arrow Pushing Rules• A few key rules should be followed3. Avoid breaking the octet rule. NEVER give C, N, O, or F

more than 8 valence electrons

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Page 65: Chapter 6 orgchem (wiley)

6.10 Arrow Pushing Rules• A few key rules should be followed4. Draw arrows that follow the 4 key patterns we outlined

– The arrow below is unreasonable. WHY?

• Practice with SkillBuilder 6.5

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Page 66: Chapter 6 orgchem (wiley)

6.10 Arrow Pushing Rules• Fill in necessary arrows for the reaction below

O

OO H

O

O

HO

O

O

H OO

O

HO+ +

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Page 67: Chapter 6 orgchem (wiley)

6.10 Arrow Pushing Rules• For each mechanism below, identify the unreasonable

arrows and redraw the mechanism with correct arrows

O O HO

Br

O

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Page 68: Chapter 6 orgchem (wiley)

6.11 Carbocation Rearrangements• When you encounter a carbocation, you must consider

all possible rearrangements (Hydride and methyl shifts)

1. Identify all adjacent carbons

2. Identify all –H and –CH3 groups on the adjacent carbons that are capable of shifting

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Page 69: Chapter 6 orgchem (wiley)

• In this case, a hydride shift will result in a more stable tertiary carbocation

6.11 Carbocation Rearrangements• When you encounter a carbocation,

you must consider all possible rearrangements (Hydride and methyl shifts)

3. Imagine each of the groups shifting to see which yields the most stable resulting carbocation

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Page 70: Chapter 6 orgchem (wiley)

6.11 Carbocation Rearrangements• Complete the same analysis for the molecule below

1. Identify all adjacent carbons2. Identify all –H and –CH3 groups capable of shifting

3. Determine which shift yields the most stable carbocation

• Recall that allylic carbocations are especially stable

• Practice with SkillBuilder 6.6

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Page 71: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• Why are some reactions are drawn as equilibria and others are essentially irreversible?

• The question of reversibility a both kinetic and a thermodynamic question. HOW?

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Page 72: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• Consider nucleophilic attack

• Draw a mechanism for the reverse reaction

• How do we judge whether it will be reversible?

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Page 73: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• If the attacking nucleophile is also a good leaving group, it will be a reversible attack– The reverse reaction will have a relatively low transition state

energy (kinetically favored)– The reactants and products of the reaction will be similar in

energy allowing significant quantities of both to exist at equilibrium (thermodynamic equilibrium)

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Page 74: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• If the attacking nucleophile is a poor leaving group, it will essentially be an irreversible attack– The reverse reaction will have a relatively HIGH transition

state energy (kinetically disfavored)– The products will be much lower in energy so an insignificant

quantity of reactant will remain at equilibrium

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Page 75: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• Consider loss or a leaving group

• Draw a mechanism for the reverse reaction

• How do we judge whether it will be reversible?

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Page 76: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• Consider proton transfer• We analyzed this in detail in chapter 3 using pKa values

• How do we judge reversiblity?

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Page 77: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• Consider proton transfer• If the pKa difference is 10 units or more, it is generally

considered irreversible

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Page 78: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• Carbocations are generally considered irreversible thermodynamically. WHY?

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Page 79: Chapter 6 orgchem (wiley)

6.12 Reversible and Irreversible Reaction Arrows

• When considering thermodynamic equilibrium, in addition to comparing relative energies, Le Châtelier’s principle must also be considered. WHY is the reaction below irreversible?

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Page 80: Chapter 6 orgchem (wiley)

Additional Practice Problems• Consider electrocyclic ring opening

• Predict the sign (+ or -) for ΔSsys

• In the reaction, 1 pi bond is converted into 1 sigma bond. Predict the sign (+ or -) for ΔHsys

• Predict the sign (+ or -) for ΔSsurr

• Predict the sign (+ or -) for ΔG• How will the spontaneity of the reaction depend on

temperature?

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-80

Page 81: Chapter 6 orgchem (wiley)

Additional Practice Problems• Explain why an equilibrium mixture is always lower in

free energy than pure products or pure reactants.

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-81

Page 82: Chapter 6 orgchem (wiley)

Additional Practice Problems• Reactants A and B can react by two different pathways.

Pathway 1 is thermodynamically favored, and pathway 2 is kinetically favored. Draw a reaction coordinate diagraph to illustrate the relative energies and explain which pathway will be favored at low temperatures versus higher temperatures.

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-82

Page 83: Chapter 6 orgchem (wiley)

Additional Practice Problems• Propose a mechanism for the reaction below that

explains its Rate Law.2A + B C + D Rate=k[A]2

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-83

Page 84: Chapter 6 orgchem (wiley)

Additional Practice Problems• Label all of the nucleophilic and electrophilic sites on

the following molecules

OH

HN

ClMgBr

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-84

Page 85: Chapter 6 orgchem (wiley)

Additional Practice Problems• Draw a mechanism for a generic nucleophilic attack

followed by a proton transfer.

• Draw a mechanism for a generic loss of leaving group followed by a carbocation rearrangement.

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-85

Page 86: Chapter 6 orgchem (wiley)

Additional Practice Problems• For each of the mechanistic steps below, identify what

is incorrect about it.LG

Nuc:

Nuc

+ LG

LG

HNuc:

+ LG + Nuc-H

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e 6-86