CH.11 - REACTIONS OF ALKYL HALIDES: ELIMINATIONS (PART 2)lightcat-files.s3.amazonaws.com/packets/organic-2... · Alkenes are also stabilized through _____ Since this is only possible

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ORGANIC - MCMURRY 9E

CH.11 - REACTIONS OF ALKYL HALIDES: ELIMINATIONS (PART 2)

CONCEPT: THE E2 MECHANISM

□ A strong nucleophile reacts with an inaccessible leaving group to produce beta-elimination in one-step.

E2 Properties (Circle One)

● Nucleophile = Strong / Weak

● Leaving Group = Unsubstituted / Highly Substituted

● Reaction coordinate = Transition State / Intermediate

● Reaction = Concerted / Two-Step

● Rate = Unimolecular / Bimolecular

● Rate = k[RX] / k[Nu][RX]

● Stereochemistry = ___________________________

EXAMPLE: Rank the following alkyl halides in order of reactivity toward an E2 reaction.



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CONCEPT: RECOGNIZING DIFFERENT β-HYDROGENS

□ Elimination reactions remove β-hydrogens to create double bonds.

● The number of non-equivalent β-carbons with at least one _____ determines the number of possible products.

EXAMPLE: Identify the number of unique products that could be obtained through elimination.

a.

b.

c.

d.



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CONCEPT: THE ANTI-COPLANAR REQUIREMENT

□ E2 reactions require an anti-coplanar arrangement in order for the orbitals to overlap and create a new pi bond.

● When this occurs on cyclohexane, the leaving group and beta-proton must be DIAXIAL to each other.

EXAMPLE: Identify which of the following E2 mechanisms would react to completion. Do not draw final products.

a.

b.

c.

d.



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PRACTICE: Provide the full mechanism and draw the final product for the following E2 reactions.

a.

b.

c.



Page 5

CONCEPT: THE E1 MECHANISM

□ A weak nucleophile reacts with an inaccessible leaving group to produce beta-elimination in two-steps.

E1 Properties (Circle One)

● Nucleophile = Strong / Weak

● Leaving Group = Unsubstituted / Highly Substituted

● Reaction coordinate = Transition State / Intermediate

● Reaction = Concerted / Two-Step

● Rate = Unimolecular / Bimolecular

● Rate = k[RX] / k[Nu][RX]

● Stereochemistry = ___________________________



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PRACTICE: Provide the full mechanism and draw the final product for the following reactions.

a.

b.



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CONCEPT: SOLVENTS

Solvents are mostly inert compounds that provide a medium for the reaction to take place in.

□ Although extremely important in lab, they rarely affect the outcome of a written reaction in Orgo 1

Classification of Solvents

● Polar solvents are solvents which contain a ______ ________________

● Aprotic solvents are solvents that cannot display __________________ ____________

● Protic solvents are solvents that display ____ ______________ (stabilize carbocations, hinder nucleophiles)

□ Therefore, we will prefer to run _____ & _____ in protic solvents, and _____ & _____ in aprotic solvents.

EXAMPLE: Identify the following solvents as apolar, polar aprotic or polar protic



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CONCEPT: LEAVING GROUPS AND NUCLEOPHILES

Leaving Groups: Alkyl halides are the most common leaving groups of organic chemistry, but there are others.

□ Sulfonate Esters are the name given to a group of leaving groups with the general formula -SO3R

□ Water is also a common leaving group, usually formed after alcohol is protonated with a strong acid



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Nucleophile: Molecule that can easily donate electrons Base: Molecule that can easily remove a proton

□ Relative Strength Rules:

1. A negative charge will always be a stronger nucleophile than its neutral counterpart.

2. The bulkier the substrate, the more ______________ and less ____________________ it is.

3.



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CONCEPT: THE BIG DADDY MECHANISM FLOWCHART

Mechanisms are rarely given. We use nucleophile and leaving group information to determine the favored mechanism.



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PRACTICE: Predict the mechanism for the following reactions. Provide the full mechanism and draw the final product.

a.

b.

c.



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PRACTICE: Predict the mechanism for the following reactions. Provide the full mechanism and draw the final product.

d.

e.

f.



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CONCEPT: ALKENES and ALKYNES

□ Alkenes/Alkynes are named by adding the suffix modifier (-________/-________) to the end of the root.

● Alkenes/alkynes receive ___________________ in numbering alkanes

● Location is assigned to the first double bonded carbon

EXAMPLE: Name the following compound:

a.



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CONCEPT: STABILITY OF ALKENES

□ Alkenes are also stabilized through _________________________________

● Since this is only possible with -R groups, the more substituted the alkene, the more ________________

EXAMPLE: Rank the following alkenes in order of lowest to highest heat of combustion.



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CONCEPT: ELIMINATION AND ZAITSEV’S RULE

□ We often find that an elimination reaction can yield more than one unique alkene as a product.

● The most stable product = ________________ ● The least stable product = ________________

Zaitsev’s Rule explains that we will always favor the more substituted, thermodynamically stable product

□ UNLESS we are using a bulky base. A bulky base promotes the formation of a less substituted, kinetic product



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PRACTICE: Predict ALL of the products of the following reactions. Label them as either major or minor if necessary.

a.

b.



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CH.11 - REACTIONS OF ALKYL HALIDES: ELIMINATIONS (PART 2)lightcat-files.s3.amazonaws.com/packets/organic-2... · Alkenes are also stabilized through _____ Since this is only possible