Slides 2 through 9 lead the students to the molecular orbital argument for backside displacement in S N 2 reactions.

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Presentation transcript:

Slides 2 through 9 lead the students to the molecular orbital argument for backside displacement in S N 2 reactions.

S N 2 Mechanism backside attack 2 explanations –less hindrance to approach of nucleophile from behind C-L bond than from front –MO theory

S N 2 Mechanism

- Is there good overlap? a. Yesb. No c. This interaction is orthogonal.

S N 2 Mechanism - Is this a stabilizing interaction? a. Yesb. Noc. Neither

S N 2 Mechanism - Is this a stabilizing interaction? a.Yesb. Noc. Neither

S N 2 Mechanism Front side attack

S N 2 Mechanism - Is there good overlap? a.Yes b.No c. This interaction is orthogonal.

S N 2 Mechanism Is this a stabilizing interaction? a.Yes b.No

S N 2 Mechanism partial bond,charge is dispersed - 2 partial bonds are weaker than 1 full bond - nonbonded interactions are greater Would you expect the intermediate structure to be higher or lower in energy than iodoethane and bromoethane? a. higherb. lowerc. approximately equal

Potential Energy Diagram of Reaction The height of the TS above reactants is the amount of energy that is required for a molecule of starting material to be transformed into product. What is this specifically known as? a. Kinetic energy b. Free energy c. Reaction energy d.Reactant energy e.Activation Energy

The following question addresses the effect of contact ion pairs and solvent separated ion pairs on the stereochemistry of S N 1 reactions.

Which enantiomer is more likely to form? a.Path ab. Path b.c. No preference

Slides 15 through 18 review the effect of substrate structure on nucleophilic reactions.

1. Effect of Substrate Rate of S N 2 reaction (from left to right) a. increasingb. decreasingc. ~ same

Why? a. electron donating ability of alkyl groups b. electron withdrawing ability of alkyl groups c. steric hindrance blocking approach of nucleophiles d.leaving group ability increasing

In the same series … Ease of carbocation formation from left to right ? a.increasingb. decreasing c. ~ same

Rate of S N 1 reaction from left to right? a.increasingb. decreasing c. ~ same

Slides 20 through 23 ensure that students understand potential energy diagrams in relation to solvent effects.

Solvents affect the energy difference between reactants and TS. It affects the height of the energy barrier. The dashed line represents how solvent affected the reaction. Would the reaction proceed faster or slower in this solvent?

Would the reaction proceed faster or slower in this solvent? a.fasterb. slowerc. ~ same The activation energy is smaller. When that is true, the reaction rate is faster.

Now the dashed line represents how another solvent affected the reaction.

Would the reaction proceed faster or slower in this solvent? a.fasterb. slowerc. ~ same

What is the approximate hybridization of the central C atom of the transition state? a. sb. spc. sp 2 d. sp 3 e. p

What is the approximate electronic geometry around the central C atom? a. Linearb. trigonal planarc. pyramidal d. tetrahedrale. trigonal bipyramidal

What are the partial charges on the I and Br atoms respectively? a.  + and  + b.  - and  + c.  + and  - d.  - and  - e. There should be no partial charges.

What type of substrate is 2-bromooctane? a. primaryb. secondary c. tertiaryd. quaternary e. methyl

Predict the product(s) of the following S N 2 reaction.

Predict the product(s) of the following S N 1 reaction.

What atom will bond to the indicated C atom in the final isolated product? a. Sb. Nc. Cld. Oe. H

Enter the #’s of the reagents in the proper sequence that will synthesize the D labeled compound from 3-methyl-1-butanol.

Enter the #’s of the reagents in the proper sequence that will synthesize the D labelled compound from 3-methyl-1butanol.

Predict the major product(s) of the following reaction.

Predict the major product of the following reaction.

Enter the #’s of the reagents in the proper sequence that will synthesize hex-3-yne from but-1-yne

Which of the anions would be the strongest nucleophile in ethanol? a.F - b.Cl - c.Br - d.I - e.They are equally reactive.

Which of the following would be predicted to be the most stable carbocation?

Which of the following substrates would be predicted to react fastest by the S N 2 reaction?

Which of the following substrates would be predicted to react fastest by the S N 1 reaction?

Based on inductive effects, which of the following anilines would be the least basic?

Which of the following anilines would be the most nucleophiic?