Reaction Mechanisms and Nucleophilicity

Professor Dave explains the SN2, SN1, E2, and E1 reaction mechanisms, focusing on factors like substrate type, nucleophilicity, basicity, steric hindrance, and temperature. He provides examples to illustrate how these factors influence which mechanism occurs, emphasizing the importance of understanding nucleophilicity and leaving group ability in different solvents. The video also covers the role of temperature in favoring substitution or elimination reactions.

Which mechanism is unlikely to occur with a tertiary haloalkane due to steric hindrance?

• E2

• SN1

• E1

• SN2

What is the relationship between nucleophilicity and basicity?

• Nucleophilicity is the same as basicity.

• Nucleophilicity parallels basicity.

• Nucleophilicity is unrelated to basicity.

• Nucleophilicity is inversely related to basicity.

In a polar aprotic solvent, which halide ion is the strongest nucleophile?

• Fluoride

• Iodide

• Bromide

• Chloride

Why is hydroxide considered a poor leaving group?

• It is not polarizable.

• It is too large.

• It is very basic and unstable.

• It forms strong bonds with carbon.

What effect does increased steric hindrance in a nucleophile have on its reactivity?

• Has no effect on reactivity

• Decreases likelihood of elimination

• Increases likelihood of substitution

• Decreases likelihood of substitution

How does temperature influence the preference for substitution or elimination reactions?

• Temperature has no effect.

• Cold temperatures favor elimination.

• Hot temperatures favor substitution.

• Cold temperatures favor substitution.

What is the role of entropy in determining reaction spontaneity at high temperatures?

• Entropy only affects substitution reactions.

• Entropy increases spontaneity.

• Entropy has no effect.

• Entropy decreases spontaneity.

In a reaction with a primary haloalkane and a strong base, which mechanism is most likely at high temperatures?

• E1

• SN2

• E2

• SN1

Why is tert-butoxide a classic E2 promoter?

• It forms stable carbocations.

• It is a weak base.

• It is too sterically hindered for substitution.

• It is a poor nucleophile.

What is the most likely mechanism for a reaction involving a tertiary haloalkane and methanol at high temperatures?

• E2

• E1

• SN2

• SN1