Question 1

Which of the following statements best describes the stereochemical outcome of an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

The configuration at the stereocenter is inverted.

Question 2

Given the following leaving groups: $$\mathrm{I^-}$$, $$\mathrm{Br^-}$$, $$\mathrm{Cl^-}$$, $$\mathrm{OH^-}$$, which will result in the fastest $$\mathrm{S_N2}$$ reaction?

Accepted Answer

$$\mathrm{I^-}$$

Question 3

Why is $$\mathrm{I^-}$$ considered a better leaving group than $$\mathrm{OH^-} in $$nucleophilic substitution reactions?

Accepted Answer

Because $$\mathrm{I^-} is $$more stable as a conjugate base and has a lower pKa of its conjugate acid.

Question 4

Which arrow-pushing convention is used to show the movement of two electrons in organic mechanisms?

Accepted Answer

Double-headed arrow

Question 5

In an $$\mathrm{S_N2}$$ reaction, what is the relationship between the nucleophile and the substrate?

Accepted Answer

The nucleophile attacks from the opposite side of the leaving group.

Question 6

Which factor most strongly predicts the rate of substitution in $$\mathrm{S_N2}$$ reactions?

Accepted Answer

The pKa of the conjugate acid of the leaving group

Question 7

Which of the following is NOT a good leaving group for $$\mathrm{S_N2}$$ reactions?

Accepted Answer

$$\mathrm{NH_2$^-}$$

Question 8

What is the effect of increasing polarizability of a leaving group on its ability to leave in a nucleophilic substitution reaction?

Accepted Answer

It increases its ability to leave.

Question 9

Which of the following best describes the difference between $$\mathrm{S_N1}$$ and $$\mathrm{S_N2}$$ mechanisms?

Accepted Answer

$$\mathrm{S_N1}$$ involves a carbocation intermediate, while $$\mathrm{S_N2}$$ does not.

Question 10

Which of the following statements about arrow pushing in organic chemistry is correct?

Accepted Answer

Arrows must start on electrons and end on atoms.

Question 11

If the conjugate base of a leaving group is very stable, what does this imply about the leaving group?

Accepted Answer

It is a good leaving group.

Question 12

Which periodic trend is most relevant for predicting the quality of a leaving group?

Accepted Answer

Electronegativity

Question 13

Which of the following is the best leaving group based on the pKa values of their conjugate acids?

Accepted Answer

$$\mathrm{I^-}$$

Question 14

A student is asked to predict which alkyl halide will react fastest in an $$\mathrm{S_N2}$$ reaction. Which should they choose?

Accepted Answer

An alkyl iodide

Question 15

Which of the following is true about the relationship between the pKa of a conjugate acid and the leaving group ability?

Accepted Answer

Lower pKa means better leaving group.

Question 16

In retrosynthesis, which direction do the arrows point?

Accepted Answer

From product to starting material

Question 17

Which of the following is a plausible reason why $$\mathrm{OH^-} is $$not a good leaving group?

Accepted Answer

Its conjugate acid has a high pKa, making $$\mathrm{OH^-} a $$strong base.

Question 18

Which of the following best describes the effect of electronegativity on leaving group ability?

Accepted Answer

More electronegative atoms make better leaving groups.

Question 19

Which of the following is true about the use of arrows in resonance structures?

Accepted Answer

Arrows show the movement of electrons.

SN2 Reaction and Leaving Groups: Substitution and Elimination Mechanisms

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