Question 1

Given the following substitution reaction, what would be the effect of changing the solvent from CH₃OH to (CH₃)₂S=O?
CH₃(CH₂)₅Br + NaOH as it goes to CH₃(CH₂)₅OH + Br?

A) The rate would decrease because S_N2 reactions are favored by polar aprotic solvents.
B) The rate would increase because S_N1 reactions are favored by polar protic solvents.
C) The rate would increase because S_N2 reactions are favored by polar aprotic solvents.
D) The rate would decrease because S_N1 reactions are favored by polar protic solvents.

The rate would increase because S_N2 reactions are favored by polar aprotic solvents.

Accepted Answer

The rate would increase because SN2 reactions are favored by polar aprotic solvents, and (CH3)2SO is a polar aprotic solvent, which would increase the rate of the SN2 reaction compared to a polar protic solvent like CH3OH.

Question 2

Which of the following statements about the Hammond postulate isnot true?&#10;A) In endothermic reactions, the transition state is closer in energy to the products.&#10;B) The Hammond postulate provides a qualitative estimate of the energy of a transition state.&#10;C) The Hammond postulate provides a quantitative estimate of the energy of a transition state.&#10;D) In exothermic reactions, the transition state is closer in energy to the reactants.

Accepted Answer

The Hammond postulate is used for making qualitative, not quantitative, predictions about the relative energies and structures of transition states.

Question 3

Which is the best reagent to carry out the following organic synthesis? A) NaOH, DMSO B) NaOMe, DMSO C) H₂O D) MeOH

Accepted Answer

NaOMe, DMSO&#10;

Question 4

Which of the following statements about the Hammond postulate is true? A) In an endothermic reaction, the more stable product forms faster. B) In an endothermic reaction, the less stable product forms faster. C) In an endothermic reaction, the activation energy, E_a, is similar for both products. D) In an exothermic reaction, lowering the energy of the transition state increases the activation energy, E_a.

Accepted Answer

In an endothermic reaction, the transition state resembles the products more closely, so the more stable product, which has a lower energy, forms faster.

Question 5

Which of the following statements isnot true?&#10;A) Equilibrium favors the products of the nucleophilic substitution when the leaving group is a stronger base than the nucleophile.&#10;B) All good leaving groups are weak bases with strong conjugate acids.&#10;C) Left-to-right across a row of the periodic table, leaving group ability increases.&#10;D) Down a column of the periodic table, leaving group ability increases.

Accepted Answer

Equilibrium favors the side of the nucleophilic substitution reaction with the weaker base. If the leaving group is a stronger base than the nucleophile, equilibrium would actually favor the reactants, not the products.

Question 6

What is the IUPAC name of the following compound?  &#10;A) 2-Chloro-4-methylpentane&#10;B) 2-Chloro-1-isopropylpropane&#10;C) 2-Chloro-2-methylpentane&#10;D) 2-Methyl-4-chloropentane

Accepted Answer

The answer of What is the IUPAC name of the...

Question 7

Which is the best reagent to carry out the following organic synthesis? A) H₂O B) H₂S C) HCl D) MeOH

Accepted Answer

The answer of Which is the best reagent to carry...

Question 8

Which of the following statements explain why aryl halides and vinyl halidesdo not undergo nucleophilic substitution by either the S_N1 or S_N2 mechanism? A) They don't undergo S_N1 reactions because a higher percents-character makes the bond longer and stronger. B) They don't undergo S_N1 reactions because the carbocation is highly electronegative. C) They don't undergo S_N2 reactions because a higher percents-character makes the bond shorter and stronger. D) They don't undergo S_N2 reactions because heterolysis of the C-X bond forms a highly unstable carbocation.

Accepted Answer

Aryl halides and vinyl halides have a higher percentage of s-character in the carbon-halogen bond, making the bond shorter and stronger. This characteristic impedes the SN2 mechanism because it requires the nucleophile to attack a carbon that is sterically hindered by the shorter, stronger bond.

Question 9

Which of the following statements about S_N2 reactions is true? A) The mechanism is a two-step process. B) The rate of reaction is dependent on just the substrate. C) Displacement occurs with inversion of configuration. D) The fastest reaction will occur with a tertiary alkyl halide.

Accepted Answer

S_N2 reactions involve a single-step mechanism where the nucleophile attacks the substrate, leading to inversion of configuration at the carbon center.

Question 10

Which of the following statements is true?&#10;A) Down a column of the periodic table, leaving group ability decreases.&#10;B) The conjugate bases of strong acids are good leaving groups.&#10;C) All good leaving groups are strong bases with weak conjugate acids.&#10;D) Left-to-right across a row of the periodic table, leaving group ability decreases.

Accepted Answer

The conjugate bases of strong acids are indeed good leaving groups because they are stable when they leave, making the reaction more favorable. Strong acids dissociate completely in water, leaving behind their conjugate bases, which are weak bases and thus do not readily reattach to the substrate, facilitating the leaving process in a reaction.

Question 11

The reaction oftert-butyl bromide, (CH₃)₃CBr, with ethanol affords the substitution producttert-butyl ethyl ether, (CH₃)₃COCH₂CH₃, in acidic conditions. What would happen to the rate of the reaction if the concentration of ethanol was doubled?

A) The rate increases by a factor of 4.
B) The rate increases by a factor of 2.
C) The rate remains the same.
D) The rate decreases by a factor of 2.

Accepted Answer

The answer of The reaction oftert-butyl bromide, (CH₃)₃CBr, with ethanol...

Deck 6: Alkyl Halides and Nucleophilic Substitution