An Overview of Organic Reactions

Question: Identify each of the colored positions—red, blue, and green—as axial or equatorial. Then carry out a ring-flip, and show the new positions occupied by each color.

What is the energy difference between the axial and equatorial conformations of cyclohexanol (hydroxycyclohexane)?

Draw the more stable chair conformation of the following molecules, and estimate the amount of strain in each:

Draw the more stable chair conformation of the following molecules, and estimate the amount of strain in each:

Despite the limitations of radical chlorination of alkanes, the reaction is still useful for synthesizing certain halogenated compounds. For which of the following compounds does radical chlorination give a single monochloro product?

Draw all of the different monochlorinated products one would obtain by the radical chlorination of these compounds. (Do not consider the stereochemistry of the products in your answer.)

Assign R or S stereochemistry to the chirality centers in the following Newman projections:

Classify each of the following reactions as an addition, elimination, substitution, or rearrangement: 

1. ${\mathrm{CH}}_3\mathrm{Br}+\mathrm{KOH}\to {\mathrm{CH}}_3\mathrm{OH}+\mathrm{KBr}$

2. ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Br}\to {\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2+\mathrm{HBr}$

3. ${\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2+{\mathrm{H}}_2\to {\mathrm{CH}}_3{\mathrm{CH}}_3$

Which of the following species are likely to be nucleophiles and which electrophiles? Which might be both?

An electrostatic potential map of boron trifluoride is shown. Is ${\mathbf{\text{BF}}}_{\mathbf{\text{3}}}$ likely to be a nucleophile or an electrophile? Draw a Lewis structure for ${\mathbf{\text{BF}}}_{\mathbf{\text{3}}}$ , and explain your answer.

What product would you expect from the reaction of cyclohexene with ? With ?

Reaction of with 2-methylpropene yields 2-bromo-2-methylpropane. What is the structure of the carbocation formed during the reaction? Show the mechanism of the reaction.

Add curved arrows to the following polar reactions to indicate the flow of electrons in each:

Which reaction is more energetically favored, one with ${\mathbf{\Delta G}}^{\mathbf{o}}$ = - 44 or one with ${\mathbf{\Delta G}}^{\mathbf{o}}$= +44 ?

Which reaction is likely to be more exergonic, one with ${\mathbf{K}}_{\mathbf{eq}}$=1000 or one with  ${\mathbf{K}}_{\mathbf{eq}}$= 0.001?

Which reaction is faster, one with ${\mathbf{\Delta G}}^{\mathbf{\#}}$= +45 or one with ${\mathbf{\Delta G}}^{\mathbf{\#}}$= +70?

Identify the following reactions as additions, eliminations, substitutions, or rearrangements:

a. 

b. 

c.

d. 

Identify the following reactions as additions, eliminations, substitutions, or rearrangements:

a. 

b. 

c. 

d. 

Identify the following reactions as additions, eliminations, substitutions, or rearrangements:

a. 

b. 

c. 

d. 

Identify the following reactions as additions, eliminations, substitutions, or rearrangements:

a. 

b.

c. 

d. 

Identify the likely electrophilic and nucleophilic sites in each of the following molecules:

a.

                                           testosterone

b. 

                                  Methamphetmine

Identify the likely electrophilic and nucleophilic sites in each of the following molecules:

a. 

                                             testosterone

b. 

                              Methanphetamine

For each reaction below identify the electrophile and the nucleophile

a. 

b. 

c. 

For each reaction below identify the electrophile and the nucleophile

(a)

(b) 

(c) 

For each reaction below identify the electrophile and the nucleophile

(a) 

(b) 

(c) 

Add curved arrows to the following polar reactions to indicate the flow of electrons in each:

(a) 

(b) 

Follow the flow of electrons indicated by the curved arrows in each of the following polar reactions, and predict the products that result:

Follow the flow of electrons indicated by the curved arrows in each of the following polar reactions, and predict the products that result:

Follow the flow of electrons indicated by the curved arrows in each of the following polar reactions, and predict the products that result:

Follow the flow of electrons indicated by the curved arrows in each of the following polar reactions, and predict the products that result:

For each alkene below, use curved arrows to show how it would react with a proton. Draw the carbocation that would form in each case.

a)

b)

c)

Add curved arrows to the mechanism shown in Problem 6-25 to indicate the electron movement in each step.

When a mixture of methane and chlorine is irradiated, a reaction commences immediately. When irradiation is stopped, the reaction gradually slows down but does not stop immediately. Explain.

Radical chlorination of pentane is a poor way to prepare 1-chloropentane, but radical chlorination of neopentane, ${\left({\mathbf{CH}}_{\mathbf{3}}\right)}_{\mathbf{4}}\mathbf{C}$, is a good way to prepare neopentyl chloride, ${\left({\mathbf{CH}}_{\mathbf{3}}\right)}_{\mathbf{3}}{\mathbf{CCH}}_{\mathbf{2}}\mathbf{Cl}$. Explain.

The following alkyl halide can be prepared by the addition of HBr to two different alkenes. Draw the structures of both (reddish-brown 5 Br).

The following structure represents the carbocation intermediate formed in the addition reaction of H-Br to two different alkenes. Draw the structures of both.

Electrostatic potential maps of (a) formaldehyde $\left({\mathbf{CH}}_2\mathbf{O}\right)$ and (b) methanethiol $\left({\mathbf{CH}}_3\mathbf{SH}\right)$ are shown. Is the formaldehyde carbon atom likely to be electrophilic or nucleophilic? What about the methanethiol sulfur atom? Explain.

Look at the following energy diagram:

(a) Is ${\mathbf{\Delta G}}^o$ for the reaction positive or negative? Label it on the diagram. 

(b) How many steps are involved in the reaction? 

(c) How many transition states are there? Label them on the diagram.

Look at the following energy diagram for an enzyme-catalyzed reaction:

  (a) How many steps are involved?

  (b) Which step is most exergonic? 

  (c) Which step is slowest?

What is the difference between a transition state and an intermediate?

Draw an energy diagram for a one-step reaction with ${\mathbf{K}}_{\mathrm{eq}}\mathbf{<}\mathbf{1}$ . Label the parts of the diagram corresponding to reactants, products, transition state, ${\mathbf{\Delta G}}^o$, and ${\mathbf{\Delta G}}^{\#}$ . Is ${\mathbf{\Delta G}}^o$ positive or negative?

Draw an energy diagram for a two-step reaction with ${\mathbf{K}}_{\mathrm{eq}}$ > 1. Label the overall ${\mathbf{\Delta G}}^o$, transition states, and intermediate. Is ${\mathbf{\Delta G}}^o$ positive or negative?

Draw an energy diagram for a two-step exergonic reaction whose second step is faster than its first step.

Draw an energy diagram for a reaction with ${\mathbf{K}}_{\mathrm{eq}}\mathbf{=}\mathbf{1}$ . What is the value of ${\mathbf{\Delta G}}^o$ in this reaction?

The addition of water to ethylene to yield ethanol has the following thermodynamic parameters:

(a) Is the reaction exothermic or endothermic?

(b) Is the reaction favorable (spontaneous) or unfavorable (nonspontaneous) at room temperature (298 K)?

When isopropylidenecyclohexane is treated with strong acid at room

temperature, isomerization occurs by the mechanism shown below to yield 1-isopropylcyclohexene:

At equilibrium, the product mixture contains about 30% isopropylidene- cyclohexane and about 70% 1-isopropylcyclohexene.

(a) What is an approximate value of K_eq for the reaction?

(b) Since the reaction occurs slowly at room temperature, what is its approximate $∆$G‡?

(c) Draw an energy diagram for the reaction.

Draw the electron-pushing mechanism for each radical reaction below. Identify each step as initiation, propagation, or termination.

(a) 

b) 

c) 

Draw the complete mechanism for each polar reaction below.

(a) 

(b) 

(c) 

2-Chloro-2-methylpropane reacts with water in three steps to yield 2-methyl-2-propanol. The first step is slower than the second, which in turn is much slower than the third. The reaction takes place slowly at room temperature, and the equilibrium constant is approximately 1.

1. Give approximate values for${\mathbf{\Delta G}}^{\pm }$ and ${\mathbf{\Delta G}}^{{}^o}$that are consistent with the above information.
2. Draw an energy diagram for the reaction, labeling all points of interest and making sure that the relative energy levels on the diagram are consistent with the information given.