Exam 4: The Study of Chemical Reactions

Which of the following is a propagation step in the free radical chlorination of dichloromethane?

Use the Hammond Postulate to explain why free radical brominations are more selective than free radical chlorinations.

Given a K of 2.2 at 25°C, calculate the corresponding DG° in kJ/mol. [R = 8.314 J/K∙ mol]

For the reaction A + B → C + D, ΔG° = -5.00 kcal/mol. What is the corresponding equilibrium constant at 25°C? R = 1.987 cal/mol∙K.

Energy is ________ when bonds are formed and is ________ when bonds are broken; therefore, bond dissociation energies are always ________.

Given a DG° of 0.8 kJ/mol at 25°C for the equilibrium shown below, calculate the percentage of the axial conformer at 25°C. [R = 8.314 J/K∙ mol]

When light is shined on a mixture of chlorine and chloromethane, carbon tetrachloride is one of the components of the final reaction mixture. Propose a series of mechanistic steps which explain this observation.

What is meant by the $\underline{\text{ mechanism }}$ of a chemical reaction?

List the following radicals in order of increasing stability (i.e., from least stable to most stable). (CH₃)₃C∙, CH₂= CHCH₂∙, CH₃CH₂∙, CH₃∙, (CH₃)₂CH∙

What is the CCC bond angle in (CH₃)₃C⁺?

Which compound has the smaller bond dissociation energy for its carbon-chlorine bond, CH₃Cl or (CH₃)₃CCl? Explain your reasoning.

The hydrogen atom abstraction step in the free radical chlorine of methane is exothermic. Use the Hammond Postulate to speculate on the extent of bond formation and bond cleavage in the transition state.

Predict the signs of DH° and DS° in the reaction of cyclohexene with H₂ to form cyclohexane.

Draw all monochlorination products expected from reaction of chlorine with 3,4-dimethylhexane. $\textbf{ Circle }$ the major product.

The major monobrominated product which results when ethylcyclohexane is subjected to free radical bromination is:

Consider the conversion of C to D via a one-step mechanism. The activation energy of this conversion is 3 kcal/mol. The energy difference between D and the transition state of the reaction is 7 kcal/mol. Estimate ΔH° for the reaction C → D.

What C₅H₁₂ isomer will give only a single monochlorination product?

What is the name of the major monobrominated product which results when methylcyclohexane is subjected to Br₂/hν conditions?

Species with unpaired electrons are called ________.

Which is a measure of the randomness of a system?