Question 1

Which of the following statements best describes the difference between kinetics and thermodynamics in a chemical reaction?

Accepted Answer

Kinetics is concerned with the rate of reaction and is determined by the activation energy, while thermodynamics is concerned with the energy difference between reactants and products and determines the equilibrium position.

Question 2

In the free radical halogenation of alkanes, which step is responsible for the formation of the reactive halogen radical?

Accepted Answer

Initiation

Question 3

Consider the following reaction: $$CH_3CH_3 + Cl_2$ \xrightarrow{hv} CH_3CH_2Cl + HCl. $$What is the major product when excess chlorine is used?

Accepted Answer

CH$$_2$$ClCH$$_2Cl$$

Question 4

Which type of hydrogen atom is most reactive in free radical bromination of alkanes?

Accepted Answer

Tertiary hydrogen

Question 5

Why is bromination more selective than chlorination in free radical halogenation?

Accepted Answer

Bromine radicals are less reactive, leading to a later transition state with more radical character, which favors formation of the most stable radical.

Question 6

Given the homolytic bond dissociation energies: $$BDE_{C-H} = 410\ \mathrm{kJ/mol}$$ and $$BDE_{H-Br} = 366\ \mathrm{kJ/mol}$$, what is the enthalpy change for the reaction $$CH_3CH_2-H + Br \rightarrow CH_3CH_2\cdot + HBr$$?

Accepted Answer

$$\Delta H = 410 - 366 = 44\ \mathrm{kJ/mol}$$

Question 7

Which of the following is NOT a requirement for a successful molecular collision in the context of collision theory?

Accepted Answer

Molecules must be of the same element.

Question 8

In the mechanism of free radical halogenation, what is the role of the propagation step?

Accepted Answer

It sustains the chain reaction by generating new radicals and products.

Question 9

Which statement best explains why tertiary radicals are more stable than primary radicals?

Accepted Answer

Tertiary radicals have more alkyl groups that donate electron density, stabilizing the radical center.

Question 10

Which of the following best describes the transition state in free radical chlorination compared to bromination?

Accepted Answer

Chlorination has an early transition state with less radical character, while bromination has a late transition state with more radical character.

Question 11

Which of the following is a correct representation of a resonance structure for acetate ion?

Accepted Answer

$$\mathrm{CH_3COO^-}$$ with negative charge delocalized over both oxygens

Question 12

Which factor most strongly influences the selectivity of free radical halogenation reactions?

Accepted Answer

The stability of the carbon radical intermediate.

Question 13

In the Finkelstein reaction, what drives the reaction to completion?

Accepted Answer

The precipitation of NaBr in acetone, shifting equilibrium by Le Chatelier's principle.

Question 14

Which of the following is true about nucleophilicity and basicity for second period elements?

Accepted Answer

Stronger base generally means better nucleophile.

Question 15

Which of the following is NOT a possible product of the free radical chlorination of propane?

Accepted Answer

3-chloropropane

Question 16

Which of the following best explains why line structures are commonly used in organic chemistry?

Accepted Answer

They simplify the representation of molecules by omitting hydrogens bonded to carbons, making connectivity clearer.

Question 17

Which of the following statements about the S$$_N2 $$reaction mechanism is correct?

Accepted Answer

It is a one-step reaction where the nucleophile attacks the electrophile simultaneously as the leaving group departs.

Question 18

Which of the following is a correct statement about the E2 elimination mechanism?

Accepted Answer

It requires a planar transition state with the leaving group and the hydrogen being eliminated anti-coplanar.

Question 19

Which of the following is the correct formula for the combustion of hexane ($$C_6H_{14}$$)?

Accepted Answer

$$C_6H_{14} + 9.5 O_2$ \rightarrow 6 CO_2$ + 7 H_2O$$

Organic Chemistry I: Free Radical Halogenation, Kinetics, Thermodynamics, and Reaction Mechanisms

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