Inorganic Chemistry Reaction Intermediates Quiz
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Questions and Answers

What is the principle that dictates the direction of a chemical reaction according to transition-state theory?

  • The highest energy pathway available
  • The most complicated pathway available
  • The lowest energy pathway available (correct)
  • The variable energy pathway available

    • Which type of reaction involves substitution at the metal center in coordination complexes?

  • Substitution at the metal center (correct)
  • Reactions that include more elaborate rearrangements of ligand structures
  • Oxidation–reduction
  • Reactions of the ligands that do not change the attachments to the metal center

    • What imposes variability on the reactivity of coordination complexes?

  • Geometries of complexes
  • Types of reactions
  • Metal atoms (correct)
  • Rearrangements

    • In free energy coordinate diagrams, what is the adopted path between the reactants and products?

    <p>The lowest energy pathway available</p> Signup and view all the answers

    What do transition-state theory describes chemical reactions as moving between?

    <p>Reactants and transition states</p> Signup and view all the answers

    What is the highest energy structure along a reaction pathway called?

    <p>Transition state</p> Signup and view all the answers

    How are transition states different from intermediates?

    <p>Intermediates have extended and weaker bonds compared to reactants, while transition states do not.</p> Signup and view all the answers

    What do reaction coordinate diagrams help to explain?

    <p>Mechanism of reaction</p> Signup and view all the answers

    What does the principle of microscopic reversibility state?

    <p>The adopted pathway between reactants and products is the same regardless of the direction of the reaction.</p> Signup and view all the answers

    What is a classic example of a substitution reaction involving [Fe(H2O)6] and SCN-?

    <p>[Fe(H2O)6] + NaCl</p> Signup and view all the answers

    Which type of ligands tend to make complexes inert?

    <p>Strong-field ligands</p> Signup and view all the answers

    What determines whether a substitution reaction is classified as dissociative (D) or associative (A)?

    <p>The coordination number of the intermediate formed</p> Signup and view all the answers

    Which metal ions have the fastest water exchange rates among the given options?

    <p>[Fe(H2O)6]3+</p> Signup and view all the answers

    What color does the initial solution turn due to the presence of Fe(III) complexes?

    <p>Yellow</p> Signup and view all the answers

    What are 'labile' and 'inert' in the context of complexes?

    <p>Kinetic terms used to describe reaction rates</p> Signup and view all the answers

    Which type of interchange intermediate forms when the incoming ligand begins forming a bond to the central atom before the departing ligand bond is weakened?

    <p>Associative interchange intermediates (Ia)</p> Signup and view all the answers

    Which type of interchange intermediate appears when the degree of assistance is small and the reaction is primarily dissociative?

    <p>Interchange intermediates (Id)</p> Signup and view all the answers

    What type of reactions typically involve a 7-coordinate intermediate and a higher coordination number?

    <p>Associative reactions</p> Signup and view all the answers

    In which type of interchanges do 5-coordinate intermediates commonly occur?

    <p>Dissociative reactions</p> Signup and view all the answers

    What are the categories of dissociative, associative, and interchange mechanisms known as?

    <p>Stoichiometric mechanisms</p> Signup and view all the answers

    What defines a dissociative (D) mechanism in coordination reactions?

    <p>The leaving group dissociates first from the complex before the incoming group binds</p> Signup and view all the answers

    What is a characteristic of an interchange (I) mechanism in coordination reactions?

    <p>The incoming group directly replaces the leaving group in the complex without intermediate formation</p> Signup and view all the answers

    What provides evidence for a dissociative (D) mechanism in coordination reactions?

    <p>Dependence of the reaction rate on the concentration of both reactants, X and Y</p> Signup and view all the answers

    What limitation exists in detecting interchange mechanisms in coordination reactions?

    <p>Lack of evidence for an intermediate in many cases</p> Signup and view all the answers

    How can experimental data exhibiting both interchange and substitution mechanisms be interpreted in coordination reactions?

    <p>As evidence for the validity of both mechanisms</p> Signup and view all the answers

    Which type of reaction involves substitution at the metal center in coordination complexes?

    <p>Associative interchange mechanism</p> Signup and view all the answers

    What influences the kinetics of dissociative substitution reactions?

    <p>LFAE values</p> Signup and view all the answers

    What is the significance of the highest LFAE values (most positive) in coordination complexes?

    <p>Inertness of ions</p> Signup and view all the answers

    What results in second-order kinetics for the associative interchange mechanism?

    <p>Steady-state approximation</p> Signup and view all the answers

    What is the function of the splitting of d-based levels from octahedral to square-planar symmetry in the transition state?

    <p>Distance and angle changes influence</p> Signup and view all the answers

    Study Notes

    • The highest energy structure along a reaction pathway is called the transition state.

    • Transition states are unstable and are not detectable intermediates.

    • The reaction process proceeds through a transition state without a detectable intermediate state.

    • Intermediates, in contrast, are detectable and they have extended bonds and weaker bonds compared to the reactants.

    • The reaction coordinate diagrams help to explain the reaction mechanism and the extent of reaction.

    • The energy profiles of reactions can be determined through kinetics experiments to find the activation energy and its components.

    • The principle of microscopic reversibility states that the adopted pathway between reactants and products is the same regardless of the direction of the reaction.

    • The pressure dependence on reaction rates provides insight into the volume of activation and the size of the transition state.

    • Large activation energies hinder the reaction rate, but large equilibrium constants favor the reaction.

    • Substitution reactions are common in coordination chemistry, where metal ions like [M(H2O)m] are involved as reactants.

    • Substitution reactions can produce colored products to identify metal ions and are generally rapid.

    • Fe(H2O)6 + SCN- is a classic example of a substitution reaction involving [Fe(H2O)6] and SCN-.

    • Other ligand species like HNO3, NaCl, H3PO4, KSCN, and NaF can be added to a solution of Fe(NO3)3.9H2O to observe the reaction.

    • If the interchange reaction is reversible, it can be approximated as a pair of opposing pseudo-first order reactions.

    • In an associative interchange mechanism, the I (incoming ligand) and D (departing ligand) bonds are broken and formed in the transition state.

    • In a dissociative interchange mechanism, the I (incoming ligand) bond is more important in the transition state.

    • The transition state of associative interchange involves the formation of an intermediate with an increased coordination number.

    • The steady-state approximation results in second-order kinetics for the associative interchange mechanism.

    • The kinetics of dissociative substitution reactions are influenced by various factors, including LFAE values.

    • The highest LFAE values (most positive) are associated with inert ions such as d3 and low-spin d4, d5, and d6.

    • The negative LFAE parameters predict low activation barriers for an octahedral complex losing a ligand.

    • The splitting of d-based levels from octahedral to square-planar (SQP, C4v) symmetry is a function of the distance and angle changes in the transition state.

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    Test your knowledge of inorganic chemistry reaction intermediates with this quiz. Identify and understand different types of intermediates and their roles in chemical reactions.

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