Question 1

Which of the following best describes the role of transition metal (TM) complexes in hydrogen activation?

Accepted Answer

TM complexes mediate the breakage of inert bonds through coordination, enabling oxidative addition or heterolytic cleavage.

Question 2

In the bis-hydride mechanism for alkene hydrogenation, which step is typically the rate-determining step (RDS)?

Accepted Answer

1,2-Insertion of the alkene into the metal-hydride bond

Question 3

Which equation correctly relates the product ratio in a selectivity-determining step to the difference in activation energies?

Accepted Answer

$$\frac{[C]}{[D]} = e$$^{-\frac{\Delta\Delta G^{\ddagger}$$}{RT}}$$

Question 4

Which catalyst has the highest turnover frequency (TOF) for alkene hydrogenation among Wilkinson, Schrock-Osborn, and Crabtree catalysts?

Accepted Answer

Crabtree catalyst

Question 5

What is the main difference between homolytic and heterolytic activation of hydrogen by transition metal complexes?

Accepted Answer

Homolytic activation produces two hydride ligands, while heterolytic activation produces a hydride and a proton.

Question 6

Which principle explains why the product ratio in a reaction with rapidly interconverting intermediates depends only on the energy barriers to product formation?

Accepted Answer

Curtin-Hammett Principle

Question 7

In hydroelementation reactions, which factor can be used to influence regioselectivity?

Accepted Answer

Using a second functional group to tether the substrate in the desired orientation

Question 8

Which Nobel Prize-winning chemists are associated with the development of asymmetric hydrogenation reactions?

Accepted Answer

William S. Knowles, Ryoji Noyori, K. Barry Sharpless

Question 9

Which of the following is NOT a hydroelementation reaction?

Accepted Answer

Hydrohalogenation

Question 10

What is the effect of increasing $$\Delta\Delta G$$^{\ddagger}$$ by 3 kcal mol$$^{-1}$$ on product selectivity in catalysis?

Accepted Answer

It leads to full selectivity for one product.

Question 11

Which step in the hydrosilylation catalytic cycle is responsible for selectivity?

Accepted Answer

1,2-Insertion

Question 12

Which mechanism is most likely when a transition metal complex activates hydrogen via coordination, but no Lewis pair is possible due to steric repulsion?

Accepted Answer

Frustrated Lewis Pair mechanism

Question 13

In the context of alkene hydrogenation, what does 'syn-addition' refer to?

Accepted Answer

Addition of hydrogen atoms to the same side of the double bond

Question 14

Which of the following is a key aspect of catalyst design to optimize performance in hydrogenation reactions?

Accepted Answer

Stabilizing the desired transition state through H-bonding or π-π stacking

Question 15

Which of the following statements about the selectivity-determining step in catalysis is correct?

Accepted Answer

It is often different from the rate-determining step.

Question 16

Which equation represents the relationship between selectivity and temperature for a given $$\Delta\Delta G$$^{\ddagger}$$?

Accepted Answer

$$s = e$$^{-\frac{\Delta\Delta G^{\ddagger}$$}{RT}}$$

Question 17

Which of the following is a real-world application of asymmetric hydrogenation catalysis?

Accepted Answer

Synthesis of L-DOPA for Parkinson's disease treatment

Question 18

What is the main advantage of using a mono-hydride cycle in alkene hydrogenation compared to a bis-hydride cycle?

Accepted Answer

Mono-hydride cycles allow for heterolytic activation of hydrogen, which can be more selective.

Question 19

Which of the following statements about hydroboration reactions is correct?

Accepted Answer

Hydroboration typically follows anti-Markovnikov addition.

Applied Organometallic Chemistry: Hydrogenation and Hydroelementation Mechanisms

Guida di studio - Domande di pratica

Study guide - Flashcard