Asymmetric synthesis, chiral auxiliaries and methods of asymmetric induction - One Line Questions

1. If a reaction yields 90% of the (R)-enantiomer and 10% of the (S)-enantiomer, what is the enantiomeric excess (ee)? — 80%
2. What is a 'prochiral' molecule? — A molecule that can be converted into a chiral molecule by a reaction that forms a new stereocenter
3. Asymmetric synthesis aims to produce: — A single enantiomer or an enantiomerically enriched product
4. What does 'stereospecificity' refer to in a chemical reaction? — A reaction where a specific stereoisomer of the reactant yields a specific stereoisomer of the product.
5. What is a 'chiral auxiliary' in asymmetric synthesis? — A chiral molecule temporarily incorporated into a substrate to induce diastereoselectivity
6. A molecule that is non-superimposable on its mirror image is called: — Chiral
7. A chiral catalyst is a catalyst that is: — Chiral and speeds up the reaction
8. Methods of asymmetric induction can involve: — Chiral catalysts, chiral reagents, or chiral auxiliaries
9. What type of substrates are commonly reduced in Noyori asymmetric hydrogenation? — Ketones and imines
10. The Jacobsen epoxidation is known for its high enantioselectivity in the epoxidation of: — Internal alkenes
11. What is a key difference between chiral auxiliaries and chiral catalysts? — Auxiliaries are used in stoichiometric amounts; catalysts are used in sub-stoichiometric amounts.
12. What is a common chiral auxiliary derived from an amino acid? — Proline
13. The Noyori asymmetric hydrogenation typically employs a chiral ruthenium-phosphine complex as a: — Chiral catalyst
14. The use of chiral phosphine ligands like BINAP in transition metal catalysis is an example of: — Chiral catalyst approach
15. The Sharpless asymmetric epoxidation is a famous example of: — Asymmetric induction using a chiral catalyst system
16. Evans' oxazolidinones are a well-known class of: — Chiral auxiliaries
17. Which of the following is NOT a method for determining enantiomeric purity? — Mass spectrometry
18. Asymmetric synthesis is particularly important in the pharmaceutical industry because: — Chiral drugs often have different pharmacological activities or toxicities for different enantiomers
19. A mixture containing equal amounts of two enantiomers is known as a: — Racemic mixture
20. Which type of molecule has internal symmetry elements such that it is superimposable on its mirror image, despite having chiral centers? — Meso compound
21. Classical resolution of enantiomers often involves forming salts with a chiral acid or base. These salts are: — Diastereomers
22. Which of the following is a key characteristic of a chiral auxiliary? — It is easily removed after the chiral center is formed
23. After the desired chiral center is formed using a chiral auxiliary, it is typically: — Hydrolyzed or cleaved to be removed
24. Which of the following is a method of asymmetric induction that does NOT typically involve metal catalysts? — Organocatalysis (e.g., using proline)
25. Which type of reaction is most likely to convert a prochiral ketone into a chiral alcohol? — Nucleophilic addition
26. What is the fundamental requirement for a molecule to exhibit optical isomerism? — Presence of a chiral center
27. In the context of Evans' auxiliaries, N-acylation followed by deprotonation creates an enolate that reacts with electrophiles with high: — Diastereoselectivity
28. Polarimetry measures the rotation of plane-polarized light by a chiral compound. A positive rotation is denoted by (+), and a negative rotation by (-). These are: — Independent of absolute configuration
29. When assigning R/S configuration, if the lowest priority group is pointing away from the viewer, a clockwise arrangement of the other three groups corresponds to: — R configuration
30. What is kinetic resolution? — Using a chiral reagent to react preferentially with one enantiomer in a racemic mixture
31. What does the term 'enantiomers' refer to? — Stereoisomers that are mirror images of each other
32. Chiral ligands are often used in conjunction with: — Achiral metal centers to form chiral catalysts
33. Which statement best describes the 'chiral pool' approach to asymmetric synthesis? — Using readily available, inexpensive chiral natural products as starting materials.
34. In the context of asymmetric synthesis, 'chiral memory' refers to: — The ability of a chiral auxiliary to transfer its chirality to the product and be recovered.
35. In the asymmetric reduction of a prochiral ketone, a chiral reducing agent or catalyst influences the approach of the hydride to: — The carbonyl carbon, leading to preferential formation of one enantiomer
36. The (R) and (S) nomenclature for stereocenters is based on: — The sequence rules developed by Cahn-Ingold-Prelog
37. Reagent-controlled asymmetric synthesis relies on: — A chiral reagent or catalyst that directs the stereochemical outcome
38. What does 'enantiomeric excess' (ee) measure? — The degree to which one enantiomer is favored over the other
39. What is 'asymmetric induction'? — The process by which a chiral influence directs the stereochemical outcome of a reaction
40. Organocatalysis, using small organic molecules as catalysts, can also be used for asymmetric synthesis. A prominent example is: — Organocatalytic Michael additions using proline derivatives
41. A key challenge in using chiral auxiliaries is: — The difficulty in their removal and recycling
42. Which concept is central to achieving asymmetric induction? — Chiral discrimination
43. What are the key components of the Sharpless asymmetric epoxidation catalyst system? — Titanium tetraisopropoxide, tert-butyl hydroperoxide, and a chiral tartrate ester
44. What is the role of a chiral resolving agent? — To temporarily attach to a racemic mixture to form diastereomers, which can then be separated
45. What is the purpose of the Cahn-Ingold-Prelog priority rules? — To assign the absolute configuration (R or S) to a stereocenter
46. What is the primary goal when using a chiral auxiliary? — To achieve high diastereomeric excess (de)
47. Which of the following is an example of a substrate-controlled asymmetric synthesis? — Using a chiral auxiliary attached to the substrate
48. Diastereoselective reactions create products with a higher proportion of one diastereomer over others. This is often achieved by: — Utilizing existing stereocenters in the substrate to influence the formation of new stereocenters
49. Which of the following is a common example of a chiral molecule? — Lactic acid
All One Line Questions
E-Book Asymmetric synthesis, chiral auxiliaries and methods of asymmetric induction Online Test Asymmetric synthesis, chiral auxiliaries and methods of asymmetric induction Question Bank Asymmetric synthesis, chiral auxiliaries and methods of asymmetric induction