Chapter 5 Multiple Choice Questions

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. Which of the following definitions of an asymmeric reaction is the most accurate?

A reaction that creates a new chiral centre in the product correct incorrect

A reaction that involves a chiral reagent. correct incorrect

A reaction which creates a new chiral centre with selectivity for one enantiomer/diasatereoisomer over another. correct incorrect

A reaction that is carried out on an asymmetric starting material correct incorrect

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. What is meant by a reaction going in 94% enantiomeric excess?

The product contains 94% of one enantiomer and 6% of the other enantiomer correct incorrect

The product contains 94% of one enantiomer and 6% of other products correct incorrect

The product contains an enantiomer which is 94% pure. correct incorrect

The product contains 97% of one enantiomer and 3% of the other enantiomer correct incorrect

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. If a prochiral ketone was converted enantioselectively to a chiral alcohol with a Grignard reagent under asymmetric conditions, which of the following statements would be false?

The prochiral ketone has different groups linked to the carbonyl group correct incorrect

A chiral product would be obtained regardless of which Grignard reagent is used correct incorrect

The reaction centre is an sp² hybridised carbon correct incorrect

Nucleophilic attack by the Grignard reagent will be selective for one enantiotopic face over the other. correct incorrect

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. Which of the following statements is true regarding the following chiral reducing agent?

There is an asymmetric centre at the position labelled a) correct incorrect

There is an asymmetric centre at the position labelled b) correct incorrect

There is an asymmetric centre at the position labelled c) correct incorrect

There is no asymmetric centre present correct incorrect

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. The following structure has an asymmetric centre marked with a blue asterisk

Which of the following diagrams correctly identifies the order of priority (labelled in red) for the groups attached to the asymmetric centres and identifies the correct absolute configuration?

Answer A correct incorrect

Answer B correct incorrect

Answer C correct incorrect

Answer D correct incorrect

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. Which of the following statements is false regarding the following asymmetric reaction?

The reaction centre is the carbonyl carbon of the aldehyde group correct incorrect

The reaction is diastereoselective correct incorrect

The nucleophile prefers to approach the si enantiotopic face of the aldehyde group correct incorrect

Structure I is acting as a chiral auxiliary correct incorrect

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. Naproxen has been synthesised as a racemate then resolved by crystallisation of diastereomeric salts.

Which of the following compounds would be suitable for preparing the necessary diastereomeric salts?

Quinoline correct incorrect

Tartaric acid correct incorrect

Malic acid correct incorrect

Cinchonidine correct incorrect

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. The following structure is amprenavir.

Amprenavir was synthesised from a chiral starting material by a multistage synthesis? Which of the following structures do you think was the most likely starting material.

Structure A correct incorrect

Structure B correct incorrect

Structure C correct incorrect

Structure D correct incorrect

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. Treatment of a diester with pig liver esterase (PLE) gave structure II, which was treated with lithium borohydride to give structure III. Which of the following statements is correct?

The esters in the starting material are enantiotopic. The enzyme catalyses the hydrolysis of one of these groups to product structure II which contains two chiral centres. Reduction with lithium borohydride shows chemoselectivity for the carboxlic acid and the resulting product cyclises to give structure III. correct incorrect

The esters in the starting material are diastereotopic. The enzyme catalyses the hydrolysis of one of these groups to product structure II which contains two chiral centres. Reduction with lithium borohydride shows chemoselectivity for the carboxlic acid and the resulting product cyclises to give structure III. correct incorrect

The esters in the starting material are enantiotopic. The enzyme catalyses the hydrolysis of one of these groups to product structure II which contains two chiral centres. Reduction with lithium borohydride shows chemoselectivity for the ester, and the resulting product cyclises to give structure III. correct incorrect

The esters in the starting material are diastereotopic. The enzyme catalyses the hydrolysis of one of these groups to product structure II which contains two chiral centres. Reduction with lithium borohydride shows chemoselectivity for the ester, and the resulting product cyclises to give structure III. correct incorrect

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. The following asymmetric reaction results in the formation of two diastereomers with one being formed in greater quantity than the other.

Which of the following Felkin-Anh models correctly predicts the major product?

Diagram A correct incorrect

Diagram B correct incorrect

Diagram C correct incorrect

Diagram D correct incorrect