Question 1

Which of the following best describes the relationship between ethyl alcohol ($$\mathrm{CH_3CH_2OH}) $$and dimethyl ether ($$\mathrm{CH_3OCH_3}$$)?

Accepted Answer

They are constitutional isomers.

Question 2

Why do cis-trans isomers exist for alkenes but not for alkanes?

Accepted Answer

Alkenes have a $$\pi$$ bond that restricts rotation, while alkanes do not.

Question 3

Which of the following compounds can exhibit cis-trans isomerism?

Accepted Answer

$$\mathrm{CH_3CH=$$CHCH_3$$}$$

Question 4

Given the following alkene, which is the E isomer?

$$\mathrm{CH_3CH=CHCl}$$

Accepted Answer

The isomer with $$\mathrm{CH_3$}$$ and $$\mathrm{Cl} on $$opposite sides of the double bond.

Question 5

Which statement about the E/Z nomenclature is correct?

Accepted Answer

The E isomer has the high-priority groups on opposite sides of the double bond.

Question 6

Which of the following molecules is chiral?

Accepted Answer

$$\mathrm{CH_3CHClCH_2CH_3}$$

Question 7

A molecule has two stereocentres. What is the maximum number of stereoisomers it can have?

Accepted Answer

$$4$$

Question 8

Which of the following statements about enantiomers is FALSE?

Accepted Answer

They have different chemical properties with achiral reagents.

Question 9

A racemic mixture contains:

Accepted Answer

A 1:1 mixture of two enantiomers.

Question 10

Which of the following best describes a meso compound?

Accepted Answer

An achiral compound with two or more stereocentres and a plane of symmetry.

Question 11

Which technique can be used to separate enantiomers?

Accepted Answer

Chiral column chromatography.

Question 12

Which of the following is true for a pair of diastereomers?

Accepted Answer

They have at least one stereocentre in common.

Question 13

Which of the following statements about the R/S system is correct?

Accepted Answer

A counterclockwise sequence from highest to lowest priority gives the S configuration.

Question 14

Which of the following would NOT result in optical activity?

Accepted Answer

A racemic mixture.

Question 15

Which of the following is a correct statement about the specific rotation $$[\alpha] of $$enantiomers?

Accepted Answer

Enantiomers have specific rotations of equal magnitude and opposite sign.

Question 16

Which of the following best describes the relationship between D-erythrose and L-threose?

Accepted Answer

They are diastereomers.

Question 17

Which of the following is true for a meso compound?

Accepted Answer

It is achiral despite having stereocentres.

Question 18

Which of the following statements about the separation of enantiomers is correct?

Accepted Answer

Enantiomers can be separated by their different interactions with chiral materials.

Question 19

Which of the following is NOT a requirement for a molecule to exhibit chirality?

Accepted Answer

The molecule must be superimposable on its mirror image.

Question 20

Which of the following statements about cis-trans isomerism in cyclohexane derivatives is correct?

Accepted Answer

Cis-trans isomerism in rings is due to the relative positions of substituents on the ring.

Isomerism in Organic Chemistry: Constitutional, Geometric, and Stereoisomers

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