Question 1

Which of the following statements best describes the difference between conformations and configurations in organic molecules?

Accepted Answer

Conformations refer to different spatial arrangements that can be interconverted by rotation around single bonds, while configurations require breaking and reforming bonds to interconvert.

Question 2

Which of the following molecules exhibits cis-trans isomerism due to restricted rotation?

Accepted Answer

$$\mathrm{CH_3CH=$$CHCH_3$$} (2-$$butene)

Question 3

A compound has two asymmetric centers. What is the maximum number of stereoisomers possible for this compound?

Accepted Answer

$$4$$

Question 4

Which of the following is true about meso compounds?

Accepted Answer

They are optically inactive because they possess a plane of symmetry.

Question 5

Which of the following best describes an enantiomeric pair?

Accepted Answer

Two molecules that are nonsuperimposable mirror images.

Question 6

A sample of a chiral compound has an observed specific rotation of $$+9.2. $$The specific rotation of the pure enantiomer is $$+23.1. $$What is the enantiomeric excess ($$\%ee) of $$the sample?

Accepted Answer

$$40\%$$

Question 7

Which of the following is NOT a requirement for a carbon atom to be considered an asymmetric center?

Accepted Answer

It must be part of a double bond.

Question 8

Which of the following statements about Fischer projections is correct?

Accepted Answer

Rotating a Fischer projection by $$180^\circ$$ retains the same enantiomer.

Question 9

Which of the following compounds is achiral?

Accepted Answer

$$\mathrm{CH_3CH_2CH_3} ($$propane)

Question 10

Which of the following best explains why a racemic mixture does not rotate plane-polarized light?

Accepted Answer

The optical activities of the two enantiomers cancel each other out.

Question 11

Which rule is used to assign priorities to substituents when naming enantiomers using the Cahn-Ingold-Prelog system?

Accepted Answer

The group with the highest atomic number gets the highest priority.

Question 12

Which of the following statements about double and triple bonds in priority assignment is correct?

Accepted Answer

Double bonds are treated as if the atoms are duplicated, and triple bonds as if the atoms are triplicated.

Question 13

Which of the following is a correct statement about the relationship between enantiomers and diastereomers?

Accepted Answer

Diastereomers are stereoisomers that are not mirror images.

Question 14

A compound with two asymmetric centers and a plane of symmetry is best described as:

Accepted Answer

A meso compound

Question 15

Which of the following is true regarding the optical activity of meso compounds?

Accepted Answer

They do not rotate plane-polarized light due to internal compensation.

Question 16

Which of the following best describes a stereocenter?

Accepted Answer

An atom at which the interchange of two groups produces a stereoisomer.

Question 17

Which of the following is a correct application of the Cahn-Ingold-Prelog rules when two substituents attached to a stereocenter have the same atomic number?

Accepted Answer

Proceed along the respective substituent chains until a point of difference is found.

Question 18

Which of the following is true about the effect of changing any two substituents in a Fischer projection?

Accepted Answer

It converts the molecule into its mirror image.

Question 19

Which of the following real-world scenarios best illustrates the concept of chirality?

Accepted Answer

A pair of gloves, where the left and right gloves are mirror images but not superimposable.

Isomerism and Stereochemistry: The Arrangement of Atoms in Space

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