Question 1

The intensity of an infrared absorption relating to a bond stretch in an organic compound depends on which of the following factors?

Accepted Answer

The overall dipole moment of the molecule in its vibrational ground state.

Question 2

In electron-ionization mass spectrometry, fragmentation patterns of the parent ion in organic compounds are largely determined by:

Accepted Answer

All of the above options.

Question 3

In infrared spectroscopy, the stronger the bond...

Accepted Answer

The higher the wavenumber frequency of the absorption.

Question 4

Torsional strain is an increase in energy caused by...

Accepted Answer

A combination of steric and electronic effects in eclipsed conformations.

Question 5

Which of the following best describes a staggered conformation of ethane?

Accepted Answer

A conformation with non-hydrogen groups having a 60° dihedral angle.

Question 6

Cyclopropane is...

Accepted Answer

A flat ring with eclipsed C–H bonds on adjacent carbon atoms.

Question 7

Molecules with a single stereocenter...

Accepted Answer

May or may not be chiral, depending on the presence of an internal mirror plane.

Question 8

Enantiomers have exactly the same chemical properties except for...

Accepted Answer

Their reaction with chiral non-racemic compounds.

Question 9

What is a meso compound?

Accepted Answer

An achiral member of a series of diastereomers in which at least one is chiral.

Question 10

Change in entropy, $$\Delta S$$, is a measure of...

Accepted Answer

The change in disorder of a system during a chemical process.

Question 11

Which of the following factors contributes most to the difference in energy between the staggered and eclipsed conformations of ethane?

Accepted Answer

Hyperconjugation between filled and empty orbitals.

Question 12

For propane, the barrier to rotation around a C–C bond is expected to be:

Accepted Answer

Larger than for ethane due to increased steric interactions.

Question 13

Which statement best explains why the primary C–H bond in 1,3-dimethylcyclohexane is stronger than the tertiary C–H bond?

Accepted Answer

Primary C–H bonds have better orbital overlap due to less steric hindrance.

Question 14

Which of the following is true about the cis and trans isomers of decalin?

Accepted Answer

The cis isomer is chiral, while the trans isomer is achiral.

Question 15

Which of the following best describes the relationship between 2,3-dichlorobutane and 2-bromo-3-chlorobutane?

Accepted Answer

They are stereoisomers.

Question 16

Which of the following statements about Newman projections is correct?

Accepted Answer

They are used to analyze the conformations of molecules around a single bond.

Question 17

Which of the following is a correct statement about bond dissociation energies (BDEs) in cyclohexane derivatives?

Accepted Answer

Primary C–H bonds have the highest BDE due to optimal orbital overlap.

Question 18

Which of the following is NOT a factor that affects the stability of carbocations?

Accepted Answer

Bond angle strain.

Question 19

Which of the following best describes the difference between enantiomers and diastereomers?

Accepted Answer

Enantiomers are non-superimposable mirror images, while diastereomers are not mirror images.

Organic Chemistry: Molecular Structure, Conformation, and Stereochemistry Study Guide

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