Skip to main content
Ch. 14 - NMR Spectroscopy
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
Chapter 15, Problem 33a(1)

For the following compounds, which pairs of hydrogens (Ha and Hb) are enantiotopic hydrogens?
1.

Verified step by step guidance
1
Step 1: Understand the concept of enantiotopic hydrogens. Enantiotopic hydrogens are pairs of hydrogens in a molecule that, when replaced by a different group, result in two enantiomers. This occurs when the molecule has a plane of symmetry or a chiral center upon substitution.
Step 2: Analyze the structure provided. The molecule is 2-methylbutane, and the hydrogens Ha and Hb are attached to the same carbon atom (the second carbon in the chain). This carbon is bonded to a methyl group, an ethyl group, and another methyl group.
Step 3: Determine if replacing Ha and Hb individually with a different group (e.g., a chlorine atom) would create two enantiomers. To do this, visualize the molecule after substitution and check for chirality. If the resulting molecules are non-superimposable mirror images, Ha and Hb are enantiotopic.
Step 4: Consider the symmetry of the molecule. The carbon atom to which Ha and Hb are attached is not part of a plane of symmetry, and the molecule becomes chiral upon substitution of either hydrogen. This indicates that Ha and Hb are enantiotopic.
Step 5: Conclude that Ha and Hb are enantiotopic hydrogens because their individual replacement leads to the formation of two enantiomers, confirming their relationship.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Enantiotopic Hydrogens

Enantiotopic hydrogens are pairs of hydrogen atoms that, when replaced by a different atom or group, lead to the formation of enantiomers—molecules that are non-superimposable mirror images of each other. This concept is crucial in stereochemistry, as it helps in identifying chiral centers and understanding molecular symmetry.
Recommended video:
Guided course
00:48
The definition of hydrogenation.

Chirality

Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image. A chiral molecule typically has at least one carbon atom bonded to four different substituents, creating two distinct forms (enantiomers). Understanding chirality is essential for recognizing how enantiotopic hydrogens contribute to the overall stereochemistry of a compound.
Recommended video:
Guided course
05:10
What is chirality?

Stereoisomerism

Stereoisomerism is a form of isomerism where molecules have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of those atoms. This includes enantiomers and diastereomers, and it is vital for understanding the behavior and reactivity of organic compounds, particularly in the context of enantiotopic hydrogens.
Recommended video:
Guided course
01:58
Determining when molecules are stereoisomers.