Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

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Mullins 1st Edition

Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space

Problem 35c

Chapter 5, Problem 35c

For the molecules shown,
(i) count the number of stereocenters present and
(ii) draw all possible stereoisomers.
(iii) Identify the relationships between stereoisomers as enantiomers or diastereomers.
(c)

Verified step by step guidance

Step 1: Identify stereocenters in the molecule. A stereocenter is a carbon atom bonded to four different groups. Analyze each carbon atom in the structure to determine if it meets this criterion. In this molecule, focus on the carbons bonded to hydroxyl (-OH) groups and other substituents.

Step 2: Count the number of stereocenters. After identifying the stereocenters, count them to determine how many are present in the molecule. Each stereocenter contributes to the possibility of stereoisomers.

Step 3: Determine the number of possible stereoisomers. Use the formula 2^n, where n is the number of stereocenters, to calculate the total number of possible stereoisomers for the molecule.

Step 4: Draw all possible stereoisomers. For each stereocenter, consider the two possible configurations (R and S). Combine these configurations systematically to generate all stereoisomers. Represent each stereoisomer with its correct 3D structure, showing the spatial arrangement of groups around each stereocenter.

Step 5: Identify relationships between stereoisomers. Compare the stereoisomers to determine if they are enantiomers (non-superimposable mirror images) or diastereomers (stereoisomers that are not mirror images). Use the configurations (R/S) of the stereocenters to establish these relationships.

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Key Concepts

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

Stereocenters

Stereocenters, or chiral centers, are atoms in a molecule that have four different substituents attached to them, leading to non-superimposable mirror images known as enantiomers. Identifying stereocenters is crucial for understanding the three-dimensional arrangement of atoms in a molecule, which directly influences its chemical properties and biological activity.

Stereoisomers

Stereoisomers are compounds that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This category includes enantiomers, which are mirror images of each other, and diastereomers, which are not mirror images. Understanding stereoisomers is essential for predicting the behavior of molecules in chemical reactions and biological systems.

Enantiomers and Diastereomers

Enantiomers are a type of stereoisomer that are non-superimposable mirror images of each other, often exhibiting different optical activities. Diastereomers, on the other hand, are stereoisomers that are not mirror images and typically have different physical properties. Recognizing the relationships between stereoisomers as enantiomers or diastereomers is vital for understanding their reactivity and interactions in various chemical contexts.

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Using chiral centers to predict types of stereoisomers.

Related Practice

Textbook Question

For the molecules shown,

(i) count the number of stereocenters present and

(ii) draw all possible stereoisomers.

(iii) Identify the relationships between stereoisomers as enantiomers or diastereomers.

(b)

986

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Textbook Question

How many stereoisomers are possible for each of the following molecules?

(c)

1243

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Textbook Question

How many stereoisomers are possible for each of the following molecules?

(a)

1284

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Textbook Question

(R)-Selegiline, a monoamine oxidase (MAO) inactivator, was approved by the FDA in 1989 for the treatment of Parkinson's disease. In pure form, it has a specific rotation, [α]²⁰_D = - 11.0°. What is the expected specific rotation of a mixture containing 64% S and 36% R?

881

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Textbook Question

For the molecules shown,

(i) count the number of stereocenters present and

(ii) draw all possible stereoisomers.

(iii) Identify the relationships between stereoisomers as enantiomers or diastereomers.

(a)

1508

views

Textbook Question

How many stereoisomers are possible for each of the following molecules?