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Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 6 - Stereoisomerism: Arrangement of Atoms in SpaceProblem 40b
Chapter 5, Problem 40b

(i) Which of the following pairs of compounds would you expect to have different physical properties?
(ii) What is the relationship between each of the pairs?
(iii) Assign the absolute configuration of each stereocenter to confirm your answer.
(b) Structural comparison of two isomer compounds with hydroxyl and aldehyde groups, highlighting differences in configuration.

Verified step by step guidance
1
Step 1: Analyze the given structures. The two compounds are stereoisomers of each other, as they have the same molecular formula and connectivity but differ in the spatial arrangement of their atoms.
Step 2: Assign the absolute configuration (R or S) to each stereocenter in both compounds. Use the Cahn-Ingold-Prelog priority rules to determine the configuration. Start by identifying the four groups attached to each chiral carbon and rank them based on atomic number.
Step 3: Compare the absolute configurations of the stereocenters in the two compounds. If all stereocenters have opposite configurations, the compounds are enantiomers. If only some stereocenters differ, the compounds are diastereomers.
Step 4: Determine the relationship between the two compounds. Enantiomers have identical physical properties (e.g., boiling point, melting point) except for their interaction with plane-polarized light. Diastereomers, on the other hand, have different physical properties.
Step 5: Conclude whether the compounds have different physical properties based on their stereochemical relationship. If they are diastereomers, they will have different physical properties. If they are enantiomers, their physical properties will be identical except for optical activity.

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Key Concepts

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

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. It is crucial for understanding isomers, particularly stereoisomers, which have the same molecular formula but differ in the orientation of their atoms in space. In this question, the compounds presented are likely stereoisomers, and their different configurations can lead to distinct physical properties.
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Physical Properties of Compounds

Physical properties, such as boiling point, melting point, and solubility, are characteristics that can vary between compounds due to differences in molecular structure and intermolecular forces. In the context of the question, the different arrangements of hydroxyl (OH) groups in the compounds can lead to variations in hydrogen bonding, affecting their physical properties. Understanding these differences is essential for predicting how the compounds will behave in various conditions.
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Absolute Configuration

Absolute configuration refers to the specific three-dimensional arrangement of atoms around a chiral center in a molecule, typically designated using the R/S nomenclature. Assigning absolute configuration is important for distinguishing between enantiomers, which are non-superimposable mirror images of each other. In this question, determining the absolute configuration of each stereocenter will help confirm the relationship between the two compounds and their differing properties.
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Related Practice
Textbook Question

(i) Which of the following pairs of compounds would you expect to have different physical properties?

(ii) What is the relationship between each of the pairs?

(iii) Assign the absolute configuration of each stereocenter to confirm your answer.

(a)

1126
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Textbook Question

Which of the following diastereomers of hexane-2,5-diol is optically inactive? Why?

1255
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Textbook Question

Convert the Fischer projections into line-angle drawings and assign (R) and (S) at each chiral center.

(c)

835
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Textbook Question

Convert the Fischer projections into line-angle drawings and assign (R) and (S) at each chiral center.

(a)

1584
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Textbook Question

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

(b)

1326
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Textbook Question

(i) Which of the following pairs of compounds would you expect to have different physical properties?

(ii) What is the relationship between each of the pairs?

(iii) Assign the absolute configuration of each stereocenter to confirm your answer.

(c)

1067
views