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Ch.5 - Stereochemistry
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 5, Problem 5

Draw a Fischer projection for each compound. Remember that the cross represents an asymmetric carbon atom, and the carbon chain should be along the vertical, with the IUPAC numbering from top to bottom.c. (S)-1,2-dibromobutaned. (R)-butan-2-ol

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Identify the chiral centers in each compound. For (S)-1,2-dibromobutane, the chiral center is at carbon 2. For (R)-butan-2-ol, the chiral center is also at carbon 2.
Draw the carbon chain vertically for each compound, with the highest priority group at the top according to IUPAC numbering. For both compounds, the carbon chain is butane, so it will have four carbon atoms.
For (S)-1,2-dibromobutane, place the bromine atoms on carbon 1 and carbon 2. Ensure that the configuration at carbon 2 is S by arranging the substituents in the correct order of priority (Br > CH2Br > CH3 > H) and using the Cahn-Ingold-Prelog rules.
For (R)-butan-2-ol, place the hydroxyl group (OH) on carbon 2. Ensure that the configuration at carbon 2 is R by arranging the substituents in the correct order of priority (OH > CH3 > CH2CH3 > H) and using the Cahn-Ingold-Prelog rules.
Convert the 3D arrangement of substituents at the chiral centers into a Fischer projection, ensuring that horizontal lines represent bonds coming out of the plane (towards the viewer) and vertical lines represent bonds going behind the plane (away from the viewer).

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Key Concepts

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

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting stereochemistry. In these diagrams, vertical lines represent bonds that project behind the plane of the page, while horizontal lines represent bonds that project out of the page. This format is especially important for visualizing chiral centers and understanding the spatial arrangement of substituents around them.
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Chirality and Stereochemistry

Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of asymmetric carbon atoms. Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. Understanding the (R) and (S) nomenclature is crucial for accurately representing the configuration of chiral centers in compounds like (S)-1,2-dibromobutane and (R)-butan-2-ol.
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IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) nomenclature provides a systematic way to name organic compounds based on their structure. It includes rules for identifying the longest carbon chain, numbering the carbon atoms, and naming substituents. For example, in (S)-1,2-dibromobutane, the '1,2' indicates the positions of the bromine substituents on the butane chain, which is essential for constructing the correct Fischer projection.
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Related Practice
Textbook Question
To show that (R)-2-butyl (R,R)-tartrate and (S)-2-butyl (R,R)-tartrate are not enantiomers, draw and name the mirror images of these compounds.
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Textbook Question
Which of the following pairs of compounds could be separated by recrystallization or distillation?b. and
Textbook Question
Draw a three-dimensional structure for each compound, and star all asymmetric carbon atoms. Draw the mirror image for each structure, and state whether you have drawn a pair of enantiomers or just the same molecule twice.Build molecular models of any of these examples that seem difficult to youe. Chlorocyclohexanef. Cis-1,2-dichlorocyclobutane
Textbook Question
Draw three-dimensional representations of the following compounds. Which have asymmetric carbon atoms? Which have no asymmetric carbons but are chiral anyway? Use your models for parts (a) through (d) and any others that seem unclear.c. ClHC═C═C(CH3)21-chloro-3-methylbuta-1,2-diened. ClHC═CH―CH═CH21-chlorobuta-1,3-diene
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Textbook Question
In Problem 5-3 , you drew the enantiomers for a number of chiral compounds. Now go back and designate each asymmetric carbon atom as either (R) or (S).e. Chlorocyclohexane f. Cis-1,2-dichlorocyclobutane
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Textbook Question
Draw a Fischer projection for each compound. Remember that the cross represents an asymmetric carbon atom, and the carbon chain should be along the vertical, with the IUPAC numbering from top to bottom.a. (S)-propane-1,2-diolb. (R)-2-bromobutan-1-ol
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