Ch.5 - Stereochemistry

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch.5 - Stereochemistry

Problem 9

Chapter 5, Problem 9

Write structural formulas for the following compounds (includes both old- and new-style names).(j) vinylacetylene(k) (S)-3-methyl-1-penten-4-yne

Verified step by step guidance

Identify the structure of vinylacetylene: Vinylacetylene is also known as 1-buten-3-yne. It consists of a four-carbon chain with a double bond between the first and second carbons and a triple bond between the third and fourth carbons.

Draw the structure for vinylacetylene: Start by drawing a four-carbon chain. Add a double bond between C1 and C2, and a triple bond between C3 and C4.

Identify the structure of (S)-3-methyl-1-penten-4-yne: This compound is a five-carbon chain with a triple bond between C1 and C2, a double bond between C4 and C5, and a methyl group attached to C3. The (S) configuration indicates the stereochemistry at C3.

Draw the structure for (S)-3-methyl-1-penten-4-yne: Begin by drawing a five-carbon chain. Add a triple bond between C1 and C2, and a double bond between C4 and C5. Attach a methyl group to C3. Ensure the stereochemistry at C3 is (S) by arranging the substituents in order of priority and using the Cahn-Ingold-Prelog rules.

Verify the stereochemistry: Check that the configuration at C3 is indeed (S) by assigning priorities to the substituents and ensuring the lowest priority group is oriented away from you.

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Key Concepts

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

Structural Formulas

Structural formulas represent the arrangement of atoms within a molecule, illustrating how atoms are bonded together. They provide insight into the molecular geometry and functional groups present, which are crucial for understanding the compound's reactivity and properties. Familiarity with drawing structural formulas is essential for accurately depicting organic compounds.

Nomenclature in Organic Chemistry

Nomenclature refers to the systematic naming of organic compounds based on established rules, such as those set by IUPAC. Understanding both old-style and new-style names is important for recognizing and converting between different naming conventions. This knowledge aids in identifying the structure and functional groups of the compounds in question.

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the context of (S)-3-methyl-1-penten-4-yne, the 'S' designation indicates a specific three-dimensional configuration of the molecule. Recognizing stereochemical descriptors is vital for understanding isomerism and the properties of chiral compounds.

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Related Practice

Textbook Question

A chiral sample gives a rotation that is close to 180°. How can one tell whether this rotation is +180° or -180°?

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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).

(c)

(d) 1-bromo-2-methylbutane

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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

A solution of 2.0 g of (+)-glyceraldehyde, HOCH₂CHOHCHO, in 10.0 mL of water was placed in a 100-mm cell. Using the sodium D line, a rotation of +1.74° was found at 25 °C. Determine the specific rotation of (+)-glyceraldehyde

Textbook Question

If you had the two enantiomers of carvone in unmarked bottles, could you use just your nose and a polarimeter to determine

a. whether it is the (+) or (−) enantiomer that smells like spearmint

b. whether it is the (R) or (S) enantiomer that smells like spearmint?

c. With the information given in the drawings of carvone above, what can you add to your answers to (a) and (b)?

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Textbook Question

A solution of 0.50 g of (−)-epinephrine (see Figure 5-16) dissolved in 10.0 mL of dilute aqueous HCl was placed in a 20-cm polarimeter tube. Using the sodium D line, the rotation was found to be −5.1° at 25 °C. Determine the specific rotation of epinephrine.

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