Textbook Question
Starting with a Fischer projection of d-glucose (and other sugars), switch only the stereocenter that gave it the designation of d. What new sugar have you made? [Hint: The answer is not l-glucose.]
Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 26, Problem 62e
Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C1 and C4 of isoprene.
(e) 
Verified step by step guidance1
Step 1: Recall that terpenes are composed of isoprene units, which are five-carbon building blocks with the formula C₅H₈. Isoprene units can be linked in various ways, including head-to-tail (C₁ → C₄), tail-to-tail (C₄ → C₄), or other irregular linkages.
Step 2: Examine the structure of β-carotene provided in the image. Identify the repeating five-carbon isoprene units within the molecule. Look for patterns of double bonds and methyl groups that correspond to the isoprene structure.
Step 3: Note that β-carotene contains irregular linkages, such as the C₄ → C₄ linkage highlighted in the image. This is a deviation from the typical head-to-tail (C₁ → C₄) linkage seen in many terpenes.
Step 4: Trace the connectivity of the isoprene units throughout the β-carotene structure. Pay attention to how the units are joined, including any cross-linking or ring formations that may occur.
Step 5: Once the isoprene units and their linkages are identified, classify the type of linkage (e.g., head-to-tail, tail-to-tail, or irregular) for each connection in the molecule. This will help in understanding the structural organization of β-carotene as a terpene.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Isoprene Units
Isoprene units are the fundamental building blocks of terpenes, consisting of a five-carbon structure with the formula C₅H₈. These units can polymerize to form larger molecules, and in terpenes, they typically connect in a head-to-tail fashion. Understanding how these units combine is essential for identifying the structure of various terpenes.
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Terpene Structure
Terpenes are a diverse class of organic compounds produced by many plants, characterized by their strong odors and roles in plant defense. They are classified based on the number of isoprene units they contain, such as monoterpenes (two units) and sesquiterpenes (three units). Recognizing the structural variations in terpenes, including cyclic and cross-linked forms, is crucial for analyzing their chemical properties.
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Linkages in Terpenes
In terpenes, linkages can occur not only between the C₁ and C₄ positions of isoprene units but also at other carbon positions, especially in cyclic or cross-linked structures. This flexibility in bonding allows for a wide variety of terpene structures and functionalities. Understanding these linkages is vital for predicting the behavior and reactivity of terpenes in chemical reactions.
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Related Practice
Textbook Question
Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C1 and C4 of isoprene.
(b)
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Textbook Question
Suggest a mechanism by which TXB2 might be formed from TXA2 in an acid-catalyzed hydrolysis reaction. [The structure has been simplified.]
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Textbook Question
Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C1 and C4 of isoprene.
(a)
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Textbook Question
The α- and β-anomers of glucose are shown here. In solution, these two epimers can interconvert through a process called mutarotation.
Given that α-D-glucose has a specific rotation of + 112.2° , why is the specific rotation of β-D-glucose not -112.2°? What molecule would have a specific rotation of -112.2°?
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Textbook Question
Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C1 and C4 of isoprene.
(c)
2
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