Textbook Question
Provide a mechanism for the formation of the hemiacetals shown. [Only (c) is favored as written.]
(a)
1171
views
Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
Not the one you use?Change textbookSelect a different textbook
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
All textbooks
Mullins 1st EditionCh. 17 - Carbonyl Addition Reactions: Aldehydes and KetonesProblem 33a
Mullins 1st EditionCh. 17 - Carbonyl Addition Reactions: Aldehydes and KetonesProblem 33aChapter 16, Problem 33a
Which of the following cyclic hemiacetals would you expect to have the highest Keq for their formation? Explain your answer.
(a) 
Verified step by step guidance1
Identify the reactant and product in the given reaction. The reactant is a hydroxy aldehyde, and the product is a cyclic hemiacetal.
Understand that the formation of a cyclic hemiacetal involves the nucleophilic attack of the hydroxyl group on the carbonyl carbon, forming a new C-O bond and resulting in a ring structure.
Consider the size of the ring formed in the cyclic hemiacetal. Smaller rings, such as three-membered rings, are generally less stable due to angle strain.
Evaluate the stability of the cyclic hemiacetal. Five- and six-membered rings are typically more stable due to minimal angle strain and favorable enthalpic and entropic factors.
Conclude that the equilibrium constant (Keq) for the formation of a cyclic hemiacetal is higher when the resulting ring is more stable, typically favoring five- or six-membered rings over smaller rings.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cyclic Hemiacetal Formation
Cyclic hemiacetals form when an alcohol group within a molecule reacts with an aldehyde or ketone group in the same molecule, creating a ring structure. This intramolecular reaction is favored when it results in a stable, five- or six-membered ring due to minimal ring strain and favorable enthalpic and entropic factors.
Recommended video:
Guided course
06:23
Monosaccharides - Forming Cyclic Hemiacetals
Equilibrium Constant (K_eq)
The equilibrium constant (K_eq) for a reaction quantifies the ratio of the concentration of products to reactants at equilibrium. A higher K_eq indicates that the products are favored at equilibrium, suggesting that the formation of the cyclic hemiacetal is more thermodynamically favorable compared to its open-chain form.
Recommended video:
Guided course
02:19The relationship between equilibrium constant and pKa.
Ring Strain and Stability
Ring strain arises from bond angles deviating from their ideal values, torsional strain from eclipsing interactions, and steric strain from atoms being too close. Five- and six-membered rings are generally more stable due to minimal ring strain, making them more likely to form and persist, thus influencing the equilibrium position towards the cyclic form.
Recommended video:
Guided course
02:46What is angle strain?
Related Practice
Textbook Question
Show the product expected by the Wolff–Kishner reduction of the following aldehydes/ketones.
(a)
957
views
Textbook Question
During an oxidation reaction, there must also be a reduction. What is reduced in the Pinnick oxidation?
715
views
Textbook Question
Identify the hemiacetal functional group in each of the following molecules. These molecules may not be stable enough to be the favorable product in an equilibrium reaction.
(c)
959
views
Textbook Question
Suggest the appropriate carbonyl and Wittig reagent to make the following alkenes.
a. (E)-7-methylnon-4-en-3-one
760
views
Textbook Question
The following molecules were named incorrectly according to IUPAC nomenclature. Give the correct name of these compounds.
(a) 3-oxo-5-methylhexan-2-ol
847
views