Textbook Question
Draw the molecular orbital picture of but-2-yne.
1
views
Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions
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. 10 - Alkynes: Electrophilic Addition and Redox ReactionsProblem 15a
Mullins 1st EditionCh. 10 - Alkynes: Electrophilic Addition and Redox ReactionsProblem 15aChapter 9, Problem 15a
Calculate Keq for the following acid–base reactions. Which is the best base to use to deprotonate acetylene and make the acetylide anion?
(a) HO- + H―C ≡ C―H ⇌ -C ≡ C―H + H2O
Verified step by step guidance1
Step 1: Understand the problem. The goal is to determine whether hydroxide (HO⁻) is a strong enough base to deprotonate acetylene (H―C≡C―H) and form the acetylide anion (⁻C≡C―H). This involves comparing the acidities of the reactants and products using their pKa values.
Step 2: Recall the concept of pKa. The pKa value is a measure of the acidity of a compound. A lower pKa indicates a stronger acid. The equilibrium of an acid-base reaction favors the side with the weaker acid (higher pKa).
Step 3: Identify the pKa values of the relevant species. Acetylene (H―C≡C―H) has a pKa of approximately 25, while water (H₂O), the conjugate acid of hydroxide (HO⁻), has a pKa of approximately 15.7.
Step 4: Compare the pKa values. Since acetylene has a higher pKa (25) than water (15.7), acetylene is a weaker acid than water. This means the equilibrium will not favor the formation of the acetylide anion (⁻C≡C―H) when hydroxide is used as the base.
Step 5: Conclude that hydroxide (HO⁻) is not a strong enough base to deprotonate acetylene effectively. A stronger base, such as sodium amide (NaNH₂, conjugate acid NH₃ with pKa ~38), would be required to deprotonate acetylene and form the acetylide anion.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acidity and Basicity
Acidity refers to the tendency of a compound to donate protons (H⁺), while basicity is the ability to accept protons. In organic chemistry, the strength of an acid is often measured by its pKa value; lower pKa values indicate stronger acids. Understanding the relative strengths of acids and bases is crucial for predicting the outcome of acid-base reactions.
Recommended video:
Guided course
06:21
Understanding the difference between basicity and nucleophilicity.
Acetylide Anion
The acetylide anion (C≡C⁻) is formed when acetylene (H―C≡C―H) is deprotonated. This anion is a strong nucleophile and is important in organic synthesis, particularly in reactions involving carbon-carbon bond formation. Identifying a suitable base to generate the acetylide anion is essential for various synthetic applications.
Recommended video:
0:58Anionic Polymerization Concept 1
Strong Bases for Deprotonation
To deprotonate a weak acid like acetylene, a strong base is required. Common strong bases include alkoxides (like NaO⁻) and hydrides (like NaH). The choice of base affects the efficiency of the deprotonation process, and understanding the relative strength of potential bases is key to selecting the best one for generating the acetylide anion.
Recommended video:
Guided course
03:10Monosaccharides - Strong Oxidation (Aldaric Acid)
Related Practice
Textbook Question
Calculate for the following acid–base reactions. Which is the best base to use to deprotonate acetylene and make the acetylide anion?
(b) H2N- + H―C ≡ C―H ⇌ -C ≡ C―H + H3N
5
views
Textbook Question
Using pKa values, calculate an approximate Keq value for the following substitution reaction.
1
views
Textbook Question
Which of the following would be expected to give a hotter flame during combustion? Explain.
1
views
Textbook Question
Calculate for the following acid–base reactions. Which is the best base to use to deprotonate acetylene and make the acetylide anion?
(c)
1
views
Textbook Question
Draw the structures that correspond to the following names.
(c) (Z)-2-chloro-7-methyloct-2-en-4-yne
2
views