Textbook Question
Amino acids exist predominantly in one of the following forms. Which is it? Explain your answer.
1039
views
Ch. 4 - Acids and Bases: Electron Flow
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
Chapter 3, Problem 68
A medicinal chemist needed to deprotonate acetylene ( HC≡CH ) for use in a coupling reaction. Among the options given, which base(s) could be used for this process?
Verified step by step guidance1
Step 1: Understand the acidity of acetylene (HC≡CH). Acetylene is a terminal alkyne, and its hydrogen atom attached to the sp-hybridized carbon is relatively acidic compared to other hydrocarbons. The pKa of acetylene is approximately 25, meaning it requires a strong base to deprotonate it effectively.
Step 2: Evaluate the strength of the bases provided. A base must have a conjugate acid with a pKa higher than 25 to deprotonate acetylene. Sodium hydroxide (NaOH) has a conjugate acid (water) with a pKa of 15.7, making it too weak. Triethylamine is an organic base with a conjugate acid (triethylammonium ion) pKa of around 10.7, also too weak.
Step 3: Consider potassium hydride (KH). KH is a strong base because it forms H2 gas upon reaction with an acid, and its conjugate acid (H2) has a pKa of approximately 35, making it suitable for deprotonating acetylene.
Step 4: Examine lithium pivalate. Lithium pivalate is a carboxylate salt, and its conjugate acid (pivalic acid) has a pKa of around 5, which is far too weak to deprotonate acetylene.
Step 5: Assess sodium amide (NaNH2). Sodium amide is a very strong base with a conjugate acid (ammonia) pKa of approximately 38, making it highly effective for deprotonating acetylene. Therefore, KH and NaNH2 are the bases that can be used for this process.
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
In organic chemistry, acidity refers to the tendency of a compound to donate protons (H+), while basicity refers to the ability to accept protons. Acetylene (HC≡CH) is a weak acid, and understanding its acidity is crucial for identifying suitable bases that can effectively deprotonate it. The strength of the base must be greater than the acidity of acetylene to achieve deprotonation.
Recommended video:
Guided course
06:21
Understanding the difference between basicity and nucleophilicity.
Deprotonation
Deprotonation is the removal of a proton from a molecule, resulting in the formation of a conjugate base. In the context of acetylene, deprotonation leads to the formation of the acetylide ion (HC≡C-), which is a strong nucleophile and can participate in various coupling reactions. Identifying the right base for this process is essential for successful reaction outcomes.
Recommended video:
4:30Step-Growth Polymers: Epoxy Resin Example 1
Strong Bases in Organic Chemistry
Strong bases are substances that can effectively deprotonate weak acids. Common strong bases used in organic chemistry include alkoxides, hydrides, and amides. For deprotonating acetylene, bases such as sodium amide (NaNH2) or lithium diisopropylamide (LDA) are often employed due to their high basicity, which allows them to remove protons from acetylene efficiently.
Recommended video:
Guided course
00:56What is an organic molecule?
Related Practice
Textbook Question
Suggest a scheme by which N-methylmorpholine, salicylic acid, and naphthalene can be separated.
1115
views
Textbook Question
Using pKa values for the conjugate acids of the bases on each side of the reaction arrow, identify which side of the equilibrium would be favored in the following hypothetical reactions.
(c)
1153
views
Textbook Question
For each of the following molecules, predict the product that would form upon reaction of a single equivalent of a strong base.
(f)
1042
views
Textbook Question
For each of the following molecules, predict the product that would form upon reaction of a single equivalent of a strong base.
(e)
1299
views
Textbook Question
Using pKa values for the conjugate acids of the bases on each side of the reaction arrow, identify which side of the equilibrium would be favored in the following hypothetical reactions.
(a)
1010
views