Textbook Question
Predict the products you would expect from the reaction of NaBH4 with the following compounds. You may assume that these reactions take place in methanol as the solvent.
(c) Ph-COOH
1647
views
Ch.10 - Structure and Synthesis of Alcohols
Wade9th EditionOrganic ChemistryISBN: 9780135213728
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 10, Problem 23b
Point out the flaws in the following incorrect Grignard syntheses.
(b) 
Verified step by step guidance1
Step 1: Analyze the starting material. The compound contains a bromine atom attached to a cyclohexane ring with a ketone and an ester functional group. The bromine atom is intended to form a Grignard reagent when treated with magnesium in ether.
Step 2: Understand the reaction conditions. The first step involves the formation of the Grignard reagent (R-MgBr) by reacting the bromine-containing compound with magnesium in ether. The second step involves the reaction of the Grignard reagent with formaldehyde (H₂C=O), followed by acidic workup (H₃O⁺).
Step 3: Identify the flaw in the synthesis. The ketone and ester functional groups present in the starting material are reactive toward Grignard reagents. When the Grignard reagent is formed, it will likely react intramolecularly with the ketone or ester group, leading to side reactions or decomposition, rather than reacting with formaldehyde as intended.
Step 4: Explain why the desired product cannot be formed. The Grignard reagent is highly nucleophilic and will attack the electrophilic carbonyl groups (ketone and ester) within the same molecule, preventing the reaction with formaldehyde. This intramolecular reaction disrupts the intended synthesis pathway.
Step 5: Suggest a correction. To avoid this issue, the ketone and ester groups should be protected before forming the Grignard reagent, or a different synthetic route should be chosen that does not involve the formation of a Grignard reagent in the presence of reactive carbonyl groups.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
6mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Grignard Reagents
Grignard reagents are organomagnesium compounds that are highly reactive and used to form carbon-carbon bonds. They are created by reacting alkyl or aryl halides with magnesium in dry ether. Understanding their reactivity is crucial, as they can react with electrophiles, including carbonyl compounds, to form alcohols. In the given synthesis, the presence of a carbonyl group is essential for the reaction to proceed correctly.
Recommended video:
Guided course
02:12
Carbonation of Grignard Reagents
Electrophilic Addition
Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile to form a new bond. In the context of Grignard reactions, the Grignard reagent acts as a nucleophile, attacking the electrophilic carbon of a carbonyl compound. The failure to recognize the correct electrophile or the presence of incompatible functional groups can lead to flawed syntheses, as seen in the provided example.
Recommended video:
Guided course
09:231,2 vs 1,4 Addition
Functional Group Compatibility
Functional group compatibility refers to the ability of different functional groups to coexist and react without interfering with each other. In organic synthesis, certain groups can be sensitive to the conditions or reagents used, leading to undesired reactions or products. In the provided synthesis, the presence of multiple oxygen-containing functional groups may hinder the desired reaction pathway, resulting in an incorrect product.
Recommended video:
Guided course
02:36Identifying Functional Groups
Related Practice
Textbook Question
Point out the flaws in the following incorrect Grignard syntheses.
(c)
(d)
1062
views
Textbook Question
Predict the products of the following reactions.
(a) sec-butylmagnesium iodide + D2O
(b) n-butyllithium + CH3CH2OH
(c) isobutylmagnesium bromide + but-1-yne
1358
views
Textbook Question
Point out the flaws in the following incorrect Grignard syntheses.
(a)
1715
views
Textbook Question
Predict the products you would expect from the reaction of NaBH4 with the following compounds. You may assume that these reactions take place in methanol as the solvent.
(a) CH3–(CH2)8–CHO
1704
views
1
rank
Textbook Question
Predict the products of the following reactions.
(d)
(e)
901
views