Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

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Mullins 1st Edition

Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions

Problem 40b

Chapter 9, Problem 40b

When doing synthesis, you will often find yourself repeating the same series of steps. To see this in action, synthesize the following aldehydes beginning with an organic molecule containing three carbons or fewer.
(b)

Verified step by step guidance

Step 1: Identify the target molecule, which is an aldehyde. Aldehydes have the general structure R-CHO, where the carbonyl group (C=O) is bonded to a hydrogen atom and an alkyl or aryl group.

Step 2: Choose a starting material containing three carbons or fewer. Common choices include propane, propene, or alcohols like ethanol or propanol. The choice depends on the functional groups needed for the synthesis.

Step 3: Introduce a functional group that can be converted into an aldehyde. For example, if starting with an alcohol, oxidize the alcohol to form an aldehyde. Use a mild oxidizing agent like PCC (Pyridinium Chlorochromate) to avoid overoxidation to a carboxylic acid.

Step 4: If starting with an alkene, perform hydroboration-oxidation. React the alkene with BH₃ (borane) followed by oxidation with H₂O₂ (hydrogen peroxide) in a basic solution (NaOH). This will yield an aldehyde via anti-Markovnikov addition.

Step 5: Verify the structure of the synthesized aldehyde using spectroscopic techniques such as IR spectroscopy (look for the characteristic C=O stretch around 1700 cm⁻¹) or NMR spectroscopy to confirm the presence of the aldehyde group.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Aldehyde Structure and Reactivity

Aldehydes are organic compounds characterized by the presence of a carbonyl group (C=O) bonded to at least one hydrogen atom. This structure makes them highly reactive, particularly in nucleophilic addition reactions. Understanding the reactivity of aldehydes is crucial for predicting the outcomes of synthetic pathways and for designing effective synthesis strategies.

Synthetic Pathways

Synthetic pathways refer to the series of chemical reactions used to convert starting materials into desired products. In organic synthesis, these pathways often involve multiple steps, including functional group transformations and rearrangements. Familiarity with common synthetic routes and strategies is essential for efficiently synthesizing complex molecules, such as aldehydes, from simpler precursors.

Functional Group Interconversion

Functional group interconversion involves transforming one functional group into another during a synthetic process. This concept is vital in organic synthesis, as it allows chemists to modify the reactivity and properties of molecules. Mastery of various reactions that facilitate these conversions is necessary for successfully synthesizing aldehydes from smaller organic molecules.

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Textbook Question

For each of the following ketones/aldehydes, indicate whether it is possible to synthesize it from an alkyne as the only compound in good ( > 50%) yield. If so, how would you do it?

(a)

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Textbook Question

For each of the following ketones/aldehydes, indicate whether it is possible to synthesize it from an alkyne as the only compound in good (> 50%) yield. If so, how would you do it?

(d)

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Textbook Question

Beginning with the molecules on the left of each chemical equation, synthesize the molecules shown. While there can be multiple ways of doing each synthesis, the minimum number of steps necessary is indicated over each reaction arrow.

(a)

(b)

When doing synthesis, you will often find yourself repeating the same series of steps. To see this in action, synthesize the following aldehydes beginning with an organic molecule containing three carbons or fewer.

(d)

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Textbook Question

Draw the ketone(s) you would expect to form by treating the following alkynes under the conditions of hydroboration–oxidation: (a) 6-methyloct-1-yne, (b) 1,10-dicyclohexyldec-5-yne, and (c) 5-phenylhex-2-yne.

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When doing synthesis, you will often find yourself repeating the same series of steps. To see this in action, synthesize the following aldehydes beginning with an organic molecule containing three carbons or fewer. (b)

Verified video answer for a similar problem:

Key Concepts

Aldehyde Structure and Reactivity

Synthetic Pathways

Functional Group Interconversion

When doing synthesis, you will often find yourself repeating the same series of steps. To see this in action, synthesize the following aldehydes beginning with an organic molecule containing three carbons or fewer.
(b)