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Questions and Answers
What type of reaction is the Wittig reaction fundamentally classified as?
What type of reaction is the Wittig reaction fundamentally classified as?
- Elimination
- Electrophilic Aromatic Substitution
- Nucleophilic Addition (correct)
- Nucleophilic Acyl Substitution
What is the primary limitation of the Wittig reaction concerning the structure of the resulting alkene?
What is the primary limitation of the Wittig reaction concerning the structure of the resulting alkene?
- It is unsuitable for preparing terminal alkenes.
- It cannot produce alkenes with _cis_ stereochemistry.
- It is limited to producing only disubstituted alkenes.
- It cannot be used to create tetrasubstituted alkenes due to steric hindrance. (correct)
Which reagent is initially used to convert triphenylphosphine into a Wittig reagent (ylide)?
Which reagent is initially used to convert triphenylphosphine into a Wittig reagent (ylide)?
- An alkyl halide (correct)
- A carboxylic acid
- An alcohol
- An ether
What type of intermediate is formed immediately after the phosphorus ylide attacks the carbonyl in a Wittig reaction?
What type of intermediate is formed immediately after the phosphorus ylide attacks the carbonyl in a Wittig reaction?
What drives the final step in the Wittig reaction, leading to the formation of the alkene?
What drives the final step in the Wittig reaction, leading to the formation of the alkene?
In a Wittig reaction, if you want to synthesize 2-methylpropene, which carbonyl compound and ylide would you react?
In a Wittig reaction, if you want to synthesize 2-methylpropene, which carbonyl compound and ylide would you react?
Which of the following best describes why alkynyl groups react poorly in conjugate addition reactions with organocopper reagents?
Which of the following best describes why alkynyl groups react poorly in conjugate addition reactions with organocopper reagents?
What is the role of cuprous iodide ($CuI$) in the formation of diorganocopper reagents?
What is the role of cuprous iodide ($CuI$) in the formation of diorganocopper reagents?
In the conjugate addition of a diorganocopper reagent to an $\alpha$,$\beta$-unsaturated ketone, what happens to the copper atom after the transfer of an R group?
In the conjugate addition of a diorganocopper reagent to an $\alpha$,$\beta$-unsaturated ketone, what happens to the copper atom after the transfer of an R group?
Which of the following best illustrates the concept of 1,4-addition (conjugate addition) to an $\alpha$,$\beta$-unsaturated ketone?
Which of the following best illustrates the concept of 1,4-addition (conjugate addition) to an $\alpha$,$\beta$-unsaturated ketone?
Why is the Cannizzaro reaction limited to aldehydes without alpha hydrogens?
Why is the Cannizzaro reaction limited to aldehydes without alpha hydrogens?
In the Cannizzaro reaction, one molecule of aldehyde is reduced to an alcohol, while another is oxidized. What type of reagent is effectively acting as the reducing agent?
In the Cannizzaro reaction, one molecule of aldehyde is reduced to an alcohol, while another is oxidized. What type of reagent is effectively acting as the reducing agent?
What is the first step in the mechanism of the Cannizzaro reaction?
What is the first step in the mechanism of the Cannizzaro reaction?
What type of intermediate is formed after the hydroxide ion ($OH^$) attacks the aldehyde in the Cannizzaro reaction?
What type of intermediate is formed after the hydroxide ion ($OH^$) attacks the aldehyde in the Cannizzaro reaction?
What is the role of the tetrahedral intermediate in the Cannizzaro reaction?
What is the role of the tetrahedral intermediate in the Cannizzaro reaction?
Which reagent is commonly used to reduce a carbonyl group to an alcohol?
Which reagent is commonly used to reduce a carbonyl group to an alcohol?
What product is formed when an aldehyde is treated with a Grignard reagent ($RMgX$) followed by aqueous workup?
What product is formed when an aldehyde is treated with a Grignard reagent ($RMgX$) followed by aqueous workup?
What type of product is formed when a ketone reacts with a Grignard reagent followed by aqueous workup?
What type of product is formed when a ketone reacts with a Grignard reagent followed by aqueous workup?
What class of compounds are formed when aldehydes or ketones react with primary amines ($RNH_2$)?
What class of compounds are formed when aldehydes or ketones react with primary amines ($RNH_2$)?
What is the product of the reaction between an aldehyde or ketone and a secondary amine ($R_2NH$)?
What is the product of the reaction between an aldehyde or ketone and a secondary amine ($R_2NH$)?
What is the correct order of steps to convert cyclohexanone to cyclohexene using a Wittig reaction?
What is the correct order of steps to convert cyclohexanone to cyclohexene using a Wittig reaction?
How would you convert butanal to butanoic acid?
How would you convert butanal to butanoic acid?
Which set of conditions would be most appropriate to convert an ester directly to an aldehyde?
Which set of conditions would be most appropriate to convert an ester directly to an aldehyde?
Which of the following reagents would be most suitable to convert an acyl chloride to a ketone?
Which of the following reagents would be most suitable to convert an acyl chloride to a ketone?
How would you convert cyclohexene to cyclohexanone in two steps?
How would you convert cyclohexene to cyclohexanone in two steps?
What is the function of Dess-Martin periodinane?
What is the function of Dess-Martin periodinane?
What reagents are needed to convert an alcohol into a ketone?
What reagents are needed to convert an alcohol into a ketone?
Predict the condition(s) used to convert 2-Cyclohexenone to 3-Methylcyclohexanone.
Predict the condition(s) used to convert 2-Cyclohexenone to 3-Methylcyclohexanone.
What series of steps will convert phenyl bromide ($C_6H_5Br$) to 1-phenylpentan-1-one ($C_6H_5C(O)CH_2CH_2CH_2CH_3$)?
What series of steps will convert phenyl bromide ($C_6H_5Br$) to 1-phenylpentan-1-one ($C_6H_5C(O)CH_2CH_2CH_2CH_3$)?
What reagents are needed to convert aldehyde to alcohol?
What reagents are needed to convert aldehyde to alcohol?
Predict the end product of reaction between ester and $R''MgX$?
Predict the end product of reaction between ester and $R''MgX$?
What reagents are needed to get imine from aldehyde?
What reagents are needed to get imine from aldehyde?
Identify the reagents for the following transformation: Alkene to vicinal dihalide
Identify the reagents for the following transformation: Alkene to vicinal dihalide
Which of the following reagents are needed for the following transformation: Alkene to epoxide
Which of the following reagents are needed for the following transformation: Alkene to epoxide
What series of reagents will complete reaction from Alkene to aldehyde/ketone
What series of reagents will complete reaction from Alkene to aldehyde/ketone
What type of reaction is happening when ketone become alcohol?
What type of reaction is happening when ketone become alcohol?
What series of reagents will change phenyl bromide ($C_6H_5Br$) with 3 carbon chain aldehyde?
What series of reagents will change phenyl bromide ($C_6H_5Br$) with 3 carbon chain aldehyde?
Predict the structure of the carbon nucleophile that reacts with carbonyl ($>C=O$) group to give tertiary alcohol.
Predict the structure of the carbon nucleophile that reacts with carbonyl ($>C=O$) group to give tertiary alcohol.
Flashcards
What is the Wittig Reaction?
What is the Wittig Reaction?
A nucleophilic addition reaction using phosphorus ylides to convert aldehydes or ketones into alkenes.
What is Triphenylphosphine?
What is Triphenylphosphine?
A good nucleophile in SN2 reactions that yields alkyltriphenylphosphonium salts.
What is the Cannizzaro reaction?
What is the Cannizzaro reaction?
A reaction where nucleophilic addition of OH- to an aldehyde gives a tetrahedral intermediate, leading to hydride expulsion and oxidation.
What is 1,2-addition?
What is 1,2-addition?
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What is Conjugate addition (1,4-addition)?
What is Conjugate addition (1,4-addition)?
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What are Organocopper Reactions?
What are Organocopper Reactions?
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What are Diorganocopper reagents?
What are Diorganocopper reagents?
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How to prepare Aldehydes?
How to prepare Aldehydes?
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How to prepare Ketones?
How to prepare Ketones?
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Study Notes
Nucleophilic Addition of Phosphorus Ylides: The Wittig Reaction
- Triphenylphosphine acts as a good nucleophile in SN2 reactions.
- This reaction yields alkyltriphenylphosphonium salts.
- Wittig reactions cannot be used to prepare tetrasubstituted alkenes because of steric hindrance.
Mechanism of the Wittig Reaction
- The nucleophilic carbon atom of the phosphorus ylide adds to the carbonyl group of a ketone or aldehyde, resulting in an alkoxide ion intermediate.
- The alkoxide ion undergoes intramolecular O-P bond formation, producing a four-membered ring.
- This four-membered ring spontaneously decomposes to give an alkene and triphenylphosphine oxide.
Additional Wittig Reaction Information
- Adding CH3MgBr to cyclohexanone followed by dehydration with POCl3 produces a mixture of two alkenes in a 9:1 ratio.
Cannizzaro Reaction
- The Cannizzaro reaction involves the nucleophilic addition of OH- to an aldehyde, creating a tetrahedral intermediate which expels a hydride ion and is oxidized.
- A second aldehyde molecule accepts the hydride ion in another nucleophilic addition, leading to its reduction.
Conjugate Nucleophilic Addition
- 1,2-addition is the direct addition of a nucleophile to the carbonyl group.
- Conjugate (1,4-) addition is the addition of a nucleophile to the C=C double bond of an alpha, beta-unsaturated aldehyde or ketone.
Conjugate Addition of Amines
- Primary and secondary amines undergo conjugate addition to alpha, beta-unsaturated aldehydes and ketones, resulting in beta-amino aldehydes and ketones.
Organocopper Reactions
- An alpha, beta-unsaturated ketone reacts with a lithium diorganocopper reagent.
- Diorganocopper reagents are created through the reaction of one equivalent of cuprous iodide with two equivalents of organolithium.
- Primary (1°), secondary (2°), and tertiary (3°) alkyl, aryl, and alkenyl groups react in these reactions.
- Alkynyl groups are poor reactants.
Diorganocopper Addition Mechanism
- A diorganocopper anion (R₂Cu⁻) adds to a ketone through conjugate nucleophilic addition.
- The transfer of an R group and the elimination of a neutral organocopper species (RCu) leads to the final product.
Preparation of Aldehydes
- Aldehydes can be prepared using Dess-Martin periodinane with CH2Cl2.
- They can also be synthesized from an ester with DIBAH in toluene, followed by H3O+.
Preparation of Ketones
- Ketones can be prepared using periodinane or CrO3 from alcohol.
- Ketones can also be prepared from an acid chloride by reaction with R'₂CuLi in ether.
Oxidation of Aldehydes
- Aldehydes undergo oxidation using CrO3 in H3O+
Nucleophilic Addition Reactions of Aldehydes and Ketones
- Aldehydes and Ketones reacts with NaBH4, ethanol followed by H3O+ to produce an alchol.
- Aldehydes and Ketones reacts with R"MgX, ether followed by H3O+ to produce an alcohol.
- Aldehydes and Ketones reacts with HCN to produce a cyanohydrin
More Nucleophilic Addition Reactions of Aldehydes and Ketones
- Aldehydes and Ketones reacts with R"NH2 producing NR"=CR' +H₂O
- Aldehydes with one H atom reacts with HNR'2 producing R(H)C=NR'2 + H₂O
- Aldehydes and Ketones reacts with H2NNH2 and KOH producing R(R')C=N + N2 + H₂O
Still More Nucleophilic Addition Reactions of Aldehydes and Ketones
- Aldehydes and Ketones reacts with 2 R"OH with an acid catalyist to produce R"O-C(R)(R')-OR" + H₂O
- Aldehydes and Ketones reacts with (C6H5)3P-CHR" in THF to produce R(R')C=C(R)(H) + (C6H5)3P=0
Conjugate Additions to α,β-Unsaturated Aldehydes and Ketones
- α,β-Unsaturated Aldehydes and Ketones reacts with R' NH2 to producing complex rings.
- α,β-Unsaturated Aldehydes and Ketones reacts with H2O to producing complex rings with OH attachments.
- α,β-Unsaturated Aldehydes and Ketones reacts with 1. R'₂CuLi, ether followed with 2. H3O+ to producing complex rings.
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