nucleophilic addition
🧲ACS ORGANIC CHEMISTRY STUDY GUIDE
Carbonyls, Carboxylic Acids, and Enolates for the ACS Exam
Study carbonyl addition, acyl substitution, enolates, aldol reactions, and reducing agents for ACS organic chemistry.
8 key ideas8 flashcards5 practice questions
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The attached groups decide the next step.
attack begins here
addition, then leaving-group departure
Key ideas to know
Start with the relationships between ideas. Then close the notes and explain each one from memory.
- 01
The carbonyl bond is polarized, making carbon electrophilic and oxygen electron-dense.
- 02
Aldehydes and ketones commonly undergo nucleophilic addition.
- 03
Carboxylic acid derivatives commonly undergo nucleophilic acyl substitution because a leaving group is attached to the acyl carbon.
- 04
Acyl-derivative reactivity generally follows chloride, anhydride, ester or acid, then amide.
- 05
Hydride reagents differ in strength and selectivity, so reagent identity predicts how far reduction proceeds.
- 06
Alpha hydrogens can be removed to form enols or enolates.
- 07
Enolates react through their carbon or oxygen positions and can make new carbon-carbon bonds.
- 08
Aldol reactions join an enolate donor to a carbonyl acceptor, first producing a beta-hydroxy carbonyl.
PART OF THE ACS ORGANIC CHEMISTRY GUIDE
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Open the full ACS Organic Chemistry guide →Two ideas worth correcting now
NOT QUITE
→Every carbonyl reaction ends as an alcohol
USE THIS INSTEAD
Acyl substitution restores the carbonyl, and selective reagents can stop at other products.
NOT QUITE
→An enolate has charge only on oxygen
USE THIS INSTEAD
Its electron distribution permits reaction through oxygen or the alpha carbon.
Flashcards
Answer before opening each card. The effort to retrieve is part of the learning.
1Why is carbonyl carbon electrophilic?Show answer ＋
Oxygen pulls electron density from the carbon-oxygen bond.
2What happens when a nucleophile adds to an aldehyde or ketone?Show answer ＋
It bonds to carbonyl carbon and pushes the pi electrons onto oxygen.
3Why can an acyl substitution occur at an ester?Show answer ＋
The tetrahedral intermediate can collapse and expel an alkoxy leaving group.
4Which is more reactive toward acyl substitution, an acid chloride or an amide?Show answer ＋
An acid chloride.
5What does sodium borohydride usually reduce in an introductory course?Show answer ＋
Aldehydes and ketones to alcohols.
6What does lithium aluminum hydride commonly reduce?Show answer ＋
Many carbonyl derivatives, including esters and carboxylic acids, subject to workup.
7What is an enolate?Show answer ＋
A conjugate base formed by removal of an alpha proton next to a carbonyl.
8What bond forms in an aldol addition?Show answer ＋
A carbon-carbon bond between an enolate donor and a carbonyl carbon.
Explain it in your own words
Use the answer as a check after you have written or spoken your response.
01Why are aldehydes usually more reactive than ketones toward nucleophilic addition?
They have less steric crowding and less electron donation from carbon substituents.
02How do you distinguish addition from acyl substitution?
If carbonyl carbon has a leaving group, addition can be followed by carbonyl reformation and leaving-group departure.
03Why is an amide less reactive than an ester?
Nitrogen donates electron density strongly into the carbonyl, and its leaving group would be strongly basic.
04How can you predict the product of an aldol condensation?
Form the aldol carbon-carbon bond, then remove water to create a conjugated carbonyl product.
05Why must a Grignard reagent be kept away from water before use?
Water protonates the carbon nucleophile and destroys the reagent.
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