Aldehyde/Ketone Reactions Flashcards
If an aldehyde or a ketone reacts with H2O What kind of product does it form?
A geminal diol which is a compound that has two alcohol groups attached to the same carbon.
What product forms if an aldehyde or a ketone reacts with a primary amine?
An imine
What product forms if an aldehyde or a ketone reacts with a secondary amine?
An enamine
If a nucleophile had to pick whether it will react with a ketone or aldehyde, which one would it choose?
The aldehyde, because aldehydes are more electrophilic.
Ketones are sterically hindered by the extra alkyl group, so they are less reactive to nucleophiles.
If an aldehyde reacts with an alcohol, it produces…?
A hemiacetal
If a ketone reacts with an alcohol, it produces…
A hemiketal
Explain the mechanism for forming a ketal
-FORMATION OF KETAL/ACETAL ONLY occurs in ACIDIC conditions
1.Ketone gets protonated by acid generating a better electrophile
2. Alcohol attacks electrophilic C
3. OH group (from ketone originally) gets protonated to form H2O+, a good leaving group
4. The alpha carbon now is a carbocation that is susceptible to attack by the 2nd alcohol
5. 2nd OH attacks forming an oxonium + charged intermediate
6. 2nd OH is deprotonated forming the final ketal product
Under what conditions do you perform hydrolysis of an acetal?
ONLY under acidic conditions.
What are the steps of acetal hydrolysis?
- Protonation of one OR group to form positively charged intermediate.
- Formation of double bond from 2nd OR group causes loss of +ROH leaving group.
- H2O nucleophilically attack C=O
- Deprotonation of newly attached H2O
When given an acetal, how do you figure out the products of the acetal hydrolysis w/o going through the mechanism?
-Find the two OR groups connected to the central carbon and circle them
-Erase the bonds that connect them to the central carbon
-To form your ketone/aldehyde, figure out how many leftover alkyl groups are connected to the central C, if only 1 alkyl, add a H
-Lastly, add a =O to the central C to form your correct carbonyl
What is the first step of an acid-catalyzed hydration of an aldehyde/ketone?
- Protonation of the carbonyl, forming a + charged intermediate
What is the first step of a base-catalyzed hydration aldehyde/ketone?
- Nucleophilic attack of the carbonyl, forming a - charged tetrahedral intermediate
What product will we get if an aldehyde or ketone reacts with hydrogen cyanide?
A cyanohydrin which is a molecule with an alcohol (OH) and CN bound to the same carbon.
How can an aldehyde be created?
It is created when a primary alcohol is partially oxidized with PCC reagent.
It CANNOT be oxidized with regular oxidizing agents like chromic acid.
What product is created if a secondary alcohol is oxidized?
A ketone
What oxidizing reagents are used to convert a secondary alcohol into a ketone?
Na2Cr2O7, K2Cr2O7, CrO3, and PCC
If we mix LiAlH4 and a ketone, what product do we get?
A secondary alcohol
In order to react with Tollen’s reagent, what is necessary for the reactant to have?
The reactant has to have hemiacetals, or in other words be able to be reduced. (Having an OH group on the anomeric carbon).
What is the chemical formula for Tollens Reagent?
Ag(NH3)2OH