Exam 2 Reactions Flashcards
What type of acetal does this reaction create?
Cyclic Acetal
What type of acetal does this reaction create?
acyclic acetal
What reagent is necessary to make a cyclic acetal?
a carbon chain with OH on either end and an acid catalyst
What reagent is necessary to make an acyclic acetal?
a two sets of carbon chains with OH at the end and an acid catalyst
What are the components of a Grignard reagent?
[carbon chain] [magnesium] [halogen]
R-Mg-X
What does a Grignard reagent do? How?
Turns a carbonyl (ketone or aldehyde) into an alcohol.
The Grignard Reagent acts like nucleophile and attacks the carbonyl, shifting the double bond to a lone pair on the oxygen. The alkoxide ion is protonated (H added) from water creating an alcohol. A new C-C bond is formed.
What two sets of reagents can be used in a Hydride reduction of a ketone or aldehyde?
LiAlH4 and THF
or
NaBH4 and an alcohol
What are three ways to prepare an aldehyde?
- Oxidation of Primary alcohols (PCC, CH2Cl2 or DMP, CH2Cl2, or 1. DMSO, (COCl)2, 2. Et3N
- ozonolysis of alkenes (1. O3, 2. DMS)
- Hydroboration-Oxidation (1. R2B-H, 2. H2)2, NaOH
What are four ways to prepare a ketone?
- Oxidation of Secondary Alcohols (Na2Cr2O7, H2SO4, H2O)
- Ozonoloysis of Alkenes (1. O3, 2. DMS)
- Acid-Catalyzed Hydration of Terminal Alkynes (H2SO4, H2O, HgSO4
- Friedel-Crafts Acylation (Cl-(C=O)-R, AlCl3)
What are the steps for a nucleophilic addition under basic conditions?
Nucleophilic Attack followed by Proton Transfer
- nucleophile attacks the Carbon of the carbonyl.
- electrons in double bond migrate to Oxygen becoming a lone pair
- Proton transfer: lone pair on Oxygen attacks the hydrogen on water
- OH created and nucleophile stays attached to Carbon
Name this reaction. Explain the mechanism steps.
nucleophilic addition under basic conditions
- nucleophile attacks the Carbon of the carbonyl.
- electrons in double bond migrate to Oxygen becoming a lone pair
- Proton transfer: lone pair on Oxygen attacks the hydrogen on water
- OH created and nucleophile stays attached to Carbon
Name this reaction and explain the mechanism steps.
nucleophilic addition under acidic conditions
- Proton Transfer: lone pairs on carbonyl oxygen attacks hydrogen on an acid.
- Nucleophilic Attack: a nucleophile attacks the Carbon of the carbonyl.
- electrons in double bond migrate to Oxygen becoming a lone pair
- OH created and nucleophile stays attached to Carbon
What are the steps for a nucleophilic addition under acidic conditions?
Proton Transfer followed by Nucleophilic Attack
- Proton Transfer: lone pairs on carbonyl oxygen attacks hydrogen on an acid.
- Nucleophilic Attack: a nucleophile attacks the Carbon of the carbonyl.
- electrons in double bond migrate to Oxygen becoming a lone pair
- OH created and nucleophile stays attached to Carbon
Name this reaction and explain the mechanism steps.
Base-Catalyzed Hydration
- Carbon of Carbonyl group attacked by lone pairs on the oxygen of a hydroxide (-OH)
- electrons in double bond migrate to Oxygen becoming a lone pair
- OH attaches and an anionic intermediate forms
- lone pair of negatively charged oxygen (previously carbonyl oxygen) attacks hydrogen in H2O and protonates
- two OH groups are now attached to carbonyl carbon
What are the steps for a base-catalyzed hydration?
Nucleophilic Attack followed by Proton Transfer
- Carbon of Carbonyl group attacked by lone pairs on the oxygen of a hydroxide (-OH)
- electrons in double bond migrate to Oxygen becoming a lone pair
- OH attaches and an anionic intermediate forms
- lone pair of negatively charged oxygen (previously carbonyl oxygen) attacks hydrogen in H2O and protonates
- two OH groups are now attached to carbonyl carbon
Name this reaction and explain the mechanism steps.
Acid-Catalyzed Hydration
- Protonation of carbonyl making it more electrophilic
- Protonated carbonyl attacked by water forming oxonium intermediate (positively charge H2O)
2b. oxygen of water molecule attaches to carbon making it positively charged - Oxonium intermediate deprotonated by water, forming the hydrate
3b. Lone pairs of another H2O attacks hydrogen on oxonium, removing the hydrogen - Creates two OH groups on carbon
What are the steps for an acid-catalyzed hydration?
Proton Transfer followed by Nucleophilic Attack followed by Proton Transfer
- Protonation of carbonyl making it more electrophilic
- Protonated carbonyl attacked by water forming oxonium intermediate (positively charge H2O)
2b. oxygen of water molecule attaches to carbon making it positively charged - Oxonium intermediate deprotonated by water, forming the hydrate
3b. Lone pairs of another H2O attacks hydrogen on oxonium, removing the hydrogen - Creates two OH groups on carbon
Name this reaction and explain the mechanism steps.
Acetal Formation
Proton Transfer»_space; Nucleophilic Attack»_space; Proton Transfer»_space; Proton Transfer»_space; Loss of Leaving Group»_space; Nucleophilic Attack»_space; Proton Transfer
- carbonyl protonates making it more electrophilic
- First alcohol (from reagent) attacks protonated carbonyl and attaches to the carbon, creating oxonium intermediate (+H2O)
- Oxonium deprotonated to form hemiacetal
- OH protonated transforming into Good Leaving Group
- Leaving Group leaves creating a R–C=O–R double bond
- Second alcohol (from reagent) attacks C=O and attaches to carbon creating oxonium intermediate
- Oxonium ion deprotonated creating acetal
What are the steps for an Acetal Formation?
Proton Transfer»_space; Nucleophilic Attack»_space; Proton Transfer»_space; Proton Transfer»_space; Loss of Leaving Group»_space; Nucleophilic Attack»_space; Proton Transfer
- carbonyl protonates making it more electrophilic
- First alcohol (from reagent) attacks protonated carbonyl and attaches to the carbon, creating oxonium intermediate (+H2O)
- Oxonium deprotonated to form hemiacetal
- OH protonated transforming into Good Leaving Group
- Leaving Group leaves creating a R–C=O–R double bond
- Second alcohol (from reagent) attacks C=O and attaches to carbon creating oxonium intermediate
- Oxonium ion deprotonated creating acetal
Name this reaction and explain the mechanism steps.
Hydrolysis of Acetals
Proton Transfer»_space; Loss of leaving group»_space; nucleaophilic attack»_space; Proton transfer»_space; proton transfer»_space; loss of leaving group»_space; proton transfer
What are the steps for the Hydrolysis of acetals?
- protonation of one carbonyl from H3O
- 1 R–OH is ejected, creating C=O with remaining oxygen
- Nucleophilic attack of C=O by water, oxonium attaches
- Water deprotonates oxonium creating OH
- protonation of hemiacetal H3O creating good leaving group
- lone pair from OH migrates creating C=O, R–OH is ejected
- H-C=O is deprotonated by water creating a ketone
What are the three criteria that must be for a nucleophilic aromatic substitution to occur?
- The ring must contain a powerful electron-withdrawing group (typically a nitro group).
- The ring must contain a leaving group (usually a halide).
- The leaving group must be either ortho or para to the electron-withdrawing group. If the leaving group is meta to the nitro group, the reaction is not observed.
