Midterm Review. Flashcards
What is an acid chloride?
What are more reactive, aldehydes or acids?
Aldehydes are more reactive than acids.
How are acid chlorides generated?
The reaction of carboxylic acids with thionyl chloride (SOCl2) generates acid chlorides.
Why are weaker reducing agents more suitable for forming acid chlorides to aldehydes.
Strong reducing agents like LiAlH4 still reduce acid chlorides all the way to primary alcohols. Milder reducing agents like lithium aluminum tri(tbutoxy)hydride (LiAlH4) can selectively reduce acid chlorides to aldehydes.
How can an acid chloride be reduced to a ketone using a LiAlH4?
Acid chloride + LiAlH4 gives an aldehyde. Aldehyde + Grignard reagent gives a ketones.
How can an acid chloride be reduced to a ketone using only a Grignard reagent or organolithium reagents?
Grignard reagent and acid chloride react. Chlorine is removed from the carbon and the new carbon chain takes its place.
What is an organolithium reagent made up of?
2R-Li + CuI = 2R-Cu-Li + Li-I.
What is the Gilman reagent?
R2-Cu-Li. Lithium dialkylcuprate.
What is the Swern reaction used for?
The oxidation of alcohols.
A primary alcohol is oxidised to what?
A primary alcohol is oxidised to an aldehyde, then to a carboxylic acid if oxidation is allowed to continue.
How can oxidation be stopped at the aldehyde stage?
By using a weak oxidising agent such as PPT or the Swern oxidation.
A secondary alcohol is oxidised to what?
A ketone.
A tertiary alcohol is oxidised to what?
No reaction occurs.
How can you recognise the Swern reaction?
DMSO is used as the oxidising agent along with oxalyl chloride and pyridine.
Why is the Swern reaction a convenient reaction?
The by-products of this reaction can be easily separated from the products, making this a convenient reaction.
Give a brief overview of the Swern reaction?
Alcohol + DMSO + Oxalyl chloride = A ketone or an aldehyde + dimethyl sulfide.
What is the mechanism of the Swern reaction?
DMSO attacks oxalyl chloride. Then the alcohol is attacked and the H is removed and a double bond is formed.
What is oxalyl choride?
O O II II Cl-C-C-Cl (COCl)2
What is the 1st step of the Swern reaction?
Reagents react then attack the alcohol.
What are the 3 Swern reagents?
Is a tosylate a good leaving group?
Yes.
What can attack C-OTS?
Any nucleophile.
When a nucleophile attacks a C-OTS, what kind of reaction takes place?
Elimination or substitution.
R-OTS + OH. Gives what?
R-OH + -OTS.
R-OTS + C=N. Gives what?
R-C(TRIPLE BOND)N + -OTS.
R-OTS + BR-. Gives what?
R-BR + -OTS.
R-OTS + R-O-. Gives what?
R-O-R + -OTS.
R-OTS + :NH3. Gives what?
R-NH3+ + -OTS.
R-OTS + LiAlH4. Gives what?
R-H + -OTS.
Why is a tosylate such a stable anion?
The tosylate ion is a particularly stable anion, with its negative charge delocalized over three oxygen atoms.
What is the Jones reagent?
Chromic acid in acetone.
What is the Collins reagent?
Cr2O3 in pyridine.
When alcohols become alkanes, how many steps are in the process?
Alcohols to alkanes is a 2 step process.
Name the 2 ways that alcohols can become alkanes?
- Alcohol + H2SO4 = Alkene. Alkene + H2 and PD = Alkane. 2. Alcohol + TsCl = Tosylate. Tosylate + LiAlH4 gives an alkane.
What kind of reaction takes place when H2SO4 is added to an alcohol?
An E2 reaction.
What is oxidation?
The gain of oxygen or loss of hydrogen.
What is reduction?
The gain of hydrogen or loss of oxygen.
What is the structure of PCC?
What can ethylene glycol be oxidised to?
Oxalic acid.
What does methanol oxidise to?
Formaldehyde then formic acid.
What does ethylene glycol look like?
What does oxalic acid look like?
What are the reactions for the oxidation of methanol and ethylene glycol?
What is the treatment for methanol poisoning?
Excess alcohol.
How does excess ethanol treat methanol poisoning?
Ethanol oxidises to acetaldehyde then acetic acid.
Acetic acid reats with the poison.
List the order of alcohols that are most reactive with the Lucas reagent?
Tertiary = Most reactive.
Secondary.
Primary = Least reactive.
How does the Lucas reagent react with a primary alcohol?
SN2 reaction.
How does the Lucas reagent react with a scondary or tertiary alcohol?
SN1 reaction.
What is the Lucas reagent?
HCl + ZnCl2.
What is the SN1 reaction with the Lucas reagent?