Chapter 18 Flashcards
Secondary alcohol to ketone
Grignard + aldehyde 1)ether and h3o+ = aldehyde 2)Na2Cr2O7 and H2SO4 = ketone
Primary alcohol to aldehyde
Primary aclohol + PCC (oxidizing agent)
Allene to keto/ald
1)O3 2) (CH3)2S ozonolysis followed by reduction
Acyl halide to ketone or aldehyde
1) AlCl3 2)H2O acylation
Why are aldehydes more reactive than ketones?
Sterics- aldehyde H provides less hindrance than methyl group of ketone
Electronics- methyl group stabilizes cation on ketone, aldehyde cation is less stable
What is the product of a carboxylic acid plus Li-R?
Ketone
What is the product of a nitrile and an organolithium?
Ketone
What do you add to an acid chloride to make a ketone?
Lithium cuprate
Why does a curate only add once to an acid chloride unlike organolithium?
Reacts via the halogen, not the carbonyl.
How do you make an aldehyde from an acid chloride?
Add a mild reducing agent like lithium aluminum t-butoxy hydride (LiAlH(O-t-Bu)3
How do you make an aldehyde from an ester?
DIBAL-H and cold temp. Splits at C-OR
What do aldehydes and ketone exist as in water?
Hydrates - germinal diols, but ketone prefers to stay in ketone form
What catalyst is necessary for acetal formation and why?
Acid. B/c the OH of the hemiacetal is a poor leaving group, turning it to water makes it a good one, and the addition of the second O-R group can occur.
What type of reactant is needed to create a cyclic acetal?
A diol.
How can acetals be used as protecting groups?
Protection of a more reactive aldehyde part of a molecule allows for restriction of other reactions to the ketone.
What reactants are used, other than toxic HCN, to form cyanohydrins?
KCN/H2O/NaOH or NaCN/H2O/NaOH
What type of amine is reacted with a ketone to form an imine?
Primary amine
What is the ideal pH for imine formation and why?
4.5 - not too basic so there is enough acid to catalyze, and not too acidic so amine isn’t protonated and made non-nucleophilic.
What is N2H4 used for?
Wolff-Kishner reduction of ketones. When reacted with a ketone, forms a hydrazone which can be reduced to an alkene
What is the product of C=-N-R reacted first with organolithium, and second with H3O+?
First forms an imine, which is then hydrolyzed to form a ketone.
Why does only a single addition occur when a nitrile reacts with a grignard?
Excess grignards is destroyed during the reaction.
