Midterm 2 Review Flashcards
What product predominates under low temperature conditions or when a very sterically-hindered amine is used?
Non-zaitsev kinetic
What product predominates in high temperature conditions?
Zaitsev alkene thermodynamic
How do 1° amines react under acidic conditions?
1° amines can react with aldehydes and ketones to give imines (aka Schiff bases)
• C=N bond
How do 2° amines react with enolizable aldehydes and ketones under acidic conditions?
2° amines can react with enolizable aldehydes and ketones (has alpha hydrogens) to give enamines
• C-N bond & C=C bonds
How do 2° amines react with non-enolizable aldehydes and ketones under acidic conditions?
2° amines can react with non-enolizable aldehydes and ketones (does not have alpha hydrogens) to give iminium ions
• C=N bond
• (+) charge
Alpha hydrogens
Hydrogens on the carbon next door to the carbonyl carbon
Enolizable
Alpha hydrogens present
Carbonyl ->
Reagents: NH3 or 1° amine, pH = 4
N substitutes carbonyl O, N loses 2 hydrogens, N has lone pair, N has its substituent (if applicable), H2O byproduct
Carbonyl with alpha hydrogens ->
Reagents: 2° amine, pH = 4
N substitutes carbonyl O and their bond becomes a single bond, N loses its hydrogen, N has its substituent(s), N has a lone pair, C=C double bond forms between reactant’s most substituted carbons
For intramolecular reactions, number carbons starting with nitrogen as 1 and carbonyl C as last #, form a ring with the number of carbons
Carbonyl with no alpha hydrogens ->
Reagents: 2° amine, pH = 4
N substitutes carbonyl O, N loses its hydrogen, N has its substituent(s), N has a + charge (loses its lone pair)
What would reagents 1) LAH, 2) H3O+ work on?
Strong reducing agent
Aldehyde -> 1° alcohol
Ketone -> 2° alcohol (racemic)
Imine -> amine (double bond becomes H)
Carboxylic acid -> 1° alcohol
Nitrile -> 1° amine (triple bond N becomes single bond NH2 (RNH2))
Ester -> 1° alcohol (double bond O on ester removed, ether O becomes OH and its non-carbonyl R group leaves bound to OH)
Amide -> amine (double bond O chopped off)
What would reagents 1) NaBH4, 2) H3O+ work on?
Mild reducing agent
Aldehyde -> 1° alcohol
Ketone -> 2° alcohol (racemic)
Imine -> amine (double bond becomes H)
What would reagents H2/Pd work on?
Alkene -> alkane
Alkyne -> alkane
Aldehyde -> 1° alcohol
Ketone -> 2° alcohol (racemic)
Imine -> amine (double bond becomes H)
Nitrile -> 1° amine (triple bond N becomes single bond NH2 (RNH2))
Why don’t hydride reducing agents react with carbon-carbon double bonds or triple bonds?
Alkenes & alkynes do not have an electrophile carbon unlike a carbonyl carbon
What would reagent NaBH3CN work on?
Imine -> amine (double bond becomes H)
Whenever you reduce imine -> amine (double bond becomes H), what do you always have to check for?
Racemic
Carbonyl ->
Reagents: NH2NH2, KOH
Double bond O goes away (works on aldehydes and ketones)
Wolf-Kishner
Carbonyl ->
Reagents: Zn(Hg), HCl
Double bond O goes away (works on aldehydes and ketones)
A 3° alcohol will go away and form the most stable C=C double bond from its original point of attachment
Clemmenson Reduction
Enol
C=C-OH
Enol to keto tautomerization
Reagent: cat acid or base
Non-alcoholic C gains a H, double bond moves to in between C and OH which loses its H so it’s just C=O
In keto-enol tautomerization, which product usually predominates and why?
Keto predominates because C=O bond stronger than C=C bond
Keto
Ketone functional group - aldehydes and ketones
In keto-enol tautomerization, when does enol predominate?
In B-diketones, enol predominates due to delocalization of pi bonds
Conjugated hydrogen bonding interaction
Keto to enol tautomerization
Reagent: cat acid or base
Double bond on one keto moves to in between that carbonyl C and most stable position, ex-carbonyl O gains a H
In a ketone, what is the nucleophile and what is the electrophile? When an enolate anion resonates into a keto, what is the nucleophile?
In a ketone, O nucleophile, C electrophile from carbonyl. When an enolate anion resonates into a keto, alpha carbon is nucleophilic (with lone pair and - charge)
Can make carbon carbon bonds
What makes a carbonyl carbon electrophilic?
The pull of the oxygen
Enolate anion
Enol but without the H that makes it an alcohol, so O would have an extra lone pair and - charge
Aldehyde or ketone
Reagents: Br2, CH3COOH
Alpha carbon loses one H and forms a bond with Br
IUPAC priority rankings
Carboxylic acid > aldehyde > ketone > hydroxy > alkene > alkyne > R, NO2, X, OR, Ph
Which is more acidic and why?
A) FCH2COOH
B) CH3COOH
A due to inductive effects (pull of electron density through sigma bonds)
Which is more acidic?
A) CH3COOH
B) PhCOOH
B
Which is more acidic and why?
A) PhCOOH
B) ClPhCOOH
B due to inductive effects
Which is more acidic and why?
A) PhCOOH
B) H3CPhCOOH
A because the H3C in B is electron donating
Which is more acidic?
A) PhCOOH
B) O2NPhCOOH
B
In YPhCOOH, where the substituent Y could be Cl, H, CH3, NO2, or COH (aldehyde), rank the substituents from most acidic to least acidic.
NO2, COH (aldehyde), Cl, H, CH3
1° alcohol ->
Reagent: H2CrO4
Carboxylic acid
Aldehyde ->
Reagent: H2CrO4
Carboxylic acid
PhMgBr ->
Reagents: 1) CO2, 2) H3O+
PhCOOH
PhCOOH + 1° alcohol <->
Reagent: cat H2SO4
PhCOO bound to alcohol’s substituent (H leaves PhCOOH, OH leaves 1° alcohol)
H2O byproduct
Fischer Esterification
HO bound to 5C chain, last C is an aldehyde <->
Reagent: cat H2SO4
You don’t draw H on OH, that O is the point of cyclization
All of the carbons form the ring, double bond O from aldehyde becomes single bond OH, and it’s racemic
Hemiacetal
What is the difference between
Reagents: 1) NaBH4, 2) H2O
Reagents: 1) NaBH4, 3) H3O+
In the first instance, double bond O (not carboxylic acid) would become racemic OH, and cat H2SO4 must be used to cyclize. The second instance does all of this in one synthetic step.
When double bond O is at the beta position, and reagent: warm, what happens to carboxylic acid?
It goes away (CO2)
1° alcohol ->
Reagents: SOCl2, pyridine Et3N
Cl substitutes OH
Carboxylic acid ->
Reagent: SOCl2
Cl substitutes OH (acid chloride)
List the carboxylic acid derivatives from most to least reactive. What is the trend for stability?
1) Acid Chloride
2) Acid Anhydride
3) Ester
4) Amide
5) Nitrile
Stability increases as you go down the pyramid (opposite of reactivity)
Lower the pKa, ____acidic the acid, ____ stable the anion/conjugate base
More acidic
More stable
Nucleophilic Acyl Substitution Reaction
C bound to R, double bond O, and LG
Step 1: attack of the nu, double bond on O becomes a lone pair with - charge
Step 2: departure of the LG, double bond on O is restored
Nucleophilic Acyl Addition Reaction
C bound to R, double bond O, and H
Step 1: attack of the nu, double bond on O becomes a lone pair with - charge
Step 2: add a proton, O grabs a H from H3O+ to become OH
Acid Chloride + H2O ->
Cl on Acid Chloride substituted by OH (forming RCOOH, a carboxylic acid) + HCl
Acid Anhydride + H2O ->
Reagent: H3O+ cat acid or cat H2SO4
Ether splits so that side with O adds H and side without O adds OH
Product: 2 RCOOH (carboxylic acid)
Ester + H2O <->
Reagent: cat H2SO4
OR substituted by OH (forming RCOOH, a carboxylic acid) + HOR
Ester + H2O ->
Reagent: NaOH base promoted
R leaves so single-bonded O gains a lone pair and - charge, + ROH
Saponification
Amide + H2O ->
Reagent: acid promoted
Products: NH2 substituted by OH, NH4+
Amide + H2O ->
Reagent: base promoted
Products: NH2 substituted by O- (3 lone pairs), neutral NH3
Nitrile ->
Reagents: H2O, acid & base cat
Imidic acid intermediate: HO added to C, triple bond becomes double bond, H added to N
Tautomerization: amide
N in a ring bound to one H and two C, one of the C has a double bond O ->
Reagent: H3O+
Double bond O side gains OH (forms carboxylic acid), N drops down and becomes NH3+
Ester in a ring bound to two C, one of the C has a double bond O ->
Reagent: NaOH
Double bond O side gains O- (3 lone pairs), other side drops down and becomes OH
N in a ring bound to one H and two C, one of the C has a double bond O ->
Reagent: NaOH
Double bond O side gains O- (3 lone pairs), N drops down and becomes neutral NH2
CN on end of carbon chain
Reagents: cat H2SO4, excess water
N goes away and carboxylic acid added, cyclizes if possible (need OH)
How can you move up the pyramid?
Fischer Esterification: carboxylic acid to acid anhydride
SOCl2: carboxylic acid to acid chloride
Acid chloride + ROH ->
Cl on Acid Chloride substituted by OR (forming RCOOR, an ester) + HCl
Acid anhydride + ROH ->
Ether splits so that side with O (leaving group) adds H and side without O adds OR
Product: RCOOR (ester) + RCOOH (carboxylic acid)