Final Exam Practice Flashcards
What is LDA?
lithium diisopropylamide
It is used as a base in reaction to favor an enol in equilibrium and allow for the alkylation of alpha ketones. Often used with THF as solvent.
**Bulky, so wil pull off less crowded alpha hydrogen
What is the result if you treat an ester with NaOet and then H+
Claison condensation. Remember R-O is a good leaving group.
what reagant allows you to reduce phNN group?
H3PO2
What is true of the reaction rate in allylic, benzylic, and vinyl halides undergoing SN2 reactions?
-Vinylic halides do not undergo SN2 reactions (No SN2 on SP2) -Allylic and benzylic halides undergo SN2 much quicker than corresponding simple alkanes
What is important to know about Michael reactions?
There are 1,2 additions and 1,4 additions.
A 1,4 addition is also known as a Michael addition or a conjugate addition.
In this situation, the nucleophile attacks the C=C bond and forms a temporary enol that rapidly tautomerizes into a ketone.
adding this to phNN
phOH
What happens when you have a ketone in basic conditons (OH)?
A beta-hydroxy ketone forms. The alpha carbon of one ketone attacks the carbonyl of the other, a tetrahedral intermediate is formed, and the protonated. (Aldol addition)
**You can also go all the way to an alpha,beta unsaturated ketone by reforming the carbonyl (Aldol condensation)
What is the result of adding the following to an amido group?
“decarbonyl”
Hofman rearrangement
What reagant allows you to add F to a benzene
- HNO3/ H2SO4
- H2/ Pt
- NaNO2/ HCl
- HBF4/ heat
Adding this to ph-NN
ph-Br or ph-Cl
What is the difference between epoxide opening in acidic and basic conditions?
Acidic conditions: epoxide is activated and then the nucleophile attacks the more positive (more substituted side).
Basic conditions: the strong nucleophile attacks the more available side (less substituted)
What are examples of common michael donors?
Michael Donors= (nucleophile)
Beta di-ketone
Beta-keto ester
Gilman (R2CuLi)
Beta-keto nitrile
alpha-nitro ketone
What are these reactants responsible for?
- deprotonate methylene carbon
- add Br group
- hydrolyze R-O-R and decarboxylate
If you are creating a cyclic acetic acid derivative from a malonic ester, how would you do this?
- NaOEt/ EtOH
- Br-R-Br (two Brs allows a cyclic compound to form at the methylene carbon)
- H3O+/ heat to hydrolyze and decarboxylate
adding this to phNN
ph-I
Adding the following to a carboxylic acid
Alpha-Bromination
Replaces hydrogen with Br in a keto enol reaction
When looking at ethers and figuring out what happens in a reaction, what should I look for specifically?
Look for ACETALS!!! Ethers don’t react unless you have lots of heat or a strong acid. Acetals react.
How can you identify if something is a Michael donor?
Has two electron withdrawing groups and an active methylene group!
POWERFUL ACTIVATOR! No catalyst necessary. Br will add in all ortho/para positions
adding this to phNN
phF
What is the result of the addition of X2 to a double bond? and why?
Anti-addition because of the formation of a halonium ion!
What is the result of you add CN to an alpha beta substituted ketone
favors conjugate 1,4 addition!
What do the following reagants do?
“de-acid chloride”
turns an acid chloride into an R-NH2. (eliminates 1 Carbon, from the carbonyl)
What is the best way to add an alkene with a 1,4 addition (Michael addition)
- R2-CuLi (Gilman’s reagant)
- H+
In ring opening of epoxides in acidic conditions, how does it attack?
The epoxide is protonated and the weak base attacks the most substituted side. The configuration at the reaction site is inverted whereas the OH configuration is retained. Always results in a trans product
adding this to phNN
phCN
In free radical polymerization. What is true of the polymer compared to the monomer?
Every atom on the polymer has the same connections as the polymer.
ex: if C1 of the monomer has 2 hydrogens, then C1 of the polymer should have 2 hydrogens.
What is the result of adding H3O+ and heat to an ether and acetal?
Acetal is more reactive so returns to a carbonyl. The ether doesn’t react in weakly acidic conditions.
In order to form a dihalide cyclopropane with CHX3, what intermediate is created, what is the general mechanim?
A strong base is ued to deprotonate the CHX3. A halide groups leaves so that you are left with the neutral, carbene (CX2).
A double bond can then attack the carbene to form a cyclopropane.
What reagant may be used to reduce amines that wont reduce aldehydes or ketones?
NaBH3CN
or Na(CH3COO)3BH
How would you determine which compound forms the greatest equilibrium concentration of the enol tautomer?
A beta-dicarbonyl!!! Just remember that the proton will be negative more often in this case. Very acidic!
What is the following reagant used for?
limitations?
alpha bromination
cannot be used on aldehydes (they oxidize to carboxylic acids)
How do you determine the change in the rate of reaction of a given equation when you are given a change in solvent concentration?
rate=k[A][B]
Figure out the order of the reaction. In the above example, it is first in A and first in B. A change in solvent concentration will dilute the concentration of A and B by an equal amount.
new rate=k[dilutedA][dilutedB]
Based on the amount of dilution, you can find the new rate increase/decrease
In alpha bromination and acidic conditions, where does bromination occur?
more substituted side
If you see an acetone derivative, how was it most likely synthesized?
Acetoacetic ester synthesis:
- NaOEt
- R-Br
- H3O+
- Heat (180 degrees)
If you have a compound with three carbons between the carbonyls, how was it probably synthesized?
Michael reaction
1,4-addition!!!!!!
If you see a substituted carboxylic acid, how could it have been synthesized?
malonic ester synthesis
- NaOet
- R-Br
- H3O+
- Heat
What is the roll of the claison condensation?
Forms a beta-keto ester from an ester.
Reactants are:
- R-O
2 H3O+
What are the necessary reagants for the hoffman elimination?
- CH3I
- Ag2O/H2O/ heat
What is the nucleophilicity of halides in polar protic solvents?
Anions are solvated by hydrogen bonding. Therefore, larger halides that distribute negative charge are better nucleophiles. I>Br>Cl>F
What is the nucleophilicity of halides in polar aprotic solvents? (DMSO, acetone, acetonitrile, DMF)
Anions are poorly solvated, therefore nucleophilicity parallels basicitiy. F>Cl>Br>I
adding this to phNN
ph-H
What is the result of adding NH3/ Heat to a carboxylic acid?
replace OH with NH2
When can you NOT form an enolate
in the presence of an acidic proton (like carboxylic acid)
hence why we have malonic ester synthesis
What is the result when you add CH3 (2eq) to an ester?
You get two groups added and an alcohol. It gets reduced!! You can’t isolate at ketone
What is the result of adding H3O+ and heat to CN?
hydrolyze into carboxylic acid!
When determining the product of an aldol condensation, what should I look for to check my work?
an unsaturdated alpha, beta product.
ex: CH=CHCN would be an example. It is conjugated and stabilized.
Don’t forget what about LiAlH4 and NaBH4 when reacting them with epoxides (or other systems)…?
LiAlH4 and NaBH4 are both strong nucleophiles. Don’t forget they can undergo nucleophilic substitution reactions…
With epoxide reactions, they will attack the least substituted side.
What are some examples of michael acceptors?
conjugated aldehydes
conjugated ketones
conjugated esters
conjugated amides
conjugated nitriles
nitroethylene
In ring opening of epoxides with strong bases, how does it attack?
With strong base, it behaves like a regular SN2 and the strong base (ex. R-O-) attacks the least substituted side. It inverts stereochemistry on this side, and stereochemistry on the other side of the OH is retained. Results in a trans product
Between ketones and aldehydes, which is more likely to spend time in hydrate form in aqueous solution?
Aldehyde carbonyls are more reactive so will spend less time as carbonyls and more time as hydrates.
**conjugation reduces reactivity so conjugated aldehyde is less reactive.
What does POCl3 or SOCl2 do when added to an amido?
turns the amido group into a cyanide group CN
What can you add to this to get R-NH2?
How do you put F on a benzene?
Replace nitrizonium ion with F
Start with NO2:
- H2/ Pt (to make NH2)
- NaNO2/ HCl (to form nitrizoniumm)
- HBF4/ heat (to add F)
How do you form nitrisonium ion?
NaNO2/ HCl
Since NO2 (analine) is a not good with FC acylation. How can you add an acyl group to a benzene with an NO2 group present?
acylate the amino group first (with an acid chloride), then it becomes a weak activator
Then, you can do FC or add a group that you want ortho/para.
To unacylate the amino group, add OH and heat.
Condensation polymerization
Functional groups combine and eliminate water. When doing this problem, just look for BEST answer. doesn’t contain double bonds! And not too many functional groups
What reagants allow you to “decarbonyl” an amido group?
What reagant allows you to take off an acid chloride and carbonyl and replace with an NH2?
- NaN3
- H20/ heat
If you see a cyclic ketone with an alpha-beta substituted double bond, what most likely occurred?
An intramolecular aldol condensation~
Adding the following to an R methyl ether
haloform reaction, forms deprotonated carboxylic acid
What is the role of NaBH3CN?
it reduces amines but not aldehydes or ketones.
particularly useful for tertiary amines.
