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ACS ORGANIC CHEMISTRY EXAM 2025
ACTUAL QUESTIONS AND ANSWERS GRADED
A+
What is PCC in DCM?
Used in oxidation of primary alcohols to aldehydes; and oxidation of secondary alcohols to ketones ; usually used to oxidize alcohols into carbonyl compounsd
What is the Wittig reaction?
Reaction which involves the reaction of an aldehyde or ketone; The phosphoran (PH3P= CR3R4 can be used to produce an alkene, but then proceed to form an unstable 4 membered ring.
What happens after phosphonium ylide is added to a ketone or aldehyde?
Alkene CH2 is formed; PH3P=O by product.
What happens when MCPBA is added to an alkene?
Forms into an epoxide!!
What happens when an workup is applied to an epoxide?
OH OH; BREAKS apart the ether
Why do we use AlCl3 in Friedel Crafts- Alkylation?
Good lewis acid catalyst
What do the reagents KOH and hydrazine (NH2NH2) do?
Wolff Kischner reduction; used to convert carbonyl functionalities into methylene groups; forms R,R=N-NH2 ; or just CH2!! The imine intermediate forms tho
What is the imine formation?
Benzene ring double bonded N-NH
What is the polymer Nylon 6,6 made from?
Polyamide ; 6 long carbonyl at each end of the chain; 4 carbons in between each of them; then 6 carbons in between each amine group
What is the polymer polyurethane made from?
To name an ester,
identify the alkyl group that is in the 'alcohol' portion of the molecule and name it; then identify the acid part of the molecule. The ester is named with the alkyl part first, and the acid part is named as a carboxylate.
The terms ortho, meta, and para are used when benzene derivatives possess
exact 2 subsituents
Is a structure with more or less covalent bonds more stable?
More covalent bonds is more stable
What is the downside to separation of charges?
Separation of charges cost energy and results in a less stable resonance contributor
What does the nitrate ion look like lewis structure?
The bonding pi orbital is lower in energy than antibonding orbital (T/F)?
True
The sigma orbital is lower in energy than the pi orbital (T/F)?
True
How do you prepare epoxides?
Reagent is peracid (COOOH) ; alkene to an epoxide; maintain stereochemistry
What are the reagents of hydroboration of alkenes?
BH3, Et2O
What is anti-markovnikov?
When the H adds to the carbon with the fewest attached hydrogens
What is syn
H and B add to the same face of the alkene.
EDG ______ the rate of reaction
increase
EWG ________ the rate of reaction
decrease
What are resonance effects?
Those that occur through the pi system and can be represented by resonance structures
What are inductive effects?
Those that occur through the sigma system due to electronegativeity type effects.
What does EDG do?
Atoms adjacent to the pi system activate the aromatic ring by increasing the electron density on the ring through a resonance donating effect. (ortho-para directing)
What does an EWG do?
EWGs with pi bonds to electronegative atoms adjacent to the pi system deactivate the aromatic ring by decreasing the electron density on the ring through a resonance withdrawing effect. (meta directing)
Halogens are deacitvaitng but have both
inductive electron withdrawing and resonance donating (electronegativity and lone pair donation)
What is the aldol condensation reaction?
reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a beta hydroxyaldehyde or b-hydroxyketone, followed by dehydration to give a conjugated enone.
How does one transform a fischer projection into a cyclic ring in chair conformation?
Freely rotate the bonds (change the position of the OH and CH2OH in the fischer projection, then the oyxgen-H bond will nucleophilically attack the carbon, kick the double bond of the oxygen to the oxygen to form an oxygen anion and then get protonated by a hydrogen from the alcohol gorup used to nucleophilically attack the carbon. (mechanism is in notebook)
is the alkaline hydrolysis of the fatty acid esters. Example: The chemical reaction between any fat and sodium hydroxide is a saponification reaction. triglyceride + sodium hydroxide (or potassium hydroxide) → glycerol + 3 soap molecules
Carbonyl attack
What is a Grignard reagent?
an organometallic chemical reaction in which alkyl, vinyl, or aryl-magnesium halides (Grignard reagents) add to a carbonyl group in an aldehyde or ketone. This reaction is an important tool for the formation of carbon-carbon bonds.
How do you prepare a Grignard reagent?
Treat magnesium, and then you treat the Grignard with a strong acid. This gives you the alkane. You can also use this to introduce deuterium (D) into molecules! The first step is to make the Grignard reagent
What's a decoupled HNMR?
shows no splitting at all; it consists of a set of single
peaks, one for each carbon or each set of equivalent carbons in a molecule. (EXAMPLE in the exam is that benzene is basically meso, so the signals must be individual 6 signals on their own.
What are the reagents of the Claisen condensation?
claisen condensation between esters containing alpha hydrogens, promoted by a base such as sodium thoxide, affords beta keto esters.
(use stronger bases to increase yield: NaH)
The reducing agent: NaBH4 reduces?
Aldehydes and Ketones
The reducing agent: LiAlH4 reduces
Carboxylic acids and esters
Why can LiAlH4 reduce more?
Because the Al-H bond is weaker and thus less stable than B-H bond.
When using LiAlH4 to reduced amides what happens? (h2o workup)
RCH2NH
How does one form an epoxide?
How to you calculate IHD?
2C+2-H-X-N/
How many stereoisomers per chiral center?
2^n
What are enantiomers?
R,R, S,S
R,S, S,R
What are diastereomers?
R,S, R, R
R,S S,S
In cyclic systems a cis compound can react and become trans product
True`
What happens in eliminated product when we use TBUOK?
Form usually with least sterically hindered 'H' -- makes least substituted Alkene
Because of steric hindrance, how must H's be removed for elimination?
Anticoplanar ~~
What are the typical acids used in dehydration?
Sulfuric acid and phosphoric acid
What is the temperature used to dehydrate an alcohol to an alkene?
Temperature dependent on the structure of the alcohol.
Which structures (primary, secondary, or tertiary) are the hardest to dehydrate?
Primary alcohols
What are geminal dihalides?
two halogens bound to the same carbon atom
Hydrogen adds to alkenes in the presence of metal catalysts
What are the catalysts used in hydrogenation?
Insoluble platinum, palladium or Ni catalysts
What are the homogenous catalysts that can be used in hydrogenation?
Rhodium or Ruthenium based; wilkinson's catalyst Rh(C6H5)3P)3cL
Why is hydrogenation called reduction?
Because an unsaturated compound becomes saturated with hydrogen compound
What are all the hydrogenating catalysts?
Ni, Pd, Pt, Rh(C6H5)3PI3Cl
What are the reagents for syn addition of hydrogen (to form cis-alkenes?)
P-2 catalyst nickel boride (Ni(COOCh3)2) results in the syn addition of one equivalent of hydrogen to a triple bond; thus yielding a cis double bond.
reagent: H2/Ni2B(P-2)
What other catalyst can be used to produce a cis-alkene from an alkyne?
Lindlar's catalyst
What are the reagents of lindlar's catalyst?
H2, Pd/CaCO3 ; quinoline
What reagents can be used to synthesize trans-alkenes?
Dissolving metal reaction which uses lithium or sodium metal in low temperature (NH3 or NH2 solvent) produces trans alkenes
reagent: Li, C2H5NH2, -78 deg C, NH4Cl
What is the reagent Li, C2H5NH2, -78 deg C, NH4CL used to form?
trans-alkene
What does the vinylic anion prefer? Trans or cis
What is the regioselective reaction?
When a reaction can potentially yield two or more constitutional isomers actually produces only one or a predominance of one isomer.
What happens when you add HBr to butene?
Get a chiral molecule, but racemic mixture (R/S) is produced becuase the carbocation is achiral (can attac with the nucleophile from both top and bottom)
What happens when cocnentated sulfuric acid is added to alkenes?
form an alkyl hydrogen sulfate which is soluble in water; isopropyl hydrogen sulfate
What happens when the isopropyl hydrogen sulfate is hydrolyzed by heating with water? Will form a 2-propanol and acid will be reformed
Will form 2-propanol
What happens when alkenes and dil. aq acids add together?
Form Markovnikov addition of water (markovnikov is adding the H to the Carbon with more H's and add nucleophile to the carbon with less H's
What is hydration favored by?
Addition of a small amount of acid and large amount of water
What is dehydration favored by?
Concentrated acid with little water present
What is oxymercuration-demercuration?
markovnikov; gives high yields of alcohols and avoids rearrangements;
What is hydroboration-oxidation?
antimarkovnikov syn hydration; adds water to alkenes;
What are the reagents of Hydroboration oxidation?
BH3, THF, H2O2, OH-
What are the reagents of oxymercuration-demercuration?
Hg(OAc)2, THF-H2O, NaBH4, OH-
