MCAT Organic Chemistry Carbonyl Chemistry Flashcards
A reaction in which the enolate anion of the carbonyl reacts with the carbonyl of another compound
Aldol condensation
A reaction between an aldehyde or ketone and a primary amine to form an ___
imine
A functional group in which a carbonyl is attached to two carbon groups
Ketone
The hydrolysis of esters by treatment with a basic solution
Saponification
Readily interconvertible constitutional isomers
Tautomers
What is a typical electrophile involved in an SN2 mechanism?
An alkyl halide because:
- electronegative
- large in size
- Conjugate bases of strong acids (except F-) make good leaving groups
Why should protic solvents be avoided when doing SN2 reactions?
The hydrogen bonding solvents are able to strongly solvate the nucleophile, they hinder the backside attack necessary for the concerted reaction
Why should you use an aprotic solvent when running an SN2 reaction?
Polar aprotic solvents like Acetone, DMF, or DMSO are polar in nature allowing the charged nucleophiles and leaving groups to remain dissolved, but not as efficient at completely solvating the nucleophile
Reactivity of a substrate in order of best to worse for an SN2 reaction
Ch3 > Primary > Secondary > Tertiary (BECAUSE OF STERIC HINDRANCE)
Are rearrangements possible for SN2 mechanisms?
NO it is a concerted (one step) mechanism. No carbocations are present in solution
What are the favorable conditions of an SN2 mechanism?
Strong, non-bulky nucleophil will favor SN2 reaction over SN1
The rate of an SN1 rxn rate is dependent on __
concentration of the electrophile (species that loses the leaving group over the course of the reaction)
Because nucleophile attacks on either side, SN1 reactions involving chiral molecules will produce a __
racemic mixture of R and S
Reactivity of a substrate to SN1 reactions
Tertiary > Secondary > Primary (due to stabilization of the carbocation intermediate)
Why do SN1 reactions favor protic solvents?
Protic solvent helps to stabilize the forming carbocation and solvate the leaving group,
Second, the solvent behaves like a nucleophile in a solvolysis reaction attacking the carbocation intermediate producing an alcohol if water was used or an ether if an alcohol was used
What are the 5 Aqeuous oxidants that can be used to form ketons from secondary alcohols?
- Chromic acid (H2CrO4)
- Chromate salts (CrO42-)
- Dichromate Salts (Cr2O72-)
- Permanganate (MnO4-)
- Chromium Trioxide (CrO3)
The only anhydrous oxidant that will not overoxidize the primary alcohol to the carboxylic acid form, but into a ketone is __
PCC
The general structure of an amine is
R-NH2
Amines behave as either ___ or __
Bronsted-Lowry bases or nucleophiles
When an aldehyde or keton reacts with a primary amine (RNH2) a __ will form
An imine will form C=N-R’
When an aldehyde or keton reacts with a secondary aine (R2NH) a __ will form
An enamine will form C-N-R2
___ is a test to detect aldehydes, ketones, and hemiacetals in sugars
Benedict’s test
Formula for carbohydrates
CnH2nOn
The bond between two saccharides
Glycosidic linkage
Interconversion between anomers
Mutarotation
All amino acids are derived from ___
L-glyceraldehyde
Animal carbohydrates are chemically derived from ___
D-Glyceraldehyde
D or L or (+) and (-) respectively tell us the precursor of the molecule either __
(+)/D or (-)/L glyceraldehyde
What are two synthetic methods employed to produce amino acids
Strecker Synthesis
Gabriel Synthesis
The peptide bond is planar and rigid because the __
resonance delocalization of the nitrogen’s electrons to the carbonyl oxygen gives substantial double bond character to the bond between the carbonyl carbon and the nitrogen, can not rotate around the peptide bond
The ___ is the first end made during polypeptide synthesis
Amino terminus
What are the two common means of accelerating the rate of peptide bond hydrolysis?
- strong acid and heat
2. Proteolytic enzymes
Six membered sugar ring structures are termed___
pyranose becasue of their resemblance to pyran
five-membered sugar rings are termed____due to their resemblance to furan
Furanoses
In a fischer projection, the groups on the LEFT in fischer notation are ___ in the rinch in chair notation
The groups on the LEFT in fischer notation are ABOVE the ring in chair notations
Sucrose is
glucose + fructose
Lactose is -
Galactose and glucose
All monosaccharides are ____sugars
reducing sugars
Aldehydes, ketones and hemiacetals give a ___ in benedict’s test for reducing sugars
Positive test (if it is positive, the sugar is in monosaccharide form, not in ring form)
Acetals give a __ on Benedict’s test because they do not react with Cu2+ and they are not in equilibrium with the open-chain (carbonyl) form
NEGATIVE result (ring formed sugars are weakly positive on Benedict’s test)
Once a monosaccharide has attacked another sugar to form a glycosidic linkage its anomeric carbon is in ___ configuartion and is thus no longer free to ___ nor
Once a monosaccharide has attacked another sugar to form a glycosidic linkage, its anomeric carbon is in an acetal configuration and is thus no longer free to mutorotate nor to reduce Benedict’s reagent`
A saturated compound with n carbon atoms has exactly ___ hydrogen atoms
2n +2 = Hydrogen atoms in compound
One degree of unsaturation indicates__
presence of one pi bond or one ring
Two degrees of unsaturation means there are___
two pi bonds (two separate double bonds, or one triple bond), or two rings, etc.
Organic intermediates are stabilized in two major ways
- Inductive effect, stabilize charge through sigma bonds
- Resonance effects, stabilize charge by delocalization through pi bonds
Give me order of Carbocation stability
Tertiary > secondary > primary > methyl
-more stable, less reactive, lower energy
Give me carbocation reactivity in order
methyl > primary > secondary > tertiary
less stable, more reactive, higher energy
Give me carbanion stability
methyl > primary > secondary > tertiary
Give me carbanion reactivity
tertiary > secondary > primary > methyl
Electron donating groups tend to stabilize ___
electron-deficient intermediates (carbocations)
Electron withdrawing groups tend to stabilize___
electron-rich intermediates (carbanions)
The stabilization of reaction intermediates by the sharing of electrons through sigma bonds is called___
inductive effect
___ is a system containing three or more atoms that each bear a p orbital, these orbitals are aligned so they are parallel, creating possibility of delocalized electrons
Conjugated system
In an SN2 reaction what is the order of reactivity?
CH3 > 1 > 2> 3 (because of steric hindrance)
In an SN2 rxn what happens to the product stereochemistry?
Complete inversion of the carbon that is attacked by the nucleophile
What are the kinetics of an SN2 rxn dependent on?
Reaction rate = k[Nucleophile][Electrophile]
What type of solvent should be used for an SN2 rxn?
Polar, aprotic (non-hydrogen bonding) solvents
What are the favoring conditions of an SN2 rxn over an SN1?
Strong, non-bulky nucleophile will favor SN2 over SN1
The rate of the SN1 reaction is dependent on the __
concentration of the electrophile (the species that loses the leaving group over the course of the reaction)
___refers to when the solvent behaves as a nucleophile and attacks the carbocation intermediate in an SN1 rxn
Solvolysis
What are the reactivity of substrates for SN1 mechanisms?
3 > 2> 1 (due to stabilization of the carbocation)
What is the stereochemistry of products formed from an SN1 reaction?
Almost complete racemization due to nucleophilic attack on either side of p orbital
What type of solvent should be used for an SN1 reaction?
SN1 reactions are favored by protic (hydrogen bonding) solvents. (This stabilizes the carbocation)
What are the favorable conditions for an SN1 reaction?
Non basic, weaker nucleophiles favor unimolecular substitutions
