Organic Chemistry Test Questions

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AMINO ACID
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    Amphoteric – act as acid and baseAll have chiral center (x/ glycine)L is the natural occurig form (NH2 on L)In neutral solution form zwitterion – dipolar ion at pI (isoelectric pH)

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EQUIVALENT POINT
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Equimolar
Mole [OH-] added = Mole [H+] present
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HALF EQUIVALENT POINT
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pH = pKa
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TITRATION OF AMINO ACID
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1. COOH deprotonated before NH3
2. 2 moles of base for 1 mole of a.a
3. Buffer capacity is greatest at pKa1 and pKa2 but smallest at pI
4. pH of equivalent point is not usually 7
5. Indicator (weak acid-not involved in rxn) – best when closest to equi. pH
HA(color 1) + H2O -> H3O + A- (color 2)
* if [H3O] > Ka, sln will be color 1
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HENDERSON- HASSELBALCH EQUATION
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pH = pKa – log [con. BASE]/ [con. ACID]
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NEUTRALIZATION
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EXOthermic rxn -> formation of something stable Always give Salt and WaterpH DOES NOT equal to 7 Depends on the acidity/basicity of the salt
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BUFFER
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    1. Weak Acid and salt of its conjugate base or2. Weak Base and salt of its conjugate acid 3. Use acid with pKa close to pH that you want to maintain 4. Increase [buffer] = Increase Efficiency

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NON-POLAR AMINO ACID
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R = CHO, Hydrophobic,↓solubilty, INSIDE or at core of proteins or transmembrane to avoid H2O

Alanine, Valine, Leucine, Isoleucine, Proline, Phenyl alanine, Glycine, Thryptophan

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POLAR AMINO ACID
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R= Polar, Uncharged

HydroPHILIC, ↑ solubility, on SURFACE of protein

Methioninine, Serine, Theroine, Cystein, Tyrosine, Asparagine, Glutamine

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ACIDIC AMINO ACID
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R = COOH group – at Physiological pH = 7.4Have 3 distinct pKa’s – 3 mole of base is needed for neutralization Important in substrate binding sites of enzymes
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BASIC AMINO ACID
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R= NH2 + at physiological pH = 7.43 moles of acid is needed to neutralize 1 mole of baseArginine, Lyscine, Histidine
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PEPTIDE
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Amino Acid subunitsPeptide bond= Amide bond formed via condensation (water is loss)Rotation about the C-N bond is limited because resonance give C-N a partial double bond character
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PROTEIN
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1° = sequence of a.a2° = local structure of neighboring a.a due to H-bondingα helix (keratin) β pleated sheet3°= 3D shape of protein due to hydrophilic/Hydrophobic interaction between R groups of a.a Disulfide bond → loops in protein chain Proline can’t fit into α helix → kink in chain Fibrous = sheets/long strands (collagen) Globulous = spherical (myoglobin> 4° = Arrangement of polypeptide subunit (Hemoglobin = 4 subunits)
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CONJUGATED PROTEINS
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Attached to prosthetic group (organic molecules or metal)
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DENATURIZATION
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Loss of 3D (3° structure → random coil state- disruption of INTERmolecular forces)
Due to detergent, change in pH, Temp, [solute]
Some protein can REnature
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EPIMERS
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Different in configuration at ONLY ONE carbon
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ANOMERS
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Differ in conjugation ONLY at the newly formed chiral center
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KETOSE
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Fructose
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ALDOSE
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Glucose
Galactose
Manose
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MUTAROTATION
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Allow α → α + β
or
β → α + β
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GLYCOSIDIC REACTIONS
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[image]Hemiacetal + Alcohol → Acetal Both α and β linkages are formed
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DISACCHARIDES
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Due to glycosidic linkages between C1-C4, C1-C6 or C1-C2
α or β
In body, enzymes ar eneeded to ensure the right glysidic bond is form.
Without enzymes, reactions are NONspecific and never stopping at disaccharide level
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GLUCOSE POLYSACCHARIDES
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Cellulose = β 1,4 Structure components of PLANT
Starch = α 1,4(some 1,6) Stored energy in PLANT
Glycogen= α 1,4 (some 1,6) Stored energy in ANIMAL
* Cellulose can’t be ingested by human
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IR
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Measure vibrations- Stretching, bending and rotation of a molecule- Stretching and bending can be Symmetric or AsymmetricLight → excited state (3500-300 cm-1
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FINGER PRINT
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400-1500 cm-1Characteristic of a molecule, frequently used to identify a substance
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SYMMETRIC STRETCH
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DO NOT show in IR because no net change in dipole moment
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IR ALKANES
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C-H 2800-3000
C-H 1200
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IR ALKENES
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=C-H 3080-3140
C=C 1645
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IR ALKYNES
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C ≡ C 2200
≡ C-H 3300
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IR Aromatic
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C-H 2900-3100
C-C 1475-1625
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IR ALCOHOL
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O-H (broad) 3100-3500
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IR ETHER
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C-O 1050-1150
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IR ALDEHYDE
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(0)C-H 2700-2900
C=O 1725-1750
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IR ACIDS
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C=O 1700-1750
O-H (broad) 2900-3300
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IR KETONES
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C=0(Sharp) 1700-1750
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IR AMINES
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N-H (Sharp) 3100-3500
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C-NMR
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Larger sample
NO coupling except between carbons and hydrogens directly attached to them
Spin decoupling: record without coupling of adjacent protons
Show: # of C’s with relative chemical environment
# of H’s (spin coupling NMR’s)
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UV
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Pass light, observe Absorbance
Beer Law
A= ebc
Most useful for studying compound wit double bonds and heteroatoms with lone pairs
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MASS SPECTROSCOPY
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Pass light, measure mass of particle
Sample is ruined afterward
1. cation radical decompose → mass/charge ratio
2. base peak = tallest peak (% of 100)
3. Molecular ion peak = highest m/e peak
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CARBOXYLIC ACID
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– suffix – ate1. Polar2. Able to form H-bond3. Greater bp than alcohol4. Acidity is due to resonance stabilization of conjugate base 5. β H’s are extremely acidic because its loss → stable carbanion6. Acidity can be enhanced by adding EN gr. or other potential resonance structre
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NITRILES
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aka CYANIDEhas CN- group = good [NUC-] for 1°, 2° SN2 reactions
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SYNTHESIS OF CARBOXYLIC ACID
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1. Oxidation of alcohol (using KMNO4)2. Ginard reagents (1 additional C)3° alkyl halide → carboxylic acid3. Hydrolysis of nitriles (1 additional C)CH3Cl → CH3CN→ CH3COOH + NH4
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SOAP FORMATION
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RCOOH + NaOH → ROO-Na+ (soap) + H2OSoap tends to rearrange into micelles (like mb) with polar head outward and nonpolar tails inward to dissolve greaseMicelle (as a whole) is soluable in water because of polar shell
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ORDER OF REACTIVITY
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Acyl halide > anhydrides> Esters> Amindes
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ANHYDRIDES
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= without water
2 ACID → condensation→ Anhydrides
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AMIDES
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[image]Form from 1° or 2° amine
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HOFFMANN REARRANGEMENT
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Amides → 1° with loss of carbon[image]
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ESTERS
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ACID + ALCOHOL → ESTER[image]
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SAPONIFICATION
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Fats( triacylglycerols) are hydrolyzed under basic condition
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AMINES[image]
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prefix amino-Boiling point is lower than alcohol because N has lower EN3° amine can’t H-bond thus have lower bp than 1° and 2°sp3 – able to undergoes nitrogen inversion (low Ea – 6 kcal/mol)* optically active if inversion is hinderedWeak Acid
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DRUGS WITH AMINES GROUP
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Nitroglycerine relaxants: relieve coronary arteries spasms for chest pain Nitrous oxide relaxants : dental anesthetic
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GABRIEL SYNTHESIS
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Primary Akyl halide → 1° amine (no side products)[image]
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EXHAUSTIVE METHYLATION
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aka Hoffmann Elimination [image]
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MICHAEL ADDITION
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[image]
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ALDOL CONDENSATION
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[image]
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STRUCTURAL ISOMERS
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Most Different
Different in MOLECULAR FOMRMULA
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CHIRALITY
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Chiral = nonsuperimposable
Achiral – super imposable
*rotation doesn’t change chirality
Differences in chirality can produce enantiomers (nonsuperimposed mirror images) or diastereomers ( diff, in chirality but not mirror images)
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GEOMETRY ISOMERS
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Different around DOUBLE BOND
cis vs. trans
Different in physicial properties (mp or bp)
Similar Reactivity
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ENANTIOMERS
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Chiral moleculesIdentical properties but different in optical activity
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MESO COMPOUND
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Chiral but not optical active because of internal plane of symmetry
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OPTICAL ACTIVITY
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Ability to rotate plane in polarized light
+ dextrorotary – R
– Levorotary – L
α (angle of rotation) – observed oration/ [] g/ml x leight dm
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RACEMIC MIXTURE
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Mixture of equal concentration of + and = enantiomers
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DIASTERIOMERS
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2+ chiral centers

Different in chirality but not mirror images

R,S vs. R,R

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CONFORMATION ISOMERS
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Different ONLY by rotation about 1 or more single bond“gauche” vs ” eclipse”
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ALKANES
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↑ chain length → ↑ bp, mp , density
→ ↓ bp, mp, density
Stablity of carbocation and free radical
3° > 2° > 1° > methyl
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PYROLYSIS
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Molecules is broken down by heat
aka: craking → radicals
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NUCLEOPHILES
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1. Basicity
RO-> HO->RCO2-> ROH> H2O
2. Size and Polarity
– Protic solution (able to H-bonding)
CN-> I-> RO-> HO-> Br-> Cl-> F-> H2O
– Aprotic solution
F-> Cl> Br> I
3. Larger atom = better Nuc
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LEAVING GROUP
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Weak acid = best
I> Br > Cl > F
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SN1
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Rate is dependant on the formation of carbocationCondition is chosen so that the second step is IRREVERSIBLErate = k[S]
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ACCELERATE FORMATION OF CARBOCATION
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1. Structural factors: more subs → more stable carbocation → better SN12. Solvent effect: Polar Solvent (better at surrounding and isolating ions) Protic polar is best (solvation stabilize intermediate)3. LG : weak bases dissociate more easily
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INTERMEDIATE
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Well defined species with a finite lifetime
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TRANSITION STATE
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Theoretical structure used to define mechanism
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SN1 vs SN2
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SN1
2 steps
Favored : polar PROTIC solvent
3>2>1
racemic products (loss of optical activity)
Favored the use of bulky [Nuc]

SN2
1 step – concerted
Favor: polar APROTIC solvent
1>2>3
rate = k[RX][Nuc]
Optically active / inverted products

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