Cheatography
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Reactions, reagents and mechanisms included for Exam 1
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Starting Material → Alkene
Name |
|
Reagents |
Regiochemistry |
Stereochemistry |
Functional Outcome |
Mechanism |
Hydrohalogenation
(HX Addition) |
|
HX (HCl, HBr, HI) |
Markovnikov
(X attaches to more substituted carbon) |
Racemic |
Alkyl Halide |
* |
Hydrodrohalogenation
(HX Addition with Peroxide) |
|
HBr, ROOR (peroxide) |
Anti-Markovnikov
(X attaches to less substituted carbon) |
Racemic |
Aklyl Halide |
* |
Acid-Catalyzed Hydration |
|
H2SO4, H2O (or H3O+) |
Markovnikov |
Racemic |
Alcohol |
Oxymercuration-Demurcuration |
|
1. Hg(OAc)2, H2O
2. NaBH4 |
Markovnikov |
Anti-Addition |
Alcohol |
Hydroboration-Oxidation |
|
1. BH3, THF
2. H2O, NaOH |
Anti-Markovnikov |
Syn-Addition |
Alcohol |
Halogenation
(X2 Addition) |
|
X2 (Br2, Cl2) |
None |
Anti-Addition |
Vicinal Dihalide |
Halohydrin Formation |
|
X2, H2O |
Markovnikov |
Anti-Addition |
Halohydrin |
Hydrogenation |
|
H2, Pt/Pd/Ni |
None |
Syn-Addition |
Alkane |
Dihydroxylation (Syn) |
|
OsO4 or KMnO4 (cold, dilute), NaHSO3 |
None |
Syn-Addition |
Vicinal Diol |
Dihydroxylation (Anti) |
|
1. mCPBA
2. H3O+ |
None |
Anti-Additino |
Vicinal Diol |
Ozonlysis |
|
1. O3
2. Me2S (DMS) or Zn/H2O |
None |
None |
Aldehyde/Ketone |
|
Ranking Radical Stability
1. Benzylic/Allylic Radicals [MOST STABLE] |
2. Tertiary (3°) Radicals |
3. Secondary (2°) Radicals |
4. Primary (1°) Radicals |
5. Methyl Radicals |
Key Factors Affecting Stability:
Resonance Stabilization (Allylic & Benzylic > Non-resonance stablized)
Hyperconjugation
(More alkyl groups donate electron density)
Inductive Effects
(Electron-withdrawing groups destabilize)
Number of Unique Products
NBS
(Allylic Bromination) |
|
Cl₂/hv
(Radical Chlorination) |
Selective
Only abstracts the allylic hydrogen |
|
Less selective
attacks all possible C-H bonds |
Favors one major product due to resonance stabilization |
|
More radical products due to no preference |
Highly Selective → Major product at most stable radical site |
|
Non-selective → Multiple products |
Arrow Pushing in Radical Reactions
Fishhook Arrows → movement of 1 electron |
Initiation → arrows depict homolytic cleavage |
Propagation → 1 radical reacts to form another |
Termination → 2 radicals combine to form a stable molecule |
Terms to Know
Markovnikov's Rule → addition reactions proton added to the carbon with the most hydrogen atoms attached |
Geminal → 2 atoms bonded to the same side of the carbon |
Anti-Markovnivkov's Rule → addition reactions proton added to the carbon with the least hydrogen atoms attached |
Vicinal → 2 atoms bonded to same carbon |
Zaitsev's Rule → elimination reaction, major product is the more stable alkene with the highly substituted double bond |
Syn-Addition → added to same side of compound |
E/Z System → Prioritize the 2 groups attached to each carbon relative to one another.
Higher priority groups are:
cis/same side → Z
trans/opposite sides → E |
Anti-Addition → added to different sides of compounds |
|
|
Oxidation State of Carbons
C-H bond → carbon gains -1 per hydrogen |
C-C bond → no change (0) |
C-X bond → carbon loses +1 per electronegative atom |
The oxidation state of a carbon atom depends on its bonds to atoms of different electronegativities
NMR
1H NMR
|
|
13C NMR
|
Chemical Shift Trends |
|
Chemical Shift Trends |
0-2 ppm → Alkane |
|
0-50 ppm → Alkane |
2-3 ppm → Allylic, benzylic, alkynyl |
|
50-100 ppm → Alcohol, ether, alkynes |
4-6 ppm → Alkene |
|
100-150 ppm → Aromatic, alkene |
6-8 ppm → Aromatic |
|
150-200 ppm Carbonyl (ketone, aldehyde, carboxylic acid) |
9-10 ppm →
Aldehyde |
10-12 ppm →
Carboxylic acid (broad) |
Splitting Patterns (n+1 rule)
Singlet → no adjacent protons
Doublet → 1 adjacent proton
Triplet → 2 adjacent protons
IR Spectroscopy
Key Peaks |
O-H (Alcohol) → 3200-3600 cm-1 (broad) |
C-H (Alkanes) → 2800-3000 cm-1 |
C=O (Carbonyls) → ~1700 cm-1 |
C=C (Alkene) → ~1650 cm-1 |
C≡C, C≡N → ~2100-2200 cm-1 |
Starting Material → Alkyne
|
|
Substitution Reactions
SN1 (Unimolecular) |
|
SN2 (Bimolecular) |
Mechanism → Two-step; carbocation formation, nucleophilic attack |
|
Mechanism → One-step; backside attack |
Rate → Dependent only on substrate
rate=k[R-X] |
|
Rate → Dependent on both substrate & nucleophile
rate=k[R-X][Nu-] |
Stereochemistry → Racemic mixture |
|
Stereochemistry → Inversion of configuration |
Preferred Conditions → Weak nucleophile, polar protic solvent |
|
Preferred Conditions → Strong nucleophile, polar aprotic solvent |
Tertiary > Secondary > Primary |
|
Methyl > Primary > Secondary > Tertiary |
Elimination Reactions
E1 (Unimolecular) |
|
E2 (Bimolecular) |
Mechanism → Two-step; carbocation intermediate, base deprotonates |
|
Mechanism → One-step; concerted β-H abstraction |
Rate → Dependent only on substrate |
|
Rate → Dependent on both substrate and base |
Regiochemistry → Zaitsev's Rule
(more substituted alkene favored) |
|
Regiochemistry → Zaitsev's Rule
(unless bulky base → Hofmann product) |
Stereochemistry → Forms most stable alkene |
|
Stereochemistry → Anti-periplanar elimination |
Preferred Conditions → Weak base, polar protic solvent |
|
Preferred Conditions → Strong base required |
Tertiary > Secondary > Primary |
|
Primary > Secondary > Tertiary
(as long as β-H is anti-periplanar) |
|
