Organic Chemistry Exam 1 Cheat Sheet

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Reactions, reagents and mechanisms included for Exam 1

Chemistry Organic Alkene Mechanisms Alkane Alkyne

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PRs

Known Reaction Pathways

^{Reaction Type}	^Name	^{Functional Outcome}	^{Key Reagents}
Oxidation
	Alcohol Oxidation	1° OH → Aldehyde/Carboxylic acid 2° OH → Ketone	PCC (mild), CrO₃/H₂SO₄ (strong), KMnO₄
	Ozonolysis	Cleaves Alkenes → Aldehydes/Ketones	2. O₃ 2. (CH₃)₂S or Zn/H₂O
	Benzylic Oxidation	Benzylic carbon → Carboxylic acid	KMnO₄, heat
Reduction
	Catalytic Hydrogenation	Alkene/Alkyne → Alkane	H₂, Pt/Pd/Ni
	Poisioned Hydrogenation	Alkyne → Cis-Alkene	H₂, Lindlar's Catalyst
	Dissolving Metal Reduction	Alkyne → Trans-Alkene	Na, NH₃
	Carbonyl Reduction	Aldehyde → 1° OH Ketone → 2° OH	NaBH₄ or LiAlH₄
Addition
	Hydrohalogenation	Markovnikov addition of X	HX
	Hydration	Markovnikov addition of OH	H₂O, H₁SO₄
	Hydroboration-Oxidation	Anti-Markovnikov addition of OH	1. BH₃, THF 2. H₂O₂, NaOH
	Halogenation	Anti-Addition of X-X	X₂
	Hydrogenation	Syn-Addition of H-H	H₂, Pd/Pt
Cyclization
	Epoxidation	Alkene → Epoxide	mCPBA
	Halohdrin Cyclization	Halohydrin → Epoxide	X₂, H₂O to NaOH
Substitution
	S_N1	Forms Carbocation; Racemic	Weak nucleophile, Polar protic solvent
	S_N2	Inversion of Configuration	Strong nucleophile, polar aprotic solvent
Elimination
	E1	Carbocation intermediate, Zaitsev's Rule	Weak base, polar protic solvent
	E2	Concerted, anti-periplanar	Strong base (NaOEt, NaOMe, tBuOK)
C-C Bond Formation
	Grignard Reaction	Adds R group to carbonyl	RMgX
Protecting Groups
	Alcohol Protection	ROH → ROTMS	TMSCl, pyridine
	Alcohol Deprotection	ROTMS → ROH	TBAF

Starting Material → Alkane

^Name	^Reagents	^{Regiochemistry}	^{Stereochemistry}	^{Functional Outcome}	^Mechanism
Radical Halogenation	X₂, hv or heat	Tertiary > Secondary > Primary Selectivity	Racemic (if chiral)	Alkyl Halide	*
Allylic Bromination	NBS, hv (or heat), CCl₄	Selective for allylic position ^{(next to a C=C bond)}	Mixture if allylic radical is symmetric	Allylic Bromide	*
Benzylic Bromination	NBS, hv (or heat), CCl₄	Selective for *benzylic	None, unless chiral center formed	Benzylic Bromide	*
Benzylic Oxidation	1. KMnO₄ or Na₂Cr₂O₇ 2. H₂SO₄, heat	Oxidation occurs only at the benzylic carbon	None	Carboxylic acid

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	Alcohol
Hydroboration-Oxidation	1. BH₃, THF 2. H₂O, NaOH	Anti-Markovnikov	Syn	Alcohol
Halogenation (X₂ Addition)	X₂ ^{(Br₂, Cl₂)}	None	Anti	Vicinal Dihalide
Halohydrin Formation	X₂, H₂O	Markovnikov	Anti	Halohydrin
Hydrogenation	H₂, Pt/Pd/Ni	None	Syn	Alkane
Dihydroxylation (Syn)	OsO₄ or KMnO₄ (cold, dilute), NaHSO₃	None	Syn	Vicinal Diol
Dihydroxylation (Anti)	1. mCPBA 2. H₃O⁺	None	Anti	Vicinal Diol
Ozonlysis	1. O₃ 2. Me₂S (DMS) or Zn/H₂O	None	None	Aldehyde/Ketone

Starting Material → Alkyne

^Name	^Reagents	^{Regiochemistry}	^{Stereochemistry}	^{Functional Outcome}	^Mechanism
Hydrohalogenation (HX Addition)	HX ^{(HCl, HBr, HI) (1 or 2 equivalents)}	Markovnikov	None	Alkyl Dihalide	*
Halogenation (H₂ Addition)	X₂ ^{(Br₂, Cl₂) (1 or 2 equivalents)}	None	Anti	Vicinal Tetrahalide	*
Acid-Catalyzed Hydration	HgSO₄; H₂SO₄, H₂O	Markovnikov	None	Enol → Ketone ^{(tautomerization)}	*
Hydroboration-Oxidation	1. 9-BBN or BH₃, THF 2. H₂O₂, NaOH	Anti-Markovnikov	Syn	Enol → Aldehyde ^{(tautomerization)}
Hydrogenation	H₂, Pt/Pd/Ni	None	Syn	Alkane
Poisioned Hydrogenation	H₂, Lindlar's catalyst	None	Syn	Cis-alkan
Dissolving Metal Reduction	Na⁰ or Li⁰; NH₃	None	Anti	Trans-alkene
Ozonolysis	1. O₃ 2. H₂O	None	None	Carboxylic acid (CO₂ if terminal)

Starting Material → Alcohol

^Name	^Reagents	^{Regiochemistry}	^{Stereochemistry}	^{Functional Outcome}	^Mechanism
Oxidation (^{Primary → Aldehyde)}	PCC/PDC, CH₂Cl₂ or (COCl₂), DMSO; Et₃N, CH₂Cl₂ (-78 to 22°C)	N/A	N/A	Aldehyde	*
Oxidation ^{(Primary → Carboxylic Acid)}	1. Na₂Cr₂O₇ 2. H₂SO₄, H₂O	N/A	N/A	Carboxylic acid	*
Williamson Ether Synthesis	1. NaH (or KH), 15-Crown-5 (or 18-C-6) 2. RX	N/A	N/A	Ether	*
Protecting Alcohol	TMSCl in Et₃N (or Pyridine)	None	Retained	Converts -OH to -OTMS
Deprotecting Alcohols	TBAF or H₃O⁺	Removes silly group from OH	Retained	Restores -OH
Intramolecular Williamson Ether Synthesis	1. X₂ ^{(Br₂ or Cl₂)}, H₂O 2. NaOH ^{(or NaH, NaNH₂, KOH)}	1. Markovnivkov 2. None	1. Anti 2. Inversion	Converts halohydrin → Epoxide

^{Secondary → Ketone} PCC/PDC, Swern, or Jones Oxidation

Starting Material → Epoxide

^Name	^Reagents	^{Regiochemistry}	^{Stereochemistry}	^{Functional Outcome}	^Mechanism
Acidic Opening	HX H₂O, H₂SO₄ ROH (or RSH), H₂SO₄	More substituted carbon attack	Anti	Vicinal Diol	*
Basic Opening	1. NaCN (or NaSR, RMgBr, LiAlH₄, NaN₃ 2. H₂O (or NaOH)	Less substituted carbon attack	Anti	Vicinal Diol	*

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)}

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

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

Synthesis

1. Identify Target Molecule	Determine functional groups & backbone	What is the most complex feature?
2. Work Backward	Identify possible precursors	What reactions introduce those functional groups?
3. Select Key Transformations	Use known reaction pathways	Oxidation, Reduction, Substitution, Addition, Elimination
4. Consider Stereo- & Regio- Chemistry	Identify selective pathways	Anti vs Syn, Markovnikov vs Anti-Markovnikov
5. Check for Side Reactions	Minimize unwanted byproducts	Use protecting groups if necessary
6. Verify Pathway	Double check feasibility & efficiency	Are reagents compatible? Do steps make sense?

Starting Material → Ether

^Name	^Reagents	^{Functional Outcome}
Acidic Cleavage	xsHX ^{(HBr or HI)} in heat	Alkyl Halide

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

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

Formation of Grignard Reagent

Mg(0); THF (or Et₂O)

Forms Gignard Reagent (RMgX)
Can be used to form C-C bonds

Substitution Reactions

S_N1 ^{(Unimolecular)}		S_N2 ^{(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)}

Nomenclature

^{Functional Group}	^{Suffix (Highest Priority)}	^{Prefix (Lowest Priority)}
Alcohol (-OH)	-ol	hydroxy-
Alkyne	-yne	alkynyl-
Ether (R-O-R')	uses parent name	alkoxy-
Epoxide	oxirane (cyclic naming)	epoxy-

Key Naming Rules →

Number the longest chain to give OH the lowest number

Number to give triple bond the lowest number, unless -OH is present

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