Organic Chemistry Reviewer

Organic Chemistry 1. Introduction: Vital Force Theory – Only living materials can produce organic compounds Friedrich Wohler – Synthesized urea (organic) from ammonium cyanate (inorganic) Valence - Combining ability of organic compound based on the fixed number of bonds Catenation - Ability of carbon to bond with other carbons Ionic Bond – Gaining or Losing electron Covalent Bond – Sharing of electrons Formal charge = Group number – ½ shared e - number of unshared e Resonance – Molecules represented in different Lewis structure that differ in the positions of e Bond length – Optimum distance between the nuclei of two bonded atoms Bond energy – Energy required breaking the bonding between a pair of atoms Bond angle – Angle between two adjacent bonds Hybridization – Mixing of two or more atomic orbitals to give the same number of new orbitals Constitutional Isomers – same molecular formula but different connectivity of atoms Higher boiling point: 1. Look for dipole-dipole interaction (higher) 2. Look for hydrogen bonds (higher) 3. Look for higher molecular weight (higher) 4. Look for branching (lower) Functional Group:

2. Acids and Bases: Bronsted Lowry Acids - proton donor Bronsted Lowry Base – proton acceptor Weaker Acids are always favored in equilibrium reaction Acidity Prediction: (ARIO)

Lewis Acid – electron acceptor Lewis Base – electron donor 3. Stereoisomerism: Stereoisomers – same connectivity but differ in spatial arrangement Enantiomer – mirror images but not superimposable Chiral center – four different bonded atoms Cahn-Ingold-Prelog System – R (to the Right) and S (to the left) enantiomer Optical activity – ability of the molecule to rotate the plane of a plane polarized light Dextrorotatory – positive rotation Levorotatory – negative rotation Racemic mixture – equal amount of enantiomers in solution

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n

No. of stereoisomers = 2 , n= chirality centers Mesocompound – has multiple chirality centers but still achiral due to symmetry 4. General Organic Reactions Hammond Postulate – Transition state resemble reactant if exergonic(-ΔG) or product if endergonic (+ΔG) Tertiary carbocation are more stable that secondary and primary because of hyperconjugation Electrophiles are reagents which in their reactions seek the extra electrons that will give them stability Nucleophiles are reagents that seek a proton or some other positive center Substitution Reaction:

Concerted Process – nucleophilic attack and loss of leaving group occurs simultaneously nd SN2 is a concerted process and 2 order kinetics st SN1 is a stepwise process and 1 order kinetics Polar protic solvent favors SN1 Polar aprotic solvent favors SN2

5. Alkanes and Cycloalkanes - also called paraffins or unsaturated hydrocarbons, sp3 hybridized At room temp: C1-C4 – gases C5-C17 – liquids C18- Cn – solids Chair conformation – most stable cyclohexane conformation Others: half chair, boat, twist boat Primary reactions: radical reactions – reaction with light and heat forming radicals 6. Alkenes - also called olefins, sp2 hybridized Bredt’s rule - eight-membered ring is the smallest size ring that can accommodate a trans double bond in a bridged bicyclic compound Trans is more stable than cis Elimination Reactions:

E2 (Elimination Bimolecular) -One step mechanism, similar to SN2, Zaitsev is favored E1 (Elimination Unimolecular) -Two-step mechanism, similar to SN1, Zaitsev is always favored Zaitsev product – double bond on the more substituted side Hoffmann product – double bond on the less substituted side If the base is bulky , Hoffmann product is favored

Addition Reactions:

7. Alkynes - has triple bonds, sp hybridized - One sigma bond and two pi bonds Addition Reactions:

8. Aromatic Compounds - benzene derivatives - planar - cyclic - follows Huckel’s Rule: 4n+2= pi electron, n is a whole number Bond order of benzene is 1.5 Annulenes – compounds containing single ring that contains fully conjugated pi electrons Benzene is also known as [6]Annulene Ortho-Para Director: Strongly activating – N in Amine, O in OH Moderately activating – N attached to carbonyl, O attached to R Weakly Activating – R group, Weakly Deactivating - Halogens Meta Directors: Moderately Deactivating – Cyanate, sulfonate, carboxyl, carbonyl + Strongly Deactivating – Nitro, -NR3 , -CX3,

Aromatic Substitution Reactions:

Other Aromatic Reactions:

9. Alcohols, Thiols, Sulfides and Ethers Alcohols – has hydroxyl (-OH) functional group Ethers – has alkoxy (-OR) functional group Thiols – has marcapto (-SH) group Sulfides – has -S-S- group Boiling Point: Alcohol > Ethers Grignard Reagents- carbon nucleophiles (usually with Mg) that can attack electrophiles Oxirane- three membered ringed ethers Epoxide- substituted oxirane Reactions: Alcohols and Phenols:

Ethers, Thiols, and Sulfides

10. Aldehydes and Ketones - contains carbonyl group - soluble in water Reactions:

11. Carboxylic Acids and Derivatives - contains Carboxyl group (-COOH) Gilman Reagent – lithium aluminum dialkyl cuprate Fischer Esterification – carboxylic acids are converted to esters by reacting with alcohols with acid catalyst Saponification – Hydrolysis of esters in basic condition to form carboxylic acids Reactions:

12. Amines - contains amino functional group (-NH2) o

o

o

Basicity: 2 > 1 >3 > Amine Reactions: