Fundamental Organic Chemistry

Material Covered in CHEM241 Organic Chemistry I

Instructor: Jean-Claude Bradley at Drexel University

Type of content: vodcast, podcast, PDF, transcript

Electronic Configuration

Pauli Exclusion Principle: -Only 2 electrons per orbital (opposite spin) -Electrons like to be unpaired if possible

Types of bonds: covalent and ionic

Valence Periodic Table

Solving Lewis Structures

Resonance Hybrids and curved arrow formalism

Lewis, skeletal and condensed structural formulae

Molecular and empirical formulae

Acids and Bases Lowry-Bronsted Acid: PROTONS (H+) Lewis Base: Lone pair of electrons

Molecular Orbitals and Functional Groups

Atomic and Molecular Orbitals: the geometry of electron probability distribution s, p,

Hybrid orbitals sp, sp2, sp3

2 groups of electrons

linear sp

3 groups of electrons

trigonal planar (120o) sp2

4 groups of electrons

tetrahedral (109o)

sp3

Pi and Sigma bonds-the ethylene example

Rigidity of Double Bonds

Isomerism- structural isomers and stereoisomers (geometrical isomers)

Bond polarity and dipole moment Molecule Polarity: sum of dipole moments

Intermolecular Forces Dipole-Dipole interaction (e.g. CH3COCH3 acetone) Hydrogen bonding (e.g. HF, H2O) NEED F,O or N and H van der Waals forces (e.g. He, CH4)

Structure and physical properties Melting point (higher for stronger intermolecular forces) Boiling point (higher for stronger intermolecular forces) Solubility (like dissolves like)

Alkanes, Alkenes, Alkynes, Alcohols, Ethers, Aldehydes and Ketones, Carboxylic Acids Acid Chlorides, Esters, Amides, Amines

Hydrocarbons

Alkanes have a general formula of C_nH_n+2 (where n is a variable whole number). Alkanes have single carbon to carbon bonds and thus are saturated hydrocarbons and are the least reactive of all hydrocarbons. The boiling tempreture of alkanes increases as the number of carbon atoms increase. The first ten names of the first 10 alkanes are: Let’s count to 10: methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane

Nomenclature: isopropyl, isobutyl, n-butyl, sec-butyl, t-butyl,

Primary, Secondary, Tertiary, Quaternary centers

Reactions of Alkanes 1) combustion 2) cracking 3) halogenation

Conformations of ethane, propane, butane Newman projections Steric Hindrance

Cycloalkanes Cis-trans isomerism of cycloalkanes Chair and boat configurations of cyclohexane Axial and Equatorial positions

Halogenation of alkanes

Bromination of methane Bond Dissociation Energy Homolysis and Heterolysis Transistion State (Predicting the geometry using the Hammond Postulate) Rate-limiting step

Bromination of propane Chlorination of propane (loss of selectivity) Free-radical stabilities

Carbocations/Carbanions

Chirality

R and S configurations Optical activity: dextrorotatory and levorotatory Specific rotation Racemic mixture Fisher Projection Diastereomers and Enantiomers Reactions involving chiral centers

Alkyl halides

Nomenclature

Preparation

1) Free-radical halogenation 2) Hydrohalogenation of alkenes 3) From alcohols 4) From other alkyl halides

Reactions 1) elimination 2) nuleophilic substitution

SN1 and SN2 reactions Solvent effects on nucleophilicity Walden inversion Rearrangements in SN1 reactions (hydride and methyl shifts of carbocations) E-1 and E-2 Reactions Satyzeff Rule

Alkenes

Alkenes have the general formula C_nH_2n (where n is a variable whole number). Alkenes contain a double carbon to carbon bond, thus making them more reactive and unsaturated. Alkenes undergo addition reactions in the presence of eg Bromine, where the double carbon to carbon bond is broken the molecule becomes an alkane. Alkenes are non-polar molecules, insoluble in water and the first four alkenes are gases, the others liquids at room tempreture.

   Alkenes are named similar to alkanes except the ene is added onto the end of the name eg a alkene with the formula C₂H₄ is called ethene.

Unsaturation Nomenclature Z and E, cis and trans 8 Carbon Rule Preparation 1) Dehydrohalogenation 2) Dehalogenation 3) Dehydration of alcohols 4) Catalytic cracking of alkanes 5) Wittig synthesis

Reactions

1) elimination

2) nuleophilic substitutionSN1 and SN2 reactions

Solvent effects on nucleophilicity

Walden inversion

Rearrangements in SN1 reactions (hydride and methyl shifts of carbocations)

E-1 and E-2 Reactions

Saytzeff's Rule

Alkenes

Unsaturation

Nomenclature

Z and E, cis and trans

8 Carbon Rule

Preparation

1) Dehydrohalogenation

2) Dehalogenation

3) Dehydration of alcohols

4) Catalytic cracking of alkanes

5) Wittig synthesis

Reactions:

Electrophilic addition Markovnikov’s rule Anti-Markovnikov addition Hydration of Alkenes Anti-Markovnikov hydration by hydroboration Catalytic hydrogenation Simmons-Smith reaction Halogenation Hydrohalogenation Epoxidation Permanganate hydroxylation (cold, dilute) Permanganate (warm, concentrated) Ozonolysis OsO4 Carbenes

Alkynes

Nomenclature

Acidity of alkynes

Preparation

From dihalides From acetylides

Reactions

Hydrogenation Partial hydrogenation (Lindlar’s catalyst) Halogenation Markovnikov addition of HBr Hydration to ketones Permanganate (cold, dilute) Permanganate (warm, concentrated)

Isomers

molecules such as many larger hydrocarbons can have the same molecular formula but more than one structural formula, these are known as isomers. For example the molecular formula C₄H₁₀ has two isomers. One structual isomer forms butane while the other molecule can be rearranged to form methylpropane. The larger the molecule the more isomers that can be formed.