Review Organic Chemistry Chemistry 203

Goal of atoms Filled valence level Noble gases (Stable) Bonding 1.Ionic bonds 2. Covalent bonds

Ionic bonds result from the transfer of electrons from one element to another. Bonding Metals: lose 1, 2 or 3 e - Cation (Y + ) Nonmetals: gain 1, 2 or 3 e - Anion (X - ) Ions Cation (Y + ): Na + Li + Ca 2+ Al 3+ Anion (X - ): Cl - F - O 2-

Bonding Ionic bonds Metal-Nonmetal Na: 1s 2 2s 2 2p 6 3s 1 Cl: 1s 2 2s 2 2p 6 3s 2 3p 5 Anion Cation Na + : 1s 2 2s 2 2p 6 Cl - : 1s 2 2s 2 2p 6 3s 2 3p 6 Ne Ar

Bonding Covalent bonds result from the sharing of electrons between two atoms. Nonmetal-Nonmetal Metalloid-Nonmetal Sharing of valence electrons

Lewis Dot Structure H He Li C Al NCl H H Or H H Cl H Lewis Structure H Cl Cl: 1s 2 2s 2 2p 6 3s 2 3p 5 H: 1s 1 He: 1s 2 Ar: 1s 2 2s 2 2p 6 3s 2 3p 6

Intermolecular Forces London dispersion forces Dipole-dipole interaction Hydrogen bonding Ionic bonds Covalent bonds < Intramolecular (Bonding) Forces Intermolecular Forces

London dispersion forces Attractive forces between all molecules Only forces between nonpolar covalent molecules 2+ No Polarity Original Temporary Dipole δ-δ He Original Temporary Dipole Induced Temporary Dipole __ _ _ He 2+ __ _ _ δ-δ+ He _ _ 2+ δ-δ+ He _ _ 2+

London dispersion forces T ↓ Kinetic energy ↓ Move slower Attractive forces become more important liquid He:T = -240°C (1 atm) → liquid

Dipole-Dipole Interactions Attractive forces between two polar molecules stronger than London dispersion forces boiling point ↑

Hydrogen bonding Between H bonded to O, N, or F (high electronegativity) → δ+ and a nearby O, N, or F → δ- Stronger than dipole-dipole interactions & London dispersion forces H2OH2O

Hydrogen bonding CH 3 COOH Acetic acid δ- δ+

H-bonding in our body DNA H-bond Protein (α-helix) H-bond

Intermolecular Forces

Solubility polar dissolves polar Nonpolar dissolves nonpolar like dissolves like octaneCCl 4 octane + CCl 4

Organic Compounds

Hydrocarbons Large family of organic compounds Composed of only carbon and hydrogen Saturated hydrocarbons Alkanes Unsaturated hydrocarbons Alkenes, Alkynes & Aromatics C - C C = CC

Alkanes

Chemical reactions of Alkanes Low reactivity 1- Combustion: Alkanes react with oxygen. CO 2, H 2 O, and energy are produced. Alkane + O 2 CO 2 + H 2 O + heat CH 4 + 2O 2 CO 2 + 2H 2 O + energy

2- Halogenation: Alkanes react with Halogens. CH 4 + Cl 2 CH 3 Cl + HCl Heat or light Chemical reactions of Alkanes Low reactivity CH 3 Cl+ Cl 2 CH 2 Cl 2 + HCl CH 2 Cl 2 + Cl 2 CHCl 3 + HCl CHCl 3 + Cl 2 CCl 4 + HCl Heat or light Chloromethane Dichloromethane Trichloromethane Tetrachloromethane

Alkenes & Alkyens

Chemical properties of Alkenes & Alkynes More reactive than Alkanes Addition of Hydrogen (Hydrogenation-Reduction) Addition of Hydrogen Halides (Hydrohalogenation) Addition of water (Hydration) Addition of Bromine & Chlorine (Halogenation)

Chemical properties of Alkenes & Alkynes Addition reactions Exothermic reactions –C = C – – C – C– Products are more stable (have the lower energy).

A hydrogen atom adds to each carbon atom of a double bond. A catalyst such as platinum or palladium is used (Transition metals). H H H H │ │ Pt │ │ H–C=C–H + H 2 H– C – C– H │ │ H H Ethene Ethane 1. Hydrogenation (Reduction): Pt More reactive than Alkanes Chemical properties of Alkenes & Alkynes

A hydrogen halide (HCl, HBr, or HI) adds to alkene to give haloalkane. H H H H │ │ │ │ H–C=C–H + HCl H– C – C– H │ │ H Cl Ethene Chloroethane 2. Hydrohalogenation: More reactive than Alkanes Chemical properties of Alkenes & Alkynes

2. Hydrohalogenation: - reaction is regioselective. - Markovnikov’s rule: H adds to double bonded carbon that has the greater number of H and halogen adds to the other carbon. The rich get richer! Chemical properties of Alkenes & Alkynes

3. Hydration (addition of water): Water adds to C=C to give an alcohol. Acid catalyst (concentrated sulfuric acid). A regioselective reaction (Markovnikov’s rule). Chemical properties of Alkenes & Alkynes

A halogen atom adds to each carbon atom of a double bond. Usually by using an inert solvent like CH 2 Cl 2. H H H H │ │ │ │ CH 3 –C=C–CH 3 + Cl 2 CH 3 – C – C– CH 3 │ │ Cl Cl 2-Butene 2,3-dichlorobutane 4. Halogenation: CH 2 Cl 2 More reactives than Alkanes Chemical properties of Alkenes & Alkynes

Aromatic Hydrocarbons

Halogenation Nitration Sulfonation No addition reactions (almost unreactive) Chemical properties of aromatics Aromatic substitution: One of the H atoms is repalecd by some groups.

Chemical properties of benzene 1. Halogenation: Cl and Br react rapidly with benzene in the presence of an iron catalyst.

2. Nitration: Chemical properties of benzene In presence of concentrated nitric acid and sulfuric acid, one of the H atoms is replaced by a nitro (-NO 2 ) group.

3. Sulfonation: Chemical properties of benzene In presence of concentrated sulfuric acid and heat, one of the H atoms is replaced by sufonic acid (-SO 3 H) group. Heat

OH Alcohols

Chemical Properties of Alcohols 1. Acidity of Alcohols: 2. Acid-Catalyzed Dehydration: CH 3 CH 2 OHCH 2 = CH 2 + H 2 O H 2 SO 4 180°C 3. Oxidation of Alcohols: C = C + H 2 0 Dehydration Hydration - C – C - H OH

Alkene having the greater number of alkyl groups on the double bond generally predominates. Acid-Catalyzed Dehydration

In the oxidation [O] of a primary alcohol 1 , one H is removed from the –OH group and another H from the C bonded to the –OH. primary alcohol aldehyde OH O │ ║ CH 3 ─C─H CH 3 ─C─H + H 2 O │ H ethanol ethanal (ethyl alcohol) (acetaldehyde ) Oxidation of 1° Alcohols K 2 Cr 2 O 7 H 2 SO 4 [O]

The oxidation of 2  alcohols is similar to 1°, except that a ketone is formed. secondary alcohol ketone OH O │ ║ CH 3 ─C─CH 3 CH 3 ─C─CH 3 + H 2 O │ H 2-propanol 2-propanone Oxidation of 2° Alcohols [O] K 2 Cr 2 O 7 H 2 SO 4

Tertiary 3  alcohols cannot be oxidized. Tertiary alcoholno reaction OH │ CH 3 ─C─CH 3 no product │ CH 3 no H on the C-OH to oxidize 2-methyl-2-propanol Oxidation of 3° Alcohols K 2 Cr 2 O 7 H 2 SO 4 [O]

Thiols

Chemical Properties of Thiols 1. Thiols are weak acids (react with strong bases). CH 3 CH 2 SH + NaOH CH 3 CH 2 S - Na + + H 2 O H2OH2O 2. Oxidation to disulfides:-S-S- disulfide 2HOCH 3 CH 2 SH + O 2 HOCH 2 CH 2 S-SCH 2 CH 2 OH Oxidation Reduction Sodium ethanethiolate

CH 3 -NH 2 CH 3 -NH-CH 3 NH 2 Amines

Chemical properties of Amines They are weak bases (like ammonia): react with acids. N H H CH H – O – H.... N H H CH 3 H + O – H (to form water-soluble salts)

Aldehydes & Ketones

Chemical properties of Aldehydes and Ketones 1. Oxidation: only for aldehydes (not for ketones). K 2 Cr 2 O 7 H 2 SO 4 CH 3 ─CH 2 ─CH 2 ─CH 2 ─C─OH = O CH 3 ─CH 2 ─CH 2 ─CH 2 ─C─H = O Pentanal Pentanoic acid K 2 Cr 2 O 7 : Oxidizing agent Liquid aldehydes are sensetive to oxidation. No oxidizing agent

Chemical properties of Aldehydes and Ketones 2. Reduction: Like reducing the alkene (C = C) to alkane (C – C): –Reduction of an aldehyde gives a primary alcohol (-CH 2 OH). –Reduction of a ketone gives a secondary alcohol (-CHOH-). H 2 transition metal catalyst + 1-Pentanol CH 3 ─CH 2 ─CH 2 ─CH 2 ─C─ H = O Pentanal CH 3 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─ OH H 2 transition metal catalyst + CH 3 ─C─CH 2 ─CH 3 = O CH 3 ─CH─CH 2 ─CH 3 - OH 2-butanol 2-butanone

3. Addition of alcohols (hemiacetals): H of the alcohol adds to the carbonyl oxygen and OR adds to the carbonyl carbon. unstable Chemical properties of Aldehydes and Ketones

O-CH 2 CH 3 H COCH 2 CH 3 H O CH 2 CH 3 + Ethanol An Acetal COCH 2 CH 3 H O-H A hemiacetal + H2OH2O Acid 3. Addition of alcohols (Acetals):

3. Addition of alcohols (hemiacetals): If –OH is part of the same molecule that contains C=O. Chemical properties of Aldehydes and Ketones

Carboxylic Acids carbonyl group O  CH 3 — C—OH hydroxyl Carboxyl group

1- Reaction with bases: Chemical properties of Carboxylic Acids

2- Reduction: Chemical properties of Carboxylic Acids Resistant to reduction Using a powerful reducing agent: LiAlH 4 (Lithium aluminum hydride). 1° alcohol COH = O LiAlH 4, ether H2OH2O CH 2 OH 3-cyclopentene- carboxylic acid 4-Hydroxymethyl- cyclopentene

Chemical properties of Carboxylic Acids 3- Fischer Esterification: - A carboxylic acid reacts with an alcohols to form an ester. - Using an acid catalyst such as concentrated sulfuric acid. The best way to prepare an ester.

4- Decarboxylation: Chemical properties of Carboxylic Acids Loss of CO 2 from a carboxyl group. Heat

Esters & Amides CH 3 — C — NH 2 O Amide group

Formation of Esters RCOH O A carboxylic acid = Fischer Esterification RCOR ' O RC-OH O H - O R ' = = An alcohol A carboxylic acid An ester H 2 SO 4 + H 2 O

Chemical Reactions of Esters 1. Hydrolysis: reaction with water. (breaking a bond and adding the elements of water) RCOR' O RC-OH O H - O R ' = = An alcohol A carboxylic acid An ester + H 2 O + Heat Acid

2. Saponification (Hydrolysis): an ester reacts with a hot aqueous base. RCOR ' O RCO-Na O H - O R ' = = An alcohol A sodium salt An ester + NaOH + H2OH2O Heat - + CH 3 CO CH 2 CH 3 O CO-Na O CH 3 CH 2 OH = = Ethanol Sodium acetate Ethyl Ethanoate + NaOH CH 3 Chemical Reactions of Esters

3. Esters react with ammonia and with 1° and 2° amines to form amides. Thus, an amide can be prepared from a carboxylic acid by first converting the carboxylic acid to an ester by Fischer esterification and then reaction of the ester with an amine. Chemical Reactions of Esters

Formation of Amides RCOH O A carboxylic acid = RCNHR ' O RC-OH O H - N HR = = An Amine A carboxylic acid An amide Heat + H 2 O ' H 2 OCH 3 C-NHCH 2 CH 3 O HHNCH 2 CH 3 CH 3 C-OH O + + Acetic acid Ethanamine N-ethylethanamide

Chemical Reactions of Amides Such as esters: Hydrolysis in hot aqueous acid or base.

Amides do not react with ammonia or with amines. Chemical Reactions of Amides