Chapter 15 Organic Chemistry

“Organic chemistry …is enough to drive one mad. It gives me the impression of a primeval forest, full of the most remarkable things, a monstrous and boundless thicket, with no way of escape, into which one may well dread to enter.” -Friedrich Wöhler

Which of these are “organic”? CH 3 CH 2 CH 2 OH NaCN CH 3 COOH CH 3 (CH 2 ) 16 COOH HC  CH CaCO 3 CH 3 CH=CH 2 What is special about carbon?

Carbon 1. Electron configuration, electonegativity, and covalent bonding 2. Bond properties, catenation, and molecular shape 3. Molecular stability

Hydrocarbons “Aliphatic” Alkanes Alkenes Alkynes “Aromatic” C H H HHC H H C H C H H H CC HH

Single, double, and triple bonds CHH H H CH H CH H CHCH CH 4 C2H4C2H4 C2H2C2H2

Alkanes, C n H 2n+2 “Saturated” C 9 H 20

Single Bonds - sp 3 (tetrahedral) 109.5°

Staggered Conformations

Single bonds - unrestricted rotation

Structures & Rotation Ethane C 2 H 6 CH 3 Staggered Eclipsed

Conformations Different spatial arrangements generated by rotation around a single bond

Constitutional (structural) isomers

Naming 1.Longest C-C chain:root name 2.Suffix:compound type 3.Prefix for rings: “cyclo” 4.Branches:root + “yl” alphabeticalnumbered

Alkane examples © Mc-Graw-Hill Companies, Inc. All rights reserved.

Physical Properties Straight:lower melting points, higher boiling points Branched:higher melting points, lower boiling points

Ring strain - cyclopropane

Conformations of cyclohexane

Enantiomers

Alkenes, C n H 2n - sp 2 “Unsaturated”

Geometric Isomers

Light energy temporarily excites  bond electrons Bond breaks - allows rotation

Alkynes, C n H 2n-2 - sp “Unsaturated”

Aromatic - Benzene derivatives Delocalized (conjugated)  electron cloud

Free-Radical Substitution Reactions Alkanes:

Functional Groups - Reactive Sites

Important Reactions 1 - Substitution C bonded to same number of atoms | R— C — X | :Y:Y R— C — Y | :X:X

Important Reactions 2 - Addition Two  bonds from one  bond and one  bond R— C — C — RX—Y X Y | | R— C — C — R | |

Important Reactions 3 - Elimination Elimination of small, stable molecule + entropy R— C — C — RX—Y X Y | | R— C — C — R | |

Oxidation-reduction Oxidation: – More bonds to O – Less bonds to H Reduction: – Less bonds to O – More bonds to H O R— C H | R— C — OH | O R— C OH | R— C —H |

Functional Groups with Single Bonds Alcohols & Ethers HaloalkanesAmines R—O —H  R—X: X = halogen  R— N — |  R—O —R 

Alcohol Reactions Elimination – Elimination of H 2 O in acid Dehydration to C=C – Elimination of 2 H w/ strong ox.agent Oxidation to C=O Substitution – Single bonded products – “Reactive” C bonded to electronegative atom

Haloalkane Reactions Elimination of HX in very strong base C=C product Substitution in base – Single bonded products —OH, —OR, —CN, —SH, —NH 2, … – “Reactive” C bonded to electronegative atom

Amine Reactions Substitution – Single bonded products – Lone pair on N attacks  + on another molecule | 2R— C — NH 2 | R’—C H 2 — Y  | R— C — NHR’ | | + R— C — NH 3 Cl |

Functional Groups with Double Bonds AlkenesAldehydesKetones Carboxylic Acids     e - rich R— C — C — R O R— C H O R— C OH  e - rich

Alkenes Addition reactions R— C — C — RH3O+H3O+ OH H | | R— C — C — R | | R— C — C — RHX X H | | R— C — C — R | |

Aromatic - Substitution Reactions Delocalized  electrons stabilize ring

Charge Distribution & Reactivity Can undergo substitution or oxidation-reduction

Oxidation of aldehydes to acids

Substitution Z—Y O—Z | R— C — OH | Y O R— C OH O R— C Y Z—OH 1. Addition 2. Elimination

Substitution dehydration

Substitution of —OH by N in amines

Functional Groups with Triple Bonds AlkynesNitriles  e - rich R— C — C — R R— C — N: e - rich Reactions:addition Formation increases C chain by 1 Reactions:subsitution/hydrolysis, reduction, …

Types of polymers Addition Polymerization: monomers “add together” to form the polymer, with no other products. (Teflon) Condensation Polymerization: A small molecule, such as water, is formed for each extension of the polymer chain. (Nylon)

Biological Polymers Carbohydrates, saccharides, polysaccharides Amino acids, peptides, proteins Fatty acids, lipids, fats, oils, waxes, steroids, phospholipids Nucleotides, nucleic acids

Saccharides/Carbohydrates

C C C C C CH 2 OH OH HO OH OH H H H H C C C C C CH 2 OH O OH HO OH H H H H H C C C C C CH 2 OH O OH HO OH H H H H H O H H H H H CH 2 OH OH O H H H H H CH 2 OH OH D-glucose  -D-glucopyranose  -D-glucopyranose

O H H H H H OH CH 2 OH OH O H H H H H CH 2 OH O O H H H H H OH CH 2 OH OH O H H H H H CH 2 OH O  -1-4-glycosidic bond  -1-4-glycosidic bond Glycosidic linkages (dehydration)

Disaccharides

Polysaccharides AmyloseAmylopectinStarchGlycogenCellulose

Amino acids H H | O N—C—C H | OH R  Amine  Acid  -carbon

Amide Linkage (“peptide bond”) H O H H H | || | | O N—C— C — N — C — C +H 2 O H | | OH R  R’ peptide bond (dehydration)

Levels of Structure 1

Levels of Structure 2

Levels of Structure 3