Chapter 20 Organic Chemistry

1. Chapter 20 Organic Chemistry • What is Organic Chemistry? • Organic Chemistry = chemistry of carbon containing (organic) molecules • Most Familiar compounds are “organic” • Cotton in clothing 4) Plastics • Gasoline 5) Drugs • Food 6) Dyes • Natural Products vs. Synthetic Organic compounds • Natural Products are compounds we find in the environment • May need to be refined or isolated from the source • Are starting materials for synthetic compounds • Synthetic Organic compounds do not occur naturally and must be synthesized from simpler compounds • Caffeine: an important organic molecule • Hydrocarbons: simplest organic molecules

2. C4H10 C4H10 II. Alkanes • Structure (Carbon always has four bonds) • Hydrocarbons = molecules containing only hydrogen and carbon atoms • Saturated = hydrocarbon containing all of the hydrogen possible (all single bonds) • Unsaturated = hydrocarbon with less than maximum H’s (double/triple bonds) • Normal Alkanes = straight chain, with no branching • Branched Alkanes = no longer just one chain; main chain has “branches” • Structural Isomers = same chemical formula, but different order of attachment; straight-chain and branched alkanes are structural isomers of each other • Nomenclature: systematic naming by IUPAC rules • Straight Chain Alkanes • C1 = Methane C2 = Ethane C3 = Propane C4 = Butane • C5-C10 = pent-, hex-, hept-, oct-, non-, dec- -ane Unsaturated = Alkene Saturated = Alkane Generic Formula: CnH2n+2

3. 2) Rules for naming Branched Alkanes (or drawing structure from name) • Find the longest chain and name it as a straight chain alkane • Name substituents as alkyl groups • Number the main chain starting from the end closest to a substituent • Write the name • Alphabetize by sub. (di-, tri-count only if part of sub. name) • Order #’s from low to high; use smallest possible numbers • Capitalize the first letter only • Write as one word with commas and hyphens as needed • Complex substituents in parentheses 1 1 5-Ethyl-2,2-dimethyloctane 4-ethyl-3,6-dimethyldecane 1’ 1 1 4-(1-Ethylpropyl)-2,3-dimethylnonane 5-(1,1-Dimethylethyl)-3-ethyloctane

4. Cycloalkanes • Remove 2 terminal H’s and join the terminal carbons • General formula = CnH2n • Names: prefix cyclo- is added to the n-alkane name • Homologous series as ring size increases by CH2 • Not Structural Isomers of other alkanes, because different formulas • Reactions of Alkanes • Not very reactive; all bonding positions occupied by H • Combustion Reactions: Always make CO2 and H2O CH3CH3 + 7/2O2 -----> 2CO2 + 3H2O Important as energy sources: gasoline contains alkanes (octane) • Substitution Reactions: by halogens to make haloalkanes CH4 + Cl2 -----> CH3Cl + HCl (Chloromethane) New Functional Group Haloalkanes = replace H with F,Cl,Br,I on an alkane 4) Dehydrogenation Reactions: removing H makes unsaturated hydrocarbons H H cyclopentane methylcyclohexane ethylcyclobutane Cr2O3, 500 oC

5. cis-2-butene III. Alkenes • Structure: Hydrocarbons containing at least one double bond • Generic formula = CnH2n • Hybridization is sp2, rather than the sp3 hybridization of alkanes • Can have cis and trans isomers • Nomenclature • Name similarly to the alkanes, but with an –ene ending (Ethene, not Ethane) • Indicate the position of the double bond with a number (Structural Isomers) CH2=CHCH2CH3 is 1-butene CH3CH=CHCH3 is 2-butene • Stereoisomers = same formula/attachment, different spatial orientation (cis/trans) • Reactions • Addition Reactions = carbons can add atoms because of unsaturation Hydrogenation: CH2=CHCH3 + H2 --------> CH3CH2CH3 Halogenation: CH2=CHCH3 + Br2 --------> CH2BrCHBrCH3 trans-2-butene catalyst

6. CH3CCCH3 IV. Alkynes • Structure: Hydrocarbons containing at least one triple bond • Generic formula = CnH2n-2 • Hybridization is sp, rather than the sp2 hybridization of alkenes • Nomenclature • Name similarly to the alkenes, but with an –yne ending (Ethyne, not Ethene) • Indicate the position of the triple bond with a number (Structural Isomers) • HCCCH2CH3 is 1-butyne • CH3CCCH3 is 2-butyne • Reactions • Addition Reactions = carbons can add atoms because of unsaturation • Hydrogenation: HCCCH3 + 2H2 --------> CH3CH2CH3 • Halogenation: HCCCH3 + 2Br2 --------> CHBr2CBr2CH3 catalyst

7. Aromatic Hydrocarbons • Structure: must contain a six-membered ring having three double bonds • Benzene is the simplest aromatic; sp2 hybridization at every carbon • There are two equivalent resonance forms; a circle in the center is a shortcut • Nomenclature: number and name the substituents as prefixes to “benzene” • There are three structural isomers of disubstituted benzenes • An older system called them ortho-, meta-, and para- • Reactions • Very unreactive compared to other hydrocarbons: resonance stabilization • Substitution of hydrogen atoms is possible with the right catalysts Cl FeCl3 AlCl3 + Cl2 + CH3Cl

8. CH3CH2CH2OH 1-butanol Primary alcohol • Alcohols, Aldehydes, and Ketones • Structure of Alcohols: replace an -H on a hydrocarbon with an –OH Short chain alcohols are water soluble (Hydrogen Bonding) Most hydrocarbons are not water soluble because they are non-polar • Nomenclature • Modify the alkane name by dropping –e and adding –ol • Name based on longest chain containing -OH • Number each carbon starting from the closest to –OH • Reactions: Oxidation to Aldehydes and Ketones • Classifying alcohols: Primary at the end of a chain; Secondary within the chain • An Aldehyde is an oxidized Primary Alcohol (reduced aldehyde) • A Ketone is an oxidized Secondary Alcohol (reduced ketone) • Aldehydes are named with –al endings, Ketones are named with –one endings Secondary alcohol

9. Carboxylic Acids and Derivatives • Structure: Carboxylic Acids contain an O=C—OH ; a complicated functional group • Nomenclature • Assign number 1 to carboxy carbon and number longest chain including it • Replace –ane ending of an alkane with –oic acid ending • Carboxylic acids have priority over any other functional group studied • Reactions: Carboxylic Acids can become several related functional groups • Addition-Elimination Reaction: New molecule adds, while OH leaves

10. Amines and Ethers • Amines are derivatives of Ammonia, in which hydrogen is replaced by alkyl groups • Primary Amine: Only one H atom is replaced • Secondary Amine: Two H atoms are replaced • Tertiary Amine: All three H atoms are replaced • Can be Aromatic or Heteroaromatic • Basic due to nitrogen lone pair • Ethers are Derivatives of Water, in which both Hydrogens are replaced by alkyl groups • Related to alcohols, in which only one H atom of water is replaced • Fairly Unreactive; Similar polarity to the alkanes, unless very small • Non-polar and unreactive—much like alkanes Aminobenzene (Aniline) Pyridine

11. Polymers • Long-chain molecules built from many small molecule units (monomers) • Plastics, synthetic fibers (nylon), and many other materials are polymers • One of the most important chemical discoveries effecting daily life • Types of Polymerizations • Addition Polymerization = identical monomers add together with no biproducts Polymers based on alkenes are common examples • Condensation Polymerization = two molecules add, with a biproduct given off • Co-polymer = 2 different monomers, Homopolymer = 1 type of monomer Dacron Polyester