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ORGANIC CHEMISTRY Organic chemistry is the study of carbon chemistry and the compounds of carbon. Majority of chemical compounds on earth are organic. The main elements involved in organic chemistry are C, H, O, & N; shorthand notation: HC = hydrocarbon Organic chemistry reminds us of plants and animals but is not limited to such. Natural medicines: penicillin, cortisone, streptomycin Manmade medicines: novocaine, sulfa drugs, aspirin. Natural textile fibers: nylon, Dacron, latex, rayon Polymers: saran, Teflon, Styrofoam, plastics, polyethylene, PBC’s CLASSIFICATION OF HYDROCARBONS HYDROCARBONS ALIPHATIC HYDROCARBONS SATURATED HYDROCARBONS AROMATIC HYDROCARBONS (unsaturated hydrocarbons) UNSATURATED HYDROCARBONS BENZENE AND DERIVATIVES alkenes (CnH2n) Alkanes (CnH2n + 2) Cycloalkanes (CnH2n) alkynes (CnH2n - 2) FUSED-RING AROMATIC HYDROCARBONS Combustion of Hydrocarbons • Hydrocarbons combine with oxygen to produce carbon dioxide and water. • All the products are gases: – Carbon dioxide (CO2) – Water (H2O) • No solid residues. • Maximize pressure to perform mechanical work. Theory and Reality • Combustion equations are expressions of ideal combustion where only CO2 and H2O are products. • In limited oxygen incomplete combustion occurs: – Carbon monoxide is also produced. – (21 O2 compared with 25 O2 with complete combustion). Fractional Distillation • Crude oil is a fossil fuel – organic matter decomposed over time. • Complex mixture of different sized hydrocarbons. • Refinement is achieved by distillation. • Lighter fractions condense higher up the fractionating column. Emissions and the Environment • • • • Typical car engine results in about 5 % CO. CO2 and CO are both greenhouse gases. CO is also a health hazard. Catalytic converters convert CO into CO2. What Makes a Good Fuel? • In the combustion process: – C-C and C-H bonds are broken. – C-O and H-O bonds are made. • The bonds that are made are stronger than those that are broken – energy is released – exothermic reaction. Checking the Ratings • Molecular structure affects combustion. • Octane number describes combustion efficiency. • Straight chain is worse than branched: – 2,2,4-trimethylpentane has octane rating 100. – n-heptane has rating 0. • Gasoline is a complex mixture of different hydrocarbons and additives with octane ratings from 85 – 97. I Hear You Knocking • For efficient operation, combustion must occur at the right moment to drive the piston up and move the crankshaft. • Premature combustion is inefficient and results in “knocking.” GASOLINE The combustion engine operates: 1. Gasoline is allowed into the cylinder 2. Compression concentrates the gasoline and air (mixes) 3. Spark plugs ignite the mixture producing gas (pressure/volume) work. The compression step causes ignition. Knocking is pre-mature ignition of the more volatile components of the gasoline/air mixtures. GASOLINE ANTI-KNOCKING AGENTS 1. Pb(C5H5)4 tetra ethyl lead 1920’s 2. MTBE methyl-tert butyl ether 1990’s & EtOH ethanol (oxygenated) 3. Reformulated Gas (RFG) - contains less volatile hydrocarbons like benzene (C6H6) 1995 (note: volatile hydrocarbons contribute to O3 production in troposphere) Cleaning Up Our Act • The Clean Air Act of 1991 introduced new standards to reduce hazardous exhaust emissions – maximize conversion of CO to CO2. • Oxygenates: Adding O to the fuel before combustion rather than afterwards. • Two options: – Ethanol – expensive to produce – Methyl tert-butyl ether (MTBE) Unwanted Consequences of MTBE • Ethers are more polar than hydrocarbons and dissolve slightly in water. • Gasoline containing MTBE poses environmental hazard: – MTBE is carcinogenic. – MTBE does not degrade. • MTBE contamination of water supplies is a major health issue. • Ethanol poses a safer, but a more expensive alternative. ORGANIC NOMENCLATURE REVIEW 1. NAMING BASED ON # OF CARBONS IN THE MOLECULE #C NAME (prefix) 1 meth 2 eth 3 prop 4 but 5 pent #C 6 7 8 9 10 NAME (prefix hex hept oct non dec 2. NAMING BASED ON CARBON-CARBON BONDING. single bond – ane ending double bond – ene ending triple bond – yne ending ORGANIC NOMENCLATURE 3. FUNCTIONAL GROUPS containing oxygen R - OH -ol alcohol R-O-R ether ether R- HC = O -al aldehyde R-C=O l R -one ketone R - C - O-H ll O -oic acid carboxylic acid R-C-O-R ll O -oate ester carbonyl C=O ORGANIC NOMENCLATURE 3. FUNCTIONAL GROUPS containing nitrogen R – NH2 -amine amine R – C=O l NH2 -amide amide ALCOHOL MeOH – wood alcohol – methanol CH3OH - oxidized in body to formaldehyde - 1oz MeOH causes blindness EtOH – grain alcohol – ethanol C2H5OH - not poisonous in low concentrations - 500 mL 200 proof rapidly ingested will kill IPA – Isopropyl alcohol (rubbing alcohol) - C3H7OH 2-propanol -toxic (dosage) causes nerve damage, blindness and/or death, it’s a poison. - FAS - depressant - heavy drinking alter brain cell functions, causes nerve damage, shortens life span ETHERS - solvent - flammable - react w/O2 to form unstable peroxides - Diethyl ether anesthetic 1842; side effects include nausea & vomiting. - MODERN ANESTHETICS include methy propyl ether (Neothyl) and methoxyflurane (penthrane; CHCl2CF2OCH3) - MTBE (methyl tert-butyl ether) – reduce CO emissions in automobiles but is a suspected carcinogen. - ethylene oxide (C2H4O; cyclic) is used to make ethylene glycol which in turn is used to make polyester fibers and antifreeze. The Ether • Molecules beside hydrocarbons function as fuels. • Ether contains two hydrocarbon groups separated by an O atom. • General formula is: R-O-R' Naming Ethers • When the hydrocarbon groups are different, the name orders the two group alphabetically and ends in ether. – Butyl methyl ether: H3CCH2CH2CH2-O-CH3 • When the groups are the same the prefix diis used. – Dimethyl ether: H3C-O-CH3 ALDEHYDES/KETONES - formaldehyde - makes plastic - embalming - disinfectant - benzaldehyde (oil of almond) - maraschino cherry flavor - perfume, flavoring - acetone C3H6O - nail polish remover; common solvent for fats, rubber, plastics, & varnishes. Used in paint and varnish removers. - MEK – methyl ethyl ketone – solvent in oil paints and glues. Also formed in the blood stream in ketosis (a problem in diabetes). Ketone functional group • Ketone functional group is basis for soft contact polymer • Carbonyl group is C=O • Ketone contains two hydrocarbon chains attached to carbonyl group Naming ketones • Obtain root name – Count total number of C atoms • Remove –e and replace with –one • Location of carbonyl group – Count carbon atoms from shortest end CABOXYLIC ACIDS - carboxylic acids are polar and form hydrogen bonds thus leading to higher boiling points. (formic acid; 46 g/mol has bp of 101oC whereas ethanol; 46 g/mol has bp of 78oC). They are weak acids and react with bases to form salts. -formic acid – methanoic acid - ant sting - CH2O2 -acetic acid – ethanoic acid - vinegar - CH3COOH -butyric acid – butanoic acid – rancid butter -benzoic acid – Listerine -citric acid – sour flavor in oranges, lemons, & limes -lactic acid – imparts tartness to pickles, sauerkraut, & sweat. -cause of muscle pain & sorenss after exercise. Carboxylic Acids Are Acidic • The –COOH group loses protons “easily.” – Prostaglandin is ionized and is partly soluble in water. Naming Carboxylic Acids • Replace terminal “e” by “-oic acid.” a) Seven carbon atoms: – heptanoic acid. b) Ten carbon chain and ethyl group on C-7: 7-ethyldecanoic acid. ESTERS carboxylic acid + alcohol ester + H2O - sodium benzoate - preservative - fragrances - pineapple = ethyl butyrate - rum = ethyl formate - wintergreen = methyl salicylate - oil of jasmine = has benzyl acetate (C6H6)-CH2-O-CO-CH3 -rose = benzyl butanoate Ester group • Ester functional group • Esters have flavor and fragrance • Esters and their uses as flavoring agents and perfumes The name game • Ester contains two name parts – First: attached to O atom in main chain – Second: all C atoms in main chain, subtract -e and add -oate AMINES/AMIDES Organic bases – similar to ammonia NH3 in odor and basicity. Many amines have unpleasant odors like trimethylamine (smell of rotting fish) & putrescine (component of decaying animal flesh) H2N-(CH2)4-NH2 Amines are biologically important for example some illicit drugs like amphetamine & methamphetamine are amines and amino acids & proteins contain amines/amides. Nylon is a polyamide. Carboxylic acid + amine = amide + H2O Amide groups • Amide group contains carbonyl group – Hydrocarbon group attached to C atom – Nitrogen atom attached to C atom • Rotation about C-N bond is not possible Functional group review Functional group review Penicillin G shown below, a drug that inhibits the production of bacterial cell walls: H H O O S N CO2H Functional group review derivative of Neomethymycin, synthetic analog of bryostatin, a natural anticancer agent: an antibiotic H O O O O O O HO HO O N(CH3)2 OH O H3C O O OCH3 O HO O HO O O The polymer century • Polymers came of age in the 20th century • Plastics became stronger, lighter, more flexible, more rigid, more colorful, more durable • Disposal becomes a major issue • Future challenge is to meet dual demands of high performance and biodegradability Poly = many • Chemical names that begin with poly- mean big molecules • Polymers are made up of monomers – small molecules connected together • Polymer chains: – Long or short – Straight or branched – Hydrophilic or hydrophobic – Flexible or rigid POLYMERS Polymers are macromolecules Polymers are composed of monomers: smallest unit Polymers are long chains of monomers Polymerization: the process by which monomers are converted to polymers. Natural Polymers: starch, protein, cotton, wool Synthetic Polymers - Polyethylene – bags, squeeze bottles, films Polypropylene –carpeting, fabrics, battery cases Polystyrene - styrofoam cups, building insulation Polyvinyl chloride - PVC pipes, floor tile, raincoats polytetrafluoroethylene – Teflon, gasket & pan coating Some historical polymers • Shell lacca (from insect secretions) was used as a varnish • Rubber (natural from Hevea brasiliensis tree, C5H8) emulsion of rubber particles in water; elastic, waterrepellent, & sticky. • Vulcanized rubber (short chains of sulfur bonded to natural rubber) reduces stickiness, increases elasticity of material. 1839 Charles Goodyear • Frankincense and myrrh (from tree resins) were used as incense and perfumes • Gutta-percha was used a coating 20th century and the polymer age • New synthetic materials: rubber, polystyrene, polyethylene, polyvinylchloride, polyesters, nylon • World polymer consumption is now vast • Disposal presents environmental challenge Models for polymer growth a) Polymer grows by adding units on end of a chain b) Polymer grows by linking of shorter chains Two routes to a polymer • Addition polymerization: add monomers to one end • Condensation polymerization: joining of longer chains is possible Structure is function • Monomer for rubber is cis-isoprene • Rubber is cispolyisoprene • Each double bond has a cis- orientation • Chains are curvy and intertwined – allows stretching Dacron polymerization • First monomer has ester group on each end: diester • Second monomer has alcohol group on each end: dialcohol • End of first monomer reacts with end of second monomer – Ester group is slightly positive, alcohol group is slightly negative Sweet smell of esters • • • • Individual ester molecules are fragrant Polyesters are fragrance-free Dacron® is most widely used polyester in fabrics Dacron® is a copolymer polymer containing 2 or more monomers Nylon and Polyamides • Amide group is formed when an amine group and a carboxylic acid group combine and eject H2O (condensation). Cutting the suit to fit the cloth