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Chemistry
Course
Chemistry 1027A/B
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Prof
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Chapter 12 Fossil fuels are currently our primary source of energy. Formed through anaerobic(w.out oxygen) decay of plants and animals over time. Three forms: Natural Gas, Coal and Crude Oil, or Petroleum. Petroleum - mixutre of many hydrocarbon compounds. Refined by separation into "fractions" based on boiling points Octane Rating - scale for rating knocking properties of gasoline knocking occcurs when fuel burns too quickly and "explodes" the % of isooctane in the mixture with identical knocking properties More hydrocarbons added to a gasoline mixture INCREASES octane rating Octane is a bad fuel ; isooctane is a good fuel Octane - octane number is -20 Heptane - octane number is 0 Iso octane - octane number is100 Benzene - octane number is 106 Methane - octane number is 107 Ethanol- octane number is 108 Good fuel is one that has a high octane rating thus iso-octane is better fuel than octane Octane is C8H18 and iso-octane is 8/18 page 1 Octane Rating is the scale for rating knocking properties of gasoline. Knocking occurs when fuel burns too quickly and “explodes”. Octane rating increases as branched hydrocarbons are added to a gasoline mixture. The more it knocks the lower the octane rating heptane (0) iso-octane(100) reg unleaded gasoline has an octane number of 87 Knocking characteristics correspond to a mixture that is 13% heptane and 87% iso-octane. ----------- Catalytic reforming uses a catalyst to convert straight chain hydrocarbons into branched chain hydrocarbons. Results in higher octane numbers. Catalytic cracking breaks larger hydrocarbons into smaller ones that will be in the gasoline range***. P219 top right The catalytic cracking process uses a zeolite catalyst and involves heating saturated hydrocarbons under pressure in the absence of air. The hydrocarbons break into shorter chain hydrocharbons – both alkanes and alkenes, some of which will be in the gasoline range. Part of the petroleum refining process – helps separate and fractionate! Octane enhancers increase octane rating; lead used to be used, but now use a variety of organic compounds. Oxygenated gasoline contains oxygenated organic compounds(such as alcohols or ethers)…allows gasoline to burn more cleanly. reduce CO and hydrocarbon emissions oxygenated fuel assists in more complete combustion by adding O as part of the fuel itself. Thus, lower CO and hydrocarbon emissions. Lower combustion temp reduced NOx Reformulated gasoline has the amount of aromatics (like benzene) and sulfur reduced and oxygenated compounds added. Difference is in the refining process itself Oxygenated gasoline is produced by adding oxygenated organic compounds to refined gasoline. VS. Reformulated gasoline requires changes in the refining process to alter the percentage composition of the different types of hydrocarbons, particularly olefins(alkenes) and aromatics -------- Natural Gas Mixture of gases with 1 to 4 carbon atoms per molecule; mostly methane, CH 4 Methane is the principal component of natural ags Used for home heating, cooking and a vehicle fuel Usually contains small amounts of H S2(smells bad) as an alert for leaks Coal Approximate formula is C 135 96O NS 9 Most coal is used for production of electricity (88%) Coal represents about 91% of fossil fuel reserves*; only a small amount has been mined to date coal is the most abundant fossil fuel Usage is expected to increase Coal Conversion May be converted to "synthesis gas" (coal gasification) page 2 Synthetic gas is used both as a fuel and as a starting material for the production of organic chemicals and gasoline Coal is pulverized and treated with superheated steam, a moxiture of CO and H(2) (synthetic gas) is obtained in the proceess Methane may also be produced by coal gasification (newer coal gasification way) page 3 New coal gasification process • Methane is the end product • Crushed coal is mixed with an aqueous catalyst, the mixtures is dried, and CO and H(2) are added. The resulting mixture is then heated to 700”C to produce methane and carbon dioxide. • Although the overall reaction is slightly endothermic(absorb energy), the subsequent combustion of the methane produced releases 192 kcal/mol, thus the process is an energy-efficient way to obtain methane, an environmentally clean fuel Coal may also be liquefied to produce hydrocarbons lke those in petroleum; the the moment his cost twice as much as crude oil Methanol and Ethanol as Fuels Methanol and ethanol burn more cleanly than gasoline; levels of troublesome pollutants(CO,unreacted HC, NO, O3) are reduced. M85 is 85% methanol, 15% gasoline Ethanol based fuels growing in popularity. Problems with decay, and energy content Flexibility necessary as methanol and ethanol are not readily available Methanol has a high octane rating of 107 (racing) while Ethanol is 108 Methanol and ethanol are “alcohol-powered vehicles” Each only have about one-half the energy content of gasoline, which would require fuel tanks to be twice as large to give the same distance per tankful This is particularly compensated since alcohol fuels typically cost half the price Methanol burns with a colourless flame – add something like gasoline in order to see that it’s burning Ethanol burns with a blue flame They both corrode steel, thus stainless steel fuel tanks or some sort of resistance coating is necessary *p.224 top left. Formulas for converting methanol to make gasoline Methane is the principle component in natural gas Classes of Hydrocarbons Alkane : general formula C n 2n+2 Geometry around each carbon atom in an alkane is tetrahedral (109.5degrees) all carbon atoms in saturated HC have 4 single bonds page 4 Isomers : compounds w/ same molecular formula but different arrangements of atoms have slightly different properties differ in one or more physical or chemical properties such as BP, colour, solubility, reactivity, and/or density structural isomers differ in the order that the atoms are bonded together straight chain compounds have no side chaines or brances branched chain isomers have side chains of carbon atoms Alkyl group is an alkane with a H removed page 5 page 6 T-Butyl --> T stands for teriary, tert, which means that the central C atom is bonded to 3 other C atoms Alkene have a C=C general formula C H n 2n Simplest alkene is ethylene(where n is 2) structural isomers arepossibel depending where the double bond is page 7 Geometric isomers (also known as cis and trans or E-Z isomersim) is a form of stereoisomerism Cis isomers have groups on the same side of the C=C Trans isomers have groups on opposite sides of the C=C page 8 Sicne tehre is no rotation arond a C=C, these are differnt compounds w different properties Alkynes have C---(3)C - triple bond general formula iCnH 2n-2 Isomers depend on the placement of the C-C triple bond Cyclic Hydrocarbons can form rings as well as chains Commonly represented as polygons: each corner is a C atom w 4 H bonds treat like an alkene CnH2n page 9 Aromatic Compounds : contain 1+ benzene rings page 10 Derivatives are formed by adding other groups to the benzene ring page 11 Structural isomers are formed when 2+ substituents on a ring a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. Polyciclic Aromatic Compounds : 2 or more benzene rings sharing ring edges smoke and char on the meat bbqed contain polycyclic aromatic compounds Alcohols are organic compounds which contain a hydroxyl (OH) functional group page 12 the anion form (OH-high) is called the hydroxide anion - it bears 1 negative charge largly residing ont eh more electronegative oxygen Ethers = compounds which have an oxygen atom linking 2 alkyl groups R-O-R R reps hydroCARBONS nothing else bonded to the oxygen page 13 Chapter 14 Organic compounds are those which contain carbon - 85% of chemcompoounds. Why are there so many organic compounds? 1) The ability of many carbon atoms to be linked in sequence with stable carbon-carbon single, double, and triple bonds in a single molecule 2) The occurrence of isomers. (3) The variety of functional groups that bond to carbon (discussed in this chapter) OH group makes something water soluable Alcohol and their oxidation products page 14 "R" indicates an alkyl group can be R or R' or R'' - different ways of indicating alkyl groups Common alcohols page 15 Oxidation of Alcohols Either : Aldehydes , Ketones, or Carboxylic Acids Depends on the alcohol used and the extent of the oxidation page 16 Oxidaion of Ethanol Page 17 Oxidation of 2- Propanol page 18 ???Hydrogen bonding occurs in alcohols and explains why there are liquids at room temp : similar sized molecules are gases Alcohol for industrail use must be DENATURED ; toxic additives added render it unfit to drink Ehthanol in BEER 5% Alcohol in the body page 19 Ethylene glycol (an Anti-freeze) contains more than 1 alcohol / hydroxyl group and is toxic 2 hydroxyl groups make it a DIOL ; 3 make it a TRIOL page 20 Antifreeze - Oxalic acid - intake see p 21 calcium oxalate crystallized in the kidneys adn int eh brain leading to serious illness or even death Propylene glycol has an extra C - cant be converted to oxalic acid Glycerol has 3 C's and 3 OH groups - used in food products and in drugs and cosmetics page 22 Carboxylic Acids contain the (R)–COOH functional group ...the H is what makes in an acid prepared by oxidizing aldehydes or(of?) primary alcohols react w bases to form "salts" bases seem to be NaOH(aq) page 23 Di Carboxylic acids are 2 carboxylic acids seperated by pretty much anything (R) Esters are formed from the reaction of a carboxylic acid and an alcohol carboxylic acid + an alcohol the OH and the H react to form H2O *you don't see the H2O in the reaction formula because it is LOST Polymer = a large molecule composed of repeating units derived from smaller molecules called monomers Addition Polymers - monomer units joined directly together - usually contain double or 3 bonds simplest is polyethylene from ethylene monomers page24 high density polyethylene is composed of primarily linear, unbranched chains of polyethylene in a close packing arrangement. All plastics are polymers (not all Polys are plastics) Polymers of Ethylene Derivatives - reaction with an ethylene derivative page 25 - 32 Rubber - natural - is elastic page 33 gutta - percha rubber is brittle (trans) Elastomers - substances which may be stretched and then spring back to their origin shape and size Vulcanized rubbre contains sulpfur cross links Condensation Polymers - 2 molecules react to form a larger molecule and a smaller molecule (often water) is eliminated ex; the formation of an ester page 34 Polyester - molecules with many ester linkages ex PETE page 35 PETE used in beverage bottles Polyesters can take many forms : sheets / films and fibres(marketed as Dacron or Terylene) Amide = formed by a condensation reaction between a carboxylic acid and a primary amine a primary amine contains an NH2 group bonded to the rest of the molecule Amino Acid : contains a primary amine (NH2) and a carboxylic acid Because condensation happens, H2O is formed by the reaction page 36 Polyamides (Nylons) = formed from the reaction of a di-aid and a di-amine Making Nylon Di-acid dissolved in hexane, an organic solvent Di-amine is dissolved in water Layers do not mix, nylon is formed at the interface(border) continues to form as rope is pulled away Kevlar is anothre Polyamide - Police Vest Reinforced plastics (or composites) are used in body panels for automobiles Composites have added fibres in the polymer matrix and are stronger, on a weight basis, than steel Recycling Plasitcs Can be costly due to seperation costs Recycled PETE is used mostly (58%) for fibres .. many uses 5 large pop bottles can make a T-Shirt! When 2 amino acids bond together, the amide bond formed is called a "peptide bond" Chapter 15 Carbohdrates - general formula C xH O2 y page 1 Monosaccharide - simplest sugar - can't be broken down into smaller carbohydrate units C6 12 -6all simple sugars page 2 Disaccharides - formed from 2 monosaccharides joined together (a water molecule is eliminated in the process) 3 disaccharides we need to know Sucrose – Glucose and Fructose - table sugar 40% of the world’s sucrose production comes from sugar beets and 60% comes from sugarcane Lactose – Glucose and Galactose - milk sugar (sugar found in milk) used as a sweetener in prepared foods used in formulating drugs and infant foods in making and in making yeast Maltose - Glucose and Glucose - found in starches that we eat The formula for these disaccharides (C12H22O11) is not simply the sum of 2 monosaccharides. A water molecule is eliminated as 2 monosaccharides are united to form the disaccharide. In the body, enzyne catalyze the breakdown (hydrolysis) of disacchardies to their monosaccharides Sweetness of sugars - Sucrose is our reference assigned the value of 1 sucrose - 1 glucose - 0.74 aspartame - 180 saccharin - 300 splenda - 600 Polysaccharides Nature’s most abundant polysaccharides are the starches , glycogen, and cellulose. Some polysaccharides have more than 5000 monosaccharide monomers. The monosaccharide most commonly used to build polysaccharides is D-Glucose Starches and Gylcogen VS Cellulose Amylose is aplant startch that is soluble in hot water Glycogen is an animla "starch"; stored in muscles and the liver Glycogen used for "instant energy" Cellulose : compound which makes up woody parts of trees, leaves, grasses, etc also composed of glucose units, but eh bonding is different humans cannot digest cellulose (we don't have the appropriate enzyme) Difference between starches and cellulose is so subtle but the small difference in compounds is huge page 3 Lipids - organic substance found in living systems limited solubility in water ; soluable in organic solvents includes fats, oils, steroids, and waxes majority of lipids are fats and oils Naturally occurring molecules Energy storage Not polymaerican in nature Fats and oils are triglycerides - 3 esters of glyceral and fatty acids formation of fat and oil result in the release of 3 water molecules page 4 - basic structure of a fat or oil triester Saturated fat - single carbon bonds Unsaturated fat - double carbon bond A fat is generally solid at room temp Oils are generally liquids at room temp – unsaturated Olive oil is an unsaturated fat Unsaturated fats possess a CIS arrangement about the double bond. can't pack as tightly, resulting in a liquid.....CIS is weaken than TRANS Hydrogenated Fats (H2) Process which adds H(2) to fats by breaking a C=C results in more stable fat and makes the fat more solid (oil--> margarine) Trans fats are a by-product of the hydrogenation process the hydrogenation process converts CIS arrangements to TRANS, resulting in a compound whose structure resembles a fully saturated fat Steroids - all have the same basic structure found in all plants and animals important for synthesis of cholesterol and many hormones Three 6-membered rings and One 5-membered ring joined together Cholesterol is synthesized in the liver necessary starting material for the production of many hormones, Vit D adn cortisone page 5 Synthetic Steroids Waxes - esters of long chain (16 + Carbon atoms) fatty acids and long chain alcohols general formula is :RCOOR' natural waxes are combinations of several different esters Soaps, Detergents, and Shampoos Fats may be hydrlyzed to produce glycerol and salts of fatty aicds : the latter are soaps page 6 Sodium Hydroxide is poured down clogged drains to clean them Soaps : Sodium Stearate molecule Hydrophilic (dissolves in water( which is one end COO-NA+ (sodium comes off and itss a negatively charged ion which will attract water) Hydrophobic - HydrCarbon part(doesn't dissolve in water but in organic solvents or grease) Soap molecules are water soluble, but the -ve end can form precipitates with Ca2+ or Mg2+ Detergent molecules form soluble compounds with Ca2+ or Mg2+, so no soap scum. Detergent molecule has a benzene ring and instead of the ionic form of the carboxylic acid its SO3-Na+ There are different classes of Detergents anionic -ve charge; when Na+ is removed) form suds (laundry) cationic +ve charge, usually quaternary ammonium halides Shampoos - workt o remove oily dirt from the hair the same way as soap or detergents work agitation allows the dirt to be rinsed away conditioners attempt to replenish some of the natural oils removed by shampooing Many aren't effective - because - most protein and other complex molecules are too large to penetrate the hair shaft Creams and Lotions Moisturizers are substances which hold moisture in the skin They are oily and lubricate the skin, making it feel smoother Emollient is another name for substances that hold moisture in the skin Emollient added to oil and mixture to keep the product consistent Both creams and lotions are used for this purpose. Difference is in the p
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