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Chapter 20: Organic ChemistryThe chemistry of carbon compounds.Mainly carbon and hydrogen atoms.Many organic compounds occur naturally.Thousands more can be synthesized by man.1

NaCl versus ButaneNaCl, 58.5 g/molBonding is ionicM.P. = 801oCB.P. = 1413oCDissolves in waterWill not burnC4H10, 58.1 g/molBonding is covalentM.P. = -138oCB.P. = 0oCNot soluble in waterWill burn in air2

Molecular GeometryThere are three hybridization states and geometries found in organic compounds:sp3 Tetrahedralsp2 Trigonal planarsp Linear3

Classes of Organic Compounds4AliphaticAromaticSaturatedUnsaturatedAlkanesCycloalkanesAlkenesAlkynesBenzene RingAlkanesSaturated hydrocarbonsAll C-C single (sigma) bondsFormula = CnH2n+25

FormulasStructure is very important in organic chemistry.Propane = C3H8, chemical formulaComplete structural drawing shows every single bond. H H H H C C C H H H H6FormulasCondensed structural drawing collapses the H atoms that are bonded to EACH carbon atom.CH3 CH2 CH3 , condensed formula.This is how a formula is written.7FormulasThe molecule is really NOT linear, though.The sigma bonds in the alkanes have free rotation.8

First Ten Alkanes: Base Names

9Structural Isomers For four carbons, there are two ways to arrange.For five carbons, there are three ways to arrange.10

IUPAC NomenclatureA name of a compound consists of three parts.Prefix, Base, and Suffix11prefixbasesuffixsubstituentslongest chain(how many Cs)familyIUPAC NomenclatureA substituent is any group that is attached to the longest chain of carbon atoms.CH4 = methane, -CH3 = methylCH3CH3 = ethane, -CH2CH3 = ethylCl = chloro, Br = bromo, I = iodo12IUPAC NomenclatureFind the longest chain in the molecule.Number the chain from the end nearest the first substituent encountered.List the substituents as a prefix along with the number(s) of the carbon(s) to which they are attached.LEP #113CycloalkanesA ring structure can be constructed from alkanes of three or more carbons by removing two hydrogen atoms.Because they form a geometric shape, a shorthand method for their structure is that shape.Rings with 5 and 6 carbons are the most stable.14

IUPAC NomenclatureFor ring structures, a mono-substituted ring does not need a number.Why???For di-substituted ring structures, number starting from the location of one the substituents and then go CW or CCW to give the next one the lowest number.15HaloalkanesA haloalkane is placing a halogen (group 7A) atom in place of a hydrogen atom.Naming uses the fluoro, chloro, bromo, and iodo names.Haloalkanes are used as refrigerants (CF3CH2F) and anesthetic agents (CF3CHClBr).16Stereoisomerism and Optical IsomerismStereoisomers = molecules in which the atoms have the same connectivity, but have a different spatial arrangement.Geometric = cis / trans (alkenes)Optical isomers = are two molecules that are non-superimposable.Optical isomers are much like your hands they are not superimposable!17

ChiralityAny carbon with four unique groups bonded to it are said to be chiral.18

Chirality

19If one of the two optical isomers is present, then it will rotate plane-polarized light to the left or to the right.An equal amount of both isomers will not rotate the light and is said to be a racemic mixture.ChiralityMany important biochemical molecules are chiral.Many important pharmaceuticals have at least one chiral carbon.Ex) Ibuprofen20

Chiral CarbonProperties and Reactions of AlkanesAlkanes are non-polar and, thus, do NOT dissolve in water.Alkanes typically have a density of 0.65 0.70 g/mL and will float on the surface of water.Alkanes are relatively unreactive.They burn in air, though, to produce energy.Halogenation: CH3CH3 + Cl2 21AlkenesCalled unsaturatedContain at least one C=C double bondSimplest alkene = C2H422

AlkenesThe double bond does not allow for free-rotation.23

IUPAC NomenclatureNaming an alkene.Find the longest chain that includes the double bond. Suffix name uses ene ending.Number the chain so that the double bond gets the lowest numbers (has priority over other substituents). Only four carbons or longer will need a number for the double bond position. Use only the lowest number for start of double bond.Number substituents based on this numbering.Cycloalkenes the double bond is ALWAYS position #1 and #2.24Geometric IsomersSome alkenes can have geometric isomers due to rigid shape around double bond.Requires two different sets of groups on each side of the double bond one large and one small.ABC = CBAOpposite = trans, Same side = cis25Addition ReactionsAlkenes undergo an addition reaction by adding a small molecule across the double bond.HydrogenationHalogenationHydration26Aromatic HydrocarbonsBenzene, C6H6, is a ring structure like the cycloalkanes.However, it is very different from the cycloalkanes, whose ring structures are fairly easy to break open.Benzene is VERY stable and found in many important molecules like aspirin, vanillin, and acetaminophen.What makes it unique?27

IUPAC NomenclatureMono-substituted benzene needs no number.Some have special (common) names.Toluene, Phenol, and Aniline.Di-substituted benzene rings are numbered like the cycloalkanes.Substituted toluenes, phenols, and anilines have those groups as the first position.28Functional GroupsAddition of atoms like O, N, and S add reactivity and polarity to the alkanes.Can occur in many different ways.Will need to know the nomenclature and reactions of some and be able to identify all.The letter R is a generic designation for an alkyl group.2930

AlcoholsAlcohols contain the hydroxyl (OH) group.R-OHAlcohols are classified as primary, secondary, and tertiary.31Primary (1) Secondary (2) Tertiary (3)1 group 2 groups 3 groups H CH3 CH3 | | | CH3COH CH3COH CH3COH | | | H H CH3IUPAC NomenclatureAlcohols get an ol suffix.The OH group MUST have the lowest number it has priority.On a cycloalkane, it is carbon #1.On benzene it is called phenol.32Properties of AlcoholsThe OH group can make the molecule soluble in water due to HB force.C1 to C4 are very soluble in water.More than five carbons, though, is virtually insoluble.CH3 CH2 CH2 CH2 CH2 CH2 - OH 33long chain is non-polar (dominates)Reactions of AlcoholsOxidation = loss of two Hs or gain of O.Depends on primary, secondary or tertiary.Primary Alcohol Aldehyde Carboxylic Acid

Secondary Alcohol Ketone

Tertiary No Reaction34EthersAn O atom separating two alkyl groups.R O ROxygen atom is polar, so smaller ones are soluble in water.CH3 CH2 O CH2 CH3MTBE35ThiolsA sulfur atom usually with an H attached.R SHCH3 CH2 SH, EthanethiolThese compounds smell BAD!One amino acid has this thiol group.36Carbonyl GroupMany functional groups contain a C = O group.Aldehyde = the C = O group is terminal.R-CHOCH3 CH2 C H O37Carbonyl GroupAldehydes use the al suffix.The carbonyl carbon is automatically the first position.Ketone = the carbonyl group is in the middle of the chain.Smallest ketone has three carbons38

Carbonyl GroupKetones use an one suffix.Number is needed for five or more Cs.Carboxylic Acid = carbonyl group with a hydroxyl group attached.R COOHAre many of the weak acids seen in Ch. 16.39Carbonyl Group

40Formulas are written differently!Ex) Acetic AcidCarbonyl GroupNaming acids use the oic suffix plus the name acid.Like aldehydes, the COOH group is terminal, so it is C #1.Esters = has both the carbonyl and the ether type O atom.R COO R41Carbonyl GroupAn ester is made by the reaction of an alcohol and a carboxylic acid.R C OH + HO R R C O R O OThe OH and H produce water.42AmineAn amine contains the N atom.These can be primary, secondary, or tertiary.R NH2 , R2 NH , and R3 N.The N group has a lone pair that will accept a protonTherefore, these are the weak bases from Ch. 16.43AmideContain the carbonyl group AND the amine group.R (C=O) NH2The N group can also have an R group.Made by the reaction of a carboxylic acid plus an amine.Similar to ester reaction.44PolymersA polymer is a long chain of repeating units called monomers.Monomers are typically small alkenes.Reaction is called an addition reaction and are referred to as addition polymersInitiated by organic peroxide, R-O-O-R, which is split into two fragments, 2 R-O

45Benzoyl peroxide

Common MonomersCH2=CH2, ethylene makes polyethylene.Two forms low density and high densityUses:CH2=CHCl, vinyl chloride makes PVC.Uses:CH2=CHCH3, propene makes polypropylene.Uses:CF2=CF2, tetrafluoroethene makes Teflon.Uses:

46Common MonomersCH2=CCl2, 1,1-dichloroethene makes Saran.Uses:CH2=CH(C6H5), phenylethene makes polystyrene.Uses:Recycling uses a series of symbols and numbers to identify the type.47

Condensation PolymersPolyurethanes, Nylons, Rayons, etc. are produced using the ester and/or amide reaction.Monomer units have two functional groups per molecule.PETE = ethylene glycol + terephthalic acidNylon 6,6 = adipic acid + hexamethylenediamine48