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Organic Chemistry Chapter 22
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Hydrocarbons Alkanes Saturated Relatively unreactive due to the strong C-C and C-H bonds Contains all C-C single bonds C3H8C3H8 C n H 2n+2 Boiling breaks.... The longer the chain the higher the boiling point
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You need to know First ten alkanes Name and formula Located p.662 Table 1 This is the names for straight chained alkanes
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Nomenclature Branched chains Lowers the boiling point Suffix Find the longest continuous C chain butane
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prefix Methyl, ethyl, propyl, butyl Use numbers to indicate where the branching occurs (smallest numbers possible) Use numerical prefixes to indicate how many branches occur 2,2-dimethylbutane
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2,3,4-trimethylpentane 3-ethyl-2-methylheptane Try
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alkenes Unsaturated Contains at least one C=C double bond C 2 H 4 Ethene C n H 2n
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Geometric isomers---CIS and TRANS III III (II) and (III) are cis and trans isomers (I) and (II) are structural isomers CIS TRANS
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Structural isomers Same molecular formula-different arrangement of atoms C 4 H 10
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DO Pentane C 3 H 6 Cl 2
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alkynes Unsaturated Contains at least one C=C triple bond C 2 H 2 Ethyne
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Aromatics Derivatives of benzene C 6 H 6
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Ortho (o-) Meta (m-) Para (p-)
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Functional groups Alcohol (alkanol) R-OH Hydrogen bonding so shorter chains are water soluble methanol ethanol propanol 2-propanol (isopropyl alcohol)
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Acids Carboxyl group Hydrogen bonding ---water soluble Methanoic acid (formic acid) Ethanoic acid (acetic acid)
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esters Used as natural and artificial flavoring, solvents, perfumes, and plasticizers (that is what makes polymers more flexible) Dipole force Methyl ethanoate
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aldehydes propanal 2,5-dimethylhexanal Dipole force
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ketones propanone 2-pentanone Dipole force
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ethers Dimethyl ether Diethyl ether
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amine R – NH 2 Aminoethane or ethylamine 2-aminopropane Hydrogen bonding
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halogenoalkanes bromoethane 1,2 -dichloropropane
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Optical isomers Chiral C Has four different functional groups attached Mirror image Optically active Rotate polarized light to the right or left Same physical properties Chemical properties are the same unless the molecule is interacting with an optically active substance
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Optical isomers HOOC
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Find the chiral C
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Addition reactions Alkenes are relatively reactive Bond enthalpy of the C=C is 612 kJ/mol, while the bond enthalpy for a C-C bond is 348 kJ/mol; therefore it is easier to break half of a double bond (306 kJ/mol) than a single bond
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Br 2 H 2 O H 2 SO 4 catalyst H2H2 HBr Ni catalyst 180 C halogenoalkane dihalogenoalkane alkane alcohol H 2 C CH 2 CH 2 n Addition polymer
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Addition polymerization n n may be > 2000 C 2 H 4 units Polyethylene (polythene) formed from C=C Polyvinyl chloride (polychloroethene) Head to tail monomer polymer
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Useful addition reactions Bromination Test for the presence of alkenes. Br 2 is a yellow/orange liquid that turns colorless when added to an alkene Hydration Addition of water Makes ethanol Hydrogenation Addition of hydrogen Makes margarine Decreases the # of C=C solidifying the vegetable oil at room temp
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Condensation reactions Alcohol + carboxylic acid ester + water + + H 2 O Methanol + acetic acid methyl acetate + water
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Dehydration of alcohol H 2 SO 4 reflux + H 2 O
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Primary alcohols are oxidized by acidified potassium dichromate Cr 2 O 7 2- /H + Ethanol ethanal ethanoic acid Used in breathalyzer tests Ethanal can be distilled off Or ethanoic acid can be produced by heating under reflux
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Secondary alcohols are oxidized by acidified potassium dichromate Cr 2 O 7 2- /H + 2-propanol Propanone
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Tertiary alcohols cannot be oxidized 2-methyl-propanol
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Substitution reactions Heterolytic substitution One atom gets both of the shared electrons-resulting in a positive and negative ion + + + -
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Homolytic substitution Homolytic fission Each of the two atoms retain one of the shared e- resulting in two free radicals
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Chlorination of methane
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benzene + Br 2 AlBr 3 + HBr Benzene has delocalized pi electrons. This means it is more stable and undergoes electrophilic substitution instead of addition.
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