Organic Chemistry Chapter 22

Hydrocarbons Alkanes Saturated  Relatively unreactive due to the strong C-C and C-H bonds  Contains all C-C single bonds C3H8C3H8  C n H 2n+2  Boiling breaks....  The longer the chain the higher the boiling point

You need to know First ten alkanes  Name and formula  Located p.662 Table 1 This is the names for straight chained alkanes

Nomenclature Branched chains  Lowers the boiling point  Suffix Find the longest continuous C chain butane

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

2,3,4-trimethylpentane 3-ethyl-2-methylheptane Try

alkenes Unsaturated  Contains at least one C=C double bond  C 2 H 4  Ethene  C n H 2n

Geometric isomers---CIS and TRANS III III (II) and (III) are cis and trans isomers (I) and (II) are structural isomers CIS TRANS

Structural isomers Same molecular formula-different arrangement of atoms C 4 H 10

DO Pentane C 3 H 6 Cl 2

alkynes Unsaturated Contains at least one C=C triple bond C 2 H 2 Ethyne

Aromatics Derivatives of benzene C 6 H 6

Ortho (o-) Meta (m-) Para (p-)

Functional groups Alcohol (alkanol)  R-OH  Hydrogen bonding so shorter chains are water soluble methanol ethanol propanol 2-propanol (isopropyl alcohol)

Acids Carboxyl group  Hydrogen bonding ---water soluble Methanoic acid (formic acid) Ethanoic acid (acetic acid)

esters Used as natural and artificial flavoring, solvents, perfumes, and plasticizers (that is what makes polymers more flexible)  Dipole force Methyl ethanoate

aldehydes propanal 2,5-dimethylhexanal Dipole force

ketones propanone 2-pentanone Dipole force

ethers Dimethyl ether Diethyl ether

amine R – NH 2 Aminoethane or ethylamine 2-aminopropane Hydrogen bonding

halogenoalkanes bromoethane 1,2 -dichloropropane

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

Optical isomers HOOC

Find the chiral C

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

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

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

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

Condensation reactions Alcohol + carboxylic acid ester + water + + H 2 O Methanol + acetic acid methyl acetate + water

Dehydration of alcohol H 2 SO 4 reflux + H 2 O

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

Secondary alcohols are oxidized by acidified potassium dichromate Cr 2 O 7 2- /H + 2-propanol Propanone

Tertiary alcohols cannot be oxidized 2-methyl-propanol

Substitution reactions Heterolytic substitution One atom gets both of the shared electrons-resulting in a positive and negative ion

Homolytic substitution Homolytic fission  Each of the two atoms retain one of the shared e- resulting in two free radicals

Chlorination of methane

benzene + Br 2 AlBr 3 + HBr Benzene has delocalized pi electrons. This means it is more stable and undergoes electrophilic substitution instead of addition.