1 Introduction to Organic Chemistry Chapter 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Common Elements in Organic Compounds

3 Classification of Hydrocarbons Hydrocarbons are made up of only hydrogen and carbon.

4 Alkanes Alkanes have the general formula C n H 2n+2 where n = 1,2,3,… only single covalent bonds saturated hydrocarbons because they contain the maximum number of hydrogen atoms that can bond with the number of carbon atoms in the molecule CH 4 C2H6C2H6 C3H8C3H8 methaneethanepropane

5 Structural isomers are molecules that have the same molecular formula but different structures

6 How many structural isomers does pentane, C 5 H 12, have? CCCC C HHHHH H HHHHH H CCC C HCH 3 HH H HHHH H CC C H H H HH H n-pentane 2-methylbutane 2,2-dimethylpropane

7 Physical Properties of Some Alkanes

8 Alkane Nomenclature 1.The parent name of the hydrocarbon is that given to the longest continuous chain of carbon atoms in the molecule. CH 3 CH 2 CHCH 2 CH heptane 2.An alkane less one hydrogen atom is an alkyl group. CH 4 CH 3 methane methyl 4-methylheptane

9 Alkane Nomenclature 3.When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. Number in the direction that gives the smaller numbers for the locations of the branches. CH 3 CHCH 2 CH methylpentane CH 3 CH 2 CHCH methylpentane

10 Alkane Nomenclature 4.Use prefixes di-, tri-, tetra-, when there is more than one alkyl branch of the same kind. CH 3 CH CH 2 CH ,3-dimethylhexane CH 3 CHCCH 2 CH ,3-dimethylhexane

11 Alkane Nomenclature 5.Use previous rules for other types of substituents. CH 3 CH CH 3 Br 1234 NO 2 2-bromo-3-nitrobutane CH 2 CHCH 3 Cl 1234 F 1-chloro-3-fluorobutane

12 What is the IUPAC name of the following compound? CH 3 CHCH 2 CHCH 2 CH 3 C2H5C2H5 CH 2 CH 3 2-methyl-4-ethyloctane What is the structure of 4-ethyl-2-methylhexane? CH 3 CHCH 2 CHCH 2 CH 3 C2H5C2H5

13 Alkane Reactions CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O (l)  H 0 = kJ/mol Combustion Halogenation CH 4 (g) + Cl 2 (g) CH 3 Cl (g) + HCl (g) light Cl 2 + energy Cl + Cl Cl + CH H H H CH H H + HCl CH H H + Cl Cl CCl H H H + Cl

14 Cycloalkanes Alkanes whose carbon atoms are joined in rings are called cycloalkanes. They have the general formula C n H 2n where n = 3,4,…

15 Geometry of Cycloalkanes more stable

16 Alkenes Alkenes have the general formula C n H 2n where n = 2,3,… contain at least one carbon-carbon double bond also called olefins CH 2 CHCH 2 CH 3 1-butene CH 3 CH CH 3 2-butene CC Cl HH CC H H cis-dichloroethylenetrans-dichloroethylene

17 Cis-Trans Isomerization in the Vision Process electron micrograph of retinal rods

18 Alkene Reactions Cracking Addition Reactions CH 2 CH 2 (g) + HBr (g) CH 3 CH 2 Br (g) CH 2 CH 2 (g) + Br 2 (g) CH 2 Br CH 2 Br (g) C 2 H 6 (g) CH 2 CH 2 (g) + H 2 (g) Pt catalyst

19 Markovnikov’s rule: in the addition of unsymmetrical (that is, polar) reagents to alkenes, the positive portion of the reagent (usually hydrogen) adds to the carbon atom that already has the most hydrogen atoms. and/or

20 Alkynes Alkynes have the general formula C n H 2n-2 where n = 2,3,4,… contain at least one carbon-carbon triple bond 1-butyne2-butyne CH CCH 2 CH 3 CC Production of acetylene CaC 2 (s) + 2H 2 O (l) C 2 H 2 (g) + Ca(OH) 2 (aq)

21 Alkyne Reactions Addition Reactions Hydrogenation CH CH (g) + H 2 (g) CH 2 CH 2 (g) CH CH (g) + HBr (g) CH 2 CHBr (g) CH CH (g) + Br 2 (g) CHBr CHBr (g) CH CH (g) + 2Br 2 (g) CHBr 2 CHBr 2 (g)

22 Aromatic Hydrocarbons C C C CC C H H H H H H C C C CC C H H H H H H Electron micrograph of benzene

23 Delocalized molecular orbitals are not confined between two adjacent bonding atoms, but actually extend over three or more atoms. Example: Benzene, C 6 H 6 Delocalized  orbitals

24 Other Representations of Benzene

25 Aromatic Compound Nomenclature CH 2 CH 3 ethylbenzene Cl chlorobenzene NH 2 aminobenzene NO 2 nitrobenzene Br 1,2-dibromobenzene Br 1,3-dibromobenzene

26 Aromatic Compound Reactions H H H H H H Br H H H H H + HBr+ Br 2 FeBr 3 catalyst H H H H H H CH 2 CH 3 H H H H H + HCl+ CH 3 CH 2 Cl AlCl 3 catalyst Substitution reaction

27 Polycyclic Aromatic Hydrocarbons

28 Functional Group Chemistry Alcohols contain the hydroxyl functional group and have the general formula R−OH.

29 C 6 H 12 O 6 (aq) 2CH 3 CH 2 OH (aq) + 2CO 2 (g) enzyme CH 2 CH 2 (g) + H 2 O (g) CH 3 CH 2 OH (g) H 2 SO 4 Biological production of ethanol Commercial production of ethanol Metabolic oxidation of ethanol CH 3 CH 2 OH CH 3 CHO + H 2 alcohol dehydrogenase

30 Functional Group Chemistry Ethers have the general formula R−O−R′. CH 3 OH + HOCH 3 CH 3 OCH 3 + H 2 O H 2 SO 4 catalyst Condensation Reaction

31 Functional Group Chemistry Aldehydes and ketones contain the carbonyl ( ) functional group. O C R C H O aldehydes have the general formulaR C R′ O ketones have the general formulaH C H O H C O CH 3 C O H3CH3C formaldehydeacetaldehydeacetone

32 Functional Group Chemistry Carboxylic acids contain the carboxyl ( −COOH ) functional group.

33 Generally weak acids React with alcohols to form esters Neutralization Production of acid halides (intermediates in syntheses) Properties and Reactions of Carboxylic Acids

34 Functional Group Chemistry Esters have the general formula R′COOR, where R is a hydrocarbon group. Hydrolysis Alkaline hydrolysis (saponification) Characteristic odors and flavors

35 Functional Group Chemistry Amines are organic bases with the general formula R 3 N. CH 3 NH 2 + H 2 O RNH OH - CH 3 CH 2 NH 2 + HCl CH 3 CH 2 NH 3 + Cl - Neutralization

36 Chirality Enantiomers are nonsuperimposable mirror images. chiralachiral