Organic Chemistry Chapter 24 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Dr. Ali Bumajdad Chapter 24 Topics Classes of organic Compounds Aliphatic Hydrocarbons Aromatic Hydrocarbons Chemistry of the Functional Groups Organic Chemistry

Common Elements in Organic Compounds

Classification of Hydrocarbons

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

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

Q) 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

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 methylheptane 2.An alkane less one hydrogen atom is an alkyl group. CH 4 CH 3 methane methyl

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

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

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 Br 1234 NO 2 1-bromo-3-nitrobutane

Q) What is the IUPAC name of the following compound? CH 3 CHCH 2 CHCH 2 CH 3 C2H5C2H5 CH 2 CH 3 4-ethyl-2-methyloctane Q) What is the structure of 3,5 di-methylheptane 6. When there are two or more different alkyl groups, the names of the groups are listed alphabetically CH 3 CHCH 2 CHCH 2 CH 3 C2H5C2H5 7

Alkane Reactions CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O (l)  H 0 = kJ 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

achiralchiral

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,…

Cycloalkanes

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 Unsaturated Atoms or groups are adjacentAtoms or groups are across Geometric Isomers

Cis-Trans Isomerization in the Vision Process

Alkene Reactions Cracking Addition Reactions (because unsaturated) 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

Markovnikov’s rule

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) Unsaturated

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) Markovnikov’s rule

Chemistry In Action: Ice That Burns Methane Frozen water

Aromatic Hydrocarbons C C C CC C H H H H H H C C C CC C H H H H H H Resonance

Aromatic Compound Nomenclature CH 2 CH 3 ethylbenzene Cl chlorobenzene NH 2 aminobenzene NO 2 nitrobenzene Br 1,2-dibromobenzene Br 1,3-dibromobenzene Ortho- o meta- m

Br NO 2 2-nitrobromobenzyne CH 3 -CH-CH 3 2-phenylpropane

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 ( otherwise electron delocalization will be destroyed ) Benzene is not too reactive

Polycyclic Aromatic Hydrocarbons

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

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

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

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

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

Functional Group Chemistry Esters have the general formula R’COOR, where R is a hydrocarbon group. CH 3 COOH + HOCH 2 CH 3 CH 3 C O CH 2 CH 3 + H 2 O O ethyl acetate

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

Chemistry In Action: The Petroleum Industry Crude Oil