Chapter_24_Organic_chemistry.pps

Organic Chemistry Chapter 24

Common Elements in Organic Compounds

24.1

Common Elements in Organic Compounds

24.1

Classification of Hydrocarbons

24.1

 Alkanes  A lkanes have the general formula CnH2n+2 where n = 1,2,3,… • only single covalent bonds • s aturated hydrocarbons because they contain the maximum number of hydrogen atoms that can bond with the number of carbon atoms in the molecule

CH4

C2H6

C3H8

methane

ethane

propane

24.2

 S tructural is omers are molecules that have the same molecular formula but different structures

24.2

How many structural isomers does pentane, C 5H12, have?

H

H

H

H

H

H

C

C

C

C

C

H

H

H

H

H

H H

CH3 H

C

C

H

CH3 H

n-pentane

H

H

H

CH3 H

H

C

C

C

C

H

H

H

H

2-methylbutane

H

C

H

2,2-dimethylpropane

24.2

 Alkane Nomenclature 1. The parent name of the hydrocarbon is that given to the longest continuous chain of carbon atoms in the molecule. CH3 CH3 1

CH2 2

CH2 3

CH 4

CH2 5

2. An alkane less one hydrogen atom is an alkyl group. CH4

methane

CH3

methyl

CH2 6

CH3 4-methylheptane 7

 Alkane Nomenclature

24.2

 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. CH3 CH3 1

CH 2

CH2 3

CH2 4

CH3 5

CH3

2-methylpentane CH3 1

CH2 2

CH2 3

CH 4

CH3 5

4-methylpentane 24.2

 Alkane Nomenclature 4. Use prefixes di-, tri-, tetra-, when there is more than one alkyl branch of the same kind.

CH3 1

CH3

CH3

CH

CH

2

3

CH2

CH2

4

CH3

5

6

2,3-dimethylhexane CH3 CH3 1

CH 2

C 3

CH2 4

CH2 5

CH3 6

CH3 3,3-dimethylhexane

24.2

 Alkane Nomenclature 5. Use previous rules for other types of substituents.

CH3 1

Br 

NO2

CH

CH

2

3

CH3 4

2-bromo-3-nitrobutane Br  CH2 1

NO2 CH2 2

CH 3

CH3 4

1-bromo-3-nitrobutane 24.2

What is the IUPAC name of the following compound? CH3 CH3 1

CH

C2H5 CH2

2

3

CH 4

CH2 5

CH2 6

CH2 7

CH3 8

2-methyl-4-ethyloctane What is the structure of 2-propyl-4-methylhexane? C2H5 CH3 1

CH 2

CH3 CH2 3

CH 4

CH2 5

CH3 6

24.2

 Alkane Reactions Combustion CH4 (g ) + 2O2 (g )

CO2 (g ) + 2H2O (l )

DH0

= -890.4 kJ

Halogenation light

CH4 (g ) + Cl2 (g )

CH3Cl (g ) + HCl (g )

Cl2 + energy

Cl• + Cl•

H

H

Cl• + H

C

H

H

•C

H

H H

C• + Cl

H + HCl

H Cl

H

C

Cl + Cl• 24.2

achiral

chiral 24.2

Cycloalkanes  Alkanes whose carbon atoms are joined in rings are called cycloalkanes. They have the general formula C nH2n where n = 3,4,…

24.2

Cycloalkanes

24.2

 Alkenes  A lkenes have the general formula CnH2n where n = 2,3,… • contain at least one carbon-carbon double bond • also called olefins CH

CH2

CH2

CH3

CH3

CH

1-butene Cl

H

Cl

C

H C

H

cis-dichloroethylene

CH3

2-butene

Cl C

CH

H  

C Cl

trans-dichloroethylene 24.2

Cis-Trans Isomerization in the Vision Process

24.2

 Alkene Reactions Cracking C2H6 (g )

Pt catalyst

CH2

CH2 (g ) + H2 (g )

 Addition Reactions CH2

CH2 (g ) + HBr (g )

CH3

CH2

CH2 (g ) + Br 2 (g )

CH2Br

CH2Br (g ) CH2Br (g )

24.2

 Alkynes  A lkynes have the general formula CnH2n-2  where n = 2,3,4,… • contain at least one carbon-carbon triple bond CH

C

CH2

1-butyne

CH3

CH3

C

C

CH3

2-butyne

Production of acetylene CaC2 (s) + 2H2O (l )

C2H2 (g ) + Ca(OH)2 (aq)

24.2

 Alkyne Reactions Hydrogenation CH

CH (g ) + H2 (g )

CH2

CH2 (g )

 Addition Reactions CH

CH (g ) + HBr (g )

CH2

CH

CH (g ) + Br 2 (g )

CHBr

CH

CH (g ) + 2Br 2 (g )

CHBr 2

CHBr (g ) CHBr (g ) CHBr 2 (g )

24.2

Chemistry In Action: Ice That Burns

 Aromatic Hydrocarbons H H

H

H

C C

C

C

C C H

H

H

H

H

C C

C

C

C C

H

H

H

24.3

 Aromatic Compound Nomenclature ethylbenzene

aminobenzene

CH2CH3

Cl

NH2

NO2

chlorobenzene

6

2

5

3 4

Br 

Br 

1

nitrobenzene

Br  Br  1,2-dibromobenzene

1,3-dibromobenzene 24.3

 Aromatic Compound Reactions Substitution reaction H

Br  H

H

+ Br 2 H

FeBr 3

H

H

+ HBr 

catalyst

H

H

H

H

H

H

CH2CH3 H

H

+ CH3CH2Cl H

H H

 AlCl3

H

H

+ HCl

catalyst

H

H H 24.3

Polycyclic Aromatic Hydrocarbons

24.3

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

24.4

Biological production of ethanol C6H12O6 (aq)

enzyme

2CH3CH2OH (aq) + 2CO2 (g )

Commercial production of ethanol CH2 CH2 (g ) + H2O (g )

H2SO4

CH3CH2OH (g )

Metabolic oxidation of ethanol CH3CH2OH

alcohol dehydrogenase

CH3CHO + H2

24.4

Functional Group Chemistry Ethers have the general formula R-O-R’. Condensation Reaction CH3OH + HOCH3

H2SO4 catalyst

CH3OCH3 + H2O

24.4

Functional Group Chemistry  A ldehydes and ketones contain the carbonyl ( C functional group.

 O

)

O

• aldehydes have the general formula R C H O • ketones have the general formula R C R’ O

O

O

H C H

H C CH3

H3C C CH3

formaldehyde

acetaldehyde

acetone

24.4

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

24.4

Functional Group Chemistry Esters have the general formula R’COOR, where R is a hydrocarbon group.

O CH3COOH + HOCH2CH3

CH3 C O CH2CH3 + H2O ethyl acetate

24.4

Functional Group Chemistry  A mines are organic bases with the general formula R 3N.

CH3NH2 + H2O

CH3CH2NH2 + HCl

RNH3+ + OH-

CH3CH2NH3+Cl-

24.4

24.4