1

C-H bonds in methane

Figure 22.2: (a) Lewis stucture of ethane (C2H6). (b) molecular structure of ethane

HYBRIDIZATION?

Name calling

CH

HH

H

methane

Name calling

CH

HH

CH

HH

ethane

Name calling

CH

HH

CH

HCH

HH

propane

2

Name calling

CH

HH

CH

HCH

HHC

H

H

butane

Name calling

CH

HH

CH

HCH

HHC

H

HCH

H

pentane

Name calling

CH

HH

CH

HCH

HHC

H

HCH

HCH

H

hexane

Name calling

CH

HH

CH

HCH

HHC

H

HCH

HCH

HCH

H

heptane

Name calling

CH

HH

CH

HCH

HHC

H

HCH

HCH

HCH

HCH

H

octane

Name calling

• CH4 methane• C2H6 ethane• C3H8 propane• C4H10 butane• C5H12 pentane• C6H14 hexane• C7H16 heptane• C8H18 octane

3

Figure 22.3: Structures of (a) propane (b) butane

HYBRIDIZATION?

CH

HH

CH

HCH

HH C

HH

HCH

HCH

HHC

H

H

Figure 22.3: Structures of (a) propane (b) butane

CH

HH

CH

HCH

HH C

HH

HCH

HCH

HHC

H

H

Figure 22.3: Structures of (a) propane (b) butane

C

C

C C

C

C

C

Figure 22.3: Structures of (a) propane (b) butane

C

C

C

C

4

CH3

CH

CH

CH3CH

HH

HCH

HCH

CH

Reactions of Alkanes

Combustion

alkane + O2 CO2 + H2O + heat

Learning Check Alk3

Complete and balance the reaction for the complete combustion of C7H16

Solution Alk3

Step 1

C7H16 + O2 CO2 + H2O

Step 2

C7H16 + O2 7 CO2 + 8 H2O

Step 3

C7H16 + 11 O2 7 CO2 + 8 H2O

Combustion In the Cell

Metabolic oxidation is combustionC6H12 O6 + 6O2 6CO2 + 6H2O + heat

glucose

• How does this reaction occur in living organisms?

5

Aerobic Oxidation Occurs in a Mitochondrion Located within a Cell

Branched AlkanesStructural FormulasStructural Isomers

Alkyl GroupsBranches on carbon chains

H

H C H methane

HH H

H C C H ethane

H H

Alkyl GroupsBranches on carbon chains

H

H C CH3 methyl

HH H

H C C CH3CH2 ethyl

H H

Branched Alkanes

CH3

CH3CHCH3

methyl groupsCH3 CH3

CH3CHCH2CHCH3

6

Naming Branched Alkanes

CH3 methyl branch

CH3CH2CH2CHCH2CH3

6 5 4 3 2 1 Count

Naming Branched Alkanes

CH3 methyl branch

CH3CH2CH2CHCH2CH3

6 5 4 3 2 1 Count3-Methylhexane

on third C CH3 six carbon chaingroup

Naming Summary1. Count the C’s in the longest chain

2. Name each attached group

3 Count the longest carbon chain to give the first attached group the smallest number

4. Name and locate each group

Learning Check Alk4A. CH3 CH3

CHCH2CH

CH3 CH3

B. CH3 CH3

CH3CH2CHCH2CH

CH3 CH2CH3

Solution Alk4A. CH3 CH3

CH3CHCH2CHCH3 2,4-dimethylpentane

B. CH3 CH3

CH3CH2CHCH2CHCH2CH3

CH3 3,3,5-trimethylheptane

Learning Check Alk5

Write a condensed structure forA. 3,4-dimethylheptane

B. 2,2-dimethyloctane

7

Solution Alk5

A. 3,4-dimethylheptane CH3

CH3CH2CHCHCH2CH2CH3

CH3

B. 2,2-dimethyloctane CH3

CH3CCH2CH2CH2CH2CH2CH3

CH3

IsomersSame molecular formulaSame number and types of atomsDifferent arrangement of atoms

Butane structures

n-butane

methylpropane

Learning Check Alk6

Write 3 isomers of C5H12 and name each.

Solution Alk6CH3CH2CH2CH2CH3 pentane or n-pentane

CH3

CH3CHCH2CH3 2-methylbutane

CH3

CH3CCH3 2,2-dimethylpropane

CH3

Cyclopropanestructure

Cyclic Alkanes

8

Cyclohexanestructure

Figure 22.11: The structure of benzene

Naming Cycloalkanes with Side Groups

Number of Namingside groups

One Side group name goes in front of the cycloalkane name.

Two Number the ring in thedirection that gives the lowest numbers to the side groups.

Cycloalkanes with Side GroupsCH3

CH3

CH3

CH3

CH3

CH3

methylcyclopentane

1,2-dimethylcyclopentane

1,2,4-trimethylcyclohexane

Learning Check Alk8Name the following cyclic alkanes

CH3

CH3

CH3

CH3

CH3

Solution Alk8

1,3-dimethylcyclohexane

methylcyclopentane

1,2-dimethylcyclobutane

CH3

CH3

CH3

CH3

CH3

9

Saturated and Unsaturated Compounds

Saturated compounds (alkanes) have the maximum number of hydrogen atoms attached to each carbon atomUnsaturated compounds have fewer hydrogen atoms attached to the carbon chain than alkanesUnsaturated compounds contain double or triple bonds

AlkenesCarbon-carbon double bondsNames end in -ene

H2C=CH2 ethene (ethylene)

H2C=CH-CH3 propene (propylene)

cyclohexene

Alkynes

Carbon-carbon triple bondsNames end in -yne

HC≡CH ethyne(acetylene)

HC≡C-CH3 propyne

Naming Alkenes and Alkynes

When the carbon chain has 4 or more C atoms, number the chain to give the lowest number to the double or triple bond.1 2 3 4

CH2=CHCH2CH3 1-butene

CH3CH=CHCH3 2-butene

CH3C≡CCH3 2-butyne

Learning Check HA3

Write the IUPAC name for each of the following unsaturated compounds:

A. CH3CH2C≡CCH3

CH3

B. CH3C=CHCH3 C.

CH3

Solutions HA3

Write the IUPAC name for each of the following unsaturated compounds:

A. CH3CH2CH=CHCH3 2-pentyne

CH3

B. CH3C=CHCH3 C.

2-methyl-2-butene 3-methylcyclopentene

CH3

10

Calling names

• ALKANES

• ALKENES

• ALKYNES

• CYCLO-

• ALKYL-

HydrogenationAdds a hydrogen atom to each carbon atom of a double bond

H H H H+ Ni

H–C=C–H H–C–C–H

H H H H

ethene ethane

Products of Hydrogenation

Adding H2 to vegetable oils produces compounds with higher melting points

Margarines

Soft margarines

Shortenings (solid)

Figure 22.11: The structure of benzene

Figure 22.12: Some selected substituted benzenes and their names

Compounds containing aromatic rings are often used in dyes, such as these for

sale in a market in Nepal

Source: Getty Images

11

Bonding in ethane Bonding in ethylene

Bonding in acytylene Cis and Trans Isomers

Double bond is fixedCis/trans Isomers are possible

CH3 CH3 CH3

CH = CH CH = CH

cis trans CH3

Vision begins with a light induced cis-trans isomerization reaction of retinal

12

isomers

• Structural – chain

• Structural - position

• Structural – function

• Stereo - geometrical

• Stereo - optical

butanemethyl propane

2methylhexane3methylhexane

cistrans

STEREO-ISOMERS

Non-Superimposable Mirror Images

13

COOH

CH3

HHO

C C

COOH COOH

CH3 CH3

HO HH OH

lactic acid

Electromagnetic Radiation

(b)

Figure 20.13: Unpolarized light consists of waves vibrating in many different planes

Figure 20.14: Rotation of the plane of polarized light by an optically active substance.

14

Optical Isomer and Interaction with LightEnatiomers rotate the plane of polarized light.Enatiomers rotate the plane of polarized light.

DextrorotatoryDextrorotatory-- “d” isomer “d” isomer Complex which rotates plane of polarized light to the right.Complex which rotates plane of polarized light to the right.

LevorotatoryLevorotatory-- “l” isomer“l” isomerComplex which rotates plane of polarized light to the left.Complex which rotates plane of polarized light to the left.

Chiral molecules are optically active because effect on lightChiral molecules are optically active because effect on light

Polarizing sun glasses reduce glare of polarized reflections from surfaces