Chemical Nature of Carbon

• Valence electrons?

• Ionic bonding?

• Number of bonds?

2

Uses of HydrocarbonsNumber of

C atomsState Major Uses

1-4 gasheating and cooking fuel

5-7liquids,

(low boiling)solvents, gasoline

6-18 liquids gasoline

12-24 liquidsjet fuel; camp stove fuel

18-50liquids,

(high boiling)

diesel fuel, lubricants, heating oil

50+ solidspetroleum jelly, paraffin wax

1-4 gasheating and cooking fuel

5-7liquids,

(low boiling)solvents, gasoline

6-18 liquids gasoline

12-24 liquidsjet fuel; camp stove fuel

18-50liquids,

(high boiling)

diesel fuel, lubricants, heating oil

50+ solidspetroleum jelly, paraffin wax

Tro, Chemistry: A Molecular Approach 3

Saturated Hydrocarbons

• a saturated hydrocarbon has all C-C single bonds– it is saturated with hydrogens

• saturated aliphatic hydrocarbons are called alkanes

• chain alkanes have the general formula CnH2n+2

4

FormulasCH4

C

H

H

H

H

C2H6 CH3CH3 C

H

C

H

H

H

H

H

C3H8 CH3CH2CH3 C

H

C

H

H

H

C

H

H

H

H

C4H10 CH3CH2CH2CH3 C

H

C

H

H

H

C

H

H

C

H

H

H

H

C4H10 C(CH3)2 C

H

C

H

H

H

C

C

H

H

H

H

H

H

Tro, Chemistry: A Molecular Approach

Formulas

6

Isomerism• Isomers = different molecules with the same

molecular formula• Structural Isomers = different pattern of atom

attachment

Tro, Chemistry: A Molecular Approach 7

Rotation about a bond is not isomerism

Tro, Chemistry: A Molecular Approach 8

Possible Structural IsomersCarbonContent

MolecularFormula

PossibleIsomers

4 C4H10 25 C5H12 36 C6H14 57 C7H16 98 C8H18 189 C9H20 3510 C10H22 75

10

3.4 Naming Alkanes• Compounds are given systematic names by a process that uses

• Follows specific rules– Find parent hydrocarbon chain– Carbons in that main chain are numbered in sequence– Substituents are identified numbered– Write compound name is single word – Name a complex substituents as though it were a compound itself

11

Naming Alkanes1) Find the longest continuous carbon chain

2) Number the chain from end closest to a branch– if first branches equal distance use next in

3) Name branches as alkyl groups– locate each branch by preceding its name with the carbon number

on the chain

4) List branches alphabetically– do not count n-, sec-, t-, count iso

5) Use prefix if more than one of same group present– di, tri, tetra, penta, hexa– do not count in alphabetizing

Tro, Chemistry: A Molecular Approach 12

Alkyl GroupsC

C C

C C C

C C

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

CH3

CH3-, METHYL

CH3CH2-, ETHYL

CH3CH2CH2-, PROPYL

(CH3)2CH-, ISOPROPYL

Tro, Chemistry: A Molecular Approach 13

More Alkyl GroupsC C C C

C C C

C

H

H

H

H

H

H

H

H

H

H

H

H

H

H H

CH3

CH3

CH3

H3C

C C C

CH3H

H

H H

H

H

(CH3)2CHCH2-, ISOBUTYL

CH3CH2(CH3)CH-, sec-BUTYL

CH3CH2CH2CH2-, n-BUTYL

(CH3)3C-, tert-- BUTYL

Tro, Chemistry: A Molecular Approach 14

Drawing Structural Formulas

• draw and number the base chain carbon skeleton

• add the carbon skeletons of each substituent on the appropriate main chain C

• add in required H’s

4-ethyl-2-methylhexane

C C C CC C

C C C

CH3 CH2 CH2 CH3CH CH

CH3 H2C CH3

C C C C C C1 2 3 4 5 6

Tro, Chemistry: A Molecular Approach 15

Reactions of Hydrocarbons

• all hydrocarbons undergo combustion• combustion is always exothermic

– about 90% of U.S. energy generated by combustion2 CH3CH2CH2CH3(g) + 13 O2(g) → 8 CO2(g) + 10 H2O(g)

CH3CH=CHCH3(g) + 6 O2(g) → 4 CO2(g) + 4 H2O(g)

2 CH3CCCH3(g) + 11 O2(g) → 8 CO2(g) + 6 H2O(g)