Chapter 9 Energy and Hydrocarbons

Chapter Outline Energy from Fuels Alkanes: Backbone of Organic Chemistry Petroleum Refining Octane ratings

9.1 Energy from Fuels Most of our energy comes from Fossil Fuels (Petroleum, Coal, Natural Gas) Source of Energy used in the United States

Combustion of Natural Gas Natural Gas is mostly Methane Consider the complete combustion of methane ____ CH 4 + ____ O 2 -> ____ CO 2 + ____ H 2 O Methane Oxygen Carbon dioxide Water Is Energy Produced? How much?

What determines if Energy is released or absorbed in a chemical reaction? Bond Energies!!

BOND ENERGIES

Complete combustion of Methane CH O 2 -> 2H 2 O + CO 2 E= Energy bonds broken – Energy bonds formed = 4(411 kJ/mol) + 2(494 kJ/mol) - [2(918 kJ/mol)+2(-799kJ/mol)] = kJ/mol Using molecular weight of Methane = 16 g/mol = kJ/g or kcal/g

Your Turn Let’s try Propane and Gasohol Propane is C 3 H 8 Gasohol is ethanol CH 3 CH 2 OH

Energy Values for Some Fuels SubstanceHeat (kcal/g) Hydrogen34.0 Natural Gas (mostly methane) 11.9 Gasoline11.5 Anthracite coal7.4 Wood4.3

9.2 Alkanes: Backbone of Organic Chemistry Naming Hydrocarbons!

Alkanes The simplest alkane is methane – the primary component in Natural Gas. Some Definitions: Alkanes - contain carbon-carbon single bonds Alkenes – contain carbon-carbon double bonds Alkynes – contain carbon-carbon triple bonds

See Table 9.3 Have the General Formula: C n H 2n+2 Where n=the number of carbons n=1 Methanen=6 Hexane n=2 Ethanen=7 Heptane n=3 Propane n=8 Octane n=4 Butanen=9 Nonane n=5 Pentanen=10 Decane

Straight and Branched-Chain Isomers of Alkanes Methyl – Ethyl - Propyl - Isopropyl – Butyl – tert-Butyl -

Naming Branched Chain Alkanes IUPAC (International Union of Pure and Applied Chemistry) Find the longest chain of Carbons(this determines the parent name) Number them from the end with the most branching. When two or more substituents are identical, indicate this by the use of prefixes di, tri, tetra, etc. If there are more different groups, the groups are listed alphabetically (ignore prefixes).

Naming Alkanes 2,4- di methylheptane

Naming Alkanes 3-Methylheptane

Naming Alkanes 3,3,5,6-tetramethyloctane

Naming Alkanes 3-ethyl-2,2-dimethyl-hexane

Naming Alkanes 2,2,4-Trimethylpentane AKA Isooctane ISOMERS