1

Separating Mixtures of OrganicCompounds Crude oil is a

mixture of manydifferent compounds

Crude oil cannot beused until itscomponents areseparated

Separation methods can bephysical or chemical Fractional

distillation is aphysical method

It separates amixture on the basisof boiling points

Oil refineries use atower to do this

2

Crude oil enters thebottom of the towerand is heated until itvaporizes

The temperature ishighest at thebottom of the tower

The lower the boilingpoint of acomponent thehigher up in thetower it will go

As fractions cool totheir boiling pointthey condense andare collected

Solvent extraction is used to purify theresidue of fractional distillation

The residue contains hydrocarbons witha high molar mass

Solvents are mixed with this residue todissolve impurities

Chemical Refining

The fractions can also be chemicallyrefined to make them more useful

Two processes:– Cracking

– Reforming

3

Cracking

Heating a hydrocarbon in the absence of air– Causes carbon carbon bonds to break

– Takes long chain hydrocarbons and breaks theminto smaller ones

Reforming

Uses heat, high pressure and catalysts toconvert straight chain alkanes into branchedand cyclic alkanes and aromatics (which havebetter burning properties)

Assignment

Page 582 Questions 1-8 (you may have toread Section 14.4 in your textbook)