Transcript Organic PowerPoint

Chapter 22
Hydrocarbon
Compounds
Organic Chemistry and
Hydrocarbons
 Organic
originally meant chemicals
that came from organisms
 1828 German chemist Friedrich
Wohler synthesized urea in the lab
 Today, organic chemistry is the
chemistry of virtually all compounds
containing the element carbon
Organic Chemistry and
Hydrocarbons
 Over
a million organic compounds,
with a dazzling array of properties
 Why so many? Carbon’s unique
bonding ability!
 Let’s start with the simplest of the
organic compounds: Hydrocarbons
Organic Chemistry and
Hydrocarbons
 Hydrocarbons
contain only two
elements: hydrogen and carbon
– simplest hydrocarbons called
alkanes, which contain only single
covalent bonds
– methane (CH4) with one carbon is the
simplest alkane. It is the major
component of natural gas
Models of Methane
Organic Chemistry and
Hydrocarbons
 Review
structural formula- p. 698
 Carbon has 4 valence electrons,
thus forms 4 covalent bonds
– not only with other elements, but also
forms bonds WITH ITSELF.
 Ethane
(C2H6) is the simplest alkane
with a carbon to carbon bond
Straight-Chain Alkanes
 Straight-chain
alkanes contain any
number of carbon atoms, one after
the other, in a chain -meaning one
linked to the next
C-C-C
 Names
C-C-C-C
etc.
of alkanes will always end
with -ane
Straight-Chain Alkanes
 Combined
with the -ane ending is a
prefix for the number of carbons
– Table 22.1, page 700
 Homologous
series- a group of
compounds that have a constant
increment of change
 In alkanes, it is: -CH2-
Alkane Hydrocarbons
Name
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Molecular Form
CH4
C2H6
Alkane Prefixes –
C3H8
The root indicates the
C4H10
number of carbon atoms
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
Straight-Chain Alkanes
 Many
alkanes used for fuels:
methane, propane, butane, octane
 As the number of carbons increases,
so does the boiling and melting pt.
– The first 4 are gases; #5-15 are liquids;
higher alkanes are solids
 Condensed
structural formulas?
Note examples on page 702
Alkane Melting and Boiling Points
Functional Groups
 Most
organic chemistry involves
replacing one or more of the hydrogen
atoms with a ‘substituent group’
– Groups often contain C, O, N, S, or P
– They are also called “functional groups”the chemically functional part of the
molecule. They change the properties or
function of the molecule.
Alcohols
 Alcohols
- a class of organic
compounds with an -OH group
–The -OH functional group in
alcohols is called a “hydroxyl”
group; thus R-OH is the formula
 How
is this different from the
hydroxide ion with basics? (covalent
bonding with carbon- not ionic with a metal such
as sodium)
Methanol Structure
Ethanol Ball and Stick
Alcohols
 Both
IUPAC and common names
 For IUPAC:
–drop the -e ending of the parent
alkane name; add ending of -ol,
number the position of -OH
–parent is the longest chain that
contains the carbon with the
hydroxyl attached.
Alcohols
 Common names:
–similar to halocarbons,
meaning name the alkyl
group followed by the word
‘alcohol’
–One carbon alcohol = methyl
alcohol
Properties of Alcohols
 Denatured
alcohol- means it has
been made poisonous by the
addition of other chemicals, often
methyl alcohol (methanol, or wood
alcohol). As little as 10 mL of
methanol has been known to cause
permanent blindness, and 30 mL
has resulted in death!!!
Alkenes
 Multiple
bonds can also exist
between the carbon atoms
 Hydrocarbons containing carbon to
carbon double bonds are called
alkenes
C=C
C-C=C
 Called “unsaturated” hydrocarbons
if they contain double or triple
bonds
Alkynes
 Hydrocarbons
containing carbon to
carbon triple bonds called alkynes
-C C Alkynes are not plentiful in nature
 Simplest is ethyne- common name
acetylene (fuel for torches)
 Table 22.5, page 715 for b.p. and m.p.
Section 22.5
Hydrocarbons from the Earth

OBJECTIVES:
–Identify three
important fossil
fuels and
describe their
origins.
Natural Gas
 Fossil
fuels provide much of the
world’s energy
 Natural gas and petroleum contain
mostly aliphatic (straight-chain)
hydrocarbons
 Natural gas is an important source
of alkanes of low molecular mass
Natural Gas
 Natural
gas is typically:
– 80% methane, 10% ethane, 4%
propane, and 2% butane with the
remainder being nitrogen and higher
molar mass hydrocarbons
– also contains a small amount of He,
that is recovered and used in various
industries, including balloons
Natural Gas
 Natural
gas is prized for
combustion, because with
adequate oxygen, it burns with a
hot, clean blue flame:
CH4 + 2O2 → CO2 + 2H2O + heat
 Insufficient
burning has a yellow
flame, due to glowing carbon parts,
as well as making carbon monoxide
Petroleum
 The
compounds found in petroleum
(or crude oil) are more complex
than those in natural gas
 Usually straight-chain and
branched-chain alkanes, with some
aromatic compounds also
 Crude oil must be refined
(separated) before being used
Petroleum Fractional Distillation
Crude Oil Components
Petroleum
 It
is separated by distillation into
fractions, according to boiling pt.
 Fractions containing higher molar
mass can be “cracked” into more
useful shorter chain components,
such as gasoline and kerosene
– involves catalyst and heat
– starter materials for plastics and
paints
Petroleum Cracking
Coal
 From
huge fern trees and mosses
decaying millions of years ago
under great pressure
 Stages in coal formation:
1. Peat- soft, fibrous material much
like decayed garden refuse; high
water content. After drying will
make a low-cost, smoky fuel
Coal
2. Lignite- peat left in the ground
longer, loses it’s fibrous texture,
and is also called brown coal
– harder than peat; higher C content
(50%); still has high water content
3. Bituminous, or soft coal- formed
after more time; lower water
content, higher C content (70-80%)
Coal
4. Anthracite, or hard coal
– carbon content exceeding 80%,
making it an excellent fuel source
 Coal
may be found close to the
surface (strip-mined), or deep
within the earth
 Pollutants from coal are common;
soot and sulfur problems
Scrubbing Sulfur From Coal
Coal
 Coal
may be distilled for many
products
– coal gas, coal tar, coke, and ammonia
– further distilled into benzene, toluene,
naphthalene, phenol, and pitch
– Coke is almost pure carbon; produces
intense heat and little or no smoke,
thus used in industrial processes