Chapter 19: Organic Chemistry

1

• Chapter 19 Organic Chemistry

2
Organic Compounds

• Organic Compounds are compounds containing
  carbon.
• In the past these compounds were thought to be
  derived only from living sources due to a vital
  force.
• Friedrich Wöhler disproved this by synthesizing
  urea from inorganic sources.

3
Inorganic Compounds

• Inorganic compounds do not contain carbon.
• Some carbon-containing compounds are classified
  as inorganic
• CO, CO2
• Compounds containing the following ions
• CO32-, HCO3-, CN-, CNO-
• The element carbon ( C ) in the form of graphite
  or diamond is inorganic.

4
Properties of Compounds

• Organic
• Low melting points
• Insoluble in water
• Soluble in organic solvents
• Less dense than water
• Flammable
• Molecules with covalent bonds.
• Water solutions do not conduct electricity.

• Inorganic salts
• High melting points
• Soluble in water
• Insoluble in organic solvents
• Nonflammable
• Ionic bonds
• Water solutions conduct electricity

5
Hydrocarbons

• Hydrocarbons are compounds that only contain
  hydrogen and carbon.
• In saturated hydrocarbons, each carbon atom in
  the compound is bonded to four other atoms by
  single bonds. (No double or triple bonds.)
• Alkanes are examples of saturated hydrocarbons.

6
Example Alkanes

• Methane, CH4

These formulas and structural formulas do not
accurately reflect the geometry of the
molecules. Each carbon atom is surrounded by
hydrogens or carbons in a tetrahedral shape, with
109.5o bond angles
H H C H H
Ethane, C2H6
H H H C C H
H H
7
Tetrahedral Shape of Carbon Compounds
Insert figure 19.3 b
8
Alkanes

• The general formula of alkanes is CnH2n2
• The name of an alkane is a prefix plus ane.
• Where n is an integer 1,2,3
• Name n 2n2 formula
• Methane 1 4 CH4
• Ethane 2 6 C2H6
• Propane 3 8 C3H8
• Butane 4 10 C4H10
• Pentane 5 12 C5H12

9
Isomers

• Isomers are compounds with the same molecular
  formula but a different structural formula.
• Isomers have different properties.
• For example C4H10

mp -138oC bp 0.5oC
mp -159oC bp -12oC
10
Homologs

• Homologs are a series of compounds like the
  alkanes that differ from each other by the number
  of CH2 groups
• Methane, ethane, propane, butane, pentane,
  hexanes, heptane
• Properties vary in a regular and predictable
  manner.
• Properties of the alkanes (a homologous series)
  vary as the molar mass increases.
• Melting point, boiling point, and density
  increase as molar mass increases.

11
Properties of Alkanes

• Physical
• Less dense than water, insoluble in water,
  dissolve non-polar substances like fats oils and
  waxes.
• Chemical
• Combustion
• CH4(g) 2O2(g) CO2(g) 2H2O(g) heat
• Formation of alkyl halides
• CH4(g) Br2(l) CH3Br(g) HBr(g)

12
Condensed Structural Formulas

• Condensed structural formulas show hydrogens
  right next to the carbon atoms to which they are
  attached
• Structural Formulas

Condensed Formulas
CH3CHCH3 CH3
CH3CH2CH2CH3
13
IUPAC Nomenclature

• Rules for naming chemical compounds are given by
  the International Union of Pure and Applied
  Chemistry, IUPAC.
• Rules for naming alkanes
• 1. Name the longest continuous chain-this is the
  parent name.
• 2. If there are branches, name these as alkyl
  groups
• -CH3 methyl
• -CH2CH3 ethyl
• -CH2CH2CH3 propyl

14
Alkane Nomenclature (cont.)

• Name the alkyl groups in alphabetical order, then
  name the parent compound.
• Indicate the position of the alkyl group by a
  numerical position based on counting the number
  of carbons from one end of the continuous chain.
  Count from the end that gives the lowest numbers
  to each alkyl group.
• If there is more than one alkyl group of the same
  type indicate the number of groups with a prefix

penta 5 hexa 6 hepta 7
di 2 tri 3 tetra 4
15
Example Problem

• Name the following compound

1. Identify the longest continuous chain
-The longest continuous chain (shown in blue) is
5 carbons long. The parent name is pentane.
16
Example Problem (continued)

• Identify the alkyl groups

The alkyl groups are all shown in red. They are
all -CH3 or methyl groups.
There are three methyl groups, making it trimethyl
The compound name is now trimethylpentane
17
Example Problem (continued)

• Number the chain

or
Methyl groups are 2,4,4
Methyl groups are 2,2,4
Lowest combination, choose this one
18
Example Problem (continued)

• Putting it all together, the compounds name is
• 2,2,4-trimethylpentane

19
Unsaturated Hydrocarbons

• Alkenes contain one or more double bonds.
• For example ethene or ethylene

Ethylene is used in the production of
polyethylene, a plastic, and ethylene glycol, an
antifreeze.
Propene or propylene is another important alkene
Propylene is used in the production of
polypropylene, a plastic, and isopropyl
alcoholrubbing alcohol.
20
Unsaturated Hydrocarbons

• Alkynes contain one or more carbon-carbon triple
  bond.
• An important alkyne is acetylene, C2H2.

Acetylene is used in welding torches and in
making other organic chemicals.
21
IUPAC Nomenclature of Alkenes and Alkynes

• 1. Find the longest continuous chain containing
  the double or triple bond.
• 2. Name the corresponding alkane and change the
  ane ending to ene for alkenes, diene for
  alkenes with two double bonds, and yne for
  alkynes.
• 3. Number the chain so as to give the double or
  triple bond the lowest number. Place a numerical
  prefix in front of the parent name to indicate
  the position of the first carbon in the double or
  triple bond.
• Number and name alkyl groups as with alkanes.

22
Name the following compound
The longest continuous chain containing the
double bond is 5 carbons long and is indicated in
blue, below
The parent compound is derived from pentane. The
parent alkene is pentene.
23
Naming Alkenes
Number the chain to give the double bond the
lowest number
This would make the parent name be 1-pentene.
There are two methyl groups in the 2 and 3
positions.
The compound name is 2,3-dimethyl-1-pentene
24
Cis and Trans Isomers

• Some alkenes can have the same connection of
  atoms, but have a different arrangement in three
  dimensional space.
• This is due to the lack of free rotation about
  the double bond.
• The different arrangements are geometric isomers.
• One of the isomers is cis- the other is trans.

25
2-butene
CH3 groups opposite sides
CH3 groups same side
mp -139oC
mp -106oC
26
Geometric Isomers of 2-butene
Insert figure 19.11
27
Reactions of AlkenesAddition Reactions

• Addition of hydrogen yields an alkane

Ni
Note the Ni catalyst.
H2
ethene

• Addition of a halogen yields a dihaloalkane

Br2
ethene
28
Hydration of Alkenes

• Addition of water with a sulfuric acid catalyst
  yields an alcohol

H2SO4
H2O
29
Polymers

• Alkenes can be added together in a polymerization
  reaction. For example, ethylene (the monomer)
  can be polymerized to form polyethylene (the
  polymer).

H H H H H H C C
C C C C H H H H
H H


30
Part of the Polyethylene Chain
INSERT FIGURE 19.12
31
Aromatic Hydrocarbons

• Aromatic Hydrocarbons are based on the compound
  benzene, C6H6. Aliphatic compounds do not have
  the benzene ring.
• Kekulé found the structure to be a ring

Benzene can be represented as
32
Resonance Hybrids

• Structural evidence shows that there are not
  alternating double and single bonds in benzene.
  The electrons in the double bonds seem to be
  delocalized over all bonds. This is represented
  as a resonance hybrid

or
33
Some Important Aromatic Compounds
34
The Phenyl Group

• The benzene ring can be used as a branch in an
  alkane. In this case it is called the phenyl
  group.
• The phenyl group has the formula -C6H5, and is
  represented

CH3CHCH2CH2CH2CH3
This compound is 2-phenylhexane
35
Alcohols

• Alcohols have one or more OH groups in place of
  hydrogen in an alkane.
• The OH group is called a functional group.
• Functional groups serve to classify compounds and
  are responsible for the compounds chemical
  reactivity.
• To name an alcohol, replace the e ending of the
  alkane with ol.

36
Ethylene
Insert figure 19.8
37
Classification of Alcohols

• Primary, 1o

Secondary, 2o
Tertiary, 3o
38
Classification of Alcohols
Insert figure 19.15
39
Phenols

• Alkyl groups (methyl, ethyl, etc.) can be
  represented by R.
• Phenyl groups and substituted phenyl groups can
  be represented as Ar.
• An alcohol would be ROH.
• A phenol is ArOH
• For example

40
Ethers

• Ethers have the formula ROR, ROAr, or ArOAr.
• They have a C-O-C bond arrangement.
• For example

41
Aldehydes and Ketones

• Aldehydes and Ketones have the Carbonyl
  functional group

Aldehydes have one or two hydrogens attached to
the carbonyl carbon
Ketones have two alkyl or aryl groups attached to
the carbonyl carbon
Or
42
Carboxylic Acids

• Carboxylic acids contain the carboxyl group

Or -COOH

• Example carboxylic acids are
• Methanoic (formic) acid HCOOH
• Ethanoic (acetic) acid CH3COOH

43
Esters

• Esters are prepared by reacting acids with
  alcohols
• RCOOH ROH RCOOR H2O

H
For example, ethyl acetate is prepared by
reacting acetic acid with ethanol
H
CH3COOH CH3CH2OH
H2O
44
Amines

• Amines contain the amino group
• (R or Ar)-N

Tertiary, 3o
Secondary, 2o
Primary, 1o
45
Amides

• Amides are formed by the reaction of acids and
  ammonia or 1o or 2o amines and then heating
• RCOOH R2NH

D
RNH2RCOO-
H2O
For Example
D
NH4 CH3COO-
H2O
NH3
ammonia
Ammonium acetate