Chapter 20: Organic Chemistry
 The chemistry of carbon compounds.
 Mainly carbon and hydrogen atoms.
 Many organic compounds occur naturally.
 Thousands more can be synthesized by man.
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NaCl versus Butane
 NaCl, 58.5 g/mol
 C4H10, 58.1 g/mol
 Bonding is ionic
 Bonding is covalent
 M.P. = 801oC
 M.P. = -138oC
 B.P. = 1413oC
 B.P. = 0oC
 Dissolves in water
 Not soluble in water
 Will not burn
 Will burn in air
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Molecular Geometry
 There are three hybridization states and
geometries found in organic compounds:
 sp3 Tetrahedral
 sp2 Trigonal planar
 sp Linear
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Classes of Organic Compounds
Aliphatic
Saturated
Alkanes
Aromatic
Unsaturated
Cycloalkanes
Benzene Ring
Alkenes
Alkynes
4
Alkanes
 “Saturated” hydrocarbons
 All C-C single (sigma) bonds
 Formula = CnH2n+2
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Formulas
 Structure is very important in organic chemistry.
 Propane = C3H8, chemical formula
 Complete structural drawing – shows every single bond.
H H H



H–C–C–C–H



H H H
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Formulas
 Condensed structural drawing collapses the H atoms
that are bonded to EACH carbon atom.
 CH3 – CH2 – CH3 , condensed formula.
 This is how a formula is written.
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Formulas
 The molecule is really
NOT linear, though.
 The sigma bonds in the
alkanes have free
rotation.
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First Ten Alkanes: Base Names
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Structural Isomers
 For four
carbons,
there are two
ways to
arrange.
 For five
carbons,
there are
three ways to
arrange.
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IUPAC Nomenclature
 A name of a compound consists of three parts.
 Prefix, Base, and Suffix
prefix
substituents
base suffix
longest chain
family
(how many C’s)
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IUPAC Nomenclature
 A substituent is any group that is attached to the
longest chain of carbon atoms.
 CH4 = methane, -CH3 = methyl
 CH3CH3 = ethane, -CH2CH3 = ethyl
 Cl = chloro, Br = bromo, I = iodo
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IUPAC Nomenclature
1.
2.
3.
•
Find the longest chain in the molecule.
Number the chain from the end nearest the first
substituent encountered.
List the substituents as a prefix along with the
number(s) of the carbon(s) to which they are
attached.
LEP #1
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Cycloalkanes
 A ring structure can be constructed from alkanes of
three or more carbons by removing two hydrogen
atoms.
 Because they form a geometric shape, a shorthand
method for their structure is that shape.
 Rings with 5 and 6 carbons are the most stable.
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IUPAC Nomenclature
 For ring structures, a mono-substituted ring does not
need a number.
 Why???
 For di-substituted ring structures, number starting
from the location of one the substituents and then go
CW or CCW to give the next one the lowest number.
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Haloalkanes
 A haloalkane is placing a halogen (group 7A) atom in
place of a hydrogen atom.
 Naming uses the fluoro, chloro, bromo, and iodo
names.
 Haloalkanes are used as refrigerants (CF3CH2F) and
anesthetic agents (CF3CHClBr).
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Stereoisomerism and Optical Isomerism
 Stereoisomers = molecules in which
the atoms have the same
connectivity, but have a different
spatial arrangement.
 Geometric = cis / trans (alkenes)
 Optical isomers = are two molecules
that are non-superimposable.
 Optical isomers are much like your
hands – they are not
superimposable!
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Chirality
 Any carbon with four unique groups bonded to it
are said to be chiral.
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Chirality
• If one of the two optical isomers is present, then it will
rotate plane-polarized light to the left or to the right.
• An equal amount of both isomers will not rotate the light
and is said to be a racemic mixture.
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Chirality
 Many important biochemical molecules are chiral.
 Many important pharmaceuticals have at least one
chiral carbon.
 Ex) Ibuprofen
Chiral Carbon
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Properties and Reactions of Alkanes
 Alkanes are non-polar and, thus, do NOT dissolve
in water.
 Alkanes typically have a density of 0.65 – 0.70
g/mL and will float on the surface of water.
 Alkanes are relatively unreactive.
 They burn in air, though, to produce energy.
 Halogenation: CH3CH3 + Cl2 
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Alkenes
 Called “unsaturated”
 Contain at least one C=C double bond
 Simplest alkene = C2H4
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Alkenes
 The double bond does not allow for free-rotation.
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IUPAC Nomenclature
 Naming an alkene.
1. Find the longest chain that includes the double bond.
Suffix name uses –ene ending.
2. Number the chain so that the double bond gets the
lowest numbers (has priority over other substituents).
Only four carbons or longer will need a number for the
double bond position. Use only the lowest number for
start of double bond.
3. Number substituents based on this numbering.
4. Cycloalkenes – the double bond is ALWAYS position #1
and #2.
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Geometric Isomers
 Some alkenes can have geometric isomers due to
rigid shape around double bond.
 Requires two different sets of groups on each side
of the double bond – one large and one small.
A
B
C=C
B
A
 Opposite = trans, Same side = cis
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Addition Reactions
 Alkenes undergo an “addition” reaction by adding a
small molecule across the double bond.
 Hydrogenation
 Halogenation
 Hydration
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Aromatic
Hydrocarbons
 Benzene, C H , is a ring
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structure like the
cycloalkanes.
 However, it is very different
from the cycloalkanes, whose
ring structures are fairly easy
to break open.
 Benzene is VERY stable and
found in many important
molecules like aspirin,
vanillin, and acetaminophen.
 What makes it unique?
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IUPAC Nomenclature
 Mono-substituted benzene needs no number.
 Some have special (common) names.
 Toluene, Phenol, and Aniline.
 Di-substituted benzene rings are numbered like
the cycloalkanes.
 Substituted toluenes, phenols, and anilines have
those groups as the first position.
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Functional Groups
 Addition of atoms like O, N, and S add reactivity and
polarity to the alkanes.
 Can occur in many different ways.
 Will need to know the nomenclature and reactions of
some and be able to identify all.
 The letter “R” is a generic designation for an alkyl
group.
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Alcohols
 Alcohols contain the hydroxyl (OH) group.
 R-OH
 Alcohols are classified as primary, secondary, and
tertiary.
Primary (1º)
1 group
H
|
CH3—C—OH
|
H
Secondary (2º)
2 groups
CH3
|
CH3—C—OH
|
H
Tertiary (3º)
3 groups
CH3
|
CH3—C—OH
|
CH3
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IUPAC Nomenclature
 Alcohols get an –ol suffix.
 The –OH group MUST have the lowest number – it has
priority.
 On a cycloalkane, it is carbon #1.
 On benzene it is called phenol.
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Properties of Alcohols
 The –OH group can make the molecule soluble in
water due to HB force.
 C1 to C4 are very soluble in water.
 More than five carbons, though, is virtually
insoluble.
 CH3 – CH2 – CH2 – CH2 – CH2 – CH2 - OH
long chain is non-polar (dominates)
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Reactions of Alcohols
 Oxidation = loss of two H’s or gain of O.
 Depends on primary, secondary or tertiary.
 Primary Alcohol  Aldehyde  Carboxylic Acid
 Secondary Alcohol  Ketone
 Tertiary  No Reaction
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Ethers
 An O atom separating two alkyl groups.
 R – O – R’
 Oxygen atom is polar, so smaller ones are soluble in
water.
 CH3 – CH2 – O – CH2 – CH3
 MTBE
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Thiols
 A sulfur atom – usually with an H attached.
 R – SH
 CH3 – CH2 – SH, Ethanethiol
 These compounds smell BAD!
 One amino acid has this thiol group.
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Carbonyl Group
 Many functional groups contain a C = O group.
 Aldehyde = the C = O group is terminal.
 R-CHO
 CH3 – CH2 – C – H

O
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Carbonyl Group
 Aldehydes use the –al suffix.
 The carbonyl carbon is automatically the first
position.
 Ketone = the carbonyl group is in the middle
of the chain.
 Smallest ketone has three carbons
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Carbonyl Group
 Ketones use an –one suffix.
 Number is needed for five or more C’s.
 Carboxylic Acid = carbonyl group with a hydroxyl
group attached.
 R – COOH
 Are many of the weak acids seen in Ch. 16.
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Carbonyl Group
•Formulas are written differently!
•Ex) Acetic Acid
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Carbonyl Group
 Naming acids – use the –oic suffix plus the name acid.
 Like aldehydes, the –COOH group is terminal, so it is
C #1.
 Esters = has both the carbonyl and the ether type O
atom.
 R – COO – R’
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Carbonyl Group
 An ester is made by the reaction of an alcohol and a
carboxylic acid.
 R – C – OH + HO – R’  R – C – O – R’


O
O
 The –OH and –H produce water.
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Amine





An amine contains the N atom.
These can be primary, secondary, or tertiary.
R –NH2 , R2 –NH , and R3 –N.
The N group has a lone pair that will accept a proton
Therefore, these are the weak bases from Ch. 16.
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Amide
 Contain the carbonyl group AND the amine group.
 R – (C=O) – NH2
 The N group can also have an R group.
 Made by the reaction of a carboxylic acid plus an
amine.
 Similar to ester reaction.
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Polymers
 A polymer is a long chain of repeating units called
monomers.
 Monomers are typically small alkenes.
 Reaction is called an addition reaction and are referred to
as addition polymers
 Initiated by organic peroxide, R-O-O-R’, which is split into
two fragments, 2 R-O
Benzoyl peroxide
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Common Monomers
 CH2=CH2, ethylene makes polyethylene.
 Two forms – low density and high density
 Uses:
 CH2=CHCl, vinyl chloride makes PVC.
 Uses:
 CH2=CHCH3, propene makes polypropylene.
 Uses:
 CF2=CF2, tetrafluoroethene makes Teflon.
 Uses:
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Common Monomers
 CH2=CCl2, 1,1-dichloroethene makes Saran.
 Uses:
 CH2=CH(C6H5), phenylethene makes polystyrene.
 Uses:
 Recycling – uses a series of symbols and numbers to
identify the type.
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Condensation Polymers
 Polyurethanes, Nylons, Rayons, etc. are produced
using the ester and/or amide reaction.
 Monomer units have two functional groups per
molecule.
 PETE = ethylene glycol + terephthalic acid
 Nylon 6,6 = adipic acid + hexamethylenediamine
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