Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Chapter 1 – Structure and Physical Properties of Organic Compounds
Section 1.1 – Introducing Organic Compounds
The Modern Definition of Organic Compounds
 Organic Compounds: type of compound in which carbon atoms are nearly always
bonded t each other, to hydrogen atoms, and occasionally to atoms of a few specific
elements (O, F, Cl, N, Br, S, P, I)
o Exceptions: Carbonates (CO32-), cyanides (CN-), carbides (C22-) and oxides of
carbon (CO, CO2)
 These do not contain any carbon-carbon or carbon-hydrogen bonds
 Inorganic Compounds: A type of compound that includes carbonates, cyanides,
carbides, and oxides of carbon, along with all compounds that do not contain carbon
atoms
The Special Nature of Carbon Atoms
 Why is carbon so special? What is it about carbon that makes it the basis for all living
things?
 Recall: Carbon has four valence electrons (Electron Configuration: 1s22s22p2). This
means that the outer valence shell is exactly half full and therefore carbon can form 4
covalent bonds. These outer electrons can hybridize to sp3, sp2, and sp orbitals, which
means they can form single, double and triple bonds. Additionally, carbon has
intermediate electronegativity (EN = 2.5), which means it is far more likely to share
electrons than to gain or lose enough electrons to form ions.
 Shapes of carbon structures
Shape
Hybridization
Diagram and Example
H
Tetrahedral
sp3
H
C
H
H
CH4
H
Trigonal Planar
H
sp2
C
O
CH2O
H
Linear
C
sp
N
HCN
Representing Molecules
In organic chemistry, there are many ways to represent molecules: the molecular formula, the
structural formula, the ball and stick model, and the space-filling model are some examples,
each one gives different information about the molecule
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
For example: Ethane (C2H6)
Molecular Formula
C2H6
Structural Formula
H
H
H
C
C
H
H
Ball and Stick Model
Space Filling
H
Additionally: Chemists often abbreviate structural diagrams, because organic molecules often
contain a lot of hydrogen and carbon.
Example: C4H10
H
H
H
H
H
C
C
C
C
H
H
H
H
CH2
vs.
H
Structural Formula
H3C
CH3
CH2
vs.
Condensed
Structural Formula
Line Structural Formula
Each bend or end-point represents a carbon atom, it is assumed that there are enough
hydrogens to complete the octet and form 4 bonds unless otherwise written.
Isomers
 Carbon atoms can form bonds with each other, which often results in long straight or
branched chains of atoms. Each carbon can also be boned to hydrogen or atoms of other
elements. However, once you have enough carbons and hydrogen, the atoms can attach
to each other in different ways; that is, they have the same molecular formula but they
have a different structural formula
For Example: Each of the following molecules has the formula C5H12 – they all contain 5 carbons
and 10 hydrogens.
H
H
H
H
C
C
C
C
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
H
H
H
C
H
H
H
H C H
H
H
H C
H
C
C H
H
H C H
H
Each one of these molecules would have different physical properties, because the arrangement
of the atoms is different


Isomers: molecules that have the same molecular formula but their atoms are in
different arrangements
Constitutional Isomers: molecules that have the same molecular formula but their
atoms are bonded together in different sequences (i.e. the examples above)
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds

Note: sometimes it is hard to tell if two molecules are isomers – remember, molecules
are free to rotate, and individual atoms can rotate around a single bond.
Consider the following:
H
H
H
H
H
C
C
C
C
H
H
C
H
H
H
H
H
H
H
H
H
C
C
C
C
H
H
H
vs.
H
H
H
C
H
H
These two molecules look structurally different, as drawn. BUT, they aresimply rotated
180, or flipped horizontally
OR:
H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
H
vs.
H
H C HH
H
H
H C
C
C
C
H
H
H
H
H
Because atoms can rotate around a single bond, these are the molecule and are not
isomers of each other.
Carbon atoms can also for ring structures with three or more atoms. For example, each of the
following molecules is a constitutional isomer of the formula C5H10
H
H
H
H
C
C
C
H
H
H
H
H
C
C
H
H
H
H
H
C
C
C
C
H
H
H
H
C
H
H
H
H
H
H
C
H
H
C
C
C
H
H
C
HH
H
H
C
H
H
C
H
C
H
H
C
H
H
C
C
H H
H
H
H
C
H
H
C
C
C HH
H
Stereoisomers
 An important property of double bonds is that they ‘lock’ a structure in place: atoms
cannot rotate around them. These make the molecule flat and rigid
 This leads to another type of isomer called a stereoisomer
 Stereoisomer: molecules that have the same molecular formula and their atoms are
bonded together in the same sequence, but differ in the three-dimensional orientations
of their atoms
o There are two kinds of stereoisomers: enantiomers and diastereomers
Diastereomers
 Diastereomers: stereoisomer based on a double bond, in which different types of atoms
or groups are bonded to each carbon in the double bond
H
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Example: C4H8, the molecules shown below contain a double bond between the second and
third carbon
H
CH3
C
H3C
H3C
C
CH3
C
H
trans-2-butene
C
H
H
cis-2-butene
The trans- isomer has the identical CH3 groups on opposite sides of the double bond, the
cis- isomer has identical CH3 groups on the same side of the double bond. The groups do
not have to be identical, as long as the larger groups are on the same side of the double
bond, it is cis and if they are on different sides then it is trans
The difference between cis- and trans- isomers is very important, especially in metabolic
processes.
Note: triple bonds do not form diastereomers
Enantiomers
 Enantiomers: are non-superimposable mirror images of each other. They occur when a
single carbon is bonded to four different types of atoms or groups
 Example: CHFClBr


A more common example of enantiomers is your hands: they are perfect mirror images
but you cannot superimpose them on each other. We even distinguish between different
forms by conventions of right-handed or left-handed enantiomers
Catch: these have IDENTICAL chemical properties, but are often metabolized differently,
which makes this property incredibly important in pharmaceuticals and can be deadly if
not taken in to account in synthesis processes
o Example: Thalidomide
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Section 1.2 – Hydrocarbons

Hydrocarbons: organic compounds that contain only carbon atoms and hydrogen
atoms
o Example: fossil fuels such as natural gas and gasoline
Alkanes
 Alkane: the simplest hydrocarbon in which all carbon atoms are joined together by
single covalent bonds
o Also called Saturated Hydrocarbons: hydrocarbons that contain only single
bonds, no double or triple bonds, that is, each carbon atom is bonded to the
maximum possible atoms and all of them are sp3 hybridized
 The simplest alkane is methane (CH4) and each additional alkane adds either a CH2 or
CH3 to the chain
 The general formula for a straight or branched alkane is CnH2n+2
o Therefore: if you have an alkane with 5 Carbons: C5H2×5+2 = C5H12
H
H
C
H
H3C
H
Methane

CH3
H3C
Ethane
CH2
CH2
CH3
Propane
H3C
CH3
CH2
Butane
Alkanes can also have substituent groups, where an atom or groups of atoms has been
substituted in place of a hydrogen, often called a side group
Naming Alkanes
The International Union of Pure and Applied Chemistry (IUPAC) has a system for naming
organic compounds. Each organic compound name has the following components:




Root: denotes the number of carbon atoms in the longest continuous chain of carbon
atoms
Prefix: gives the positions and names of any branches from the main chain
Suffix: indicates the series to which the molecule belongs. The suffix for alkanes is ‘-ane’
Alkyl Groups: a side group based on an alkane; to name them you use the same root as
the main chain, but instead of the suffix ‘-ane’ you use ‘-yl’
Number of
Carbon
Atoms
1
2
3
4
5
Root Name
Side Group
Name
methethpropbutpent-
methylethylpropbutpent-
Number of
Carbon
Atoms
6
7
8
9
10
Root Name
Side Group
Name
hexheptoctnondec-
hexyl
heptyl
octyl
nonyl
decyl
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Steps for Naming Alkanes
Name the following compound:
CH3
CH2 CH3
CH2 C HC
H3C
CH3
CH2 CH3
CH3
1. Identify Root
CH2 CH3
a. Identify the longest continuous carbon
CH2 C HC
chain
b. Find the root for the number of H C
CH2 CH3
3
CH3
carbons in the chain
2.
3.
a.
b.
c.
d.
e.
f.
4.
The longest chain is six carbon atoms,
therefore the root is hexIdentify the Suffix
The compound is an alkane, therefore the
suffix is ‘-ane’
Identify the Prefix
a. Two side groups have one C atom, the
The prefix indicates the position and
other has two
CH3
type of side groups on the main chain.
CH2 CH3
To identity the prefix:
CH2 C HC
Identify the number of carbon atoms in
each side group
H3C
CH2 CH3
CH3
Determine the number of each side
group according to the number of
b. The side groups with one carbon atom
carbons
are methyl groups, the other side group
If there is more than one side group,
is an ethyl group.
write their names in alphabetical order
c. Alphabetical order: ethyl, methyl
Find the position of each side group.
d.
Numbering must begin at the end of
CH3
CH2 CH3
the chain that gives the lowest possible
5
6
numbers.
CH2 C HC
Precede the name of each side group
2
3
4
with the number of carbon atoms to H3C
CH2 CH3
CH3
1
which it is attached on the main chain.
Use a hyphen to separate numbers and
words, and use a comma to separate The compound is numbered from left to right.
This gives the side numbers 3, 3, 4. The two
the numbers
Use a prefix to indicate how many of methyls are on C-3, and ethyl is on C-4.
e. The prefix is now: 4-ethyl-3,3-methyl
each type of side group there are if
f. The two methyl groups make the
there is more than one of the same
prefix: 4-ethyl-3,3-dimethylgroup: di, tri, tetra, penta. These
additional prefixes do not affect the
alphabetical order established before
Name the Compound
4-ethyl-3,3-dimethylhexane
Combine the prefix, root, and suffix.
Note: no space, dash, or comma between
prefix, root, and suffix
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Practice 1: Name the following alkanes
a.
b.
(answer: 2,3,4-trimethylpentane)
(answer: 4,5-diethyl-3,6-dimethyloctane)
Drawing Alkanes
Example: Draw the line structural formula for 3-ethyl-3-methylpentane
1. Identify the root
The root is pent- so there are five carbons in
The root of the name gives the number of the main chain
carbon atoms in the main chain
2. Identify the suffix
The suffix is –ane, so the compound contains
only single bonds
3. Draw and number the main chain,
but do not add any hydrogen atoms C—C—C—C—C
yet
4. Identify the prefix and draw the side The prefix is 3-ethyl-3-methyl-. Therefore,
groups
there is an ethyl group and a methyl group
attached to carbon atoms 3 of the main chain.
You can place the side groups on either side of
the main chain
CH3
5. Complete the condensed structural
formula
H3C
CH2 C
CH2 CH3
CH2
CH3
6. Draw the line structural formula
Practice 2: Draw the line and condensed structures for the following molecules:
a. 3-ethyl-2-methylheptane
b. 2,3,3,-triethylpentane
Physical Properties of Alkanes
 Non-polar, therefore not soluble in water; but soluble in non-polar solvents like benzene
 Low carbon alkanes (1-4) are gases at room temperature, medium length alkanes are
liquids; long length (over 26) are solid at room temperature; property is due to
increasing number of London Dispersion Forces
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Alkenes
 Alkenes are any hydrocarbon that has at least one double bond in the carbon chain
o When a carbon has one double bond it is sp2 hybridized; when it has two double
bonds it is sp hybridized
 Unsaturated hydrocarbons: hydrocarbons that contain a double or triple bonds,
whose carbon atoms can potential bond to additional atoms if those bonds are broken.
 When naming alkenes you must include the location of all the double bonds, the carbon
indicated is the lower numbered carbon
 The suffix for alkenes is ‘-ene’
 Remember: double bonds can result in diastereomers if different side groups are
present
Examples:
H
H
H
C
H
H
H
H
H
C
H
C
H
H
Ethene
H
C
H
C
C
C
H
H
H
H
C
C
C
H
H
C
H
H
C
H
Propene
H
C
H
H
H
1-butene
1-butene
H
H
H
H
C
C
H
H
C
C
H
H
H
H
Trans-2-butene
C
H
C
H
C
HH
C
H
H
cis-2-butene
Note: cis-double bonds form kinks in long carbon chains (important for later)
Properties of Alkenes
 Non-polar, therefore do not dissolve in water; dissolve in non-polar solvents (like
benzene)
 Boiling points increase as more carbons are added
 However: alkenes have lower boiling points than alkanes of similar carbon lengths
 Slight difference in location and shape around the double bond change the boiling points
o But-1-ene = -6.3C
o Trans-but-2-ene = 0.88C
o Cis-but-2-ene = 3.71C
Naming Alkenes:
The process is the exact same as naming alkanes, except the suffix is –ene; if there is more than
one double bond, you must use ‘di’, ‘tri’, etc. to indicate the number, just as with alkyl prefixes
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Example: Name the following alkene
H3C
H3C
CH3
C
CH
HC
CH3
1. Identify the root
a. Identify the longest chain that
CONTAINS THE DOUBLE BOND(S)
b. Find the root for the number of
carbons in the chain.
H3C
H3C
CH3
C
HC
CH
CH3
The longest containing the double bond is five
carbons, therefore the root is pent-
2. Identify the suffix
a. Number the main chain by starting at
the end of the chain nearest the double
bond, giving the double bond the
lowest numbers possible
(Note: this takes precedence over any
rule for numbering alkanes)
b. If the alkene contains four or more
carbons, you must give the position in
the suffix.
3. Identify the prefix
Name the side groups on alkenes as
you would for alkanes
H3C
H3C
1
CH3
C
CH
3
HC
5
4
2
CH3
Numbering from left to right gives the lowest
possible carbon numbers
The compound is an alkene. It contains four or
more carbons. The double bond is between C2 and C-3.
The suffix is -2-ene
H3C
H3C
1
CH3
C
CH
2
3
HC
5
4
CH3
There are two methyl groups, one on C3, the
other on C4.
The prefix is 3,4-dimethyl4. Name the compound
3,4-dimethylpent-2-ene
Practice:
a.
b.
5-ethyl-3,4,5-trimethyloct-3-ene
3-ethyl-4-methylhex-2,4-diene
Practice: Draw the line structural diagram of 3-ethyl-4-methylhex-3-ene
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Alkynes
 Alkynes are hydrocarbon that contain one or more triple bonds, these are also
unsaturated hydrocarbons
 General Structural Formula: CnH2n-2
 Note: the presence of triple bonds means both carbons are sp hybridized, therefore the
structure is linear
 Triple bonds do not cause stereoisomers
Examples:
HC
HC
C
HC
ethyne
H3C
CH3
CH
propyne
C
C
C
CH3
but-1-yne
CH2
CH3
but-2-yne
Naming and Drawing Alkynes
Example: Name the following alkyne
H3C
C
CH
CH
H2C
CH3
1. Identify the root
The longest chain that includes the triple bond
a. Identify the longest chain that
is five carbon atoms, so pent- is the root
CONTAINS THE TRIPLE BOND(S)
c. Find the root for the number of
carbons in the chain.
2. Identify the suffix
Numbering starts at the end that gives the
a. Number the main chain by starting at
triple bond the lowest number, in this case Cthe end of the chain nearest the triple
1, the compound contains a triple bond.
C
bond, giving the triple bond the lowest H3C
CH 2 CH
numbers possible
1
3
(Note: this takes precedence over any
H2C
4 CH
rule for numbering alkanes, and takes
3
5
precedence over double bonds)
b. If the alkyne contains four or more
The suffix is -1-yne
carbons, you must give the position in
the suffix.
3. Identify the prefix
There is a methyl group on C-3
Name the side groups on alkynes as
The prefix is 3-methylyou would for alkynes
4. Name the compound
3-methylpent-1-yne
Example: draw the following alkyne: 4-ethylhex-2-yne
H3C
CH2
CH C
C
CH3
H2C
CH3
Physical Properties: Have higher MP/BP then analogous alkenes and alkanes
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Cyclic Hydrocarbons
 Cyclic Hydrocarbons are hydrocarbons that form rings
 These are the foundation of many biological molecules, including cholesterol and the
steroid hormones.
 Can be alkanes, alkenes, or alkynes (but alkyne-based rings are extremely unstable)
 The prefix ‘cyclo’ is added to indicate it
Examples:
CH2
H2C
CH2
Cyclopropane
H2C
CH2
H2C
CH2
Cyclobutane
H2C
CH2
CH2
CH2 CH
2
H2C
CH2
CH2
H2C
CH2
CH2
Cyclopentane
Cyclohexane
Naming Cyclic Hydrocarbons
Example:
CH3
H3C
1. Identify the root
Determine the root of carbon atoms in the ring
in order to find the root. This is the same as
the straight chain alkane, alkene, or alkyne
with the same number of carbon atoms,
preceded by cyclo2. Identify the suffix
Determine whether the molecule has all single
bonds, at least one double bond, or at least one
triple bond. The suffix is –ane, -ene, or –yne
accordingly. It is not necessary to indicate the
location of the double or triple bond, because
they are assumed to be on C-1
3. Identify the prefix
Note: if there are no side groups, then it is not
necessary to indicate the position of the side
groups; however if there are, then the double
or triple bond must be between C-1 and C-2,
numbering must go according to that
4. Name the compound
There are five carbon in the ring, therefore
cyclopent- is the root
The ring has one double bond, therefore the
suffix is -ene
CH3
H3C
3
4
5
2
1
The prefix is 3,4-dimethyl3,4-dimethylcyclopentane
Physical Properties: MP/BP are slightly higher than analogous straight chain hydrocarbons
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Aromatic Hydrocarbons
 Benzene: a cyclic aromatic hydrocarbon, C6H6, in which all six carbon-carbon bonds are
intermediate in length between a single and double bond; results from delocalized
electrons in sp2 hybridized orbitals (unhybridized p-orbitals form the delocalized pelectrons)
o Results from the resonance structures formed
o Unusually stable
 NOTE: because of the sp2 hybridization, benzene rings are FLAT
H
H
H
C
C
C
C
C
H
C
H
H
Structural Diagram


Alternating resonance forms
Resonance hybrid
Showing delocalized e-
Aromatic Hydrocarbons: compound that contains only carbon and hydrogen and
based on the structure of benzene
Aliphatic hydrocarbon: compound containing only carbon and hydrogen in which
carbon atoms form chains and/or non-aromatic rings
Naming and Drawing Aromatic Hydrocarbons
Note: the root for ALL aromatic hydrocarbons is benzene
CH3
H3C
1. Identify the root
The root is -benzene
2. Identify the prefix
a. Determine the position number of the
side groups in order to write the
prefix. The carbons in a benzene ring
are numbered if there is more than one
side group
b. Prioritize alkyl groups with six or
fewer carbons in alphabetical order.
Then continue to number in the
direction of the nearest side group
c. Write the prefix as you would for any
other hydrocarbon
3. Name the compound

CH3
CH2
-benzene
CH3
CH3
2
H3C
CH2
3
1
4
6
5
There are two methyl groups and one ethyl
group. Numbering is counterclockwise to give
the lowest numbers.
1-ethyl-2,3-dimethyl1-ethyl-2,3-dimethylbenzene
If a benzene ring is present as a side group off an alkyl chain, then it is called a phenyl
group
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Example: Name the following compound
H3C
CH2
CH
CH3
CH2
CH2
CH2
(answer: 3-phenylheptane)
Physical Properties of Aromatics:



Benzene is a liquid at room temperature, and is a common solvent for non-polar
compounds
Often have very similar MP/BP to aliphatic compounds with the same number of
carbons
These compounds often have strong odours
Section 1.2 – Hydrocarbons, Summary
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Section 1.3 – Hydrocarbon Derivatives



Organic compounds are classified according to their functional groups
Functional gropu: in a molecule, a certain gropu of atoms responsible for chemical reactions
that are characteristic of the molecule
o Responsible for chemical and physical properties of the molecules
o Change the suffix or the prefix of the compound
Hydrocarbon Derivative: a a compound made up of carbon atoms and at least one other
atom that is not hydrogen
Functional Group and the Suffix/Prefixes
Organic Compound
Alcohol
Haloalkane
General Formula For Functional Group
R
OH
Hydroxyl group
R X
(X=halogen)
Prefix or Suffix
-ol
Prefix varies with halogen
F = fluoro; Cl = chloro; Br =
bromo; I = iodo
O
Aldehyde
C
R
-al
H
(formyl group)
O
Ketone
C
R
-one
R'
(carbonyl group)
O
C
Carboxylic Acid
R
-oic acid
OH
(carboxyl group)
O
C
Ester
H
R
-oate
O
(carboxyl group)
O
Ether
R'
-oxy; -yl
R
(alkoxy group)
R'
N
Amine
R
R''
-amine
(amine group)
O
C
Amide
R
R'
N
-amide
R''
(amide group)
Note: R, R’, and R’’ can represent either a hydrogen or unspecified hydrocarbon chains
Unit 2 – Organic Chemistry
Chapter 1 Summary Notes – Structure and Properties of Organic Compounds
Alcohols