Review of First-Semester Organic Chemistry
and
Functional Groups
(20 Points)
During this lab period, we will review some of the important principals of organic
chemistry. The functional groups that were introduced during the first semester will also be
reviewed and some new ones introduced. Your grade on this lab will be your score on a 20-point
diagnostic evaluation of your knowledge of bonding and organic families, as presented in the
following pages. After you complete the two self-quizzes, see the instructor who will give you
the 20-point evaluation. Complete the 20-point evaluation and turn it in to the instructor.
Organic Compounds
Organic compounds contain carbon. The word compound means an electrically neutral
aggregate or collection of molecules or ions. As a simplification, there are three kinds of organic
compounds, covalent compounds. salts and organometallic compounds. The most common type
of organic compound contains only carbon and other nonmetals such as hydrogen, oxygen or
nitrogen. Atoms of nonmetals are joined together by covalent bonds to form molecules. Thus, the
compounds that contain only nonmetals are called covalent compounds. If a metal is part of the
compound, the compound is an ionic compound, because metals form ions. When the metal is
bonded to an atom other than carbon, the ionic compound is a salt. When the metal is bonded to
carbon, the ionic compound is an organometallic compound.
Covalent Compounds
Carbon is a nonmetal and forms covalent bonds with other nonmetals. A covalent bond is
two electrons or a pair of electrons that hold two atoms together. Thus, when carbon and another
nonmetal form a bond, that bond is a covalent bond. When only carbon and hydrogen form a
molecule, that molecule is a hydrocarbon. The simplest compound between carbon and hydrogen
contains only one carbon. Carbon has a normal covalence of four and hydrogen one. Therefore,
the simplest molecule is methane, CH4. The compound methane contains an aggregate or
collection of methane molecules. Depending on the circumstances, the word methane can refer to
one molecule of methane or to a collection of methane molecules. The context of its usage
determines the meaning.
H H
H
H C H
H C C OH
H H
H
methane
ethanol
Covalent Compounds
Ionic Compounds—Salts and Organometallics
1
When a compound contains a metal, it is either a salt or an organometallic compound.
Organic acids are readily converted into salts by sodium hydroxide. The product is a salt,
because the sodium is bonded to oxygen, a heteroatom. When butyl bromide reacts with lithium
metal to form lithium bromide and butyl lithium, the butyl lithium is an organometallic
compound because lithium is bonded to carbon.
O
O
CH3CH2Li
CH3CO-Na+ or CH3CONa
ethyllithium
sodium acetate
Salt (formal charges may
or may not be shown)
Organometallic
Compound
Problem 1. Classify each of the following compounds as a covalent compound, a salt, or an
organometallic compound.
acetone
ethyl alcohol
butane
sodium acetate
sodium acetylide
Solution 1. Step 1. Draw the structure of each compound, showing the bonding.
O
O
CH3CCH3
CH3CH2OH
acetone
ethyl alcohol
CH3(CH2)2CH3
butane
CH3CONa
sodium acetate
HC CNa
sodium acetylide
Step 2. Look at each structure. If the structure has no metal atoms, it is a covalent compound. If
the structure has one or more metal atoms, it is either a salt or an organometallic compound.
Thus, acetone, ethyl alcohol and butane are covalent compounds, and butane is a hydrocarbon.
Step 3. If the structure contains a metal, determine whether the metal is bonded to carbon or to a
heteroatom. In sodium acetate, the metal sodium is bonded to oxygen. Therefore, sodium acetate
is a salt. In sodium acetylide, the metal sodium is bonded to carbon. Therefore, sodium acetylide
is an organometallic compound.
Bonding in Organic Compounds
One property of carbon is that it forms single bonds, double bonds and triple bonds. Two
carbon atoms can join by single, double or triple bonds. In a complete molecule, each carbon
atom will have four bonds. Let us consider two carbon atoms joined in turn by a single bond, a
double bond and a triple bond. Carbon must have four bonds. Thus, hydrogen is necessary to
make sure carbon always has four bonds in stable organic molecules. We classify organic
2
compounds into families. Hydrocarbons with only single bonds are alkanes, those with double
bonds are alkenes, and those with triple bonds are alkynes.
H H
H
H C C H
H H
ethane
an alkane
H
C C
H
H C C H
H
ethene
an alkene
ethyne
an alkyne
Hydrocarbon Families
The hydrocarbon families are very useful in the study of covalent bonding. A covalent
bond is a pair of electrons that join two atoms. Another way of looking at a covalent bond is that
the two electrons exist in a space between the two atoms. In most cases, one electron comes from
each atom. In an ideal or hypothetical way, we can consider the individual atoms joining to make
a molecule. Thus, we need two carbon and six hydrogen atoms to make ethane. When the atoms
join, only the valence electrons will be involved in bonding. Valence electrons are found in the
outermost shell of an atom. Each main shell of an atom has subshells that consist of orbitals. Any
given orbital can have zero, one or two electrons in it. For hydrogen, there is only one main shell
(1) and one orbital (s). Thus, we can describe the one electron of a given hydrogen atom as a 1s
or simply s electron. Every hydrogen atom contains an s electron in an s orbital. The shape or
geometry of an s orbital is a sphere. The one electron gets its name from its orbital. Remember
that the orbital is the three-dimensional space where the electron is found. A general principal
is that an orbital can hold a maximum of two electrons. The lone s electron of
hydrogen is a valence electron, because it is found in the outermost main shell. A carbon atom
contains six electrons and has the electron configuration 1s22s22p2. The outermost main shell of
carbon is shell 2, which has four electrons. Thus, carbon has four valence electrons. The second
main shell of carbon has two subshells s and p. Like the first main shell, this s subshell is simply
one spherical s orbital that can hold two electrons as a max. The p subshell contains three p
orbitals. These three orbitals are labeled px, py, and pz just so we can tell them apart. Each of
these orbitals can hold a maximum of two electrons. From the electron configuration, we see that
carbon has two p electrons. One of these electrons is found in the px orbital and the other in the
py orbital. Each p orbital gets one electron before any p orbital gets two electrons (Hund’s rule).
The shape of p orbitals is like a dumbbell, with a node in the middle. The orbital representations
of hydrogen and carbon atoms are shown on the next page. In our hypothetical model, we will
have these atoms join to make molecules.
3
Orbitals of One Carbon Atom
Orbital of One Hydrogen Atom
main
shell
1
s orbital
s electron
2
s orbital
p orbitals
Valence electrons
Figure 1. Atomic Orbitals of Hydrogen and Carbon
Atomic and Molecular Hydrogen
Consider the formation of molecular hydrogen from atomic hydrogen. Molecular
hydrogen has the formula H2 and forms from two hydrogen atoms. That is, we make a covalent
bond between two hydrogen atoms. The covalent bond is two electrons, which hold the molecule
together. The following equation shows the formation of H2 from two hydrogen atoms.
2 H•  H2 = H-H
Let’s look at the actual formation of the covalent bond. The one electron of each
hydrogen atom is found in an s orbital. The orbitals are where the electrons are found.
The s orbitals are spherical spaces where the electrons are found. The two orbitals that contain
valence electrons come together and share the same space. When two orbitals share the same
space, they are said to overlap. The two electrons, one from each orbital of each H atom can now
be found in the overlapped space. The two electrons in the same space make a covalent bond
when they join two atoms together. That is, they are bonding electrons, because they make a
bond. When two valence electrons share the same space but do not form a bond between two
atoms, they are called nonbonding electrons.
Overlap of Two s Orbitals
4
s electron
s orbital
Two atomic orbitals
in two hydrogen atoms
 orbital
 * orbital
Two molecular orbitals
in one hydrogen molecule
Note that we start with two atoms of hydrogen and we form one hydrogen molecule. We
also start with two atomic orbitals, and we form two molecular orbitals. Thus, when we overlap
two atomic orbitals, we make two new molecular orbitals. The two atomic orbitals are in
different atoms. The two molecular orbitals are within the same molecule.
All orbitals can hold a maximum of two electrons, whether they are atomic or molecular
orbtials. Thus, the two electrons go into the lowest energy molecular orbital called a sigma ()
orbital. The higher energy orbital called sigma star (*) is empty, because we have only two
electrons. In the valence-bond theory of bonding, we generally ignore the * orbital. The *
orbital is an antibonding orbital. Antibonding orbitals are important in the molecular orbital
(MO) theory of bonding. The bond between two hydrogen atoms is a single bond that forms by
the overlap of one s orbital with another s orbital. The bond is called a sigma or  bond. The
bond is called a  bond because it is formed by the overlap of two s orbitals. That is s + s =
sigma is a Greek s). The two electrons share the space on a straight line between the two
hydrogen nuclei. Since a hydrogen atom has only one s orbital, a hydrogen atom can only make
 bonds. This is true when H bonds with itself to form H2 and when it bonds with carbon or any
other nonmetal atom. In a sense, hydrogen is simply necessary in many organic compounds to
fill up the bonding sites of carbon. For example, hydrocarbons are made up of carbon backbones
and filled in with hydrogen. Every time hydrogen forms a bond with carbon, that bond is called a
sigma bond. Let us see how hydrogen bonds with carbon to make methane.
Methane
In order to make methane, four hydrogen atoms must form bonds with one carbon atom. Since
hydrogen is involved, we know that every bond will be called a sigma bond. Let us see how
these four  bonds are formed. To understand how the atomic orbitals overlap, we must go back
to Figure 1 and see how the valence electrons are distributed in carbon. We know that the four
hydrogen atoms each have one valence electron in an s orbital.
5
s orbital
p orbitals
Valence electrons of a Carbon Atom
Figure 2. Valence Electrons in a Carbon Atom
The valence electrons in a carbon atom are distributed as shown in Figure 2. The s orbital
has two electrons, and two p orbitals each have one electron. Four H atoms cannot bond to one C
atom that has this orbital arrangement and give four identical bonds. Linus Pauling recognized
this fact and concluded that the four valence orbitals of a carbon atom must change into four
identical orbitals. We now call this process hybridization. To form methane, a carbon atom
undergoes hybridization and forms a hybridized carbon atom called a sp3-hybridized carbon
atom. The four valence electrons are then redistributed so that each of the four identical sp3
orbitals gets one electron. Figure 3 shows the sp3 hybridization of a carbon atom.
s orbital
p orbitals
four orbitals
Valence electrons of a Carbon Atom
Four identical sp3-hybrid orbitals
one electron in each orbital
Figure 3. sp3 Hybridization of a Carbon Atom
When atomic carbon goes to an sp3 carbon, the name of the carbon atom and the name of
the four identical orbitals are sp3. Thus, an sp3-hybridized carbon atom has four sp3-hybrid
orbitals. The symbol sp3 means that four atomic orbitals—an s and three p orbitals have changed
into four new sp3 orbitals. The symbol is pronounced ess pee three. From the pronunciation, we
get one s and three p orbitals. The symbol tells us exactly how many and which orbitals were
combined to make an sp3-hybridized carbon atom.
Three general principals about hybrid orbitals are:
1. Hybrid orbital all have the same shape—a teardrop shape.
2. Hybrid orbitals always repel each other and orient as far away as possible from
other hybrid orbitals.
3. Hybrid orbitals always form sigma () bonds.
How will the four sp3 orbitals of an sp3-hybridized carbon orient?
6
Answer: The four hybrid orbitals repel each other and orient to be as far away from each other as
possible. That gives a tetrahedral orientation of the four orbitals. Figure 4 shows how the four
hybrid orbitals orient in an sp3-hybridized carbon atom to make methane.
3
Four identical sp -hybrid orbitals;
one electron in each orbital
tetrahedron
center of sp3-hybridized carbon atom
4 sp3-hybrid orbitals in an sp3-hydrbidized carbon atom orient toward the corners of a
regular tetrahedron
Figure 4. Orientation of sp3-hybrid orbitals of a sp3-hybrid carbon atom.
When carbon is part of a molecule, it is always a hybridized carbon atom. Hybrid orbitals
always make sigma bonds. Therefore, when we form the four bonds of methane, they will all be
sigma bonds. Covalent bonds are made by the overlap of two orbitals, making a three
dimensional space for two electrons. The sp3-hybridized carbon atom has four sp3–hybrid
orbitals that must overlap with four s orbitals from four hydrogen atoms. Figure 5 shows how
these orbitals overlap.
center of carbon atom
3
Four s orbitals overlap with four sp orbitals
Figure 5. Orbital Overlap in Methane
Methane has four bonds. Each bond is made by the overlap of an sp3 orbital with an s
orbital. Each bond is a sigma bond. An sp3 + s = sigma bond (Note: a sigma bond forms
whenever two orbitals that start with the letter s overlap). Now, let’s start with methane, and
7
determine its bonding. Methane has the formula CH4. We know that hydrogen can form only
sigma bonds. So the four bonds must all be sigma bonds. We also know that the carbon atom of
methane has four identical sp3-hybrid orbitals and that all hybrid orbitals only make sigma
bonds. So all four bonds must be sigma bonds. Sigma bonds from one atom always orient as far
away from each other as possible. How do we know this? Because these bonds are made up of
hybrid orbitals, and the hybrid orbitals, where the electrons are found, are as far away from each
other as possible. Therefore, electrons, which are found in these orbitals, are also as far away
from each other as possible. The structure of methane is shown below.
H
H
C
H
H
We can tell from the structure whether hybrid or unhybridized orbitals are involved.
From the structure we see that the carbon atom has four sigma bonds. That means that all four of
the carbon atom’s bonding orbitals are hybrid orbitals, because hybrid orbitals always make
sigma bonds. To get four hybrid orbitals we need to blend or hybridize four atomic orbitals--one
s and three p atomic orbitals, and we get four sp3-hybrid orbitals. The carbon atom must be sp3
hybridized, because it has four sp3 orbitals. The name of the hybridized carbon atom is the same
as the name of its hybrid orbitals. An sp3-hybridized carbon atom has four sp3 orbitals.
Ethane
Ethane has the structure shown below.
H
H
H
C
C
H
H
H
All of the bonds are  bonds. What kinds of orbitals overlap to make the  bond between
the two carbon atoms? Answer: An sp3 hybrid overlaps with an sp3 hybrid. An sp3 + sp3 makes a
sigma bond. A general rule is that anytime an orbital with an s in its symbol
overlaps with another orbital with an s in its symbol, we get a sigma bond. Ethane
is made up of two carbon and six hydrogen atoms. Each hydrogen has one electron to donate to
its bond with carbon, and each carbon has four electrons to donate, one to each bond. Hydrogen
can only make sigma bonds, so the s orbital of each H atom overlaps with an sp3 orbital of a
carbon atom to make a  bond. Therefore, a sigma bond can arise from the overlap of a spherical
s orbital with a teardrop hybrid orbital. A sigma bond can also arise from the overlap of two
hybrid orbitals. Hybrid orbitals always make sigma bonds. Figure 6 shows the formation of
sigma bonds.
8
+
s

s
+

s
hybrid
+
hybrid

hybrid
Figure 6. Three Ways to Make a Sigma Bond
Ethene
Ethene has the structure shown below.
H
H
C C
H
H
Ethene has a double bond. The double bond is between two carbon atoms, because hydrogen (H)
never has a double bond. H always has a single bond or  bond. The double bond is not two
sigma bonds, because only two electrons can be in the same space. A double bond contains four
electrons in two bonds. The first bond between the two carbon atoms is a sigma bond formed by
the overlap of two hybrid orbitals. The second bond between the two carbon atoms is called a pi
() bond. The  bond is made by the overlap of unhybridized p orbitals. We only make a  bond
after we have made a  bond. The  bond is made by the end-to-end overlap of two hybrid
orbitals, and the  bond is made by the side-by-side overlap of two unhybridized p orbitals. Just
as carbon always has four bonds in stable molecules, carbon always has four valence orbitals.
Valence orbitals are orbitals that hold valence electrons. Valence electrons are the electrons in
the outermost main shell of an atom. A carbon atom has four valence orbitals, three of which
hybridize into three sp2-hybrid orbitals when a double bond forms. Figure 7 shows the formation
of three sp2 orbitals from a carbon atom.
9
2
s orbital
p orbital
sp orbitals
four orbitals
p orbitals
four orbitals
Valence electrons of a Carbon Atom
2
Three identical sp -hybrid orbitals
and one unhybridized p orbital
one electron in each orbital
Figure 7. sp2 Hybridization of a Carbon Atom
As always, the hybrid orbitals repel each other and orient as far from each other as
possible, in a plane and 120o apart. The remaining unhybridized p orbital is perpendicular to the
three hybrid orbitals. Figure 8 shows how a sp2-hybridized carbon forms.
sp2
sp2
2
sp
2
sp orbitals
p orbital
p
sp -hybridized carbon
four orbitals
2
four orbitals
Figure 8. Orbital Arrangement of an sp2-Hybridized Carbon
During hybridization, the number of hybrid orbitals formed equals the number of
unhybridized orbitals blended to make the hybrid orbitals. Thus, when we make an sp2
hybridized carbon atom, we make three hybrid orbitals from three unhybridized orbitals.
Whether hybridized or unhybridized, carbon always has four valence orbitals.
When we change three orbitals into hybrid orbitals, one orbital is not changed. That orbital is a p
orbital. The p orbital that is left can overlap side-by-side with a p orbital from another carbon
atom and make a pi () bond. Thus, a p + p overlap =  bond (p in Greek is ). A  bond forms
after a  bond has formed. In the case of ethene, two carbon atoms are joined by a double bond.
First, two sp2 orbitals (each containing one electron) overlap end-to-end to make a sigma bond
(sp2 + sp2 orbitals =  bond). Then the two p orbitals overlap to make the  bond (p + p orbitals
=  bond). Figure 9 shows the two carbon atoms of ethene making a double bond, one sigma and
one pi bond.
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 bond
2
sp
sp2
sp2
sp2
bond
sp2
sp2
bond
sp2
sp2
sp2
sp2
p
p
sp2-hybridized carbon sp2-hybridized carbon
carbon-carbon double bond
Figure 9. Overlap of Two sp2-Hybridized Carbon Atoms to Make a Double Bond.
An sp2-hybridized carbon atom has four valence orbitals, three sp2 orbitals and one p
orbital. The general principal is that the name of the hybrid orbitals is the same as
the name of the hybridized carbon atom. Each orbital contains one electron. Thus, when
two sp2 –hybridized carbon atoms form a double bond, we start with eight valence electrons.
Two of these electrons, one from each carbon, make a  bond. These two electrons, like all 
electrons, are found in the space on a straight line between the nuclei of the two atoms. Likewise,
two electrons make a  bond. All six atoms in ethene lie in a plane, so the geometry of a double
bond is planar. The  bond lies above and below the plane of the six atoms. This leaves four
electrons to make  bonds with hydrogen. Figure 10 shows the orientation of the  bond relative
to the plane.
C C

C C

one  bond and one  bond
each bond has two electrons
Figure 10. Orientation of  Bond
The  bond in Figure 10 is shown as a straight line, but actually consists of a space
formed by the overlap of an sp2 orbital from one carbon with an sp2 orbital of the other carbon
atom. Figure 11 shows the complete bonding orbital picture of ethene.
11
 bond
s
bond


sp
sp
s
sp2
2

s
sp2
2
s

bond
ethene
five bonds and one  bond
Figure 11. Ethene
Problem 2. What kinds of orbitals overlap to make the carbon-carbon  bond in ethene? What
kinds of orbitals overlap to make the  bond in ethene? What kinds of orbitals overlap to make
the carbon-hydrogen bonds in ethene?
Solution 2. Step 1. Draw the structure of ethene.
H
H
H
C
C
H
Step 2. Determine what kinds of bonds ethene has.
From the structure, ethene has five  bonds and one  bond. In stable molecules, carbon always
has hybrid orbitals.
Step 3. Determine what kinds of hybrid orbitals each of the carbon atoms has?
Remember that  bonds are made by the overlap of p orbitals. So each carbon atom must have
one p (unhybridized) orbital and three hybrid orbitals (carbon always has a total of four bonding
orbitals). The three hybrid orbitals must be sp2 orbitals, made by blending the one s atomic
orbital with the remaining two p atomic orbitals (i.e. p orbitals that are not used in  bonds must
be in hybrid orbitals).
Step 3. For the carbon-carbon  bond, two hybrid orbitals must overlap. Each carbon atom has
three sp2-hybrid orbitals. Thus, the  bond between the two carbon atoms involves the overlap of
an sp2 orbital from one carbon atom with an sp2 orbital of the other carbon atom.
Step 4. Pi bonds are always made by the overlap of two p orbitals.
Step 5. Each of the carbon-hydrogen  bonds involves the overlap of one of carbon’s sp2 orbitals
with an s orbital of hydrogen.
Ethyne (Acetylene)
Ethyne, which is also known by the common name of acetylene, is shown in the structure below.
H C
C H
Acetylene contains a carbon-carbon triple bond.
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Problem 3. What kinds of orbitals overlap to make the carbon-carbon  bond in acetylene?
What kinds of orbitals overlap to make the two  bonds in acetylene? What kinds of orbitals
overlap to make the carbon-hydrogen  bonds in acetylene?
Solution 3. Step 1. Draw the structure of acetylene.
H C C H
Step 2. From its structure, determine the kinds of bonds acetylene has.
The first bond of a multiple bond is a  bond and the second and third bonds are
 bonds. Thus, acetylene has three  bonds and two  bonds.
Step 3. Determine what kind of hybrid orbitals each carbon atom has.
Each carbon has two  and two  bonds. The  bonds are made from hybrid orbitals, so each
carbon has two  orbitals (unhybridized) and two hybrid orbitals, which must be sp orbitals
because they are made from the remaining s and p atomic orbitals. Thus, the carbon-carbon 
bond is made from the overlap of an sp orbital with an sp orbital.
Step 4. Pi bonds, including both  bonds in acetylene, are always made by the overlap of two p
orbitals.
Step 5. The carbon-hydrogen bonds are made by the overlap of a hybrid sp orbital with an s
orbital.
Summary
Organic molecules that contain only nonmetals in the structure are covalent molecules. Covalent
molecules are held together by covalent bonds. Covalent bonds can be  bonds or  bonds. The
 bonds in hydrocarbons can be made between a carbon and hydrogen or between two carbon
atoms. The  bonds in hydrocarbons must be between two carbon atoms. A covalent bond is a
pair of electrons that are found in a three-dimensional space between two atoms. When a  bond
is formed between two atoms, we can envision that one electron comes from each atom of the
pair. These electrons are found in orbitals, either a hybrid orbital (sp, sp2, or sp3) or an
unhybridized orbital (s or p). When the bond forms, the orbitals, each containing one electron,
come together along the axis joining the atoms in a process that we call orbital overlap. Thus, the
two electrons of a  bond are located on a straight line between the two atoms, whereas the
electrons of a  bond are found in a dumbbell or figure-eight shaped space perpendicular to the
straight line between the two atoms. The space in which  electrons are found is formed by the
overlap of an s orbital of an H atom with a hybrid orbital of a carbon atom. Since carbon can
have three different kinds of hybrid orbitals, sp, sp2, or sp3, a C-H  bond can be made by the
overlap of the s orbital of the H atom with an sp, sp2, or sp3 hybrid orbital. The name of the
hybridized-carbon atom is the same as the name of its hybrid orbitals. An sp3-hybridized carbon
has four sp3 hybrid orbitals; an sp2-hybridized carbon has three sp2 hybrid orbitals and an
unhybridized p orbital; and an sp-hybridized carbon atom has two sp orbitals and two
unhybridized p orbitals. In molecules, each carbon atom will be hybridized and have a total of
four bonding orbitals. In molecules, carbon never has nonbonding valence electrons; all of
carbon’s valence electrons are bonding electrons. Thus, a carbon atom that has four  bonds is an
sp3-hybridized carbon. A carbon atom that is part of one double bond is an sp2-hybridized carbon
atom. A carbon atom that is part of two double bonds or one triple bond is an sp-hybridized
carbon atom. Hybrid orbitals always repel each other. Thus, two sp-hybrid orbitals orient 180
degrees apart (linear). Three sp2-hybrid orbitals orient 120 degrees apart (trigonal planar). Four
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sp3-hybrid orbitals orient 109.5 degrees apart (tetrahedral). Because these valence orbitals,
occupied by two electrons, repel each other, Pauling originated the name Valence-ShellElectron-Pair-Repulsion Theory. We use the acronym VSEPR Theory. To find out what kinds of
orbitals overlap to make a particular bond, first find the hybridization of the two atoms that make
the bond. For a carbon atom, the hybridization gives the name of its hybrid orbitals, and each one
of its hybrid orbitals makes a  bonds. For hydrogen, there is no hybridization. Hydrogen always
overlaps as an unhybridized s orbital. A valence orbital from one atom overlaps with a valence
orbital from a second atom to make a bond. Thus, two orbitals are required to overlap to make a
space for a pair of electrons.
Complete the following self-quiz and obtain the answers from the instructor.
Self-Quiz 1 Bonding in Organic Molecules
1. How many  bonds and  bonds are found in cis-2-butene?
2. What kinds of orbitals overlap to make the  bond between C-2 and C-3 in cis-2-butene?
3. What kinds of orbitals overlap to make the  bond in cis-2-butene?
4. What kinds of orbitals overlap to make a C-H  bond at C-1 of cis-2-butene?
5. What kinds of orbitals overlap to make the C-H  bond at C-2 of cis-2-butene?
6. What is the hybridization of the C-2 carbon atom in cis-2-butene?
7. What kinds of orbitals overlap to make the  bond between C-1 and C-2 in cis-2-butene?
8. What is the hybridization of the C-4 carbon atom in cis-2-butene?
9. What is the geometry around the  bond of cis-2-butene?
10. What is the C-1—C-2—C-3 bond angle in cis-2-butene?
Functional Groups and Organic Families
What is a functional group? A functional group is a partial structure, made up of a
collection of atoms that are bonded together in a specific manner. Each functional group is
associated with a single organic family of compounds. The functional groups subdivide the large
number of organic compounds into smaller groups or families. There is a fine line between a
group and a functional group. For example, a carbonyl group is found in several organic families
such as aldehydes, ketones, acids, esters, and amides. Thus, a carbonyl group is not a true
functional group, because it is not associated with a single family. The carbonyl group must be
bonded to some other atoms to make unique partial structures that can distinguish the families.
Once we understand the functional groups, we can identify them within an organic compound.
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The members of a family have similar properties. For example, aldehydes are easily oxidized to
acids (a chemical property). First semester, we studied several families of organic compounds,
including alkanes, alkenes, alkynes, alkyl halides, alcohols, and ethers. This semester we will
study aromatic compounds, amines, aldehydes, ketones, acids, and acid derivatives. We will also
study some biologically important compounds, including sugars, amino acids, and proteins,
which contain multiple functional groups.
During this lab, we will focus on 14 organic families and their functional groups. Since
functional groups are partial structures, they must be bonded to other atoms to make a complete
organic structure. Thus, the functional groups are shown below with one or more bonds
represented by a wavy or squiggly line to show where the other atoms must be bonded. We
generally think of a functional group being bonded to an alkyl group. For the most part, you will
be asked to identify a functional group or groups in a given structure. You might also be asked to
draw the structure of a given functional group. You may also be asked to identify the family or
families present in a given structure.
Hydrocarbons
Organic compounds contain carbon. Because carbon must have four bonds, organic compounds
must contain some other atoms. Hydrogen is the most common element, other than carbon. You
might say that hydrogen just goes along for the ride—like a passenger in an automobile. Thus,
hydrocarbons are organic compounds that contain only carbon and hydrogen. Excluding
aromatic compounds, there are three organic families that contain only carbon and hydrogen.
The presence or absence of multiple bonds distinguishes these families. The hydrocarbon
families are shown in Table 1.
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Table 1. Hydrocarbon Families and Functional Groups
Family
Alkane
Example
Functional Group
H H
H H
C C
H C C H
H H
H H
CH3
Alkene
C C
CH3
C C
H
Alkyne
C
C
CH3
H
C
C H
We can think of most organic families as being derivatives of alkanes. That is, we can
start with an alkane and remove two hydrogen atoms and get or derive an alkene, etc. The
replacement of any hydrogen atom of an alkane by a halogen (i.e., F, Cl, Br, or I) gives an alkyl
halide. The word alkyl comes from the word alkane. An alkane has a formula CnH2n + 2. The
removal of one H from the formula of an alkane gives an alkyl group of formula CnH2n + 1. Thus,
CH4 is methane; the removal of one H gives CH3, a methyl group. Thus, alkyl means alkane
minus a H. Replacing the H of an alkane with a halogen gives an alkyl halide. A group similar to
halogens is the cyano group. Unlike the halogen atoms, a cyano group contains two atoms, a
carbon and nitrogen joined by a triple bond. When the cyano group is joined to an alkyl group,
the structure is a member of the nitrile family. Table 2 shows the simple derivatives of alkanes.
Table 2. Alkane Derivatives
Family
Example
Functional Group
H
Alkyl
halide
H H
C X
Cl
H
C C H
H H
X = a halogen
(F, Cl, Br, or I)
Nitrile
C
N
CH3
C
N
Note that the alkane derivatives contain a heteroatom—an atom other than C or H.
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Oxygen-Containing Compounds
Alcohols and Ethers
Oxygen has a covalence of two, meaning it normally forms two covalent bonds. In
organic families, the two bonds can either be two  bonds or one and one  (a double bond).
Thus, it is convenient to divide oxygen-containing compounds into two groups. One group of
compounds contains a carbonyl group, a carbon-oxygen double bond, and the other group does
not. The oxygen-containing compounds that do not contain a carbonyl group may be considered
as derivatives of water. These compounds are alcohols and ethers. Alcohol and ether families
contain oxygen as the only heteroatom and have no multiple bonds. Non-hetero atoms are carbon
and hydrogen. Therefore, to make an alcohol, start with a carbon atom and bond an oxygen atom
plus hydrogen to it. To make an ether replace the H atom of an alcohol with another C atom. An
–OH group is called a hydroxyl group. Alcohols contain a hydroxyl group. Table 3 shows
alcohol and ether families.
Table 3. Alcohols and Ethers (One oxygen, no double bond)
Family
Functional Group
Example
H H
Alcohol
C OH
HO C
C H
H H
H
Ether
C O C
H
H C O C H
H
H
Aldehydes and Ketones
Aldehydes and ketones contain a carbonyl group (C=O) as their only functional feature.
Like alcohols and ethers, they contain only one oxygen atom as the heteroatom. Starting with a
carbonyl group and only carbon and hydrogen, we can make aldehydes and ketones. Aldehydes
can have an H atom on one or both sides of the carbonyl group, but ketones can only have carbon
atoms next to the carbonyl group. Table 4 shows aldehyde and ketone families. An aldehyde
must always be a terminal group (i.e., the carbonyl group is at the end of a chain).
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Table 4. Aldehydes and Ketones (One oxygen heteroatom in carbonyl)
Family
Example
Functional Group
O
O
Aldehyde
Ketone
C H
H C H
O
H O H
C C
C
H C C
H
C H
H
Acids and Acid Derivatives
Organic acids are called carboxylic acids, because they contain a carboxyl group. Joining
a carbonyl group with a hydroxyl group makes a carboxyl group. Like an aldehyde, the
functional group must be at the end of a chain. Thus, the acid’s carbonyl group contains carbon
atom number one, which has an –OH group bonded to it. In other words, an acid contains two
oxygen heteroatoms. This is an important distinction between acids and the oxygen-containing
families covered above. A general principal is that acids and acid derivatives contain
a carbonyl group with a heteroatom bonded directly to the carbonyl carbon atom.
When the H atom of an acid’s hydroxyl group is replaced by an alkyl group, the compound
becomes an ester. When a nitrogen atom replaces the oxygen atom of an acid’s hydroxyl group,
the compound becomes an amide. These families are shown in Table 5.
Table 5. Acids and Acid Derivatives (Two Hetero Atoms, one in a carbonyl)
Family
Example
Functional Group
O
Acid
C OH
O
CH3
O
O
Ester
Amide
C O C
CH3
C OCH3
O
O
C N
C OH
CH3
C NCH3
H
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A compound contains a carbonyl group with a chlorine atom bonded to the carbonyl group. Is
the compound an alkyl halide or an acid derivative?
Aromatic Compounds
Benzene is an aromatic hydrocarbon. It was originally classified as aromatic because of
its odor, but now aromatic compounds are classified primarily by virtue of the number and
arrangement of  electrons in the structure. Aromatic compounds were not included in
hydrocarbons above, because many aromatic compounds contain heteroatoms. For example, the
replacement of a hydrogen atom by a chlorine atom makes an aryl halide, which is an aromatic
compound but not a hydrocarbon. When an H atom is removed from benzene, the resulting
partial structure is called a phenyl group. When a phenyl group is joined directly to a carboxyl
group, we have an aromatic acid. We call compounds that are not aromatic aliphatic. Thus, acetic
acid is an aliphatic acid, whereas benzoic acid is an aromatic acid. Table 6 shows some aromatic
compounds.
Table 6. Aromatic Compounds
Family
Functional Group
Example
Aromatic
hydrocarbon
X
Br
Aryl halide
Aromatic
and aliphatic
CO2H
CO2H
Aryl acid
H
C
C
H
H
Amines
Amines are derivatives of ammonia. Since organic compounds must contain carbon,
amines contain a nitrogen atom bonded directly to a carbon. Unlike amides, which are acid
derivatives, amines do not contain a carbonyl group. Carbon atoms may replace one, two or three
hydrogen atoms of ammonia. These compounds are called primary, secondary, and tertiary
amines, respectively. Table 7 shows amines.
Table 7. Amines
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Example
Functional Group
Family
H
Primary
Amine
C NH2
H C NH2
H
H
H
Secondary
Amine
C N C
H C N C H
H
H H H
Tertiary
Amine
C N C
H C N C H
C
H C H
H H H
H
H
Complete the following self-quiz and obtain the answers from the instructor. After you
have checked your answers to Self-Quiz 2 and you are ready to take the diagnostic evaluation.
Self-Quiz 2 Families of Organic Compounds
(24E)-3-hydroxy-7,24-euphadien-26-oic acid (Compound 1) is a potential anti-cancer drug that
chemists have recently isolated from two different plants.
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18
19
1
26
24
COOH
25
20
17
11
27
9
15
3
7
HO
30
4
29
28
Compound 1
1. What organic family is found in Compound 1 at C-3?
2. What organic family is found in Compound 1 at C-26?
3. What family is found in Compound 1 at C-7?
4. Draw the structure of a nitrile that has three carbon atoms.
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5. Draw the structure of a ketone that has three carbon atoms.
6. Draw the structure of an aldehyde that has three carbon atoms.
7. Draw the structure of an amide that has two carbon atoms.
8. The amide of problem 7 is a derivative of what organic acid?
9. Draw the structure of two different esters that have three carbon atoms each.
10. Draw the structure of ethyl alcohol and diethyl ether.
Diagnostic Evaluation
Obtain the diagnostic evaluation from the instructor. You will complete the diagnostic evaluation
without the use of notes, etc. and turn it in to the instructor; it is worth 20 points toward your
overall lab grade.
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