CHAPTER 1
INTRODUCTION TO ORGANIC CHEMISTRY
1.1 Historical Background of Organic Chemistry
Organic chemistry is the area of chemistry that involves the study of carbon
and its compounds. Carbon is now known to form a seemingly unlimited number
of compounds. The uses of organic compounds impact our lives daily in medicine,
agriculture, and general life.
In theory (Oparin, 1923) organic chemistry may have its beginnings with the
big bang when the components of ammonia, nitrogen, carbon dioxide and methane
combined to form amino acids, an experiment that has been verified in the laboratory
(Miller, 1950). Organic chemicals were used in ancient times by Romans and
Egyptians as dyes, medicines and poisons from natural sources, but the chemical
composition of the substances was unknown.
In the 16th century organic compounds were isolated from nature in the pure
state (Scheele, 1769) and analytical methods were developed for determination of
elemental composition (Lavoisier, 1784).
Scientists believed (Berzelius, 1807) that organic chemicals found in nature
contained a special "vital force" that directed their natural synthesis, and therefore, it
would be impossible to accomplish a laboratory synthesis of the chemicals.
Fortunately, later in the century Frederich Wöhler (1828) discovered that urea, a
natural component in urine, could be synthesized in the laboratory by heating
ammonium cyanate. His discovery meant that the natural "vital force" was not
required to synthesis organic compounds, and paved the way for many chemists to
synthesize organic compounds.
By the middle of the nineteenth century many advances had been made into
the discovery, analysis and synthesis of many new organic compounds.
Understanding about the structures of organic chemistry began with a theory of
bonding called valence theory (Kekule, Couper, 1858).
Organic chemistry developed into a productive and exciting science in the
nineteenth century. Many new synthetic methods, reaction mechanisms, analytical
techniques and structural theories have been developed. Toward the end of the
century much of the knowledge of organic chemistry has been expanded to the
,2 Ch 1 Introduction
study of biological systems such as proteins and DNA. Volumes of information are
published monthly in journals, books and electronic media about organic and
biological chemistry.
The vast information available today means that for new students of organic
chemistry a great deal of study is required. Students must learn about organic
reactions, mechanism, synthesis, analysis, and biological function.
The study of organic chemistry, although complex, is very interesting, and
begins here with an introduction of the theory of chemical bonding.
1.2 The Chemical Bond
1.2a Atomic Theory
The atomic theory of electrons began in the early 1900s and gained
acceptance around 1926 after Heisenberg and Schroedinger found mathematical
solutions to the electronic energy levels found in atoms, the field is now called
quantum mechanics.
Electrons exist in energy levels that surround the nucleus of the atom. The
energy of these levels increases as they get farther from the nucleus. The energy
levels are called shells, and within these shells are other energy levels, called
subshells or orbitals., that contain up to two electrons. The calculations from
atomic theory give the following results for electron energy and orbitals. The results
for the first two energy levels (shells 1 and 2) are the most important for bonding in
organic chemistry.
Orbitals
Shell s p d f Total Electrons Possible
1 1 2
2 2 3 8
3 3 3 5 18
4 1 3 5 7 32
*energy level 1 contains up to two electrons in a spherical orbital called
a 1s orbital.
*energy level 2 contains up to eight electrons; two in an 2s-orbital and
two in each of three orbitals designated as 2p-orbitals. The p-orbitals have
, 1.2 Bonding 3
a barbell type shape and are aligned along the x, y, and z axes. They are
thus called the px, py, and pz orbitals.
z
z
x x
y y
1s orbital 2s orbital
z z
z
x x x
y y y
2px orbital 2py orbital 2pz orbital
*energy level 3 contains up to eighteen electrons, two electrons in a 3s
orbital, six electrons in the three 3p orbitals, and ten electrons in the five 3d
orbitals.
*energy level 4 contains up to thirty-two electrons, two electrons in a
4s-orbital, six electrons in the three 4p-orbitals, ten electrons in the five
4d-orbitals, and fourteen electrons in the seven 4f-orbitals.
Electrons fill the lower energy levels first until all of the electrons are used
(Aufbau Principle). An element contains the number of electrons equal to its
atomic number. For the first and second row elements the electron configurations
are relatively simple.
Element (atomic number) Electron Configuration
H (1) 1s1 (1st shell, s orbital, one electron)
He (2) 1s2
Li (3) 1s2, 2s1
INTRODUCTION TO ORGANIC CHEMISTRY
1.1 Historical Background of Organic Chemistry
Organic chemistry is the area of chemistry that involves the study of carbon
and its compounds. Carbon is now known to form a seemingly unlimited number
of compounds. The uses of organic compounds impact our lives daily in medicine,
agriculture, and general life.
In theory (Oparin, 1923) organic chemistry may have its beginnings with the
big bang when the components of ammonia, nitrogen, carbon dioxide and methane
combined to form amino acids, an experiment that has been verified in the laboratory
(Miller, 1950). Organic chemicals were used in ancient times by Romans and
Egyptians as dyes, medicines and poisons from natural sources, but the chemical
composition of the substances was unknown.
In the 16th century organic compounds were isolated from nature in the pure
state (Scheele, 1769) and analytical methods were developed for determination of
elemental composition (Lavoisier, 1784).
Scientists believed (Berzelius, 1807) that organic chemicals found in nature
contained a special "vital force" that directed their natural synthesis, and therefore, it
would be impossible to accomplish a laboratory synthesis of the chemicals.
Fortunately, later in the century Frederich Wöhler (1828) discovered that urea, a
natural component in urine, could be synthesized in the laboratory by heating
ammonium cyanate. His discovery meant that the natural "vital force" was not
required to synthesis organic compounds, and paved the way for many chemists to
synthesize organic compounds.
By the middle of the nineteenth century many advances had been made into
the discovery, analysis and synthesis of many new organic compounds.
Understanding about the structures of organic chemistry began with a theory of
bonding called valence theory (Kekule, Couper, 1858).
Organic chemistry developed into a productive and exciting science in the
nineteenth century. Many new synthetic methods, reaction mechanisms, analytical
techniques and structural theories have been developed. Toward the end of the
century much of the knowledge of organic chemistry has been expanded to the
,2 Ch 1 Introduction
study of biological systems such as proteins and DNA. Volumes of information are
published monthly in journals, books and electronic media about organic and
biological chemistry.
The vast information available today means that for new students of organic
chemistry a great deal of study is required. Students must learn about organic
reactions, mechanism, synthesis, analysis, and biological function.
The study of organic chemistry, although complex, is very interesting, and
begins here with an introduction of the theory of chemical bonding.
1.2 The Chemical Bond
1.2a Atomic Theory
The atomic theory of electrons began in the early 1900s and gained
acceptance around 1926 after Heisenberg and Schroedinger found mathematical
solutions to the electronic energy levels found in atoms, the field is now called
quantum mechanics.
Electrons exist in energy levels that surround the nucleus of the atom. The
energy of these levels increases as they get farther from the nucleus. The energy
levels are called shells, and within these shells are other energy levels, called
subshells or orbitals., that contain up to two electrons. The calculations from
atomic theory give the following results for electron energy and orbitals. The results
for the first two energy levels (shells 1 and 2) are the most important for bonding in
organic chemistry.
Orbitals
Shell s p d f Total Electrons Possible
1 1 2
2 2 3 8
3 3 3 5 18
4 1 3 5 7 32
*energy level 1 contains up to two electrons in a spherical orbital called
a 1s orbital.
*energy level 2 contains up to eight electrons; two in an 2s-orbital and
two in each of three orbitals designated as 2p-orbitals. The p-orbitals have
, 1.2 Bonding 3
a barbell type shape and are aligned along the x, y, and z axes. They are
thus called the px, py, and pz orbitals.
z
z
x x
y y
1s orbital 2s orbital
z z
z
x x x
y y y
2px orbital 2py orbital 2pz orbital
*energy level 3 contains up to eighteen electrons, two electrons in a 3s
orbital, six electrons in the three 3p orbitals, and ten electrons in the five 3d
orbitals.
*energy level 4 contains up to thirty-two electrons, two electrons in a
4s-orbital, six electrons in the three 4p-orbitals, ten electrons in the five
4d-orbitals, and fourteen electrons in the seven 4f-orbitals.
Electrons fill the lower energy levels first until all of the electrons are used
(Aufbau Principle). An element contains the number of electrons equal to its
atomic number. For the first and second row elements the electron configurations
are relatively simple.
Element (atomic number) Electron Configuration
H (1) 1s1 (1st shell, s orbital, one electron)
He (2) 1s2
Li (3) 1s2, 2s1
