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Course Outline
• What is Organic Chemistry?
Organic chemistry is the chemistry of compounds that
contain the element of carbon.
Organic chemistry affect every facet of our lives, and
therefore it is important and useful to know something
about them.
C
Course
IInstructor:
t
t
D Y
Dr.
Yuming
i Zh
Zhao
Teaching Assistant: TBA
Lectures: Mon, Wed, Fri 11:00-11:50
Room: SN 2019
Text: Organic Chemistry, 6th Ed, by Paula Bruice
Marking Scheme
Lab
Two Quizzes
Final exam
20%
5% of the lower mark + 25% of
the higher mark
50%
• What makes Carbon So Special?
p
(1) Carbon is in the middle, so it neither give or accept
electrons readily
(2) Carbon shares electrons with other atoms (including
carbon)
(3) Carbon
C b can fform millions
illi
off compounds
d with
ith a wide
id
range of chemical properties
Welcome to the World of Organic
g
Chemistry!
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Colon Cancer Drug
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Antidepressant
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Chapter
p
1
Electronic Structure
and
Bonding
Acids and Bases
The Structure of an Atom
nucleus
+
proton
neutron
t
+ +
+ +
+
electron
cloud
l d
In a neutral atom, the number of protons in the nucleus equals
th number
the
b off electrons.
l t
• The size
si e of atom is defined b
by the space taken
by the electrons
• The mass of the electron is quite small
compared to the mass of proton and neutron,
so can be ignored for all practical purposes
Particle
Charge (a.u.)
Mass (a.u.)
Proton
Neutron
+1
0
~1
~1
1
Electron
-1
1/2000
4A
Group number
6
Atomic number
C
Element symbol
Element name
Atomic weight
Carbon
12.011
• Atomic number: numbers of protons in its nucleus
• Mass number: the sum of the protons and neutrons of an atom
• Isotopes have the same atomic number but different mass
numbers
• The atomic weight: the average weighted mass of its atoms
• Molecular weight: the sum of the atomic weights of all the
atoms in the molecule
The Distribution of Electrons in an Atom
Electrons are added to
particular shells of orbitals
p
around the nucleus.
e
Electrons are first added to
the shell closet to the
nucleus
e
e
The modern electron shell
model of the atom was first
developed by Niels Bohr in
the early 1920s.
Each shell contains a certain
number of subshells called
orbitals.
An orbital is a region of
space that is high in electron
density.
density
• Electron configuration
g
is a description
p
of where
electron reside in atoms and molecules.
• Three rules determine how electrons occupy
orbitals
Rule
R
l #1
1: Th
There mustt b
be 0
0, 1
1, or 2 electrons
l t
iin an orbital
bit l
(Pauli exclusion principle)
Rule # 2: Fill the lowest energy orbital first (aufbau principle)
Rule # 3: Do not pair the electrons unless forced to (Hund’s
rule)
Electron configuration
g
of carbon: 1s22s22p
p2
3d
3p
3s
2p
2s
1s
V l
Valence
electrons
l t
Core electrons
Bonding
g
• Bonding is the joining of two atoms in a stable
arrangement.
• Through
Th
h bonding,
b di
atoms
t
attain
tt i a complete
l t outer
t shell
h ll off
valence electrons.
• Through bonding, atoms attain a stable noble gas
configuration of electrons
electrons.
Lewis’s theory:
y an atom will g
give up,
p, accept,
p , or share electrons
in order to achieve a filled outer shell or an outer shell that
contains eight electrons.
Ionic Bonds Are Formed by the Transfer of Electrons
Attractive forces between opposite
pp
charges
g are called electrostatic
attractions
15
Covalent Bonds Are Formed by Sharing Electrons
16
• Equal sharing of electrons: nonpolar covalent bond
(e.g., H2)
• Sharing of electrons between atoms of different
electronegativities: polar covalent bond (e
(e.g.,
g HF)
17
A polar covalent bond has a slight positive charge on
one end
d and
d a slight
li ht negative
ti charge
h
on th
the other
th
18
A Polar Bond Has a Dipole Moment
• A polar bond has a negative end and a positive end
di l momentt (D) = μ = e x d
dipole
e: magnitude of the charge on the atom
d: distance between the two charges
19
Lewis Structure
Lewis structures are electron dots representations for molecules
molecules.
1. Draw
a o
only
y tthe
e valence
a e ce e
electron
ect o
2. Give every second-row element no more than eight electrons
3. Give each hydrogen two electrons
Formal charge =
number of valence electrons –
(number of lone pair electrons +1/2 number of bonding electrons)
20
Nitrogen has five valence electrons
Carbon has four valence electrons
Hydrogen
y g has one valence electron and halogen
g has
seven
21
How to Construct a Reasonable Lewis Structure?
1.
Count the total number of valence electrons
a. B = 3, C= 4, N = 5, O = 6, F = 7
b. If the total charge is -1, -2, or -3, ADD 1, 2, or 3 valence electron respectively
c. If the total charge is +1, +2, or +3, SUBTRACT 1, 2, or 3 valence electron
respectively
2.
3.
4.
Write the Skeleton of the molecule
Subtract two electrons for each single
g valence bond
Distribute the remaining electrons as lone pairs around
the atoms
a. Start from the outside atoms and work inward
b. Attempt to achieve octet/duet on each atom
5.
If an atom is deficient of its octet/duet, convert lone
pairs from neighboring atoms into bonding pairs,
thereby creating double and/or triple bonds
Draw the Lewis Structure for NO2• Total number of valence electrons = 5(N) + 6(O) × 2 + 1 (-eV) = 18
• Draw the molecular skeleton
• Distribute
Di t ib t th
the reaming
i electrons
l t
(18 – 4 = 14)
•Convert one electron lone pair of oxygen into a covalent bond to
fulfill octet on nitrogen
Important Bond Numbers
Neutral
Cationic
Anionic
24
Kekulé
Kekul
é Structures
Condensed Structures
CH3Br
CH3OCH3
HCO2H
CH3NH2
N2
Drawing of Carbon Skeleton in the
Zigzag format
The end of every line represents a carbon atom