Chemistry 351
Dr. Gary Lampman
CB 340:
Office Hours: MTu 10 AM and WF 1PM
Text: Pavia, Lampman and Kriz/ Model set
Computer programs in CB 280
Answers to problems-- back of book
Sample tests online from my website
Test schedule listed in Syllabus
Success in Organic
Chemistry
•Read book in advance of lectures
•Come to class!
•Work problems: This is the most important
•Work sample test
•Don’t memorize---- learn by doing!!
•Keep up with the class: Don’t cram!!
Chapter One
BONDING IN ORGANIC
MOLECULES
Chapter 1
Problem Assignment
In Text Problems: 2, 3, 4, 5, 6, 7, 8, 9
10 a, b, c, d 13 b, c, d, e, f, g
14 c, d 15 a, b 16 17 a, e 18, 20
End of Chapter Problems:
24, 25 a, b, c 26 a, b, c, h 27 a, b, c, h
28 b, d, e, j
29 a, c, d, e, m
38 e, f
39 a, b, c
40 c
Organic Chemistry
H
B
C
N
O
F
Si
P
S
Cl
Br
CHEMISTRY OF THE COVALENT
COMPOUNDS OF CARBON
COMBINED WITH A FEW OTHER
COMMON ELEMENTS:
H B N O Si P S F Cl Br I
I
UNIQUE PROPERTIES OF CARBON
Carbon is TETRAVALENT
C
Carbon is one of the few elements that can form chains
C-C-C-C-C-C-C-C-C
Carbon can also form BRANCHED NETWORKS and RINGS
C C C C C
C C C
C C
C
C
C C
C
Memorize!
Classes of Organic Compounds
(Functional groups)
(Table 1-18, page 54)
Chapter 1
Sect. 1.1 Electronic structure of atoms
Sect. 1.2 Lewis dot symbols
Table 1-2 is a key table, shown on the
next slide, and on page 8 of the Text.
Lewis Dot Symbols
I
II
III
IV
V
VI
VII VIII
H
He
.
.
C
.
..
N
.
..
O
..
..
F
..
Ne
..
.
.
..
..
S
..
..
..
.
..
..
..
..
.
..
..
..
..
Li Be B
Na Mg Al Si
P
.
.
K
Ca
..
Cl
Ar
..
..
Ge
As
Se
Br
Kr
..
..
.
.
..
Sn
Sb
Te
.
.
..
I
..
Xe
..
Types of Bonding
• Sect. 1.3 Ionic bonding
Electron is fully transferred from metal to
non-metal.
Binding is by electrostatic attraction.
Na
Cl
Na
Cl
held together by electrostatic
forces
Types of Bonding
Sect. 1.4 Covalent bonding
Electrons are shared between atoms.
This is observed when carbon atoms
bond to oxygen, sulfur, nitrogen,
phosphorus, and halogens.
A Simple Covalent Bond
A pair of electrons is shared between
the two bonded atoms.
H.
.H
A Simple Covalent Bond
Bonded pair
H H
Sect. 1.5 Lewis diagrams
Organic compounds have:
single bonds
double bonds
triple bonds
Chapter 1, continued
Sect. 1.5, Table 1-6 (page 17) shows bonding
patterns in organic compounds
Carbon
Nitrogen (phosphorus)
Oxygen (sulfur)
Halogen (F, Cl, Br, I)
Hydrogen
4 bonds
3 bonds
2 bonds
1 bond
1 bond
Drawing Conventions
1. A shared pair (bond) is drawn as a line.
C
O
2. An unshared pair is shown as a pair of dots.
N:
3. The diagram includes formal charges (later).
H
.. +
O
H
H
Lewis Rules (a reminder)
1. OCTET RULE: In a completed Lewis Diagram,
Period 2 or Period 3 atoms will have a completed
octet : ( 8 electrons).
Hydrogen atoms will have a
“duet” : ( 2 electrons).
2. BONDS. Bonds are made by sharing a pair of
electrons between two atoms.
Single Bonds ( 1 shared pair )
Double Bonds ( 2 shared pairs )
Triple Bonds ( 3 shared pairs )
are all allowed in constructing a Lewis Diagram.
Hydrogen, is always singly bonded.
Lewis Rules ...... continued
3. ELECTRON PAIRS.
N:
Electrons not involved in forming bonds
(non-bonded or unshared electrons) are arranged
in pairs.
4. CORRECTNESS.
The final structure must have the correct number
(total) of valence electrons.
Lewis Diagram for Water
H
CONSTRUCTED
FROM LEWIS
DOT SYMBOLS
H.
..
O
..
H
COVALENT
BONDS
..
.O .
..
.H
H
H
O
Methane
H
.
CH4
.
H
x
xCx
x
.
H
DOTS AND
CROSSES
METHOD
.H
H
H C H
H
Some Lewis Diagrams of Organic
Molecules
H O H
H C C C H
H
H
H C N
hydrogen cyanide
acetone
H O
H C C H
H C
C O
H H
H N
H
ethylene
H
glycine
FOR MANY COMPOUNDS YOU WILL BEGIN TO SEE PATTERNS
Sect. 1.6
Incomplete-Octet Structures
Incomplete Octet Structures
SOME ATOMS DO NOT FOLLOW THE OCTET RULE
GROUP THREE ELEMENTS OFTEN FORM
INCOMPLETE OCTET STRUCTURES
.
.B.
Boron often makes structures with
an incomplete octet.
It can only form three bonds!
BF3 =
F B
F
F
Section 1.6
Sect. 1.7
Expanded-Octet Structures
Expanded Octet Structures
GROUP 5A OR 6A ELEMENTS OFTEN FORM
EXPANDED-OCTET STRUCTURES
Phosphorous can form up to 5 bonds
P
Cl
PCl5 =
Cl
GROUP 5A
P
Cl
Cl
Cl
Sulfur can form up to 6 bonds
S
GROUP 6A
Section 1.6
SF6 =
F
F
F
S
F
F
F
3d orbitals
are available
EXPANDED OCTET STRUCTURES ARE NOT
LEWIS DIAGRAMS .....
THEY DO NOT FOLLOW THE OCTET RULE !
They are specifically designated:
EXPANDED OCTET STRUCTURES
A designation often used for Phosphorous
and Sulfur structures.
O
H
O
S
O
H
O
Sulfur has 6 valence electrons
Oxygen has 6 valence electrons, total of 24 electrons
Hydrogen has valence electron, total of 2 electrons
Total is 32 valence electrons!
Check it to make sure!
Sect. 1.8 Non-polar and
polar covalent bonds
Pauling electronegativity differences:
non-polar covalant bond
polar covalent bond
ionic bond
< 0.5
0.5 to 1.7
> 1.7
Linus Pauling
Linus Pauling won two Nobel Prizes
One for chemistry and one for peace
Born in Oregon and attended Oregon State University
Pauling Electronegativities:
Carbon = 2.5
Hydrogen = 2.1
Oxygen = 3.5
Nitrogen = 3.0
Non-polar and polar covalent
bonds
C-H bonds are nonpolar: 2.5 -2.1 = 0.4
H
dC
H
H
d+
H
N
H
N-H bonds are polar: 3.0 - 2.1 = 0.9
Non-polar and polar covalent
bonds
C-H bonds are nonpolar: 2.5 - 2.1 = 0.4
d+
H
dC
H
H
H
O
O-H bonds are polar:
3.5 - 2.1 = 1.4
Dipole Moments
O
C
O
O
H
H
Dipole moments = 0
Resultant
Dipole moment > 0
Dipole Moments
H
H
Dipole Moment > 0
C
Cl
Cl
Cl
Cl
Dipole Moment = 0
C
Cl
Cl
Section 1.9
Formal Charge Calculations
• Complete the octets on atoms
• Follow rules listed in Table 1-10 (page 28)
• Formal charge = (# valence electrons)
- (# non-bonded electrons)
- (1/2 of e- in bonds)
Formal Charge
Table 1-10
Formal Charge The charge on an atom in a
molecule or ion, based on a prescribed procedure
for counting which electrons may be assigned to
each individual atom.
Unbonded
Formal Charge =
NH2-
Number of
valence electrons
in the neutral
atom
.
.N :
.
Bonded
All
One half of
unshared + all shared
electrons
electrons
5e-
( Formal Charge = 5 - 4 - 2 = -1 )
..
H . . N:
..
H
6e-
H
NH2
-
=
N
H
2 e- in bonds
4 non-bonded e6 total
Nitrogen is in group 5
Formal charge = -1
LEWIS DIAGRAM FOR SO421 x S
=
6 electrons
4 x O
=
24 electrons
- 2 charge =
2 electrons
TOTAL
SO42-
=
32 electrons
.
:S. :
.
:O. :
SULFATE SKELETON
O
O
S
O
O
32 total electrons - 8 electrons = 24 electrons
left to assign
SULFATE
..
:O
..
..
:O:
S
:
:O
..
..
:
O
..
SULFATE
_ ..
:O
..
.. _
:O:
+2
S
2-
.. _
:
O
..
:_
:O
..
Calculate formal charges
net
ionic
charge
Some structures can be drawn two ways:
.. :O :
..
O:
.. +2 ..
H O S O H
..
..
:O
..:
-
..
..
H O
S
O
H
..
..
:
O
..
LEWIS DIAGRAM
EXPANDED-OCTET
note charges
note lack of
charges
Formal Charges
• The sum of the formal charges must be
equal to the total charge on the ion or
molecule
• If there aren’t enough electrons to
provide every atom with an octet,
consider double or triple bonds
• All structures must obey the rules of
valence
Formal Charge Example
CH3NO2
H
C
H
H
Neutral molecule 24 electrons
+
N
O
O
-
Draw a Lewis diagram for the neutral
molecule, NCNO2. Are there formal
charges?
the subscript indicates that
each oxygen is bonded to N
not to each other
NCNO2
condensed formula
showing bonding order
.
N C N
. . .
.
O
O
shape of the
skeleton
+
N
C
O
N
O
-
Chapter 1, continued
• Sect. 1.10 Evaluation of Lewis formulas
Read this section -- I won’t lecture on it!
Sect. 1.11 Common
bonding patterns
Table 1-13 and 1-14
Normal bonding patterns
Group
III
IV
V
VI
VII
_______________________________________________________________
B
C
TRIVALENT
Incomplete
Octet
C
..
F:
..
..
O
..
..
N
N
..
..
O
..
MONOVALENT
+ 3 lone pairs
DIVALENT
H
C
MONOVALENT
Duet
N:
+ 2 lone pairs
TRIVALENT
C
TETRAVALENT
+ 1 lone pair
Table 1-13
COMMON BONDING PATTERNS IN WHICH
AN ATOM CARRIES A FORMAL CHARGE
CATIONS
+
+
..
+
O
+
..
O
N
C
N
+
+
N
N
ANIONS
_
B
_
C:
+
_
.. :
N
_
..
N
..
_
.. :
O
..
Table 1-14
Sect. 1.12 Condensed
structures and polygon
notation
Sect. 1.12 Condensed and Polygon
Formulas
Drawing complete Lewis Diagrams for
every molecule is time-consuming and
sometimes tedious.
Chemists have developed several types
of “shorthand” notation:
Condensed Notation
Line Notation
Polygon Notation
Condensed Notation
Condensed Notation
( examples )
Branched Alkane
H
H H H H
H
C
H C
C C C H
H H H H
H
(CH3)4C
HH C H H
H C
C
C H
HH C H H
H
CH3
CH3CH2CH2CH2CH3
CH3-C-CH3
CH3
Unbranched
(“linear”) Alkane
various
degrees of
condensation
are possible
some
bonds
shown
C(CH3)4
Condensed Notation
( examples )
H
H
C H
H
H C C
H
H C
Alkene
H
increasing
degrees of
condensation
H
CH3-C=C-CH3
H
CH3-CH=CH-CH3
CH3CH=CHCH3
Condensed Notation
( examples )
H H
H C C C C H
CH3CH2-CH=CH2
H H H H
CH3CH2CH=CH2
Alkene
H
H C C C H
H-C C-CH3
H
HC CCH3
Alkyne
or
CH CCH3
Condensed Notation
( examples )
EVEN COMPLICATED BRANCHED STRUCTURES
CAN BE WRITTEN ON A SINGLE LINE
CH3
CH3 CH CH CH2 CH3
CH2 CH3
Branched
Alkane
for this reason many
handbooks use
condensed notation
CH3CH(CH3)CH(CH2CH3)CH2CH3
note use of parentheses these atoms form a group
Line Notation
CH3
CH3
CH3CH2CH2CH2CH3
C CH3
CH3
H
CH3
CH3CH2CH CH2
C C CH3
H
H C C CH3
CH3
C C CH2CH3
Structues Involving Heteroatoms
O
O
N
Cl
There is no carbon
here, another atom
is indicated.
A “heteroatom” is any atom different from
carbon or hydrogen.
“hetero” = different (Greek)
Polygon Notation
Cyclic Molecules
• For some molecules, the carbon chain
may close on itself to form a ring.
• These types of substances are called
cyclic molecules.
Polygon Notation
CH2
CH2
CH2
CH2
CH2
CH2
examples:
O
O
N
H
Examples of Cyclic Molecules
H
H
CH2
C
H
H
C
CH2 CH2
C
H
H
Cyclopropane
H
H
H
C3H6
H
C
C
C
C
H
CH2 CH2
H
H
CH2 CH2
H
Cyclobutane
H
H
C
H
C4H8
CH2
H
C
C
CH2
H
CH2
H
C
H
C
H H
CH2 CH2
H
Cyclopentane
C5H10
More examples
CH2
CH2
CH
CH3
CH3
CH2 CH2
Methylcyclopentane
CH2
CH2
CH
CH2
CH
CH
Br
3-Bromocyclohexene
Br
CHEMISTS USE WHATEVER
COMBINATIONS ARE CONVENIENT
Example Structures
N
H
N
HO
nicotine
O
cholesterol
CH3
CH3
N
N
O
CH3
N
N
CH3
caffeine
NH2
CH3O
CH3O
OCH3
mescaline
Sect. 1.13 Constitutional
Isomers
• Substances which have the same
molecular formula but a different
structural formula.
• Isomers differ in connectivity.
Common Hydrocarbon Types
H
ALKANES
ALKENES
H H H H
H
C
H C
C C C
H H H H
H
H
H
H C
H C
C
C
HH C
H
H C
HH C
H H
H C
H
C
C
C
H
H H H H
H
H
H C
C
H H
H
ALKYNES
C
C
C
H
H
only
single
bonds
H
H
H
H
H H
H C
H
H H
C
C
C
C
H H
H
at least
one
double
bond
at least
one
triple
bond
We Cannot easily predict the
number of isomers for any formula
Sect. 1.14 Classes of organic compounds
Memorize this slide (see Table 1-18 in the text)
R
H
R
X
Alkyl Halide
R
NH2 H
Alkane
R
O
R'
Ether
R
R
C
R
H
Aldehyde
C
R'
C
R
OH
Carboxylic Acid
C
Ketone
O
O
O
R
O
R
Alkene
R
can be R
O
C
R
OH
Alcohol
Amine
R
C
R
C
Alkyne
R'
C
O
R
R'
Ester
C
NH2
Amide
R
C
Nitrile
N
H can be R
FUNCTIONAL GROUPS ….. continued
CLASS
CARBOXYLIC
ACIDS
R
O
OH
R
ESTERS
AMIDES
C
C
O
OR’
R C O
NH2
R can be H
R can be H
R’ cannot be H
R can be H
H can be R
OH
PHENOLS
R
attached to
any carbon
AROMATICS
R
not an
alcohol
Any compound which has a
benzene ring is “aromatic”
or “benzenoid”
benzene
ring
EXAMPLE
Alcohols are a class of compounds having the -OH
functional group.
All alcohols have the ending -OL in their names.
CH3-OH
methanol
methane =
one carbon
CH3CH2-OH
ethanol
ethane =
two carbons
CH3CH2CH2-OH
propanol
CH3CH2CH2CH2CH2CH2CH2CH2-OH
octanol
We will learn more about naming in a future lecture.
All the alcohols shown on the previous
slide can be abbreviated as:
R-OH
GROUPS WITH
SPECIAL ABBREVIATIONS
Special Abbreviations
KNOW THESE - including electron pairs
..
O:
-CHO
aldehyde
( note H before O,
-C-OH is an alcohol)
C H
..
-COOH
-CO2H
carboxylic acid
O:
..
C O
H
..
..
-COOR
-CO2R
ester
O:
..
C O
R
..
..
-CONH2
amide
O:
..
C N H
H
Special Abbreviations
( continued )
-C6H5
-NO2
benzene ring
nitro group
+ ..
N O:
:O
.. :..
-NH2
amino group
N H
H
(CO) or CO
-OH
carbonyl group
hydroxyl
( -C-OH or HO-C is OK, but not C-HO
because an aldehyde is -CHO )
..
C O:
..
O
..
H
MOLECULES WITH
MULTIPLE FUNCTIONAL GROUPS
Identify the functional groups
N
H
N
O
CH3
O
N
CH3
HO
CH3
N
N
CH3
N
NH2
CH3O
CH3O
OCH3
Circle the functional groups (names on next slide).
Names of the functional groups
amine
N
H
N
amine
O
CH3
O
N
CH3
amide
CH3
alkene
HO
alcohol
amine
N
N
amide
CH3
N
amine
alkene
NH2
CH3O
CH3O
amine
OCH3
ether
Constitutional Isomers:
Compounds with a Functional Group
See problems 39 and 40 at the
end of the chapter
Constitutional Isomers with a Given
Functional Group
PROBLEM ONE
DRAW ALL THE ISOMERS OF C4H10O
a) that are alcohols
b) that are ethers
As we shall see, there can be isomers both
within a class of compounds AND across
two or more classes of compounds.
C4H10O Constitutional Isomers
C
C
alcohols
C
C
OH
C
C
C
C
C
C
C
OH
C
ethers
O
C
C
C
C
C
OH
C
C
OH
C
hydrogens
omitted
C
C
C
O
C
C
O
C
C
C
TWO DIFFERENT FUNCTIONAL GROUPS - SAME FORMULA
PROBLEM TWO
Draw all the ketones that have formula C4H6O.
linear chain = C-C-C-C
O
O
C-C-C-C -H
C-C-C-C
not a ketone
wrong formula (C4H8O)
ALDEHYDE
Making a ring or a double bond
helps you lose two hydrogens.
Draw all the ketones that have formula C4H6O.
O
O
C-C-C-C -H
C-C-C-C
not a ketone
wrong formula (C4H8O)
O
O
O
C=C-C-C
These have the correct formula (- 2H)