Download ppt-01-chap-01-chem-160-fall-2016

1
H
√
H
CH3
OH
C
H3C F
H3C
F
H3C
H
O
HO
H
C
C
H
O
+
C
H

Br Mg
D
H3C
(-):CN:
H
I
C
H3C D
H
O
O

CH3
LiCu
NC
Cl
+
H3 C
X
OH
C
H
(-)I
O
CH2
2
H
CH3
H
CH3
H
H 3C
O
H2 / M
O
H
2
Text: Organic Chemistry, 6th ed. Brown, Foote, Iverson
Also: Study Guide and Problems & models are strongly
recommended!
Consider other aids: Organic As a Second Language
OWL
Different organic texts
Others?
Mid Exam: , 2016
lab-135
Chapter 1
COVALENT BONDING & SHAPES OF MOLECULES
1.1 Electronic Structure of Atoms
1.2 Lewis Model (Octet Rule, Formal Charge)
1.3 Functional Groups
1.4 Bonding Angles and Shapes of Molecules
1.5 Polar and Nonpolar Molecules
1.6 Resonance
1.7 Quantum or Wave Mechanics
1.8 Molecular Orbital & Valence Bond Theory, Covalent
Bonds, Hybridization (sp3, sp2, sp)
SUMMARY and OVERVIEW 1-11
1
3
4
Organic Chemistry: the study of compounds of carbon
WHY is CARBON SPECIAL? Li Be B
•
•
C N O F Ne
CARBON - is small, intermediate electronegativity
forms strong bonds with itself/other atoms
• C-C 83.1 kcal/mole
• 2X as strong as: N-N, O-O, SiSi
• forms strong double and triple
bonds (to C or other atoms)
Over 10 million structures identified; ~1000 new/day!
Recall the Structure of an ATOM:
5
nucleus
(neutrons + protons )
(+)
mass:
electrons(-)
1833 to 1
quantum mechanics: motion of e’s particle & wave like
electrons confined to regions of space: shells
(principle energy levels)
6
Electronic Structure of Atoms
e -s Sh ell
Shell
can h old
3
2
1
18
8
2
Relative Eenergy
of e s in Sh ells
higher
lower
each shell can hold
2n2 electrons
Ground state electronic configuration
(atoms or molecules)
Aufbau Principle:
fill orbitals lowest to highest energy
Pauli Exclusion Principle:
2 electrons per orbital, spins paired
Hund’s Rule:
degenerate orbitals, 1 electron in each
then create a pair
7
Valence8
closed
Shell
shell
3 (s)
Hund’s
Rule
Pauli
&
Lewis
next level
(p)
E
2(s)
1(s)
Li
H
Be
B
C
N
O
F
Ne
He
writing electronic configuration
9
Electronic Configuration
No. of e's electronic configuration
1H
2 He
3 Li
4 Be
5B
6C
7N
1s1
1s2
1s2 2s1
…….
………
1s2 2s2 2p2
etc.
What is the electronic configuration of OXYGEN?
1s2, 2s2, 2p4
10
Lewis Structures (Gilbert N. Lewis)
Valence shell:
the outermost electron shell
Valence electrons:
electrons in valence shell
electrons used to bonds
Lewis structure:
atom symbol = nucleus + inner edots represent valence electrons
11
Lewis Structures
• Table 1.4 Lewis Structures
1A
2A
3A
4A
5A
6A
7A
H.
.
.
Mg : Al : . Si :
.
: O:
.
.
:S:
.
:F :
: Ne :
.
:Cl : :Ar
:
:
.N :
.
.
. P:
.
.
:
B : . C:
.
:
Be :
.
:
.
:
N a.
He :
:
Li .
8A
12
Bonding extremes - IONIC or COVALENT
ionic bonds ?- loss or gain of valence electrons
+
Li
Li
Br
Br
covalent bonds -share
?
electrons to fill shells
Br
Br
Br Br
or
Br Br
Electronegativity
Electronegativity: a measure of an atom’s
attraction for the electrons it shares with
another atom
Pauling scale
increases left to right in a row
increases bottom to top in a column
13
14
Electronegativity
Table 1.6 Classification of Bonds
electronegativity difference
bond type
H3C-H
less than 0.5
covalent
2.5 2.1
+
0.5 to 1.9
H
Cl
2.1 3.0
greater than 1.9
polar covalent
Na+ -Cl
0.93 3.16
ionic
15
Chapter 1
COVALENT BONDING & SHAPES OF MOLECULES
1.1 Electronic Structure of Atoms
1.2 Lewis Model (Octet Rule, Formal Charge)
1.3 Functional Groups
1.4 Bonding Angles and Shapes of Molecules
1.5 Polar and Nonpolar Molecules
1.6 Resonance
1.6 Quantum or Wave Mechanics
1.7 Molecular Orbital & Valence Bond Theory, Covalent
Bonds, Hybridization (sp3, sp2, sp)
SUMMARY and OVERVIEW 1-11
1
16
Lewis (electron dot) structures
covalent molecules and ions
• When discussing the physical and chemical properties of
an element, chemists often focus on the electrons in the
outermost shell of the atom because these electrons are
involved in the formation of chemical bonds and in
chemical reactions.
• Carbon, for example, with the ground-state electron
• configuration 1s22s 22p 2 has four outer-shell electrons.
Outer-shell electrons are called valence electrons
• The energy level in which they are found is called the
valence shell.
17
• To show the outermost electrons of an atom, we
commonly use a representation called a Lewis dot
structure, after the American chemist Gilbert N. Lewis
(1875–1946) who devised this notation.
• A Lewis dot structure shows the symbol of the element
surrounded by a number of dots equal to the number of
electrons in the outer shell of an atom of that element. In
Lewis dot structures, the atomic symbol represents the
core; that is, the nucleus and all inner shell electrons.
• Duplet
• Octet
• Show how the loss of an electron from a sodium atom
leads to a stable octet.
18
Formation of chemical bonds
•
•
•
•
•
•
Formation of Chemical Bonds
Anion
Cation
Ionic interaction
Covalent bonds
Electronegativity (A measure of the force of an atom’s
attraction for electrons.)
• Electronegativity and Chemical Bonds (Polar and nonpolar)
19
Formation of Ions
• Ions are formed by the transfer of electrons from the
valence shell of an atom of lower electronegativity to the
valence shell of an atom of higher electronegativity.
• Example: Na and F
• Covalent Bonds
A covalent bond is a chemical bond formed between
atoms by the sharing of one or more pairs of electrons to
give a noble gas configuration at each atom. The
simplest example of a covalent bond occurs in the
hydrogen molecule(non-polar) and HCl (polar)
20
Bond length
• The distance between nuclei in a covalent bond in
Picometers
• (pm; 1 pm=10-12)
Ångstrom A0
1A0 = 10-10
21
Bond dipole moment (m)
• A measure of the polarity of a covalent bond. It is the
product of the charge on either atom of a polar covalent
bond times the distance between the nuclei.
and is given the symbol µ (Greek mu).
• The SI unit for a dipole moment is the coulomb meter, but
they are commonly reported instead in a derived unit
called the Debye (D: 1 D = 3.34 X 3 10-30 C . m).
• Bond dipole moment is
• defined as “The product of the charge, e (either the δ- or
δ + because each is the same in absolute magnitude), on
one of its atoms X the distance, d, separating the two
atoms.
22
• p=qd
where d is the displacement vector pointing from the
negative charge to the positive charge.
Thus, the electric dipole moment vector p points from the
negative charge to the positive charge.
23
• Lewis (electron dot) structures
• Formal charge
24
Charge on an atom/molecule is
formal charge, i.e. H3O+, HOTo assign Formal Charge:
1. Write correct Lewis structure
2. Assign each atom: all non-bonding e's
half the shared e’s
3. Compare this number to
valence e-s in neutral unbonded atom.
25
Formal Charge on an atom
number of
Formal
1/2
of
shared
unshared
= valence +
Charge
electrons
electrons
electrons
H
0
+1
-1
N
N
N
26
valence of N = 5
e’s belong to the first N =
[2 + 1/2(6)] = 5
5 - 5 = 0 charge
e’s belong to the 2nd N = [1/2(8)] = 4
5 - 4 = +1 charge
e’s belong to the 3rd N = [4 + 1/2(4)] = 6
5 - 6 = -1 charge
27
Chapter 1
COVALENT BONDING & SHAPES OF MOLECULES
1.1 Electronic Structure of Atoms
1.2 Lewis Model (Octet Rule, Formal Charge)
1.3 Functional Groups
1.4 Bonding Angles and Shapes of Molecules
1.5 Polar and Nonpolar Molecules
1.7 Molecular Orbital & Valence Bond Theory, Covalent
Bonds, Hybridization (sp3, sp2, sp)
SUMMARY and OVERVIEW 1-11
Functional Groups: atom(s) bonded to C
having characteristic properties
Determine:
reactions
properties
basis of nomenclature & classification
28
Functional Groups: atom(s) bonded to C
29
having characteristic properties
methyl,1o, 2o, 3o
see Hs & Cs
alcohols: hydroxyl group
C
O
H
amines:amino group
C
N
H
H
1o, 2o or 3o by
Hs on N
FUNCTIONAL GROUPS
alcohols: (hydroxyl group, sp3-> C-O-H) 1o, 2o, 3o
amines:
C
N
H
1o, 2o, 3o
H
Aldehyde / Ketone (carbonyl group C=O)
Carboxylic Acid (carbonyl + hydroxyl group -CO2H)
Carboxylic Ester - (carbonyl + alcohol -CO2R)
Carboxylic Amide - (carbonyl + amine -C(O)N-)
Others ethers, halides, etc.
Formulas: complete, condensed and/or line
30
(e-)
VSEPR - electrons
in bonds/orbitals repel
each other
 4 groups/bonds repulsion yields a
tetrahedral shape ~109.5o
 3 bonds repulsion yields a
trigonal shape ~120o
 2 bonds repulsion yields a
linear shape 180o
eg: CH4 or NH3, HCO2H, CO2
31
32
and Nonpolar Molecules
Polar if: (1) has polar bonds
(2) if the arrangement is “irregular”
  
O
C O
H
+
N
C:
33
http://cwx.prenhall.com/petrucci/medialib/media_portfolio/text_images/FG12_05.JPG
34
35
36
Orbitals for sp2 hybridization
37
3 sp2 and p orbitals on axis
hybrid
38
3 sp2 and p orbitals on axis
39
pz
40
pz
py
s
two sp hybrid
orbitals
sp
sp
px
py
sp
HYBRIDIZATION two sp hybrid orbitals
41
End of Chapter 1

2