L
TOPIC 2. ORGANIC COMPOUNDS (Chapter 2)
OBJECTIVES 1. Describe the structure of N, O and halogen containing functional groups: formal charges, hybridization, VSEPR theory, polarity, resonance. 2. Develop relationships between structure and physical properties (b.p., solubility).
D.M. Collard 2007
A BRIEF INTRODUCTION TO ChemDraw, Chem3D and MOLECULAR MECHANICS ChemDraw
N
Bond-line structures
O O
O O
Chem3D
3D structures: ball-and-stick, space-filling
S:2.1-2.2
HYDROCARBONS Molecules containing only C, H C-C bond length / Å alkanes alkenes alkynes arenes
D.M. Collard 2007
C C
C C C C
bond energy kcal/mol
1.54
88
1.34
152
1.20
200
1.40
≈115
Molecular structure of benzene H C
H C C H
H C C H
C H
H H
H
C C
C
C H
C C
H
H
Validating resonance theory
BRANCHED ALKANES, CLASSIFICATION OF CARBON ATOMS, ALKYL GROUPS Linear alkane H3C
CH2
CH2
CH2
CH3
Branched alkanes H3C H3C
C
CH2 CH3
Classification of carbon atoms CH3
CH2
D.M. Collard 2007
CH
C
X
R
X
R R X
H2C H3C
CH3
R
X
R R
CH
CH3
R = carbon, X ≠ C
R R
S:2.5 Prob: 2.20-27, 32,39,42
C R
R
CH2
CH2
CH3
CH2
CH3
Alkane
Alkyl group
CH4 methane
X─ CH3
methyl, Me
CH3 CH3 ethane
X─ CH2CH3
ethyl, Et
X─ CH2CH2CH3
propyl, Pr, n-Pr, 1-propyl
X─ CH(CH3)2
isopropyl, i-Pr, 2-propyl
X─ CH2CH2CH2CH3
butyl, Bu, 1-butyl
CH3CH2CH3 propane CH3CH2CH2CH3 butane
X │
CH3CHCH2CH3 H H3C
C
sec-butyl, s-Bu, 2-butyl
H CH3
CH3
C X CH3 H2C CH3
isobutane
X H3C
isobutyl, i-Bu
tert-butyl, t-Bu
C
CH3 CH3
X X
phenyl, Ph, Φ
D.M. Collard 2007
CH2 X
benzyl, Bn
H2C CH
vinyl
S:2.6
FUNCTIONAL GROUPS Alkyl Halides
R
ethylene dibromide (banned pesticide) chlorodane (banned pesticide) carbon tetrachloride (banned dry cleaning agent) methyl bromide (banned fumigating agent)
Hal
Classes of alkyl halides H3C H3C C
I
H3C
Cl
H3C
CH3F
CH3Cl
Br
CH3I
CH3Br
Carbon-Halogen Bonds R
Hal
Halogen
C-Hal bond length / Å
C-Hal bond dipole / D
Bond energy kcal/mol
Fluorine
1.38
1.51
116
Chlorine
1.77
1.56
79
Bromine
1.94
1.48
66
Iodine
2.21
1.29
52
We will see later that in general the reactivity of alkyl halides increases in the order: alkyl fluorides
