Transcript Organic Chemistry

Organic Chemistry
2008-2009-I
Instructors:
Associate-professor, Dr. Fu Yu-Qin (傅玉琴)
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Text:
1. Organic Chemistry, L. G. Wade, Jr., 5th Ed.
2. 有机化学, 曾昭琼, 第四版.
3. 有机化学, 邢其毅, 第二版. (参考书).
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辅导课:
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Midterm exam:
Grading:
Final Exam (期末考试)
Assignments (作业)
80%
20%
Study Tips
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4.
Read the material in the book before the lecture
(15~25 pages)
After the lecture, review the notes and the book,
summarize the contents in 24 hours.
Do the assignments by yourself without delay.
If you are confused about something, visit your
instructor.
Don’t get behind!
Work lots of problems!
You cannot cram for an organic exam!
About the Text
Study aids
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Summary tables
Reaction summaries
Mechanism (机理) boxes
Problems, Solved problems
Glossaries (词汇表)
Problem-solving strategy
Problem-solving hints
Essential problem-solving skills
2007-2008-I
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4.
Introduction and review (3 h)
Alkanes and cycloalkanes (5 h)
Stereochemistry (6 h)
Alkyl halides: nucleophilic substitution and
elimination (6 h)
5. Alkenes (6 h)
6. Alkynes and dienes (4 h)
Midterm exam
7. Alcohols, ethers, and epoxides (8 h)
8. Spectroscopic methods of structural
determination (6 h)
9. Aromatic compounds (8 h)
10. Ketones and aldehydes (8 h)
Chapter 1
Introduction and review
Reading materials:
Text 1: Chapter 1 and 2
Text 2: 第一章
Contents
1.1 The origins and development of
organic
1.2 Structure and bonding
1.3 Acidity and basity
1.4 Empirical formulas, molecular
formulas and structural formulas.
1.5 Resonance
1.6 Classification of organic compounds
1.1 The origins and development of organic
chemistry
Organic Chemistry: What is it?
• 1780: Organic compounds are very complex and only
obtained from living sources (vitalism 生机说)
• Vitalism: Belief that a "magic" vital force, present in
plants and animals, is necessary for the synthesis of
organic compounds
• 1789: Antoine Laurent Lavoisier observed that
organic compounds are composed primarily of
carbon and hydrogen
•1828: Friedrich Wohler synthesized an organic
compound (urea) from inorganic compounds (lead
cyanate and ammonium hydroxide).
氰酸铅
尿素
"The Age of Organic Chemistry"
• The modern definition of organic
chemistry is the chemistry of carbon
compounds.
> 95% of all known compounds
composed of carbon.
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Organic chemistry is crucial to our way
of life: clothing, materials (polymers),
petroleum, medicine, our bodies.
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> 50% Of chemists are organic.
Reserch topics of modern organic chemistry
STRUCTURE
Determining the Way
in Which Atoms Are
Put Together in Space
to Form Complex
molecules
MECHANISM
SYNTHESIS
Understanding the
Reactivity of
Molecules: How and
Why Chemical
Reactions Take Place
Building Complex
Molecules From
Simple Molecules
Using Chemical
Reactions
Why Carbon?
• Carbon forms a variety of strong covalent bonds (共价键) to
itself and other atoms.
• This allows organic compounds to be structurally diverse.
荷尔蒙(激素)
Why Does Carbon Bond in This Way?
1.2 Structure and bonding
1.2.1 Principles of atomic structure
(Read p 3~6)
I.
II.
III.
IV.
Structure of the atoms
Electronic structure of the atom
Electronic configurations of atoms
Atomic structure of carbon
1.2.2 Lewis Bonding Theory (Read p
6~13)
Bond formation: the octet rule (1-3)
• Atoms transfer or share electrons to gain a
filled valence shell of electrons.
A. Ionic Bonding
B. Covalent Bonding (Electron Sharing)
• electronegativity (电负性)
Lewis structures
lone pair（孤电子对）: unshared electron pair; nonbonding pair of electrons
Multiple Bonding（多重键）
• Two atoms can share more than one pair of electrons to gain a filled
shell (very common in organic molecules)
1.2.3 Molecular Orbital Theory (分子轨道理论)
(read CH 2)
Electrons Are Waves!
They Exist as 3-D Standing Waves (Orbitals).
Atomic orbitals: (s, p, d)
Linear Combination of Atomic Orbitals (LCAO): (σ, σ*, π,
π*, rules: energy, symmetry, overlap)
Molecular Orbital: Combination of atomic orbitals from
different atoms
Conservation of Orbitals（轨道对称守恒）
A. Atomic Orbitals
• s-orbitals: spherical, electrons held close to nucleus,
one sign
• p-orbitals: two lobes with opposite signs, electrons
further from nucleus
B. Sigma-Bonding (σ) s-s，s-p，p-p
bonding: (+/+ or –/–)
electron density centered
between Nuclei
anti-bonding: (+/–) generally
has a node between nuclei
node: area of zero electron
Density
1s
1s
‧In stable bonding situations,
usually only the bonding
orbitals (σ, π) are occupied.
C. Pi-Bonding (π)
p-p，(p-d)
Bond angle ?
CH3CH=CHC≡CH
1.2.4 Hybridization (杂化)
Hybridization:
Linear Combination of Atomic Orbitals (LCAO, 原子轨道线
性组合) on the same atom to form hybrid atomic orbitals.
A. sp Hybridization (Linear)
But, we only used one s- and one p-orbital!
There are two more p-orbitals.
Complete Orbital Picture of an sp Hybridized
Atom
B. sp2 Hybridization (Trigonal Planar)
C. sp3 Hybridization (Tetrahedral)
• Sigma-bonds and lone pairs involve hybrid orbitals.
• Pi-bonds involve unhybridized p-orbitals.
Assigning Hybridization to Atoms in a Molecule
(You need to be able to do this!)
Count the hybrid atomic orbitals.
# of hybrid orbitals = # of σ-bonds + # of lone pairs
1.3 Acidity and basity
1.3.1 Arrenius acids and bases(1-12)(酸碱电
离理论)
1.3.2 Brønsted-Lowry acids and bases(113)(酸碱质子理论)
1.3.3 Lewis acids and bases(1-14)(酸碱电子理论)
In organic chemistry:
Lewis acid—electrophile (亲电试剂)
Lewis base—nucleophile (亲核试剂)
1.4 Empirical formulas, molecular
formulas and structural formulas
(Read 1-11, 1-10, 2-5)
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Empirical formulas (最简式):
molecular formulas (分子式):
structural formulas (结构式):
e.g.
CH3CH3 a structural formula
C2H6
a molecular formula
CH3
a empirical formula
Structural formulas (1-10)
• Condensed structural formulas (1-10A)
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CH3CH2CH2CH3
• Lewis structure:
• Line-angle formulas (1-10B) : also called
bond-line formulas (键线式),
• Three-dimensional formulas: Dashes and
Wedges (楔形式)
Rules for Drawing Line-Angle Formulas
Brevetoxin A (!!) (双鞭甲藻毒素, “赤潮”神经毒素)
Three-dimensional formulas
Using Dashes and Wedges
• Tetra-Substituted Carbon Is Tetrahedral (more on this later).
1.5 Resonance (共振, 1-9)
• Resonance: Electronic Motion Within a Molecule
A. Rules for Drawing Resonance Structures
1. Only electrons move! Nuclei and the sigma- (single bond-)
framework are unchanged (Resonance occurs in the pi-system:
conjugated lone pairs and pi-bonds).
2. Every resonance structure must be a valid Lewis structure.
3. Keep track of lone pairs and formal charges.
4. Use arrow-pushing formalism to interconvert and identifiy
possible resonance structures.
5. Always use double-headed arrow (
) in between
resonance structures.
6. Lower energy resonance structures contribute most to the
overall structure of the molecule.
e.g. p 16 solved problem 1-2
How do you predict the relative energies of resonance structures?
B. Guidelines for Predicting Energies of
Resonance Structures (In Order of
Importance)
i) Filled Octets
ii) Negative charges on most
electronegative atoms.
iii) Minimize charge separation.
problems 1-7,8
Delocalization(离域) of Charge = Stabilization
共振式越多越稳定;
等共振结构越多越稳定.到如苯, 碳酸根等.
C. Structure and Reactivity Info from Resonance
Structures
Benzene
1.6 Classification of organic compounds
I. Classification according to carbon scheleton
1. Open chain compounds (开链化合物):
2. Carbocyclic compounds (碳环化合物):
alicyclic compounds (脂环化合物):
aromatic compounds (芳香环化合物)
heterocyclic compounds (杂环化合物):
II. Classification
according to
functional
groups
(按官能团分类)
表1-5
A. Hydrocarbons(烃)
alkanes (烷烃)
alkenes (烯烃 C=C)
alkynes (炔烃 C≡C)
aromatic hydrocarbons (芳烃)
B. Compounds containing oxygen
alcohols (醇 -OH)
ethers厚(醚 C-O-C)
aldehydes and ketones (醛和酮)
carboxylic acids (羧酸)
carboxylic acids derivatives(羧酸衍生物)
C. Compounds containing nitrogen
amines (胺)
amides (酰胺)
nitriles (腈)
Summary
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1. The origins and development of organic chemistry
2. Structure and bonding
1) Lewis Bonding Theory: the octet rule
2) Molecular orbital theory: σ,π, bonding
(antibonding) orbitals
3) Hybridization: sp, sp2, sp3
3. Acidity and basity
1) Arrenius acids and bases
2) Bronsted-Lowry acids and bases
3) Lewis acids and bases
4. Empirical formulas, molecular formulas and
structural formulas.
• 5. Resonance:
1) Drawing
2) Predicting Energies
• 6. Classification of organic compounds
Assignments
• 1-37, 41, 42, 43, 47
• 2-30, 39