Organic Chemistry

2008-2009-I

Instructors: Associate-professor, Dr. Fu Yu-Qin ( 傅玉琴 )

• 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 ). 辅导课 : ????? Midterm exam: Grading: Final Exam ( 期末考试 ) 80%

Assignments ( 作业 ) 20%

1. Read the material in the book before the lecture (15~25 pages)

2. After the lecture, review the notes and the book, summarize the contents in 24 hours.

3. Do the assignments by yourself without delay.

4. If you are confused about something, visit your instructor.

Don’t get behind!

Work lots of problems!

You cannot cram for an organic exam!

Study Tips

About the Text Study aids• 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-I1. Introduction and review (3 h)2. Alkanes and cycloalkanes (5 h)3. Stereochemistry (6 h)4. Alkyl halides: nucleophilic substitution and elimi

nation (6 h) 5. Alkenes (6 h)6. Alkynes and dienes (4 h) Midterm exam7. Alcohols, ethers, and epoxides (8 h)8. Spectroscopic methods of structural determinati

on (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

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

1.1 The origins and development of organic chemistry

•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.

Organic chemistry is crucial to our way of life: clothing, materials (polymers), petroleum, medicine, our bodies.

> 50% Of chemists are organic.

STRUCTURE

Determining the Way in Which Atoms Are Put Together in Space to Form Complex molecules

MECHANISM

Understanding the Reactivity of Molecules: How and Why Chemical Reactions Take Place

SYNTHESIS

Building Complex Molecules From Simple Molecules Using Chemical Reactions

Reserch topics of modern organic chemistry

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.

Why Does Carbon Bond in This Way?

荷尔蒙 (激素 )

1.2 Structure and bonding

1.2.1 Principles of atomic structure

(Read p 3~6)

I. Structure of the atoms

II. Electronic structure of the atom

III. Electronic configurations of atoms

IV. Atomic structure of carbon

1.2.2 Lewis Bonding Theory (Read p 6~13)

• electronegativity ( 电负性 )

• Atoms transfer or share electrons to gain a filled valence shell of electrons.

B. Covalent Bonding (Electron Sharing)

A. Ionic Bonding

Bond formation: the octet rule (1-3)

lone pair（孤电子对） : unshared electron pair; non-bonding pair of electrons

Lewis structures

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)

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）

Electrons Are Waves!They Exist as 3-D Standing Waves (Orbitals).

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 electronDensity

‧In stable bonding situations,usually only the bondingorbitals (σ, π) are occupied.

1s 1s

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 basity1.3.1 Arrenius acids and bases(1-12)(酸碱电离理论 ) 1.3.2 Brønsted-Lowry acids and bases(1-13)(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)

• 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)

• CH3CH2CH2CH3

• Lewis structure:• Line-angle formulas (1-10B) : also called bon

d-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 formulasUsing 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. II. Classification according to functional groups( 按官能团分类按官能团分类 ))表表 1-51-5

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• 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 structu

ral formulas. • 5. Resonance: 1) Drawing 2) Predicting Energies • 6. Classification of organic compounds

Assignments

• 1-37, 41, 42, 43, 47

• 2-30, 39