CH2210 An Introduction to Organic Chemistry -...

CH2210 An Introduction

to Organic Chemistry

Organic Chemistry - General Description

A. The Study of Carbon Compounds

B. “Organic” reminds us of plant or animal origins 1. “Natural” medicines: morphine, penicillin 2. “Natural” fibers: cotton, silk, wool 3. Foodstuffs: Fats, carbohydrates, proteins, vitamins 4. “Natural” rubber

C. Man-made substances can also be “organic” 1. Drugs: xylocaine, aspirin, acetaminophen 2. Fibers: nylon, dacron, rayon 3. Polymers: Saran wrap, polyesters, teflon, nylon 4. Synthetic rubber, synfuels

Differences Between Organic and Inorganic Compounds

Inorganic OrganicElements Present Metals and Nometals Mostly Carbon

Bonding Covalent and Ionic Mostly Covalent

“Particles” IONS & molecules ions & MOLECULES

Melting Points Relatively High Relatively LowBoiling Points Relatively High Relatively Low

Electrolytes ? STRONG to weak weak to NON

Comparison of Physical Properties of Organic and Inorganic Compounds

Name Salt Ethyl alcohol Benzene

Formula NaCl C2H6O C6H6

Organic/Inorganic Inorganic Organic Organic

Melting Point 804 ºC -117 ºC 5 ºC

Boiling Point 1413 ºC 78 ºC 80 ºC

Burns in O2 ? No Yes Yes

Water Soluble ? Yes Yes No

Structural Formulas and Condensed Structures

Because organic compounds are molecular in nature, the additional information conveyed in structural formulas is sometimes necessary.

Structural formulas show the connections between atoms based on their abilities to form covalent bonds.

HC

C

C

O

O

N

N

N

F

Cl

Br

Main-Group Elements have common bonding patterns

Because certain carbon and hydrogen groupings are so common, some abbreviations are used.


C

H

H

H CH3 C

H

H

CH2

C

H

CH CH2CH2 (CH2)2


C

C

C C C

H

H C

C

C C C C O

H

H HH

H

H H

H

HH

H

H

H

H

H

H

H

H H

H

H3C

CH

H3C

CH

HC CH

CH3

(CH2)4 OH

Example of a Condensed Structure: What does the molecular formula C11H22O represent ?


Abbreviations for Cyclic StructuresCH2

H2C

H2CCH2

CH2

CH2

CH2H2C

H2CCH2

CH

CH

CH2

CH2

CH2

CH2

C

C

CC

C

CH

H

H

H

H

H

Alkanes Aldehydes

Alkenes Ketones

Alkynes Carboxylic Acids

Aromatics Esters

Alcohols Amines

Ethers Amides

Families of Organic Compounds

C C

C C

C C

CC

CC

C

C

C O

H

C OC

CH

O

CC

O

C

CO

H

O

C

O

OC

N

CN

O

Alcohols Phenols Ethers Thiols Dissulfides Amines

-O- -S- -N-

OC

Alkanes Alkenes Alkynes Aromatics

Aldehydes Ketones Acids Esters Anhydrides Amides

OC-N

OC-O

Hydrocarbons

All Classes of Organic Compounds

Functionalized Hydrocarbons

Halides

F,Cl,Br O,S,N

OC

C C C C C

C

C

C

C C C C C C C

C

C C

CCC

C

C

CC

C

CC

CC

CC

C

CC

C

CC

C

C

CC

CC

Bonding Patterns of Carbon

Linear ChainBranched Chain

Cube

Simple Rings Fused Rings

Allotropes of Carbon

Hydrocarbons The Simplest Class of Organic Compounds


A. Contain only Carbon and Hydrogen B. Carbon can bond in different ways

C

H

HH

H

C

H

HH

H

CH4

180º120º

VSEPR Model

120º

180º180º

C C

H

H H

H

C C H H


B. Carbon can bond in different ways (multiple bonds)

C CH H

C CH

H H

H


C. Hydrocarbons are further subclassified

C C C C C

UNSATURATED

ALIPHATIC AROMATIC

SATURATED

Structural Formulas and Bond Angles

120º

180º

Methane (109.5º angles)

Structural Representation of Simple Alkanes

Alkanes - The Meaning of Line Structure

CH4

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH3

CH3CH2CH2CH3

CH3CH2CH3

CH3CH3

Formulas and Properties of “Normal” Alkanes

Homologous Series

n Molecular Condensed Name Melting Boiling

Formula Structural Formula point (oC) point (oC)

1 CH4 methane -182 -1622 C2H6 ethane -183 -893 C3H8 propane -190 -424 C4H10 butane -138 -15 C5H12 pentane -130 366 C6H14 hexane -95 697 C7H16 heptane -91 988 C8H18 octane -57 1269 C9H20 nonane -51 151

10 C10H22 decane -30 174

CH4

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH2CH3

CH3CH2CH2CH2CH3

CH3CH2CH2CH3

CH3CH2CH3

CH3CH3

Formulas and Properties of “Normal” Alkanes

Uses of Hydrocarbons

Supplement on

Hybridization

Carbon Bonding in Alkanes

Carbon atoms in alkanes have the following characteristics:

Carbon is tetravalent: each carbon has four bonds; The four bonds possess tetrahedral geometry; The four bonds are equivalent and have similar properties.

The angle between any two bonds of a tetrahedral carbon in any carbon compound is 109.5o, the tetrahedral bond angle.

Carbon: ground-state electron configuration

2p

2s

1s

2p

2s

1s

Carbon: excited-state electron configuration

Carbon:

sp3-hybridized electron configuration

2sp3

1s

}hybridization

excitation

En

erg

yThe sp3 Hybridization Scheme for Carbon

The sp3 Hybridization Scheme

excitation

hybridization

an s and 3 p orbitals combine

4 sp3 hybrid orbitals

which are represented as

C

The Hybrid Orbital Picture of Methane CH4

C

4 carbon sp3 hybrid orbitals

4 hydrogen 1s atomic orbitals

Methane

A. Atoms may freely “rotate” about Single bonds

B. Such rotation is not evident in very simple molecules, but can be demonstrated in models of larger molecules

1. Methane - CH4

Rotation does not change the spacial relationship between hydrogen atoms.

2. Ethane - CH3CH3

Rotation does change the spatial relationship between hydrogen atoms

“Conformations” of Alkanes

Conformations of Alkanes C. CONFORMATIONS - Different arrangements of atoms in a molecule which can be interconverted by rotation about single bonds

D. In a given sample of a compound, the molecules usually exist as a mixture of conformations. One or two conformations are usually the most stable.

E. Though they may appear different on paper, different conformers represent the same molecule

CH3 CH2 CH2 CH3 CH2 CH2 CH3

CH3

CH3

CH2 CH2

CH3 CH3

CH2 CH2

CH3

CH3 CH2

CH3

CH2

Isomerism, A Complicating Factor in Organic Chemistry

A. A molecular formula may not convey a unique structure.

B. Isomers - Compounds with identical molecular formulas, but different structural formulas.

C. Example #1: C4H10

Compound

Name Butane Isobutane

Melting point -138 oC -160 oC

Boiling point 0 oC -12 oC

Density 0.601 g/mL 0.557 g/mL

H3CCH2 CH2

CH3

H

CH3C CH3

CH3

Isomerism

A molecular formula may not convey a unique structure.

Isomers - Compounds with identical molecular formulas, but different structural formulas.

Isomerism

n-butane iso-butanebutane 2-methylpropane

Compound

Name Acetic Acid Methyl formate

Melting point 16.6 oC -99 oC

Boiling point 118 oC 31 oC

Density 1.05 g/mL 0.97 g/mL

H3CC

O

OH

HC

O

OCH3

Isomerism Example #2: C2H4O2

Compounds with the Formula C4H10O

H3CCH2

CH2CH2

OH CH3

CH2CH2

OCH3

CH3CHCH2

OH

CH3

CH3CH2

OCH2

CH3

CH3CH2

CHCH3

O

H

CH3CH

OCH3

CH3

CH3C

OH

CH3H3C

Compounds with the Formula C4H8O

H3CCH2

C

O

CH3H3C

CHC

O

H

CH3

OH2C

H2C CH2

CH2 O

H2C CH2

HC

CH3

O

CH2

C

CH3

CH3

H2C

H2C CH2

HC

O

H

C C

CH2CH2

O

H

H

H

H

Isomerism Two Compounds

The compounds cannot be isomers.

Are the chemical formulas the same ?NoYes

The compounds are constitutional isomers. Are the compounds superimposable ?

Yes

No

The compounds are stereoisomers.

The compounds are identical.

The compounds are enantiomers.

The compounds are diastereomers.

Are the connectivities of the atoms the same ?

Yes No

Are the compounds mirror images?

NoYes

Isomer Worksheet

H3C

CH

H3C

CH2 CH2 CH3

CH3 CH2

CH2 CH

CH3

CH3

1)

2) CH3 CH2

CH2 CH

CH3

CH3

CH3 CH2 CH CH2 CH3

CH3

3)

4)

C6H14 C6H14

C6H14C6H14

C6H14 C6H14

C6H14C5H12

identical

isomers

isomers

unrelated

5)

6)

7)

8)

Cl Cl

CH3

H3C CH

CH3

OH

H3C CH2 CH2 OH

H3C CH2 C

O

CH3

O

H3C CH2 CH2 C

O

HH2C CH CH2 O CH3

C6H11Cl C6H11Clisomers

C3H8O C3H8Oisomers

C4H8O C4H8Oisomers

C4H8O C4H8Oisomers

Isomerism What is the relationship between these two

molecules?

2,3-dimethylpentane 2,3-dimethylhexane

C7H16 C8H18


molecules?

and

2,4-dimethylpentane 2,2-dimethylpentane

C7H16 C7H16


molecules?

2,3-dimethylpentane 2,3-dimethylpentane

C7H16 C7H16

Supplement on

Hybridization

Carbon Bonding in Alkanes

Carbon atoms in alkanes have the following characteristics:

Carbon is tetravalent: each carbon has four bonds; The four bonds possess tetrahedral geometry; The four bonds are equivalent and have similar properties.

The angle between any two bonds of a tetrahedral carbon in any carbon compound is 109.5o, the tetrahedral bond angle.

CH2210 An Introduction to Organic Chemistry -...

Documents

Transcript of CH2210 An Introduction to Organic Chemistry -...