introduction to organic chemistry and alkanes. organic chemistry molecules made up of carbon,...

Introduction to Organic Chemistry and Alkanes

Organic Chemistry

• Molecules made up of carbon, hydrogen, and a few other elements (oxygen, nitrogen, sulfur, or halogens)

• Amazing array of organic molecules:– Many are essential to life (phospholipids and

enzymes)– Glucose and fructose– Penicillin and aspirin– Fossil fuels

Why so many Organic Compounds?

I. Carbon can form stable, covalent bonds with other carbon atoms.

3 allotropes of carbon (forms of an element that have the same physical state but different properties)

1. Diamond2. Graphite3. Buckminsterfullerene

3 Allotropes of Carbon

1. Diamond– A large 3-dimensional network

of carbon-to-carbon bonds

- results in an extremely

hard substance


2. Graphite

-Planar layers of carbon-to-carbon bonds that extend in 2-dimensions

-Planar units slide over one another


3. Buckminsterfullerene - “Buckey Ball”

-60 Carbon atoms in the shape of a soccer ball

-discovered in the 1980’s


II. Carbon can form stable bonds with other elements.

-Several families of organic compounds contain oxygen atoms bonded to carbon. Others contain nitrogen, sulfur or halogens.

-The presence of these elements allows for a wide variety of new chemical and physical properties on the organic compound.


III. Carbon can form double or triple bonds with other Carbon atoms.

This produces a variety of organic molecules with very different properties.


IV. The structure of the compounds creates limitless possibilities.

The number of ways in which carbon and other atoms can be arranged is nearly limitless. (Ex: linear chains, ring structures, and branched chains).

Isomers

ISOMERS - same number and kinds of atoms but with different structures, therefore different properties

“STRUCTURE determines FUNCTION”

Comparison of Organic and Inorganic Compounds

Property Organic Inorganic

Bonding Covalent Ionic

Terms to describe Molecule Compound

Physical state Gas Solid

Boiling Point Low High

Melting Point Low High

Solubility in water Insoluble High

Solubility in organic solvents High Insoluble

Flammable Yes No

Conducts electricity No Yes (soln and liq)

Families of Organic Compounds

Hydrocarbons

Aliphatic Aromatic

Alkanes Alkenes Alkynes

Contains only single bonds

Contains at least one double bond

Contains at least one triple bond

Contains benzene ring


Hydrocarbon – contains only hydrogens and carbon

Substituted Hydrocarbon - one or more hydrogen atoms is replaced by another atom or group of atoms

(functional group)


Aliphatic Hydrocarbon - alkanes, alkenes, & alkynes

Saturated Hydrocarbon - alkanescontain only C and Hhave only single bonds

Unsaturated Hydrocarbon – alkenes & alkynescontain only C and Hhave at least one carbon to carbon double

or triple bond

Families of Organic CompoundsCycloalkane – carbon atoms bonded to

one another to produce a ring

Aromatic Hydrocarbon – contains a “benzene

ring” (6 carbon atoms bonded to one another with alternating single and doublebonds to form a ring)

Common Functional Groups

“Structure determines Function”

Three types of formulas• Molecular formula – gives the type and number

of each atom present in a molecule but does not show bonding pattern– EXAMPLE: C3H8

• Structural formula – shows each atom and bond in a molecule – EXAMPLE:

• Condensed formula – shows all the atoms and places them in sequential order that indicates which atoms are bonded to which – EXAMPLE: CH3CH2CH3

H H H

H-C-C-C-H

H H H

Another way to draw structures

• Line or skeletal structure– Only the bonds and not the atoms are

shown.– A carbon atom is assumed to be at the ends

and junctions of the lines– Correct number of hydrogens is mentally

supplied

3-methylpentane

Cl

3-chloropentane

Alkyl GroupsNumber of carbons Name

1 Methyl

2 Ethyl

3 Propyl

4 Butyl

5 Pentyl

6 Hexyl

7 Heptyl

8 Octyl

9 Nonyl

10 Decyl

Carbons are classified according to the number of other carbons to

which they are attached.• Primary (1°) bonded to one other carbon

• Secondary (2°) bonded to two other carbons

• Tertiary (3°) bonded to three other carbons

H

C-C-

H

C

H-C-C

H

C

C-C-

C

I.U.P.A.C. Nomenclature

• International Union of Pure and Applied Chemistry – organization responsible for establishing and maintaining a standard, universal system for naming compounds

• All alkanes are the alkyl group name followed with the suffix –ane.

H H H

H-C-C-C-H

H H H

Contains 3 carbons – propyl group; Add –ane

Propane

Nomenclature of Alkanes

1. Find the parent chain.A. Find the longest continuous chain of carbon atoms

present in the molecule, and use the name of that chain as the parent name.

CH3CH2CH2CHCH3 CH2CH3

CH2CH3 CH3CHCHCH2CH3

CH2CH2CH3


1. Find the parent chain.B. If two different chains of equal length are

present, choose the one with the larger number of branches.

CH3

CH3CHCHCH2CH2CH3

CH2CH3


2. Number the atoms in the main chain.A. Beginning at the end nearer the first branch

point, number each carbon atom in the parent chain.

CH2CH3

CH3CHCHCH2CH3

CH2CH2CH3


2. Number the atoms in the main chain.B. If there is branching an equal distance away from both ends of the parent chain, begin numbering at the end nearer the

second branch point.

CH3CH2 CH3 CH2CH3

CH3CHCH2CH2CHCHCH2CH3


3. Identify and number the substituents.A. Assign a number to each substituent

according to its point of attachment to the main chain.

B. If there are two substituents on the same carbon, assign them both the

same number. There must be as many numbers in the name as there are substituents.


3. Identify and number the substituents

CH3

CH3CH2CCH2CH2CH3

CH2

CH3


4. Write the name as a single word, using hyphens to separate the different prefixes and using commas to separate numbers.

A. If two or more different substituents are present, cite them in alphabetical order.

B. If two or more identical substituents are present, use one of the prefixes di-, tri-, tetra-, etc but do NOT use these for alphabetizing purposes.

Name These Alkanes!

CH2CH3

CH3CH2CH2CHCH3

CH3

CH3CHCHCH2CH2CH3

CH2CH3

Name These Alkanes!

CH2CH3 CH3 CH2CH3

CH3CHCH2CH2CHCHCH2CH3

CH3

CH2

CH3CHCHCH2CH3

CH2CH2CH3

Name These Alkanes!

CH3

CH3CH2CCH2CHCH3

CH2

CH3

Nomenclature for HALOGENATED ALKANES

• Step 1: name the parent chain

CH3CHCH3

Br

propane

• Step 2: number the parent chain

CH3CHCH3

Br

1 2 3


• Step 3: name & number each ATOM or GROUP attached to the parent (the “substituent”)

CH3CHCH3

Br

parent: propane

substituent: 2-bromo


• Step 4: If the same substituent occurs more than once, a separate number AND a prefix (di, tri, tetra-, etc.) are used

Br Br

CH3CHCH2CH2CHCH3

Parent: hexane

Substituent: 2,5-dibromo


• Step 5: Place the names of the branches in alphabetical order before the parent name.

Separate numbers with commas

Separate names & numbers with hyphens

HALOGEN substituents are placed BEFORE alkyl substituents in the name


CH3

CH3 CH C CH2CH3

Br CH3

Parent: pentane

Subs: 2-bromo

3,3-dimethyl

2-bromo-3,3-dimethylpentane

Practice

1) CH3CH2CH2CH2CHCH3

Br

2) CH2CHCH2

Br Br Br

Practice

3) Br

HCH

CH3CCH2Br

CH3

4) CH3CHCH2CH2CHCH2Br

Cl CH3

Practice

5) CH3CHCHCH2CH2CH2Cl

CH3

introduction to organic chemistry and alkanes. organic chemistry molecules made up of carbon,...

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