Organic Chemistry

Introduction to Organic Chemistry

What is Organic Chemistry?

Organic Chemistry is the study of carbon

containing compounds

Organic compound

– Is molecular compound of carbon

– Is made up of carbon and hydrogen exclusively

(hydrocarbons) or carbon, hydrogen and small

amount of other elements such as N,P,O,S and

halogen atoms (hydrocarbon derivatives)

What is Inorganic Chemistry?

Inorganic Chemistry is the study of the rest of the elements

Examples of Organic Compounds

– Sugar, fat, oil, protein, starch

– Clothing - wool, silk, cotton, nylon, spandex, acrylic fabrics

– Cosmetics – creams, perfumes

– Medicine

– Plastic, rubber, paints

– Pesticides, herbicides

Compounds found in nature

– Produced through process called biosynthesis

– Sugar, cotton, wool…

Compounds made by man

– Synthetic compounds

– Nylon, rubber, creams

History of Organic Chemistry

Historically, organic compounds were obtained naturally from living organisms (plants and animals)

1828 – Fridrich Wohler synthesized first organic compound (urea) from inorganic reactants

We now have found ways of synthesizing these organic compounds (with the desirable properties of the natural compounds)

Synthesis of New Organic Compounds

Synthesis from elemental carbon and hydrogen (other elements) is not always possible

Majority of organic compounds is synthesized from other organic compounds (hydrocarbons)

Sources of hydrocarbons

– Wood

– Products that result from fermentation of plants

– Fossil fuels (origins in organic matter)

Coal

Petroleum (crude oil)

Natural gas

Petroleum

Main source of the hydrocarbons that are used for fuels and many other products (eg. Plastic and synthetic fabric)

Mixture of solid, liquid and gaseous hydrocarbons

Petroleum is process at oil refineries (fractional distillation)

Sooo.. Many organic compounds

There are approximately 6 times as many organic compounds as there are inorganic compounds

Why is this so?

Why is Carbon so Special?

The unique characteristics of carbon allow for large number of organic compounds

Carbon forms a total of four covalent bonds

Thus it can bond to itself or many different atoms

Carbon atoms can bond together to form a variety of geometrical structures

Forms single, double or triple bonds

Representing Organic Compounds

Organic compound

Structural diagrams

Condensed structural diagram

Complete structural diagram

Line structural formula

Skeletal structure

Molecular formula Structural models

Ball-and-stick models

Space-filling models

Dash-wedge-line structures

Molecular formula

Shows the actual number of atoms of each element in a molecule

Disadvantage : it does not provide information about structure

Eg. Draw a skeletal structure of pentane, C5H12 .

Isomers

Are compounds with the same molecular formula but different molecular structures

Named differently

Have different physical and chemical properties

Structural diagrams

Also called structural formulas

Are two dimensional representation of the arrangement of the atoms in molecules

Advantages: gives complete information about the arrangement of atoms in a molecule

Disadvantages: does not provide information about the spatial orientation of atoms

Complete Structural Diagram

Also called expanded structural diagram

Shows all the atoms in a structure and how they are bonded to one another

Bonds are shown with straight lines

Disadvantage?

“—” A single line represents one pair of electrons (a single bond)

“=” A double line represents two pairs of electrons (a double bond)

“≡” A triple line represents three pairs of electrons (a triple bond)

Condensed Structural Diagram

Shows the kind and number of atoms present

Only shows bonds between carbon atoms

The bond between hydrogen and carbon is assumed to be present

Expanded Molecular Formula

Shows groupings of atoms without drawing lines to show the actual bonds that occur, they are assumed to be present

Brackets are used to indicate the location of branched chains

Line Structural Diagram

The end of each line, and the points where lines meet, represent carbon atoms

Hydrogen atoms are assumed to be present in the correct number

Gives you a sense of the three-dimensional nature of the bonds

Representing Structures

Complete Structural Diagram

Condensed Structural Diagram

Expanded Molecular Formula

Line Structural Diagram

CH3–CH2–CH2–CH3

CH3CH2CH2CH2CH3

Common molecular shapes in organic chemistry

Classifying Hydrocarbons

Chemists group hydrocarbons and other organic compounds into categories based on their properties

The International Union of Pure and Applied Chemistry (IUPAC) developed a set of rules for naming the compounds in each category

Organic Compounds

Hydrocarbons

Aliphatic

Hydrocarbons

Saturated Hydrocarbons

Alkanes

Unsaturated Hydrocarbons

Alkenes Alkynes

Alicyclic

Hydrocarbons

Aromatic

Hydrocarbons

Hydrocarbon Derivatives

Terms To Know

Saturated

organic compounds in which each carbon atom is bonded to the maximum number of hydrogen atoms, thus containing only single bonds

Unsaturated

organic compounds in which the carbon atoms do not have the maximum number of hydrogen atoms and thus have double or triple bonds

Classifying Hydrocarbons

Look at the following compounds. If you were to classify them, how would you do it?

Single Bond Compounds

These are called Alkanes!

Double Bond Compounds

These are called Alkenes!

Triple Bond Compounds

These are called Alkynes!