*The purpose of this page is to introduce the organic chemistry basics--a simple layout of the concepts that are taught in first semester ochem college courses.For definitions of key terms and tips on passing college ochem, go here.

RIGHT: Cycloalkanes from left to right -  Cyclopropane, Cyclobutane, Cyclopentane, Cyclohexane.

How to use the numerical roots:

Assume an alkane (hydrocarbon with only single bonds) has 6 carbons; Use the root hex- and since the molecule is an alkane, add the suffix -ane. The molecule is Hexane.

Examples:

A 10 carbon straight-chain alkane: decane

A 1 carbon hydrocarbon (CH4): methane

A 5 carbon straight-chain alkane: pentane


The same rules apply for alkenes and alkyes, but a number is placed in front of the systematic name to tell the location of the double and triple bonds. An example is given below:2-Butyne (Note that the triple bond starts at the second carbon and that every carbon atom has 4 bonds.)



Nomenclature Basics (naming compounds)

The basic roots used for naming organic compounds


Root  
Number of Carbon Atoms
meth-
1
eth-
2
prop-
3
but-
4
pent-
5
hex-
6
hept-
7
oct-
8
non-
9
dec-
10


In the commonly used skeletal structure, carbon atoms are represented by corners and the endpoints of a chain. The hydrogens are inferred--you can tell how many hydrogen atoms are attached to each carbon by remembering that a carbon atom always has four bonds. If two bonds aren't visible, assume there are two hydrogens, if you see only one bond in a skeleton structure (like the carbons at the endpoints) assume there are three attached hydrogen atoms. Here's the skeleton structure of benzene below:

Organic Chemistry Basics


What is Organic Chemistry?

Organic chemistry is the study of the properties, structure, and interaction of molecules that contain carbon.


Some Examples of Organic Molecules

- DNA

- The 20 amino acids

- Aspirin, Acetaminophen, Ibuprofen

- TNT (Trinitrotoluene)

- Plastics (Eg. Polyvinylchloride)

- Alcohol

- Dopamine (the pleasure hormone)

- Testosterone


It's All About Carbon


Carbon is the sixth element of the periodic table in Group 4A, has a mass of 12.01g/mol, and has four valence electrons. One Carbon atom can only form a maximum of four covalent bonds to other atoms in a molecule. A covalent bond is formed by one electron of one atom being shared with one electron from another atom, with the positive force of each nucleus pulling on the shared pair, effectively holding the two atoms together.


The Simplest Organic Compounds: Hydrocarbons


The most basic type of organic molecule, the hydrocarbon, is made entirely of carbon (C) and hydrogen (H) atoms. There are three types of hydrocarbons:

  • Alkanes - A molecule made entirely of carbon and hydrogen that contains only single bonds joining all of the carbons. Alkanes are saturated compounds, meaning there are only single bonds throughout the molecule (the term saturated may be used outside of organic chemistry). When naming alkanes, add the suffix "-ane". (Eg. Propane, Methane, Octane, etc.)
  • Alkenes - A hydrocarbon that contains at least one double bond between Carbon atoms, there may still be other single bonds in the molecule (but no triple bonds). Alkenes are unsaturated, meaning there is at least one double bond somewhere in the molecule. Alkene names end with the suffix "-ene". (Eg. Benzene)
  • Alkynes - A hydrocarbon that contains at least one triple bond. An alkyne may have other single or double bonds elsewhere in the molecule's structure. When assigning names to alkenes, add the suffix "-ene". (Eg. Pentyne)


Drawing Organic Compounds

If this is your first time reading about organic chemistry, this may seem like a useless thing to learn. However, understanding the basic structures of organic compounds is crucial to passing any elementary course in organic chemistry or even to be able to understand the common shorthand skeleton formula's used to display organic structures in common references (even Wikipedia).


Here's an example using Pentane to illustrate the three most common ways of depicting an organic molecule.


Another frequently encountered molecule in organic chemistry is the disubstituted benzene, where the R groups in the images above are substituted with ligands. The names given to these compounds have the prefixes o-, m-, and p-. For example, if the Meta structures above had two Chlorine atoms in the place of the R groups the molecule would be named m-dichlorobenzene.

ORGANIC FUNCTIONAL GROUPS


A functional group is an arrangement of atoms that give a molecule specific reactive characteristics. It's a group that may only be a segment of a much larger molecule or it can make up most of a compound's composition. Simply put: It's a group of atoms attached to a molecule--a specific group of atoms we assigned a name. For the formula of a functional group you will see and attachment point, -R, this represents a bonding point to any other molecule by the functional group.