(1) A saturated organic molecule contains only single bonds between carbon atoms.
An unsaturated organic molecule contains 1 or more double and/or triple bonds between carbon atoms.
(2) An organic molecule may contain many different functional groups ofcourse, but our discussion will be limited to just 2.
(3) IUPAC is the abbreviation for the International Union of Pure and Applied Chemistry.
(4) There are a number of different systems for naming organic molecules.
We will be using a substitutive system which is commonly used to name most organic compounds with the notable exceptions of esters and anhydrides which are named using functional class nomenclature.
(5) Note that the name we use to refer to a functional group is different to the prefix and suffix we use when naming an organic molecule:
COOH is the carboxyl functional group, the suffix used is oic acid
OH is the hydroxyl functional group, prefix used is hydroxy, suffix used is ol
C=O is the carbonyl functional group, prefix used is oxo, suffix used is either one (non-terminal C atom) or al (terminal C atom)
(6) The rules for naming organic compounds are still being developed by IUPAC.
The most recent document for referral is "Preferred names in the nomenclature of organic compounds" (Draft 7 October 2004).
The current document recognises that there is more than one way to systematically name organic compounds, and develops rules for assigning "preferred IUPAC names", but any other name, as long as it is unambiguous and follows the principles of the IUPAC recommendations is acceptable as a "general IUPAC name".
As a result, there are examples of "preferred IUPAC" names that are based on the tradition of use, rather than a system of naming. Examples of these traditional names that students may be expected to know are acetone, acetic acid and its derivatives such as ethyl acetate and acetic anhydride, formic acid and its derivatives such as ethyl formate.
(7) Technically, a "straight chain carbon compound" is an acyclic aliphatic organic compound.
Acyclic, or non-cyclic, means that the carbon atoms form a chain and joined up in a ring.
Aliphatic comes from the Greek aleiphatos meaning "fat". Early Chemists did not know the structure of a fat, but they did know that compounds containing long hydrocarbon chains behaved in a similar way to fats. So compounds containing hydrocarbon chains came to be known as aliphatic compounds.
Organic compounds are, in general, compounds that contain carbon.
(8) Or, as many of the functional groups as possible if you are dealing with more than 2 functional groups.
Note that the "principal chain" may be unsaturated, that is, it may contain double bonds and/or triple bonds between the carbon atoms.