Chesapeake Campus – Chemistry 112 Laboratory

Objectives

• Classify organic compounds based on formula and structure.
• Determine the IUPAC name of organic compounds.
• Draw complete, condensed and line-angle structures of common organic compounds. IntroductionOrganic Chemistry. Organic chemistry refers to the science of carbon-containing compounds. Generally this includes the study of their structure, properties and reactions. Organic compounds have a wide range of properties due to the functional groups (a specific set of atoms) that can be bonded to the molecule. Each class of functional group has a specific subset of properties and is named according to the IUPAC system. Although more common names exist, scientists prefer the IUPAC system for naming compounds because it allows structural information to be gleaned from the name itself rather than through memorization. Functional Groups and IUPAC Naming. The International Union of Pure and Applied Chemistry sets the standard for naming organic compounds. The name is systematically given to a compound based on the compound’s

• Longest continuous chain of carbon atoms- sets the root of the compounds name according to a set of prefixes discussed in Table 1.
• Functional Groups – names the compound according to what functional groups are present.
• Additional substituents – functional groups with the highest priority change the suffix of the name of the compound while the rest are added as prefixes.
• Structure – compounds may be cyclic or straight chain (or a combination of both) but both options can be included in the name.

Rules for Naming Organic Compounds
1. The longest continuous chain of carbon atoms is used to establish the root of the compounds name.

2. The principal functional group is used to determine the class of the compound. (Priority of functional groups is given in Table 3). These affect either the prefix or suffix of the name.
3. If more than one of the same substituent is present, a prefix is added to denote the number according to Table 2. Mono is usually excluded from the name as it is an understood

Table 2: Prefixes for Multiple Substituents

4. The location of each substituent along the carbon chain is indicated giving the lowest possible combination of numbers.
5. The additional substituents are listed alphabetically.

For example: the following compound is
named by first counting the number of
carbons. There are 4 which means the
root of the compound must be –but.
There are all single bonds indicating the
end of the name will be –ane. There are
2 chloro- substituents that are on
neighboring carbons. This means we
will use the prefix di- and need to specify
the location of those chlorines. The carbons with the chlorines bonded are number 1 and 2 respectively instead of 3 and 4 to ensure the lowest possible combination of numbers. There is also a fluoro substituent on the carbon numbered 3. Thus the name of this compound is 1,2-dichloro;3-fluorobutane.

Types of Structures
There are 3 types of structures that can be used to draw organic compounds. The complete or most elaborate structure indicates every bond drawn. The structure of 1,2-dichloro;3-fluorobutane above is an example of a complete structure.
The line angle structure only draws non-hydrogen atoms. Carbons are indicated at line junctions. Bond angles are represented with 3-D indicators when necessary. Bonds aimed out of the paper are indicated by bold triangles with while bonds going behind the plane of the paper would be indicated by a dashed line. An example of the above structure in line angle format looks like

Example of a Line-Angle Structure

The last type of structure is the condensed
structure which indicates which atoms are bonded to which without showing 3-D orientation. You list each carbon with the atoms bonded to it, followed by the next carbon showing the atoms bonded to it. This pattern is continued until the whole molecule is listed. For example the above compound would be written as CH2Cl-CHCl-CHF-CH3 in the condensed form. Note that all atoms are indicated and listed with the specific carbon they are bonded to.

Table 3 illustrates some of the more common functional groups. They are listed in order of priority. Examples for the structure and name are given of each type of compound.