Section One

Recommended Review

Remember that chemistry must be learned by building upon previous understandings of chemistry, so it is strongly recommended that you go to the review section before proceeding in this chapter.


OBJECTIVES

  1. Learn the definition of organic chemistry and biochemistry.
  2. Understand the sources of organic compounds.
  3. Begin to grasp the three-dimensional structures of organic compounds.
  4. Be able to draw correct structural formulas for compounds.
  5. To learn the differences in properties between organic and inorganic compounds and be able to suggest whether a compound is organic or inorganic based on its properties.

I. Definitions

Where did the words organic and inorganic come from in reference to chemical compounds? The answer is in the roots of the words. Originally scientists thought that some compounds originated only from organisms (life forms) and others originated from nonlife forms, hence the terms organic chemicals and inorganic chemicals. Then scientists made from nonlife sources compounds that previously had been thought to have only life sources as their origin. So the name organic was applied to compounds containing carbon atoms. A new name was then made for the study of chemicals related to living organisms: biochemistry.

II. SOURCES OF ORGANIC COMPOUNDS

There are more organic compounds than inorganic compounds because of the many ways that carbon can form bonds with itself and with other atoms. Organic compounds have two sources:

  1. Isolation from nature is one source. Biosynthesis is the making of the organic compounds by plant and animal life. The field of natural products chemistry also is rooted (no pun intended) in biosynthesis. Chemists working in natural products chemistry try to determine what plants, roots, etc. have been used by primatives for cures for headaches or other health problems. They then take the plants and isolate the chemical compounds from the plants. At least 50% of the drugs in use today have been found utilizing natural products chemistry. Of course sometimes it is not a single chemical in the plant that has the curative nature, but a combination of chemicals so the process of determining causative effects is quite complicated.
  2. Organic compounds also can be synthesized in the laboratory without using natural sources. It is important to note that a chemical compound such as vitamin C is a compound whose structure does not depend upon the source. Vitamin C is the same whether synthesized in the laboratory from non-natural sources or if made from natural sources (rose hips or whatever). The claim "made from all natural sources" has no significance referring to the structure of any chemical compound. So aspirin is aspirin, vitamin C is vitamin C, etc.

III. STRUCTURES OF ORGANIC COMPOUNDS

But is C2H6O always representative of the same actual compound? Nope. The molecular formula of an organic compound does not infer enough information for us to know what C2H6O really is. We have to know the structural formula of C2H6O to know if it is ethanol or dimethyl ether. These two compounds have the same molecular formula but different structural formulas and very different physical and chemical properties. Such compounds are called structural isomers.

ethanol ethanol

dimethylether dimethylether

A very useful way to visualize the structural formulas of compounds is by using Chime, a plug in for Netscape. If you have Chime installed, as do the computers in the College computer lab, you can go to my Chime site to rotate some structural formulas to get a better understanding of their three-dimensional structure. On that list of molecules you will see dimethyl ether and ethanol so look at those isomers so that you can clearly see the difference.

You need to firmly implant in your mind that H forms only one bond as does F, Cl, Br, and I. Also know better than you know your name that C forms 4 bonds, N forms 3 bonds, O forms 2 bonds, and S forms 2 bonds. Never violate these rules and you will have it much easier in your task of drawing structural formulas.

Differences in properties of organic and inorganic compounds are summarized in the following table:

Organic CompoundsInorganic Compounds
Bonding is almost entirely covalent. Many compounds have ionic bonds
May exist as gases, liquids, or solids with low m.p.Mostly high melting points (>360 oC) & solids at R.T.
Most are insoluble in water.Many soluble in water.
Most are soluble in nonpolar solvents such as gasoline, benzene, CCl4 Most insoluble in nonpolar solvents.
Solutions to not conduct electricity.Water solutions conduct electricity.
Almost all burn.Very few burn
Reactions usually slowReactions often very fast

ASSIGNMENTS

Will be sent to you by e-mail and/or the WebCT site bulletin board.

QUIZ ONE

After you have studied this material and practiced some problems, take quiz one. If you score at least 80 on the test then you are ready to continue to the next section.


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Web Author: Dr. Leon L. Combs
Copyright 2001 by Dr. Leon L. Combs & Dr. Jennifer Powers & Dr. Vicky Bevilacqua - ALL RIGHTS RESERVED