The picture above shows the magnificent Cat’s Paw Nebula. The bright red cloud you see is made up of organic compounds such as formaldehyde, dimethyl ether, and methanol. Although these substances sound exotic and foreign, organic compounds are a vital part of our daily life. The same organic molecules present in the Cat’s Paw Nebula can be are found in everyday products, including hand sanitizers, household cleaners, and transportation fuels. In addition to being the key ingredients for commercial and industrial products, organic compounds are also responsible for many crucial chemical and biological processes. Understanding how to create and use various organic compounds is not just important for scientists; it is necessary for the average person in helping them make informed decisions about what they buy and what they put in their body.
Organic chemistry is the study of the properties, structures, reactions, and preparations of organic compounds. The use of the term “organic” suggests that organic chemistry is somehow connected to studying living things. In fact, organic chemistry has been once defined as the study of compounds produced by living organisms. Although it is now known that organic compounds can be synthetically produced, the name organic chemistry stuck. A compound is now classified as organic if it contains hydrogen and carbon atoms. Compounds consisting entirely of hydrogens and carbons are called hydrocarbons. However, a compound containing other atoms, such as nitrogen or oxygen, present can still be classified as organic. Generally, a molecule can be considered organic if it contains carbon-hydrogen bonds. Carbon based compounds that do not contain a hydrogen atom, such as carbon dioxide (CO2), are not organic. There are some exceptions, but these guidelines will hold for most cases.
There are millions of different organic compounds, each with its own unique properties. This chemical diversity is in no small part due to the properties of carbon. Carbon has five important properties that allow hydrocarbons to have such a vital role in our lives: the ability to form long carbon-to-carbon chains, complex branches, double or triple bonds, isomers, and strong bonds with many other elements. Scientists try to understand how these properties of carbon affect the overall properties of an organic compound in order to learn how to create useful compounds.
A carbon atom contains six protons and six electrons. Of those six electrons, four are valence electrons, or electrons in the outer shell of an atom capable of participating in chemical bonds. Carbon, with its four valence electrons, wants to form four more bonds in order to have eight valence electrons. Due to its valence electron arrangement, carbon can readily form covalent bonds with other carbons, creating long, unbroken chains of varying lengths. Having four valence electrons also means that carbon is able to participate in single, double, and triple bonds with other atoms.
In addition to chains, carbon can form complex branches and rings. An example of this would be benzene, which has a ring-like structure formed by carbon bonds:
The ability for carbon to form complex branches results in the creation of isomers. Isomers are compounds that share the same molecular formula but have different structures. For example, consider butane and 2-methyl propane. Both share the chemical formula of C4H10. However, they have different structures.
They also have different chemical properties and uses. Because the chemical structure of a compound is important to its chemical properties, compounds with the same chemical formula can have completely different chemical properties. Carbon’s versatile bonding allows for a near-infinite number of different organic compounds to exist.
Carbon is also essential for organic compounds because of its ability to form strong bonds with many other elements. Although it is commonly found bonded to hydrogen or other carbon atoms, carbon can also form strong bonds with many other elements, such as nitrogen, phosphorus, sulfur, halogens, and oxygen. When bounded to a hydrocarbon, these elements can alter the physical and chemical properties of the hydrocarbon. There are certain combinations of elements, known as functional groups, that will cause organic compounds to have similar characteristics. Some of the major functional groups include alcohols, aldehydes, ketones, carboxylic acids, esters, and ethers. These functional groups will be explored in the “Functional Group” chapters.
In this book, you will explore several common types of organic compounds. You will learn the structure and properties of each type and discover different everyday examples of these compounds. This textbook is not meant to be used for a yearlong course in organic chemistry; it simply provides a glimpse of the role organic compounds play in our daily lives and a brief explanation of why they behave the way they do.