What is Organic?
Beyond AP Physics 1
Original enrichment beyond the AP requirements; relevant foundational ideas are linked separately.
Chemistry II · original Chapter 10 · combined Chapter 18
Section Breakdown
- Defining Organic
- Classes of Organics
- Linkages
- Inorganic Functional Groups
Section 1
What is Organic?
Now for everybody’s favorite topic: Organic Chemistry!
You probably hear the term organic all the time, typically with buying fruits or veggies that are grown under no-pesticide conditions or whatnot. That definition of organic is a bit misleading. Every foodstuff you eat, no matter how it is grown, is organic, with the only exception perhaps being salt and some types of vitamins.
In chemistry, the definition of organic is limited to a chemical compound that contains carbon. Technically, not every molecule that contains carbon is organic, but very nearly all carbon-containing compounds are organic.
Carbon by itself is not organic (inorganic), as is carbon that is only bonded to oxygen, like Carbon Monoxide, Carbon Dioxide, and Carbonate. Also inorganic is cyanide () and any carbides (metallic compounds with a Carbon anion).
So what does that leave us with? Most organic compounds are hydrocarbons, or derivatives thereof. That means that most organic molecules have both hydrogen and carbon.
Interactive 10.1.1 Ethane
The source placement has no attached COLLADA geometry.
The simplest aliphatic molecules are the alkanes. These are saturated hydrocarbons, as bonds are single bonds, and the only other atoms involved are hydrogen. Here are a few examples:
Alkanes are known as “saturated hydrocarbons” as the molecule contains as much hydrogen as possible. None of the carbon bonds are wasted on double bonds to another carbon or bonded to anything but carbon or hydrogen.
Now, sometimes these compounds have double bonds between one or more of the compounds. In this case, the organic molecule becomes unsaturated. This is because it has less hydrogen atoms bonded to it than a fully saturated molecule can contain.
Interactive 10.1.2 Carboxylic Acid
Read all original figure notes
Another type of generic organic compound is the ether. This is a special type of organic molecule which has two R-groups that can be replaced by whatever compound happens by. This allows the ether to act as a linkage. Sometimes both ends of an organic compound can bond into an ether, forming long chain, like Polyethylene Glycol.
Replacing one R group in R–O–R′ with H gives an alcohol. If the remaining group is CH₃, the product is methanol, CH₃OH, rather than acetic acid CH₃COOH. Replacing both groups with H gives water. Organic functional-group naming remains retained enrichment.
Starting with our base molecule, ethene, we have:
Now if we replace one of the hydrogen atoms with a chlorine atom, then our ethene becomes vinyl chloride:
We can further replace hydrogens, to make Dichloroethene:
Trichloroethene:
And finally, tetrachloroethene:
Other compounds can undergo halogenation, and the reverse can also be accomplished. One common fully halogenated compound is carbon tetrachloride (), which used to be a common chemical for dry cleaners. This compound is derived from methane ().
Glossary and deeper reading · 10 refreshers
These editorial refreshers supplement the reading. Definitions and examples are added guidance; original source wording and recorded answers remain in their original context.
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Functional group
A functional group is a characteristic atom arrangement associated with patterns of chemical behavior in organic compounds. Its effect depends on the rest of the molecule as well as the group's identity. For example, an alcohol's hydroxyl group can support hydrogen bonding.
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Anion
An anion is a negatively charged ion. It has more electrons than needed to balance its positive nuclear charge. For example, a chlorine atom gaining one electron forms a chloride anion.
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Organic compound
Organic compounds comprise a broad class of carbon-based compounds, often built around carbon–carbon and carbon–hydrogen structures. Some carbon-containing substances, such as carbon dioxide and carbonates, are conventionally classified as inorganic. For example, ethanol is organic while sodium carbonate is usually classified as inorganic.
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Hydrocarbon
A hydrocarbon is a compound containing only carbon and hydrogen. Its carbon skeleton may contain chains, rings, or multiple bonds. For example, methane and ethene are both hydrocarbons despite having different bonding structures.
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Aliphatic compound
Aliphatic compounds are organic compounds classified as nonaromatic. They can contain open chains or nonaromatic rings and can be saturated or unsaturated. For example, hexane and cyclohexane are both aliphatic hydrocarbons.
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Aromaticity
Aromaticity describes a special stability associated with particular cyclic, conjugated electron arrangements. Having a ring alone does not make a compound aromatic. For example, benzene is aromatic while cyclohexane is not.
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Alkane
An alkane is an acyclic saturated hydrocarbon with carbon–carbon single bonds. Related saturated ring compounds are called cycloalkanes. For example, propane is an alkane containing three carbon atoms.
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Carboxylic acid
A carboxylic acid contains a carboxyl group with a carbonyl and a hydroxyl attached to the same carbon. Its acidic proton can be transferred to a base, forming a carboxylate conjugate base. For example, acetic acid forms acetate after proton donation.
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Ether
An ether has an oxygen atom bonded to two carbon-containing groups. Its oxygen can accept hydrogen bonds, but an ether lacking an O–H group cannot donate one in the usual introductory model. For example, dimethyl ether has an oxygen joining two methyl groups.
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Alcohol functional group
An alcohol contains a hydroxyl group attached to a saturated carbon atom. This group can participate in hydrogen bonding, while the surrounding carbon structure also affects properties. For example, ethanol is an alcohol that mixes readily with water.