Organic Functional Groups
The Secret to Understanding Organic Chemistry

As we learned in our Atomic Structure section, Carbon has four (4) electrons in its outer shell and for maximum stability it wants eight (8) electrons in its outer shell. Hydrogen has one (1) electron in its outer shell and because it is such a small atom, it only needs two (2) electrons in its outer shell to be full.

As we see in the upper half of the picture above, Carbon and Hydrogen can meet their chemical goals of having their outer shells full of electrons by sharing electrons with each other and forming a covalent bond between one Hydrogen and one Carbon atom. Hydrogen can achieve a full outer shell by sharing one of Carbon's four electrons. However, Carbon needs to share electrons with four (4) atoms of Hydrogen to achieve a full eight (8) shared electrons in its outer shell.

When four Hydrogen atoms share their electrons with one Carbon atom such that four covalent C-H bonds are formed the result is one of the simplest organic molecules, the hydrocarbon methane (CH₄).

When one atom of Carbon and four atoms of Hydrogen share electrons to achieve an electron-filled outer shell of each element, the resulting organic compounds formed are referred to as Hydrocarbons. The "Organic Functional Group" of Hydrocarbons is C-H.

In the lower half of the picture above, one atom of Carbon shares three of its electrons with three Hydrogens. The Carbon atom completes filling its outer shell with electrons by sharing one additional electron with Oxygen. This leaves Oxygen with just seven electrons in its outer shell. Since Oxygen wants eight electrons in its outer shell it achieves this by sharing one final electron with the fourth Hydrogen which also satisfies the outer shell requirements of Hydrogen.

The type of organic compounds formed when Carbon, Oxygen and Hydrogen share electrons in this manner are referred to as Alcohols. The "Organic Functional Group" of Alcohols is C-OH.

In the top half of the picture above we have Carbon, Hydrogen and Nitrogen combining by sharing electrons to achieve a full outer shell. The Carbon once again shares electrons with three Hydrogens to get seven electrons in its outer shell. But since Carbon needs eight electrons for a full shell it gets its final electron by sharing one electron with Nitrogen.

We can see from the atomic structure of Nitrogen that it has five electron in its outer shell and after sharing one of Carbon's electrons, the Nitrogen only has six electrons in its outer shell. To achieve the goal of a full outer shell of eight electrons, the Nitrogen shares electrons with two Hydrogen atoms. In this way Nitrogen fills its outer shell with electrons and the two Hydrogen atoms also achieve a full outer shell by sharing two of the Nitrogen's electrons.

The organic compounds formed by Carbon, Hydrogen and Nitrogen sharing electrons in this way are called Amines. The "Organic Functional Group" of Amines is -C-NH₂.

In the lower half of the picture above, one atom of Carbon combines with three Hydrogen atoms to share three electrons (not shown). The remaining electron necessary for this carbon to have a full outer shell comes from this Carbon sharing an electron with Oxygen. This leaves Oxygen with just seven electrons in its outer shell but his time instead of sharing an electron with Hydrogen as in the Alcohols or with Nitrogen as in the Amines the oxygen shares an electron with another Carbon.

The organic compounds formed by Carbon, Oxygen and Carbon sharing electrons in this manner are called Ethers. The "Organic Functional Group" of Ethers is -C-O-C-.

In the top half of the picture above we have a Carbon atom sharing electrons in a unique way with an Oxygen atom. In this case instead of sharing just one electron with Oxygen the Carbon atom is able to share two electrons and form what is called a Double Covalent Bond or more commonly just a C=O Double Bond. This leaves the Carbon atom with a total of six electrons, four from the Carbon and two from the Oxygen, while the Oxygen has its outer shell full with six from Oxygen and two from Carbon.

The Carbon atom fills its outer shell with the needed two electrons by sharing one electron with one Carbon atom and one electron with a Hydrogen atom as shown in the top half of the picture above. The organic compounds formed when two Carbons, one Oxygen and one Hydrogen atom share electrons in this manner are referred to as Aldehydes. The "Organic Functional Group" of Aldehydes is -HC=O.

In the bottom half of the picture above we again have a Carbon atom sharing electrons in a unique way with an Oxygen atom. Instead of sharing just one electron with Oxygen the Carbon atom is able to share two electrons and form what is called a Double Covalent Bond or more commonly just a C=O Double Bond. This leaves the Carbon atom with a total of six electrons, four from the Carbon and two from the Oxygen, while the Oxygen has its outer shell full with six from Oxygen and two from Carbon.

The Carbon atom fills its outer shell with the needed two electrons by sharing one electron each with two Carbon atoms as shown in the bottom half of the picture above. The organic compounds formed when three Carbon atoms and one Oxygen atom share electrons in this manner are referred to as Keytones. The "Organic Functional Group" of Keytones is -C₂=O.

In the top half of the picture above we have a Carbon atom sharing electrons in a unique way with an Oxygen atom in the same manner as we saw for Aldehydes and Keytones. As before instead of sharing just one electron with Oxygen the Carbon atom is able to share two electrons and form what is called a Double Covalent Bond or more commonly just a C=O Double Bond. This leaves the Carbon atom with a total of six electrons, four from the Carbon and two from the Oxygen, while the Oxygen has its outer shell full with six from Oxygen and two from Carbon.

However, the Carbon atom fills its outer shell with the needed two electrons by sharing one electron with one Carbon atom and one electron with a another Oxygen atom as shown in the top half of the picture above. The second Oxygen atom is left with only seven electrons in its outer shell and fills its outer shell by sharing an electron with a Hydrogen.

The organic compounds formed when two Carbon atoms, two Oxygen atoms and one Hydrogen atom share electrons in this manner are referred to as Organic Acids. The "Organic Functional Group" of Organic Acids is -C-C=O-(OH).

In the bottom half of the picture above we again have a Carbon atom sharing electron with an Oxygen atom is such a way as to once again form a C=O Double Bond. This leaves the Carbon atom forming the Double Bond with a total of six electrons, four from the Carbon and two from the Oxygen, while the Oxygen has its outer shell full with six from Oxygen and two from Carbon.

The C=O Carbon atom fills its outer shell with the needed two electrons by sharing one electron each with another Carbon atom and with a second Oxygen atom as shown in the bottom half of the picture above. The second Oxygen atom, having only seven electrons, fills its outer shell by sharing an electron with a third Carbon atom.

The organic compounds formed when three Carbon atoms, two Oxygen atoms share electrons in this manner are referred to as Esters. The "Organic Functional Group" of Esters is -C-C=O-(O-C).

In the top half of the picture above we again have a Carbon atom sharing electron with an Oxygen atom is such a way as to once again form a C=O Double Bond, just as in Aldehydes, Keytones, Acids and Esters. This leaves the Carbon atom forming the Double Bond with a total of six electrons, four from the Carbon and two from the Oxygen, while the Oxygen has its outer shell full with six from Oxygen and two from Carbon.

However, in this case the Carbon atom fills its outer shell with the needed two electrons by sharing one electron with one Carbon atom and one electron with a Nitrogen atom as shown in the top half of the picture above. The Nitrogen atom is left with only six electrons in its outer shell and fills its outer shell by sharing one electron with a third Carbon atom and one electron with a Hydrogen atom.

The organic compounds formed when three Carbon atoms, one Oxygen atom, one Nitrogen atom and one Hydrogen atom share electrons in this manner are referred to as Amides. The "Organic Functional Group" of Amides is -C-C=O-(NH-C).

In the bottom half of the picture above we have a unique functional group which is present in a unique class of Hydrocarbons called Aromatic Compounds. The functional group is basically a Benzene ring. The Benzene ring and the Aromatic Compounds will be explained in more detail in a later section.

For now we will just say that one Carbon atom shares one electron with one of the carbon atoms of the Benzene ring. The organic compounds formed when a carbon shares an electron with this Benzene ring are called Aromatic Compounds. The "Organic Functional Group" of Aromatic Compounds is this Benzene Ring which is referred to as a "Phenyl Group" and has the formula -C₆H₅.

The Organic Functional Groups along with their structures and abbreviations are given in the next two Pictures below.

If you understand the atomic structure basis for the formation of the unique covalent bonds that make up the 10 Organic Functional Groups you will be will on your way to a sound and fundamental understanding Organic Chemistry.

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