Ortho, para and meta positions refer to substituent positions on an aromatic ring in organic chemistry. When aromatic rings undergo reactions, substituents can be added to the ring in ortho, para or meta positions. Some compounds and molecules even direct new substituents to add to a certain position.
The ortho position occurs when two substituents are directly next to each other on an aromatic ring. Often, the ortho position is referred to as the 1, 2 position because a substituent will be attached to carbon 1 and carbon 2. The para position occurs when substituents are at opposite ends of the aromatic ring. This position is also known as the 1, 4 position because the substituents occupy carbon 1 and carbon 4. The meta position occurs when substituents occupy carbon 1 and carbon 3.