What do the numbers in compound names like 1,4-diaminobenzene mean?

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What do the numbers in compound names like 1,4-diaminobenzene mean?

In: Chemistry

The numbers indicate the positions of the amino groups on the arene (benzene group). The arene has the shape of a hexagon, the counting starts at the top and continues in a clockwise direction.

The compound you named is also called para-diaminobenzene, “para” meaning parallel to. In this case it means that one amino group is on the exact opposite from the other group.

The carbon atoms in the benzene molecule are typically numbered. 1,4 refers to which carbon atom in the benzene molecule the amine group is attached to. Di-amino means 2 amine molecules (Di being the prefix for 2). Therefore, we have an amino group attached to the 1 carbon atom of the benzene molecule and another amino group attached to the 4 carbon atom of the benzene molecule. I think that’s correct. Been a while since I touched organic chemistry.

Chemical names are often instructons on how to draw a molecule. The numbers tell you on which position (carbon atom) atoms or groups of atoms are attached to.

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In your example, there are 6 carbon atoms forming a hexagon. 1,4 means that the next group (here the *amino* group consisting of one nitrogen and two hydrogens) is not at the next carbon(that would be 1,2) , not at the one after that either(that would be 1,3) , but on the one after after that.

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So it looks like this: [https://en.wikipedia.org/wiki/P-Phenylenediamine](https://en.wikipedia.org/wiki/P-Phenylenediamine)