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The prefix "ortho-" means straight or right; "meta-" means beyond or after; "para-" means beside or along. How, then, did ortho-, meta- and para- come to refer to the carbon positions one, two, and three positions away from a reference point on a benzene?

If we have two groups on a benzene ring immediately beside one another, we do not denote the positions by para-, which would seem logical given its meaning, but instead ortho-. For instance, a benzene ring with two hydroxyl (-OH) groups on immediate positions of a benzene ring can be called para-hydroxybenzene (with the common name "quinone"). What is the etymological history that led to the rather counterintuitive use of these prefixes in organic chemistry?

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Wilhelm Körner between 1866-1874 was the first to use it to differentiate isomers of benzene rings. Since the Greek suffixes are fairly vague he chose them arbitrary. Its interesting he used orth- for 1,4 isomer, meta- for the 1,2 isomer , and pera- for the 1,3 isomer. While later chemists used orth- for 1,2 isomer, meta- for the 1,3 isomer , and pera- for the 1,4 isomer. Then in 1879 the Chemical Society of London officially adopted the backwards notation.

So yea its a arbitrary and backwards system. I got all my info from the one link below.

The Origins of the Ortho-, Meta-, and Para- Nomenclature

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