What does the R stand for in functional groups?

1 Answer
anor277
Feb 1, 2016

When we are not referring to optical isomerism, #R# in a formula refers to an alkyl residue, #C_nH_(2n+1)#.

Explanation:

When we write #RC(=O)H# or #RCH=CHR#, or #R_3C-X#, clearly we highlight the functional group of interest: aldehyde; olefin; halide etc. Why do we do this? Well, because the interesting chemistry is going to occur at that functional group.

The #R# substituent, of general formula #C_nH_(2n+1)# is along for the ride, and is tacked on to the end of the chain.

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