Question

R-X,where X=Cl,I etc. What is mean R in the above formula of halogens ? Why this R is used here ? Why any other alphabet is not used here ?

Answer 1

1. "R" is the IUPAC general representation of alkyl chain. The alkyl chain may contain n number of carbon atoms and may or may not have un-saturation.
2. Letter "R" is derived from the word "root". As root is the major building block of a tree,similarly alkyl chains are considered root and functional group such as X or OH as tree or fruits.