In the following dehydration of diol with `H_(3)PO_(4)` following product is formed such that isotopic `.^(18)O` goes `H_(2)O`. Explain.

Answer

`3^(@)` alcohol at `C_(2)` is more basic than `2^(@)` alcohol at `C_(5)`. Henc,e intramolecular dehydration takes place such that H of `2^(@)` alcoholic group at `C_(5)` eliminated `OH` of `3^(@)` alcoholic groupa at `C_(2)`(with isotopic `.^(18)O`)
`(##ALN_CHM_C09(II)_S01_430_A01##)`