Knowledge Bank

The addition of an olefin containing three or more carbon atoms to 96% sulfuric acid produces an absorption band at 300 mu with an oscillator strength of .08 [$ϵmax\sim 3000$]. The addition of the compounds ROH, ROR, $ROSO3H,RCl$, and $ROCOCF3$ to surfuric acid produces a similar band. It is postulated that the similarity in the spectrum is due to the production of the identical species $R+[HSO4]-$ in all reactions. {C}{n}{H}{2{n}}+{H}{2}{SO}{4}\rightarrow {C}{n}{H}^{+}{2{n}+1}[{HSO}{4}]^{-}{C}{n}{H}{2{n}+1}{X}+{H}{2}{SO}{4}\rightarrow {C}{n}{H}^{+}{2{n}+1}[{HSO}{4}]^{-}+{HX} The peak appears only in acid of strength greater than 70%. The peak also appears in methane sulfonic acid [$H0\sim 9$] but not in trifluoracetic acid [$H0\sim 7$]. It is of interest to note that alkylation which is postulated to proceed via a carbonium ion mechanism occurs under the same conditions that produce a 300-mu peak. Conduction and freezing point determinations in sulfuric acid indicate that the species $R+[HSO4]-$ is dissociated. A discussion of the spectrum and stability of the species $R+[HSO4]-$ is given based on a charge-transfer-complex and on a protonated-double bond.