Dehydration to Alkenes

$$\text{R--CH}_2\text{--CH}_2\text{OH} \xrightarrow{\text{Conc. H}_2\text{SO}_4, \, 170^\circ\text{C}} \text{R--CH=CH}_2 + \text{H}_2\text{O}$$

Rate of dehydration: $$3^\circ > 2^\circ > 1^\circ$$ (Carbocation stability order; Saytzeff alkene is major). (Corresponds to carbocation stability in the $$E1$$ mechanism).

Notation & Key Points:

Regioselectivity (Saytzeff's / Zaitsev's Rule): The major product is the more substituted, more stable alkene (alkene with more alkyl groups attached to double-bonded carbons).