# Why are lower alcohols less flammable than their corresponding alkanes?

How to compare the general trend in amount of combustion in lower alcohols? (upto five/six carbons) Does the branching or straight chain have any effect on combustion?

• Well all alcohols are not less flammable that all alkanes. The flash point of pure ethanol is 16.60 °C but the flash point of n-icosane is greater than 113 °C. Yes branching effects pretty much everything about a molecule. – MaxW Jun 30 '18 at 18:09

$$\textbf{} \\ \begin{array}{lll} \hline & \text{Flash point in °C [1]} & \text{Boiling point in °C [2]} \\ \hline \text{Methane}& \text{n.a.} & -161.48 \\ \text{Methanol} & \hphantom{-0}11 & \hphantom{-0}64.6 \\[3pt] \text{Ethane} & \text{n.a.} & \hphantom{0}{-}88.6 \\ \text{Ethanol} & \hphantom{-0}13 & \hphantom{-0}78.29 \\[3pt] \text{Propane} & -104 & \hphantom{0}{-}42.1 \\ \text{Propan-1-ol} & \hphantom{-0}23 & \hphantom{-0}97.2 \\ \text{Propan-2-ol} & \hphantom{-0}12 & \hphantom{-0}82.3 \\[3pt] \text{Butane} & \hphantom{0}{-}60 & \hphantom{00}{-}0.5 \\ \text{Butan-1-ol} & \hphantom{-0}37 & \hphantom{-}117.73 \\ \text{Butan-2-ol} & \hphantom{-0}24 & \hphantom{-0}99.51 \\[3pt] \text{Pentane} & \hphantom{0}{-}40 & \hphantom{-0}36.06 \\ \text{Pentan-1-ol} & \hphantom{-0}33 & \hphantom{-}137.98 \\ \text{Pentan-2-ol} & \hphantom{-0}34 & \hphantom{-}119.3 \\ \text{Pentan-3-ol} & \hphantom{-0}41 & \hphantom{-}116.25 \\[3pt] \hline \end{array}$$