# Can hydrobromic acid perform substitution with propane?

I am a student in the 11th grade, we recently had a chemistry exam, I lost marks because of a question that asks about the reaction between $\ce{HBr}$ and $\ce{C3H8}$. According to our teacher $\ce{HBr + C3H8}$ is going to react and form $\ce{C3H7Br + H2}$. In my opinion I don’t think that a reaction is going to happen, because $\ce{HBr}$ is an acid and acids can't react with alkanes. Can you please state your opinion and justification?

• You are right, they are not going to react, because, er, well, why would they? – Ivan Neretin Nov 30 '17 at 9:34
• I’m not sure , he said that my statement is weak. I am trying to back it up with facts. – Al-Muataz Nov 30 '17 at 9:42
• Well, technically, your statement is weak, because certain acids do react with alkanes. But HBr doesn't, that's for sure. – Ivan Neretin Nov 30 '17 at 9:47
• So C3H7Br won’t be formed , am I right? No chemical reaction is going to happen? – Al-Muataz Nov 30 '17 at 9:57
• I wouldn't think this were an acid/base reaction, but more of a (photochemically initiated) radical process. The issue is that a propyl radical would still prefer to abstract hydrogen instead of bromine from hydrogen bromide... I'd have to think about this more, but that might just be a different way to state the stability arguments other posters have made... – Zhe Nov 30 '17 at 14:38