Which product is typically not formed when boiling alcohol in HBr?

When boiling alcohol in HBr, the main reaction involves the conversion of the alcohol into an alkyl bromide through nucleophilic substitution. In this context, the alcohol can act as both a substrate for the reaction and as a solvent.

Typically, alkyl bromides are formed as the primary products when an alcohol reacts with HBr. The reaction follows a mechanism where the hydroxyl group in the alcohol is replaced by a bromine atom, resulting in the formation of an alkyl bromide. Water is also produced as a by-product during this reaction as the hydroxyl group is expelled.

While alkenes can be formed under certain conditions, such as strong acidic environments or when dehydration occurs, this is not the primary or typical outcome in a straightforward reaction of alcohol with HBr at boiling temperatures. Importantly, the original alcohol remains untouched and unchanged, as it is the starting material for the reaction, and thus, it cannot be considered a product formed during the process.

Given all this context, the alcohol itself does not transform into a product when reacting with HBr, which solidifies why it is identified as not being formed in significant amounts compared to the alkyl bromide and water that result from the reaction.