In the context of elimination reactions involving ethanol (EtOH) and bromine (Br), certain substrates are less likely to undergo elimination due to sterics or stability considerations.
Typically, secondary and tertiary alkyl halides are more prone to undergo elimination because they form stable carbocation intermediates. However, for certain primary substrates, or when steric hindrance is significant, the elimination reactions can be hindered.
This means that if you have less sterically hindered primary substrates in a more crowded environment, those are the ones that are less likely to undergo elimination. Additionally, if the medium favors substitutions over elimination due to solvation effects or solvent polarity, those reactions become less likely as well.
In summary, in the presence of EtOH and Br, look for primary alkyl halides or substrates with significant sterically hindering factors to determine the compounds that are less likely to undergo elimination.