Cyclic elimination reaction Which of the following will give cyclic elimination by heating?
  
  
  phenol
  propanoic acid
  trimethyl isopropyl ammonium hydroxide
  cyclohexyl propanoate
  


Cyclic elimination by heating is Syn Pyrolytic elimination reaction. This is given by ester, quaternary ammonium salt, and amine oxide. The reaction is according to Hoffman. This cancels out option (1) and (2). 

Option (4) is ester and hence the answer to the question.

But why does the ammonium salt not give the reaction? What am I getting wrong?
Example of a similar tertiary ammonium reaction with mechanism

The thing is, it does react but there will be no cyclic product, in the end, I think that is the reason it is not the answer here.