Reactivity and transport safety of substituted methyl benzoates
I’ve already addressed this in a comment, but now I went the lengths to check out the material safety data sheets of these compounds from Sigma Aldrich. My suspicions have proven correct: methyl benzoate is not a dangerous compound to transport so any recommendations to reduce its reactivity by adding a substituent must be moot.

In short, section 14 of the MSDSs as I access them contains transport information; and this entry for the compounds methyl benzoate (CAS 93-58-3), methyl 3-nitrobenzoate (CAS 618-95-1), methyl 2-methylbenzoate (CAS 89-71-4) and methyl 2-bromobenzoate (CAS 610-94-6) contains nothing but ‘not dangerous goods’ and the required iterations and variations of that theme to the different categories there.

Therefore, the question must be rejected as totally pointless: the starting compound is not considered a dangerous good for transportation and neither is any of the three possible substituted ones (one generic placeholder for each; I’m not going to check an additional six MSDS sheets).

Naturally, the only answer you can remove by deduction is b, because a hydrogen ‘substituent’ does not change the properties of the benzoate residue since hydrogen is already present there five times.



Considering we have found out that the compound is not dangerous to transport, how can we approach this question? Well, it’s hard. Concerning the reactivity of electrophilic aromatic substitutions — which is low anyway because of the deactivating ester substituent — of course an electron-withdrawing substituent would help; the nitro group suggests itself. On the other hand, concerning the reactivity of the ester group’s carbonyl function, only electron-donating substituents would help; the strongest being the inductive effect of the methyl group. So we are left with two possibilities and it is unclear which one we should follow.

Of course, neither the reaction with electrophiles nor the reaction with nucleophiles is inherently more dangerous than the other. We have again reached a vicious circle in which we cannot proceed at the risk of taking the wrong path.



Therefore, the best advice I can give is to ignore the question in the book. If it is given in an exam, challenge the exam for there is no reasonable answer to it.