1-Bromo-3-ethylbenzene-d5 is the deuterium labeled 1-Bromo-3-ethylbenzene[1].
References
[1] Russak EM, et al. Impact of Deuterium Substitution on the Pharmacokinetics of Pharmaceuticals. Ann Pharmacother. 2019;53(2):211-216. DOI:10.1177/1060028018797110