And no it certainly does not follow that the most potent by weight the opioid the better it is. It depends on the individual character of the opioid in question. A lot of people find fentanyl itself cold, clinical, empty and soulless. Fucking potent, yes but distinctly lacking in many respects. Its a potent analgesic alright, but in terms of recreational potential I am by no means unique in finding fentanyl pretty boring as far as opioids go.
As far as dipropionylmorphine and differences between H, morphine etc. in terms of lipophilicity it isn't just lipophilicity donated by the ester groups on the simple morphine carboxylate esters that determines euphorigenic potential. There are significant differences between H and morphine, as well as 6-MAM, I lack data on DPM in this respect but there is selectivity between alternately spliced isoforms of MOR between H and morphine, and H is different again to 6-monoacetylmorphine. Its also known that H and 6-MAM have different activities if the subject administered them is dependent on/tolerant to morphine beforehand, with H/6-MAM taking on properties as a delta-OR agonist, and the interesting thing is, that H and 6-MAM are selective in their agonism at DOR subtypes. I forget which way round it is, but one of them becomes (with respect for its delta agonism that is) DOR1 selective and the other for DOR2.
And lipophilicity increases with chain length of the ester moities does it not? since the last post where I mentioned dibenzoylmorphine, I've tried it, and I've also tried n-butyrylmorphine (what fun THAT was. Had complaints about a vacuum chamber exhausting pure distilled essence of puke from the pump for at least a week afterwards
) and whilst I've not really explored dibenzoylmorphine much, not enough to get a thorough handle on its potency and duration relative to the others, it is active, and more potent than morphine. Other than that it seemed qualitatively to be just another morphine ester without anything exceptional about it.
In the case of 3,6-di-(n)-butyrylmorphine potency dropped off significantly compared to the propionate ester (note there will almost certainly have been some 6-monoacylmorphine derivatives present in small amounts owing to the acylation not going to 100% completion, there is typically some presence of 6-monoacylmorphine, the corresponding 3-monoester (although hopefully minimal, since it seems to, according to forensic examinations of 'home bake' as done in NZ and their replicating the process comparing EPNS spoons in which the reaction has been performed with stainless steel (EPNS-electroplated nickel-silver) although these were all done in glass (although EPNS in the form of solid pieces, with the surface scratched well to ensure that if there is a catalytic process going on that involves the Ni-Ag bilayer interface that it has a chance to have sufficient surface area exposed, that where the acyl halides were used rather than acid anhydrides the halides seemed to generate relatively little unreacted morphine, a small quantity of 6-acylmorphine and the majority being the diester, with only traces detectable via GC/MS whilst anhydrides appear to have a significantly greater tendency towards some mono-acylation, and in more significant ratios between the monoesters and the diester, and EPNS (the NZ homebake cooks apparently often had preferred spoons to do their simple rxn in, being electroplated nickel-silver, and when compared with stainless in an analysis comparing various times, heats, whether morphine base or sulfate were used, and whether the process was conducted with an acyl halide or the equivalent anhydride EPNS vs stainless did seem to make a difference to the numbers. [in this case it was acetylation being studied, rather than propionylation so the precise numbers will likely differ. Shouldn't imagine that its that common for people to go for the propionate ester though or more would probably be heard of it. The halides appear to result in much less of the 3-monoester)
There are a fair few papers out there which show H to be qualitatively different from morphine.
And as for the fentanyls, all of them I've sampled or had used on me medically share that same empty soulless character. Alfentanil and lofentanil somewhat less than the others. Plain fentanyl itself though, I really wouldn't give it the time of day unless I was in opiate withdrawal. They push up tolerance like theres no tomorrow, they exhibit strong tachyphylaxis, most of them are fairly short acting and there is in my experience with them very little euphoria and less rush.
Different people respond differently to different opioids, thats something I've heard said a LOT about fentanyl. Its all quantity, no quality. I'd be glad of it if I had terminal cancer, sure, but I'd have to have nothing else before I paid anybody for it. I get more euphoria from codeine or dihydrocodeine than I do from fentanyl. Got given a script for it once and I was back the next morning to the clinic to get a script for oxycontin instead (albeit I get little euphoria from oxy and no rush but its still better than fentanyl)
) although on these I can find little, nothing so far in fact,