Ha! If you used an acid then it is likely not undergoing an oxidation reaction such as I pictured in my first reply.
It is rather an acidic isomerisation forming “abnormal” CBG (abn-CBG). In fact there should be two species (which I believe are two different abn-CBGs).
@kcalabs Do you see only one peak with the two different methods ? No secondary species ?
EDIT: in fact I’m mixing up different reactions. My comment here is wrong about abn-CBG 
I’d have to go back and look. I’m assuming I know what sample we’re talking about without asking who @Scorpio is, but it might be best to get a sample ID sent over to me.
@Scorpio, if I’m correct, is this the same sample we looked at twice a couple years apart?
What is that? I didn’t even know about abnormal CBG. How is it structurally different from CBG? Are the health benefits same as CBG?
It’s a sample from early August. I dm’ed you the sample id.
Am I tripping that there’s only one abn-CBG? The two -OHs and -R group are in the 1,3,5 positions - you could swap the -R with either -OH to make equivalent molecules (i.e. abn-CBG).
Do you mean that this second abn-CBG would have a substituent at 2 or 4 position?
I have experienced an unknown peak with cbg oxidation routes as well. Was under the impression it might be exo-thc aka d11thc.
I have a 15 standard library and some others that were marked without a standard (thco / hhc) and nothing was close.
Makes a runny product that’s similar to cbc but definitely is not cbc.
https://www.instagram.com/p/CRfN4a0ANFbXc54_K79bT0qHyvKC9000CxmPu80/?igshid=NDRkN2NkYzU=
Good information. I think we’re leaning toward acid catalyzed isomerization as the route rather than oxidation. Any experience with that?
For the unknown product I had made I was trying out the chloranil oxidation process. Though I do believe chloranil is slightly acidic to begin with and would concur with your statement and may be a contributing factor.
During the reaction, you get chloranilic acid as the byproduct as hydrogen is scavenged from the CBG. There is a paper on its use for making CBC and figured it was worth a try. Definitely made something but it is absolutely not CBC.
CBC, CBD, and the THC’s are all isomers of one another (C21H30O2).
Traditionally it was thought that exo-THC (d11thc) was only made through pure synthetic reactions, but it might be possible to also make it from CBG or other cannabinoid, since after all, it too is just an isomer of the C21H30O2 group.
Personally, I am only leaning toward exo-THC as its one of the few remaining standards I need to add to my library. It is definitely not any of the following: CBDV, THCV(8/9), CBT, CBL, CBND, CBC, CBD, D106a, D10, D8, D9, CBE, CBG, CBN, CBF, CBX, THCo, HHC, or Olivetol. 
In fact I was wrong in my previous comment.
I had not looked into this into a while and mixed up some reaction.
You are right, there is only one abn-CBG, and it is obtained upon full CBG synthesis.
While acid catalyzed cyclization yields these two unamed coumpounds:
@Scorpio,see details here on page 33 and 34.
Maybe you made only the doubly cyclized product VIII(b).
Look here 
https://www.sigmaaldrich.com/CH/en/product/cerillian/t033
These reactions we are dealing with here do not produce much exo-THC.
In your case you seem to have gone through the oxidation route I first assumed for @scorpio.
I will come back with some data to go deeper in this discussion.
Agreed, we’re not seeing much exo-THC. Not sure if some labs are misidentifying a peak, but the MS data we produce do not show high levels of exo in any samples.
Yeah it is most likely not exo-thc. Could very well be iso-thc though from what you guys are saying. I don’t have the standard for it either.
Trying to get my mass spec online so I’ll have an in-house gcms. Will help speed things along with that kind of r&d.
Just thought I would chime in since having experienced a similar peak during CBG oxidation. I’ll make another run at it and send it in this time. Definitely curious as to what it is now.
interesting information
Now I am curious about whenever I tracked D8 conversions, the CBD peak splits into two peaks right next to each other (overlapping). The Main CBD peak will shrink, the new unknown peak will grow, then at a point they both shrink as the D9 peak grows, then once the D8 peak comes in the D9 peak will shrink and the two CBD peaks go directly to D8. Have watched the dance plenty of times now.
Could this possibly be irregular/abnormal CBD that is being created before it transitions to D9 then D8?
Are you using GC ?
See my comment here (and the associated discussion):
I believe this should be the iso-THCs series.
Still, I haven’t checked this with CRMs yet.
Given that such reaction often results in some breakdown back to olivetol, we can expect formation of some abnormal cannabinoids (especially with the PTSA method). Still, they may rather be part of the numerous trace (<0.1%) side products.
Yes GC with a Rxi-35-Sil column so as to make consistent separations of CBD and CBC. Olivetol is one of the non-crm placeholders I have on my GC (made by sampling 98% source material).
It is definitely not the same location of that other molecule I made from CBG so that puts me back at completely unknown for it if that is the case. The CBG unk peak is much further to the right than this one. This one overlaps with CBD really tight. The other is completely isolated and on its own.
I had developed my own method alternate to PTSA and used Heptane instead of Toluene a few years ago.
In the case of the split CBD peak, it starts out pretty high (~50% content) then works its way down as the D8 is finalized. The original CBD peak drops off pretty quick into the new one, which stays pretty high until all of the D8 is made then it crashes out. Typical olivetol results are pretty low and on the order of less than 5% from what I have seen (estimate) during the process.
Looks like where you have exo-THC marked is almost on-top of where my CBG unk peak lands, but also really close to where D106a lands. The rest looks very similar to how my CBD to D8 conversions went.
Olivetol is not marked but comes just after the internal a fair bit before CBDv.
Here is some more data I have:
This experiment reacting CBG in presence of PTSA (ambiant conditions, heptane) resulted in 3 unknown (14%, 45%, 30% respectively), also likely some d4(8)-isoTHC (4%) and some d8-THC (2%) and a few other minors…
The main two unknowns are likely cyclized and doubly cyclized CBG. 
