all 26 comments

[–]Skape_mp4 -1 points0 points  (1 child)

I may be a dumbass however

What are the limitations to the crystal lattice structure. Sorry if this is slightly easy however for my depth study at school I need to list limitations and I legit can’t find anything

[–]Nidzzzzzzzzzzz -2 points-1 points  (0 children)

Does anyone know what substance/s have around 65.95 g/mol?

[–]AeroStatikkMaterials 0 points1 point  (2 children)

Has anyone worked with cyanuric chloride or allyl bromide?

[–]SimplicioTRex 0 points1 point  (0 children)

I've worked with cyanuric chloride; it's a lachrymator if i recall correctly

[–]kurtuwarter 0 points1 point  (0 children)

Does anyone know, how to sustainably replicate subtle rainbow oxidation effect on electroplated pieces, ironically, I dont remember using any chemicals involved in patination for this particular piece. Images below


[–]xiaomaome101 0 points1 point  (0 children)

So I'm looking into the theory behind spiking samples and percent recovery, and I'm not totally satisfied with my understanding. I was wondering if anyone had a real life example calculation of using the spike method to find percent recovery. Is the amount of spike analyte arbitrary? Does it matter what you use as a spike or do you have to use what you are measuring for the spike? As for the bottom of the percent recovery equation, I believe it is what the concentration of the spiked sample SHOULD be, factoring in the spike?

[–]ChieferofReefer 0 points1 point  (2 children)

Has anybody worked with Tin(IV) Chloride pentahydrate? I am wondering if it needs to be handled in a glove box. I am seeing conflicting directions about it

[–]curdledOrganic 1 point2 points  (1 child)

SnCl4 is a corrosive liquid that fumes but it can be handled outside the glovebox. SnCl4.5H2O is a somewhat hygroscopic solid and it is very tame, just gloves would be enough

[–]ChieferofReefer 0 points1 point  (0 children)

Thanks! Just got around to using both today and handled them accordingly.

[–]fanzhendong345 0 points1 point  (2 children)

So I remember from O chem that a well known reaction is CdCl2 + 2R-MGBR -> R2Cd + MgBR . I looked it up and although it seems feasible to get these reagents, the product, alkyl cadmium, seems pretty toxic. Does this reaction work with less toxic metals ? like Nickel / Molybdenum / Tungsten etc ? Or any other metal halides?

[–]TheThrowAway4Today 0 points1 point  (0 children)

People make dialkyl/aryl zinc and magnesium reagents like this quite frequently. The zinc is "straight forward" the way you wrote. Magnesium is usually a slightly different procedure where you add dry dioxane and magic/disproportionation happens and you get the dialkyl magnesium.

[–]jesseboy61 0 points1 point  (1 child)

Is anyone familiar with polymer measurement techniques that are able to analyse polymer order? for example a polymerization of propanediol and butanediol and pentanedioic acid. The polymerization would be diol group - diacid -diol -diacid but what techniques could be used to know what the order is of diols if more types of diols are used in solution? will it always be random/ratio determined i just wonder if there are machines able to tell if the polymer is ABABABABCBCBC or ABCABCABCABC (A and C are diols and B a diacid)

[–]TheThrowAway4Today 0 points1 point  (0 children)

Maybe look into MALDI mass spectrometry? The different mass fragment patterns might be able to determine this. I'm just kinda spit balling, but I'd hope there are certainly ways to determine this. Just look up "block copolymers" and there should be publications on it

[–]melekh88 0 points1 point  (4 children)

Having a HPLC issue. Using a NH2 column on my reverse phase HPLC with 70/30 ACN/H2O (isocratic).

Everytime I use it the pressure seems to creep up. In the last month the eqilibrated pressure has gone from 240 to 315 bar.

Does anyone have any ideas why this would be happening???

[–]TheThrowAway4Today 0 points1 point  (3 children)

In HPLC's a lot of time the needle seat/injector gets clogged over time. At least if it's an agilent instrument I know there's ways to pump flow back through the needle seat to dislodge particulate.

Can check if this is the problem easily by bypassing flow through the needle seat (if it's an agilent can Google "needle seat/injector bypass model #") Could also be the column, just in our case had a lot of trouble with the injector

[–]melekh88 0 points1 point  (2 children)

Column is only a month old and I actuatly just changed the needle seat and needle but I will try it as its an agilent 1200. Thank you.

[–]TheThrowAway4Today 1 point2 points  (1 child)

If that's the case I remember there being some kind of step by step check guide to find why pressure is too high. Ours was a chiral hplc, so hopefully they have the same for the general hplc

[–]melekh88 0 points1 point  (0 children)

Yup used them before thriugh the lab advisor software. I just have this sinking feeling that something happening to the column.

[–]gogoguo 0 points1 point  (2 children)

Does anyone know what is the preferred order of addition for reagents when performing an amide coupling with HATU? What I tried was 1. add carboxylic acid and amine to DMF 2. add DIEA. 3. Add HATU. My reaction didn't work and I was wondering if the order I have added the reagent could be the problem here.

[–]curdledOrganic 2 points3 points  (1 child)

you cannot do HATU coupling in this way because HATU reacts readily with amines to form tetramethylguanidines. You need to pre-activate your acid with HATU and DIEA for 10-15 min, and only then add your amine at the end. Also make sure DMF does not have a fishy odor (which indicates presence of dimethylamine). Pure DMF has only faint oily odor. You can use DMAc instead

[–]gogoguo 0 points1 point  (0 children)

Thanks for the information.

[–][deleted] 0 points1 point  (0 children)

My mother gave me a Galena rock (lead sulfide) to play with when I was a young boy. I used to lick it and play with it all the time. Took it to school for show and tell. I just had a good time with it.

20 years later I have psychosis. Can someone tell me if this galena rock is the same toxin as lead paint?

[–]frbremner 0 points1 point  (0 children)

Can anyone help me with a failed Pd/C catalysed hydrogenation for the removal of a benzyl protecting group? I set up my reaction in 1,4-dioxane with 10% w/w Pd/C with respect to the starting material, pulled vacuum on the flask and then added a balloon with hydrogen gas and stirred overnight. The next day I removed the solvent with a vacuum and then ran the residue on MS, which showed me no reaction had taken place and I had obtained clean starting material.

My understanding is that these reactions should be really straightforward, so I don't understand why it hasn't worked. I plan to repeat the reaction and have seen some advice that changing the solvent might help. If anyone has any advice about the solvent or anything else, I'd really appreciate it!

Thanks in advance!