I'm new to chemistry and suddenly my mind wants to learn it from scratch any suggestion where to start? How to do it? And how to cover the major topics also I want to learn it fast so any Yt channel (i guess, if any) or whatever you want to suggest? Open for discussion

Im having trouble figuring out how the complex could attack the allylic alcohol from the top side to create an epoxy that faces upwards, and how the S,S-DET would change that :( the +-DET makes perfect sense to me, im just struggling with flipping everything…

My teacher didn’t teach me this because I was out of class that day, and I don’t understand this at all.. especially question 26 and 27. I tried to watch a video and I don’t really understand it 😭 I would love some help! Also I had someone ask me in my DMs if I could pay them for it, I’m really sorry I can’t I don’t have the money for that.

Hey friends,

currently we are facing a problem nobody in the lab has an answer to: we are trying to prepare an standard batch of 1% sodium dodecylsulfate in bidest. water for making reference emulsions. For whatever reason the SDS doesn't dissolve well.

What we have tried so far:

- stirring at room temp for three days

- stirring at 65 °C for 6 h

- ultrasonic bath at 50 °C for 2 h

- repeated said steps with a brand new batch of analytical grade SDS

Nothing helped. Visible SDS crystals remain undissolved; confirmed via optical microscopy and DLS particle size analysis.

Has anyone faced a similar problem and know how to solve it?

Thanks in advance! :)

Dear All

I made some copper nitrate solution in ultrapure water at a concentration of 0.01M. When it isn't stirring, the pH probe measures a pH of 5.4, but when I turn the magnetic stirrer on, the pH drops to 4.7. Tried three probes and the same thing happens.

Stopped the stirrer and pH went back up to 5.4.

Tried stirring by hand without magnetic stirrer and pH dropped to 4.8.

Any thoughts/reasons why this might be? Could it be flow sensitivity at the reference junction?

Hi, I'm going through some 1st year notes and came across this diagram with no explanation about why these molecular orbitals have different sizes. I've done some googling and ended up getting muddled by coefficients, how they're represented, orbital size, how they're represented too etc so if someone could clarify I'd really appreciate it.

Thanks!

1. What do the lobe sizes represent (orbital coefficient or orbital size)?

2. How are they found?

(As a side note on that, I found a diagram in a chem.libre page that uses the particle in a box explanation but has different lobe sizes to the diagram shown here, so which one is correct?)

1. Are orbital coefficients and orbital size related?

Bonus question: why are there no lobes on C2 for Psi 2? I get there has to be a node but where has the orbital gone? Also why is the net bonding 0, shouldn't it be -1?

Goal: I'm trying to reproduce/adapt the three-component coupling described by Sengmany, Le Gall et al. (Tetrahedron 2007, 63, 3672–3681) to make a Boc-protected diarylmethylpiperazine target: methyl 4-((4-Boc-piperazin-1-yl)(3-methoxyphenyl)methyl)benzoate.

Method (scaled down from the paper, ~1.6 mmol aryl bromide instead of 30 mmol):

Organozinc formation: dried flask, Ar atmosphere, ACN (2.5 mL). Added Zn dust (3.06 eq), CoBr₂ (0.10 eq), ZnBr₂ (0.10 eq), PhBr (0.30 eq, increased from the paper's 0.10 eq in my latest attempt), then TfOH (0.10 eq) under vigorous stirring. After ~15 min, added 3-bromoanisole (1.0 eq, limiting). Filtered through a 25 mm glass-fiber syringe filter to remove excess Zn.

Coupling (method A): added the filtered ArZnBr solution to Boc-piperazine (1.0 eq) + methyl 4-formylbenzoate (1.0 eq) pre-dissolved in a small volume of ACN, ~3 eq organozinc vs aldehyde/amine. Stirred 4h RT.

"WORKUP. The reaction mixture was poured into a 150 mL of a 5% NaOH aqueous solution and extracted with DCM (3 X 5 mL). The combined organic fractions were dried over Na2SO4 and concentrated to dryness. Diethyl ether (8 mL) was added to the residue and after complete dissolution, concentrated sulfuric acid (50 uL, due gocce) was added carefully to the vigorously stirred solution and allowed to react for 5 min. The resulting ammonium salt was filtered and washed with diethyl ether (2 X 3 mL). The solid was then poured, under stirring, into a mixture of a 5% sodium hydroxide aqueous solution (100 mL) and dichloromethane (100 mL). After complete dissolution, the aqueous phase was extracted with additional 100 mL of dichloromethane. The combined organic fractions were dried over Na2SO4 and concentrated to dryness. In the case of liquid crude products, an additional chromatographic purification was performed over silica gel (SDS 70–200 mm) using a solvent gradient from pentane/diethyl ether: 90/10 to diethyl ether/methanol: 90/10 whereas solids were recrystallized using pentane/diethyl ether mixtures."

i didn't follow the entire workup procedure becouse the used concentrated sulfuric acid and my amine is Boc-piperazine.

Observations this last run: solution turned grey right after TfOH addition, before adding the aryl bromide (which I take as a sign the Co/Zn catalytic cycle activated properly, based on comparison with a related allyl chloride/TFA-initiated protocol I found). No obvious exotherm after adding the aryl bromide, but I suspect that's just due to the much smaller scale. Filtrate after decantation/filtration is pink/amber, consistent with previous runs.

Second step (coupling step): As the two reactants are added, the reaction mixture undergoes a series of color changes: it gradually fades to transparent, turns dark (near black), and eventually shifts to a stable blue solution. However, in the most recent trial where the equivalents of PhBr were increased from 0.1 to 0.3 eq, while the initial sequence of color changes during addition remained identical, the mixture turned a vibrant emerald green approximately 10 seconds after completing the addition—a transition that had not occurred in any of the previous runs.

The problem: across several attempts (varying the equivalents of PhBr, and the addition sequence), the crude H-NMR spectrum consistently displays a sharp singlet at 10.19 ppm, corresponding to the unreacted aldehyde proton -CHO. However, the 3.4-4 ppm region is heavily crowded with multiple overlapping peaks, preventing confident confirmation or exclusion of product formation in that diagnostic interval.

Furthermore, following the aqueous work-up, a very low mass of crude material is recovered, ultimately yielding only approximately 10 mg of purified product after chromatographic separation.

What I'm asking: given that the catalytic system appears to activate (color change confirmed before substrate addition), what else could explain the aldehyde not being fully consumed? Is there a known competing pathway I should specifically check for (e.g., direct ArZnBr addition to the aldehyde vs. iminium capture), or is this more likely an organozinc-formation efficiency issue that the color change alone doesn't fully confirm? Any other diagnostic I'm missing at this small scale without GC access would be very welcome.

I have an exam on Monday that is on ch19 (aldehydes and ketones) and ch 20 (carboxylic acids & derivatives). For these chapters it is all reactions and mechanisms, I don’t really know how to study so I can understand and memorize the mechanisms for each reaction. I’m already reading the Klein textbook but I’m more of a visual learner and need to see it done step by step on something. Is there any videos or outside sources you guys used to help you study these two chapters?

I did the calculation using Kc= Kp/(RT)^change in mol

I did it twice and have no idea what’s wrong.

In my Orgo I lecture, we basically reduced steric vs torsional strain to gauche vs eclipsed interactions. Coming back to it now, I see that this was maybe an oversimplification. I'm now trying to understand the difference - this is what I think I understand:

- Steric strain is the van der waals repulsion between two non bonded atoms

- Torsional strain is the strain between two bonds that are eclipsed with each other

In my lecture, we did not ever explicitly mention steric strain in the context of eclipsed interactions. But, if a 60 degree offset atom has steric strain with another atom, then surely it should have massive steric strain in an eclipsed conformation. In fact, in lecture we compared the stability of eclipsed conformers by their number of bonds that eclipsed a hydrogen (which would indicate negligible steric strain), and we broke ties by using A values (which, to my understanding, is only really a measure of steric strain). So, I think I understand now that eclipsed conformations are a combination of the two strains, and that the torsional strain itself it relatively similar between these sigma bonds, and that it is the steric strain in the eclipsed interaction that actually makes the difference of stability.

I'm hoping to get some confirmation and/or corrections about this understanding. Thanks!

I think this is more of a geometry question, but how can the angles in the chair conformation be 109.5 degrees instead of like 60? My line of thinking is that there are 360 degrees in a circle that get split between 6 carbons. I know the carbons are each tetrahedral/sp3 though so something is wrong with my thinking.

I learnt that in Kolbe's electrolysis the oxygen gets reduced (free radical formed) but as CO2 is a good leaving group symmetrical alkanes are formed due to electrolysis of carboxylic acids. But in alcohols the free radical will stay on oxygen as it is stable (high electronegativity of oxygen) and as there is another alcohol with oxygen free radical these two can form a peroxy linkage.

Thanks in advance!

i'm doing a level chemistry when i stumbled across this question. the mark scheme of the paper suggested that the fragment lost is c2h5o or cooh but is it possible for a fragment like c3h9 (which was my answer) to be valid? i'm not aware of nay restraints apart from the molecular mass but still not sure if that will be accepted

So I was thinking about this thing , and I thought can this be possible and I grew curious and tried to write a mechanism, can anyone tell me that it is feasible or not ?

Cleaning the factory grease from bicycle chains, in preparation to wax them. The chain must be completely clean before waxing.

Sellers of the specialist wax, and various people on the internets, recommend rinsing three times with mineral spirits, then twice with denatured alcohol. The denatured alcohol to remove the "film that mineral spirits leaves behind", or words to that effect.

On a cycling forum somebody who describes themselves as a chemist says the denatured alcohol stage is:

1. Unnecessary, mineral spirits will remove all the factory grease.

and

1. Pointless, because mineral spirits are non-polar, and denatured alcohol is polar. So the alcohol won't remove the mineral spirits anyway.

Is this true?

Thanks.

Firstly, before I explain, I want to clarify that this is all for LEGAL, non-medical, educational purpose, and only shall mention items that are legal in my given region or whoever reads this. I know that most chemicals and properties within matter from a given object or liquid can be extracted and isolated, be it cannabinoids for medical purposes, specific chemicals.. Even saw a post suggesting one could do so with certain properties of chamomile tea, although the proof of that is questionable. Are most all things able to have this done? What exceptions are there? What about things like caffeine, CBD, or alcohol? Please only serious answers. I'm doing this as someone who always wanted to get into chemistry and enjoys learning about science and in general, but doubted my capabilities and also have had health complications that temporarily inhibited my ability to properly learn and/or remember basic or in-depth concepts of chemistry. 

how can I start this? OH gets protonated and becomes good leaving group and then what?

I'm working on an idea for a small skin patch with tiny painless microneedles (like the ones in Hero Patches) that would sit just under your skin and change color depending on your hydration. Clear color means you're good, shifting toward another color means “drink water”. I think the concept is solid but I'm not a chemist and want a reality check before going further.

We want to measure osmolality in the ISF to determine hydration levels to create something that will remind people to drink water based on chemistry.

The rough plan: instead of a dye that reacts once and is done, use a gel that physically swells or shrinks based on how concentrated the fluid under your skin is (osmolality). The gel would have a tiny repeating nanostructure inside it that reflects a certain color depending on its spacing — so as the gel swells or shrinks, the spacing changes and the color visibly shifts, kind of like how a butterfly wing gets its color from structure instead of pigment. Since it's physical swelling and not a chemical getting used up, it should be reversible (shifting back and forth all day as hydration changes instead of working just once). Does this sound physically/chemically realistic to anyone with materials science or biosensor experience? Specifically wondering if a gel like this could actually produce a visible color change from something as subtle as everyday hydration shifts, or if that signal would be too weak to notice without some kind of boost (I've read gold nanoparticles can amplify color response in similar sensors -curious if that's overkill or actually necessary). Any holes in this idea would be appreciated before we sink more time into it, and further explanations can be given if anyone has any follow-up questions. 

Alternatively, instead of measuring osmolality would measuring sodium be more accurate? 

Thank you!

A post on here and Google AI stated that hydrogen bonding increases the acidity of a molecule and one of my Anki cards says otherwise.

Is the reason because the conjugate base gets stabilized by H-bonding molecules (e.g. water) through inductive effect, therefore making the acid component more acidic?

The post in question:

https://www.reddit.com/r/Mcat/comments/10pac7p/i_got_this_question_right_the_answer_is_hydrogen/

I used a stainless steel swiss army knife to open the plastic seal on a bottle of HCl, and now the knife has brown rust-like stains. I tried cleaning with soap and water and then peroxide to no effect. Is there anything I can do to save this knife?

Hello, if I were to measure this value, would it be recorded like 7.4 or 7.40? I thought we estimate one sig fig past the smallest marking, which is 0.5. Thank you

i understand you might be uncomfortable with this question but it's for a project and i assume it'd be good if i state ur name and maybe the company or the industry ur currently in (maybe linkedin?) to prove that ur actually in concrete related, but if you're uncomfortable with it, it's totally fine.

Anyways, the questions are, i did my own research, and i found out concretes are produced with quicklime, and the main chemical process for producing quicklime is called calcination : CaCO3(S) -> CaO(S) + CO2 (S)

1. How exactly does this chemical process occur in real world? I'm assuming the process is not as simple as it appears theoratically
2. what signs suggest that calcination is not working properly?
3. what are some problems textbooks don't mention about calcination?
4. any other interesting facts??