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

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?

Based on the NMR spectrum I'm looking at for my product, I've had no conversion on this reaction I'm working on:

Situation -

This reaction shows no conversion (the NMR of the product just shows the peaks corresponding to the sulfinimine), and I don't see any bromopyrazole peaks at all for some reason.

My protocol is this:

A solution of 4-Bromo-1H-pyrazole (4 mmol) in dry THF at -78∘C was treated with dropwise addition of n-Butyllithium (4 mmol) and stirred at -78∘C for 1 hour. The sulfinamide(2mmol) was added and stirred. The reaction was warmed to room temperature, then quenched with saturated aqueous ammonium chloride. Aqueous workup was performed, followed by concentration by rotary evaporation. Following this, the compound was purified by flash column chromatography to yield a pure product.

Exact quantities used were:

4-Bromo-1,3-dimethyl-1H-pyrazole (density 1.487 g/ml): 0.47 mL, 4.0 mmol, 2 eq

n-Butyllithium (2.5 M in hexanes): 1.56 mL, 4.0 mmol, 2 eq.

N-((E)-4-chlorobenzylidene)-2-methylpropane-2-sulfinamide: 487.5 mg, 2.0 mmol, 1 eq.

What I've done so far:

I did not see the bromopyrazole peak in my product's NMR so I first checked the bromopyrazole's NMR to see if something shows up. The bromopyrazole's NMR is fine.

The nBuLi and THF bottle are dry, others have used these and reactions involving these have worked for others in the lab.

The sulfinimine I'm starting with is fine as well, with no moisture.

Am I missing something? Even if there's moisture, I should have been able to see some peak corresponding to the bromopyrazole or any side-reactants. Is the nBuBr side product playing some role? Even if so, I don't see it on the nmr spectrum

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??

Hey, everyone, sorry if this is an amateur question, as I am not a chemist.

Are these correct MDMA molecular structure and they can be understood by a chemist?

Is there any version "more correct" than the rest or are they all good? Three of them are vertical named and one is horizontal.

These were generated using Claude.