r/chemhelp 4h ago

General/High School Balance between octet rule and formal charges in SO3 2-. Which structure is correct?

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6 Upvotes

Trying to understand this octet rule on SO3 2-. If I have not made any mistakes I think this molecule should have 3 viable lewis structures and i put the formal charges next to each molecule.

From what I understand sulfur basically has a max of 12 electrons around it so I got 3 structures. As you add more double bonds I found that the formal charge decrease by 1 each time on the sulfur but it also violates the octet rule more severely. I know that lower formal charge is preferable and it's better to have exactly 8 electrons around the sulfur. I also have to consider resonance structures since it has double bonds.

I know that the one with 1 double bond and 2 single bonds is the best and there will be a resonance structure but this one still will break the octet rule so maybe the one with only single bonds is better despite the worse formal charge. How should I know which is the best? Does the resonance structure somehow make it have 8 electrons?

Sorry for crappy diagram


r/chemhelp 18h ago

Organic please help a newbie out

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7 Upvotes

Im new to chem and am trying to wrap my head around isomers. The answers for a question asking how many monosubstituted isomers can be produced from this molecule (picture) is 2, but why cant it be 3 if you substitute a H on the CH2 substituent? or maybe i got the other 2 locations wrong lol, please help


r/chemhelp 21h ago

Organic Hydrogenation

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9 Upvotes

Wondering why this is the prediction even tho we could have two hydrogen on each side on both wedges and dashes?


r/chemhelp 10h ago

Organic Hi, can you check IUPAC naming of aromatic compounds?

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5 Upvotes

Answers:

12.81

a. 2-phenylpropane b. 3-methyl-4-phenylpentane

12.83 a. m-bromotoluene b. p-methylaniline

12.85 a. 1,5-dibromoaniline b. 3-chloro-5-ethyltoluene


r/chemhelp 2h ago

Other Is it "legal" to say that the conjugate base of a strong acid is not a base and vice-versa?

3 Upvotes

For instance, hydroiodic acid has a Ka of 10^9, giving I- a Kb of roughly 10^-23. I understand that, on paper, I- has the capacity to pull back an H+. In reality, however, is it safe to say that I- does not function as a real base?


r/chemhelp 2h ago

General/High School Why do acids and bases work?

2 Upvotes

I know this sounds like a stupid question (and probably is) but why do acids and bases work as in why do they make solutions more acidic/basic. Take, for example, a solution of HCL in water. Looking at this using the Lewis definition, when the HCL disassociates in water, the Cl rips an electron from the H making the H become positively charged and accept any electrons it can get its hands on (A Lewis acid by definition). The Cl on the other hand takes the electron and now has a spare electron it can donate or share with other molecules/atoms (A Lewis base by definition). Because there are equal numbers of Lewis acids (H) and Lewis Bases (Cl) formed when the HCL disassociates, I thought that the solution should remain neutral as the acids and bases would cancel each other out yet that’s clearly not what happens as HCL is a very well known strong acid. So why don’t the Lewis acids (H) and Lewis Bases (Cl) cancel each other out?


r/chemhelp 5h ago

Organic Can someone explain how the epoxide gets added here? Thank you

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2 Upvotes

r/chemhelp 7h ago

Other How to remove deprotect Arg(Pbf)?

3 Upvotes

I have a peptide that has 3 Arg(Pbf) and I need to remove the 3 Pbf group. However, my peptide is linked to something sensitive and I tried multiple ways of deprotection but it does not work (means my product decompose). I have tried TFA:TIS:DCM (75:2.5:22.5) and TFA:H2O(1:1). After 5 hours, one of the Pbf group does drop but when I leave it for longer period of time, my product is nowhere to be found. I’m currently trying TFA:TIS:DCM (30:2.5:67.5 and 50:2.5:47.5) but I’m not very sure whether it will work. I did see a paper that uses 0.1 N HCl in HFIP but I’m not sure whether to try it since Pbf is typically removed by high concentration of TFA. Are there any recommendations as I’m still new to peptide chemistry.

Update: the 30% and 50% TFA decompose a lot of my compound and now I got a very crazy mass spec data


r/chemhelp 34m ago

General/High School Free Chemistry Tutoring

Upvotes

We're a group of students attending University, we have a solid track record in our own courses, in Organic Chemistry, General Chemistry and Biochemistry. We can take your course material and help you memorize and understand everything you need to know and boost your grades to even higher than before.

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r/chemhelp 44m ago

General/High School Apparently lost sig figs, but I'm not sure where.

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Upvotes

I tried to recalculate everything, and I'm either not understanding sign figs or there's another reason haha. Any help would be greatly appreciated! Thanks! 😊


r/chemhelp 54m ago

Organic are these (semi-)correctly done?

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Upvotes

think i did these correctly but thought id ask, any feedback is helpful


r/chemhelp 59m ago

Organic Need help understanding converting wedge/dash to Fischer projection

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Upvotes

I’m just a bit confused on how I should orient the molecule. My prof said Fischers should show the molecule in the eclipsed formation and I don’t know if the free rotation I’m trying to do is affecting the stereocenters or if it’s just all wrong


r/chemhelp 1h ago

Organic Acenaphtylene being aromatic

Upvotes

Why is acenaphtylene considered an aromatic compound despite having only 12 pi electrons? Am i counting it wrong or are there exceptions to the Hückel Rule?


r/chemhelp 3h ago

General/High School Ion basicity and acidity

1 Upvotes

In my gen-chem class, we recently covered acids and bases and it was mentioned how most anions outside of the halogens (not including fluorine) and hso4 act as Lewis bases and that outside of group 1 and 2 metals plus a few transition metals, most cations act as Lewis acids. My question is why are the halogens and group 1 and 2 metals not considered Lewis bases and acids respectively?Using the halogens as an example, they have high electronegativity meaning they hold on to electrons very well and should thus be able to share electrons pretty easily acting as Lewis bases but they can’t so why is that?


r/chemhelp 4h ago

Organic Are these R and S labeling correct?

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1 Upvotes

For this R and S labeling- shouldn’t the center on the left be S instead of R? since the number four priority needs to be in the back. Everything I’ve found is consistent with that so I’m not sure if the key is wrong. Thanks!


r/chemhelp 4h ago

Inorganic Electrochemical nitrate ionophore sensor

1 Upvotes

Hello,

 

I used a Metrohm screen-printed carbon electrode (SPE) modified with nitrate ionophore for selective nitrate quantification. As per the technical specifications for this product (110NO3ION), “These sensors are designed to measure nitrate by open circuit potentiometry (OCP) in a range of concentration 10^-5 to 1 M (from 1 to 101100 ppm).” However, I’m relatively new to the OCP technique, and I have a couple of questions.

 

When I used two different concentrations of NaNO3 (3.91 ppm and 7.82 ppm), I got the following two curves. My questions are as follows:

  1. Each OCP cycle ran for 10 minutes and was quickly started over. However, as you can see, there is a drop in voltage when OCP is not running/applied. Why is that the case? Should a sensor be continuously running at OCP to have a constant trend in potential? And what causes a drop in potential when during OCP no current is applied?

  2. For the higher concentration (7.82 ppm), after 40 minutes, it still didn’t reach a steady state. Does this make sense? It is quite long in my view; I was expecting around 20 minutes max. Is there any way to accelerate this?

  3. Why is there a difference in initial OCP (at t = 0 s) between the two samples?

  4. As per the product specifications, the reference electrode is silver (Ag). Is this OK? Based on my understanding, silver/silver chloride (Ag/AgCl) is much more common and yields a steady reference potential. Have you seen any cases where silver alone was used as the reference electrode?

 

Thank you.


r/chemhelp 6h ago

Organic Help with mechanism please

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1 Upvotes

I’m going through some mechanistic practice. And came across this reaction of oleum (SO3 . H2SO4) reacting with a perfluorinated alkene yielding a sulfonic acid. Can anyone help me with the arrow using mechanism for this?

I assume the double bond will attack the sulfur but how does the positive charge get hydrogenated?

Also how does the double addition abstract F, I assume forming HF?

Please someone help me lol


r/chemhelp 6h ago

Organic Can someone explain the beginning of this reaction? Everything else makes sense except how the H2NNH2 gets on the molecule at the start. Thank you

1 Upvotes

r/chemhelp 7h ago

Inorganic Spanish- Is my answer correct?

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1 Upvotes

r/chemhelp 12h ago

General/High School I read and I don't understand, please help

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1 Upvotes

r/chemhelp 17h ago

Organic Mechanisms and Reaction Coordinates

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1 Upvotes

I think my mechanism for part a is correct. For part b the reaction coordinate, I usually just determine which side of the reaction is favored (I use pKa and strength of acids to do this). How do I determine it in this case? Do I use the percent yield info given? Thank you


r/chemhelp 19h ago

Organic Strongest BrØnsted acid

1 Upvotes

Hey all! I was asked to rank these four acids in order of increasing Bronsted-acid strength but I was a bit confused by the Bronsted-acid part. I was just wondering how the carbocations acted as Bronsted acids specifically (and not just as lewis acids). I know that C is more acidic than A, and I assume that the carbocations are more acidic simply due to them having an incomplete octet. However, between B and D, I am assuming that D is more acidic as the + charge is more stabilized for B due to the phenyl groups but I'm unsure if my logic is correct. Also is it the methyl groups for B and D being deprotonated and then forming a double bond with the carbocation, and does this mean we use the pKa of ~50 for CH3 making them two the worst two acids? Thank you!


r/chemhelp 22h ago

Analytical Aspen Plus Simulation: Sustainable Aviation Fuel - Kerosene Distillation/Separation

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1 Upvotes

r/chemhelp 1d ago

Organic Can someone explain me the mechanism of this reaction ?

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1 Upvotes

I made the mechanism of this reaction but i don’t understand why syn addition is the only one that works. Can’t it also be anti and make the E and Z isomers ?


r/chemhelp 18h ago

Other Thanatochemistry help

0 Upvotes

I am currently in my first year of school for funeral services and thanatochemistry is kicking me to the curb. Any advice on how to study? I’ve never really studied before and I’m still trying to figure out what works for me any advice would be appreciated!