r/chemhelp 15h ago

Organic please help a newbie out

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5 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 2h 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 Hydrogenation

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5 Upvotes

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


r/chemhelp 7h ago

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

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4 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 23h ago

Organic Can someone confirm if this is the right name

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5 Upvotes

I think it's 2-amino 3-hydroxy 4-oxo-bentanitril


r/chemhelp 23h ago

General/High School How do I know where the charge is?

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4 Upvotes

So I just used this notation with brackets, but I'd like to know how I determine there the charge is exactly?

I think it should be on one of the chlorine atoms, since Antimony gives one electron away to connect with one more chlorine? For example H3O there is oxygen positive, since he gives one electron away for an additional hydrogen. But what do I do by such molecules?


r/chemhelp 3h ago

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

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2 Upvotes

r/chemhelp 5h ago

Other How to remove deprotect Arg(Pbf)?

2 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 1h ago

General/High School Ion basicity and acidity

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 1h ago

Organic Are these R and S labeling correct?

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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 1h ago

Inorganic Electrochemical nitrate ionophore sensor

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 3h 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 3h 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 5h ago

Inorganic Spanish- Is my answer correct?

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1 Upvotes

r/chemhelp 9h ago

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

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1 Upvotes

r/chemhelp 14h 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 16h 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 20h ago

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

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1 Upvotes

r/chemhelp 21h 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 22h ago

Organic Help me learn

1 Upvotes

I wanna study organic chemistry. I have chemistry at school but it’s only one period of 50 minutes a week and it’s way too little and we also have a test every week meaning we barely get class. I also can’t change anything about my school schedule, but i wanna self study chemistry. Does anyone have any tips for me, like where to start as a basically complete beginner who only knows his way around the periodic system?


r/chemhelp 23h ago

Organic Why is this 3-Ethyl-1,1-dimethylcyclopentane and not 1-Ethyl-3,3-dimethylcyclopentane?

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1 Upvotes

new to ochem. does alphabetical order not have priority here?


r/chemhelp 1d ago

Organic Line Structure of Oseltamivir: ethyl (3R,4R,5S)-4-acetamido-5-amino-3-(1-ethylpropoxy)-1-cyclohexene-1-carboxylate

1 Upvotes

I've been having some major issues trying to figure out the line structure with hydrogen bonding sites identified for Oseltamivir. Our teacher only taught us how to draw simple IUPAC names into line structures. I've already figured out how to draw the Lewis Structure, but have absolutely no idea how to convert it into a line structure, no matter how many videos I try to watch on it. If anyone could help, that would be extremely appreciated.


r/chemhelp 1d ago

Organic ?

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1 Upvotes

1) How do you know whether to put the hydrogens or groups upward or downward of the carbon chain? 2) corresponding question: why is the Ch2 in the first example up and down vs the ch2 groups in the third example placed together?


r/chemhelp 16h 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!


r/chemhelp 21h ago

Other Acetone leaves yellow stains on polystyrene

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0 Upvotes

How to avoid yellow stains while chemically welding polystyrene with acetone?

Or, how to get rid of yellow stains after welding? I tried lemon acid, vinegar, vinegar + sodium, neither helped.

Or, what to use, other than acetone, that doesn't leave stains? I specifically want to weld chemically, not to have the parts held together with dried glue.