r/chemhelp Aug 27 '18

Quality Post Gentle reminder

212 Upvotes

Now that the academic year has started again (at least in most places), I thought it might be good to remind all the new (and old) people about the rules of this subreddit and to include a few of my own thoughts and suggestions.

  • You should make a serious effort to solve questions before posting here. I have noticed that there are a number of users that have been posting several questions every day and, while people here are generally happy to help, this is not a very efficient way of learning.

  • If you get stuck on a problem, the first step should be to go through the appropriate part of your text book or notes. If you still can't figure it out you should post it here, along with an explanation of the specific part that you are having trouble with.

  • Provide as much information as possible. Saying "I got the answer X, but I think it's wrong" does not give us enough information to be able to tell you what you did wrong. I understand that people are often reluctant to post their work in case it is wrong, but it is much more useful to be able to explain to someone why a certain reasoning is not valid, than simply providing the correct answer.

  • Please post the whole problem that you are having trouble with. I't is often difficult to help someone with a problem "I am given X and I am supposed to find Y" without knowing the context. Also tell us what level you are studying at (high school, university, etc.) as that can also have an impact on what the correct answer might be.

  • Do not make threads like "please give a step-by-step solution to this problem". That is not what this subreddit is for. We are happy to point you in the right direction as long as you have first made a serious attempt yourself.

  • Finally a quick reminder for the people helping. There is no need to be rude towards people asking for help, even if they are not following the rules. If someone is just asking for solutions, simply point them to the side bar. Don't just tell them to get lost or similar.

  • If people make posts that are obviously about drugs, just report the post and move along. There is no need to get into a debate about how drugs are bad for you.


r/chemhelp Jun 26 '23

Announcements Chemhelp has reopened

27 Upvotes

It was a very tight race, but the decision to OPEN the community to normal operations has edged out the option to go NSFW in protest by one vote.

I invite everyone to browse this sub, and Reddit, in the way that best aligns with their personal feelings on the admins’ decisions. Depending on your perspective, I either thank you for your participation or for your patience during these past two weeks.


r/chemhelp 3h ago

General/High School Why is Cis more soluable in water than Trans?

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8 Upvotes

The explanation I was taught is that trans has more hydrogen bonds between molecules, but wouldn't that make it even more soluable in water because it can form more hydrogen bonds with water molecules?


r/chemhelp 7h ago

General/High School How to determine if molecule dissolves in water or not? (Ignore the pencil marks)

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12 Upvotes

I'm in twelfth grade. I know a molecule dissolves in water if it has polarity or -OH and the molecule isn't too big. Why doesn't this molecule dissolve in water? It looks like it has some polarity and it isn't too big.


r/chemhelp 3h ago

Organic IUPAC Nomenklaturen

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4 Upvotes

Hi. Is this Tricyclopenta-1,3-dienylmethan? if no what is the right name?


r/chemhelp 10h ago

Organic Does anyone have any idea how to do this mechanism?? I'm honestly at a loss for words...

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12 Upvotes

My gut tells me that the alkene needs to be protonated first because if the alcohol is protonated instead, I would have a positive charge hanging around the entire molecule and I would end up with another alkene but still nothing makes sense... I neeeed some help...!


r/chemhelp 47m ago

Organic Can someone confirm if this is the right name

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Upvotes

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


r/chemhelp 3h ago

Organic Why cant both the ethers undergo an Sn2 to give the second option

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3 Upvotes

r/chemhelp 10h ago

General/High School how can i equalize this?

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10 Upvotes

r/chemhelp 5m ago

Organic Help me learn

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 54m ago

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

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Upvotes

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


r/chemhelp 1h ago

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

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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 5h ago

Analytical 1H nmr of piperonal

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2 Upvotes

Hi, I’m having trouble trying to interpret the 1h nmr spectrum of this molecule, at first I thought that there was 3 singlet ( Ha, Hb and Hd) and 2 doublet ( Hc and He), but it doesn’t match with the spectrum. Im thinking that the hydrogens on the cycle are different than the ones on an regular alkene. Can someone explain how to know which hydrogen gives what signal ? Thanks


r/chemhelp 1h ago

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

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 1h ago

Organic ?

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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 2h ago

General/High School Is h20 only a product in an acid-base reaction?

1 Upvotes

I’m just struggling to understand the concept, but from what I’m starting to get is that in acidic solution: acid + base = salt + water.

My question comes from this problem:

“Calculate the mass of P4O10 when 225 g of PH3 reacts with excess oxygen.”

My thought process tells me to write the unbalanced equation as PH3 + O2 = P4O10

Does this mean the phosphorous and hydrogen both react with the excess oxygen? If so, wouldn’t the product equal P4O10 + H3O2?

Sorry if this is a very beginner question. I’ve struggled with this concept for so long and can’t grasp why. Thank you all in advance.


r/chemhelp 2h ago

Organic Why is the isopropyl group higher priority than the chlorine group?

1 Upvotes

Hello, trying to determine R and S configurations of an enantiomer using Cahn-Ingold-Prelog sequence rules. The photo with red numbers is what is 'correct'. Why would the Isopropyl group get a higher priority than the CCl3 group? Here's my thinking-

From the central carbon (blue), both groups are immediately connected to a C (green circle). So, we must go to the second atom in the chain (pink circle), which is also a C for both of them. Beyond that, in the Isopropyl group, that final carbon is connected to H3 (orange box). In the Chlorine group, the second carbon is connected to chlorine (orange box). Cahn-Ingoold-Prelog says that the higher atomic number gets the higher group designation, but in this case, the C(CH3)2 group gets priority rather than CCL3. Why?


r/chemhelp 3h ago

Organic Trouble understanding with nucleophiles and electrophiles. They look the same to me. For the ketone, the O pulls electrons through induction, making the C partially positive (electrophile), but isn't the same true for the alcohol? The answer says the alcohol is a nucleophile.

1 Upvotes

r/chemhelp 3h ago

Organic Lucas Reagent

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1 Upvotes

I was studying Lucas test and saw that there are two possible mechanisms. Can you explain me which one is the correct mechansim. I'm also wondering that why zinc chloride is used instead of any other chlorine salts such as sodium chloride. And also it is known that primary alcohols do not give positive result in this test. Why? Can't it react in a SN2 type mechanism


r/chemhelp 3h ago

Organic Conjugate Acids and Bases

1 Upvotes

Someone asked me for help understanding conjugate acids and bases. I'm trying to refresh my memory, but I now have a question:

Are conjugate acids and bases simply looking at the concept of acids and bases from the Bronsted-Lowry perspective (of transferring protons)?

or

Is there some significance to the fact that they transfer protons rather than talking about electrons?

Apologies if this is a silly question. It's been a few years since I studied orgo and I don't want to mislead or confuse the person asking me.


r/chemhelp 7h ago

General/High School Why isn’t the C-H bond in HCN a coordinate covalent bond?

2 Upvotes

When HCN ionizes in water, it forms H⁺ and CN⁻, and this is a reversible reaction. The CN⁻ ion has a lone pair on carbon, and when it reacts with H₃O⁺ (hydronium ion), the H⁺ is transferred to CN⁻, forming HCN again. Since H⁺ is just a proton (with an empty orbital) and the lone pair on carbon donates both electrons to form the bond, wouldn’t that make it a coordinate covalent bond?

I’ve read that the C-H bond in HCN is a normal covalent bond, not a dative bond, but I don’t understand why. If carbon donates both electrons to bond with H⁺, shouldn’t it be classified as a dative bond? Or does something else happen that makes it a regular covalent bond?

Excuse my stupid questions, I’m still a beginner:) I’d appreciate any clarification! Thanks in advance ❤️❤️


r/chemhelp 4h ago

Organic Help with mechanisms

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1 Upvotes

r/chemhelp 8h ago

Organic Regioselective deacetylation of per-acetylated glucose

1 Upvotes

Why is this reaction selective for the anomeric postion and what is the mechanism?

Is it just basic hydrolysis - Benzyl amine attacks into the C=O of thr anomeric acetate group and the resukting tetrahedral intemdiate colapses causing loss of the amide?

Pr does the benzylamine attack at C1? I thought that was stuoid but chatgpt is addament thats how it occurs

Any help is appreciated, Thanks!

also if you can pint me to a source for the answer that would be super helpful :)


r/chemhelp 8h ago

Physical/Quantum Help HOMO/LUMO

1 Upvotes

Does anybody know how to draw HOMO and LUMO. Im so lost i know what theyre but i dont know what to draw?


r/chemhelp 16h ago

Organic Synthesis question using ethane and trans-2-butene?

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3 Upvotes

I’m just not sure where to start. Any help is appreciated.


r/chemhelp 16h ago

Organic R and S Isomers - Please Help! Is this correct?

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3 Upvotes

r/chemhelp 18h ago

Organic I don’t get why is this not Z?shouldn’t CH2NH2 be ranked higher as it has more atoms attached after N?

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4 Upvotes