The Periodic Table

user228700

12:14 AM

Hey, guys :-) I've a very quick question.

user228700

When comparing the stability of two organic compounds attached to a heteroatom, what characteristics must I look for? Seriously, things like "possesses vacant d-orbital to stabilize charge" (in case of a negatively charged carbon) etc.?

Loong

@Kaumudi The simple characteristics are electronegativity and lone pairs. Next you should check possible resonance structures.

user228700

Why lone pairs?

Loong

@Kaumudi any lone pairs on the heteroatom

user228700

Why..? To draw possible canonical structures?

Loong

12:25 AM

Yes, the lone pairs could participate in resonance structures.

!!img/furan

Chemobot

user32720

HI

What should be the ratio of the concentration of chlorous acid, HClO 2, and potassium chlorite, KClO 2, to give a buffer solution with pH = 3.82? Ka = 1.0x10-2.
How to assemble expressions to relate substances?

user228700

Right. Okay, thanks :-) Can u help me w/ a quick homework-tsy problem? I've been asked to compare the stability of the following two structures. Only 2 resonance structures are possible for both and the only condition to be checked is the inductive effect, apparently, but I'm unable to understand it:

user32720

Any?

user228700

Loong

12:31 AM

@user32720 Do you know the Henderson–Hasselbalch equation?

@Kaumudi Is there a negative charge on those -CH2 groups?

user228700

Clearly, the -I effect exerted by F is more than that exerted by Cl, but how does that matter?

user228700

Yes, there is a negative charge on it and damn, I've just realized that no resonance structures are possible for either.

user32720

@Loong yes I know

But how will I relate the two substances?

user228700

Well, I guess that the inductive effect sort of makes sense, here.

user228700

It does, it definitely does.

user228700

12:34 AM

Nvm :-)

Loong

@Kaumudi It matters, because a localized charge is not so nice. You could stabilize the ion if you delocalize or distribute the charge more over the entire molecule.

user32720

@Loong Can you help me?

Loong

@user32720 HClO2 is an acid. KClO2 is a salt of this acid. So ClO2- is the corresponding base.

@user32720 The Henderson–Hasselbalch equation is: pH = pKa + log([base]/[acid])

user32720

@Loong So HCl02 + H20 --> KCl02 + H3O^+

Loong

@user32720 where did that K come from in your equation?

user228700

12:39 AM

@Loong Yep, OK, thankss :-)

user32720

@Loong You did not say it was an acid salt?

Loong

@user32720 Yes, KClO2 is a salt. The acid–base reaction is HClO2 + H2O <=> ClO2^- + H3O^+

or short: HClO2 <=> ClO2^- + H+

user32720

@Loong And where does K appear?

Loong

In solution, the salt KClO2 will dissociate into K^+ + ClO2^-

So the K^+ is not relevant for the Henderson–Hasselbalch equation.

user228700

Wokay, I think I've another quick question, very much related to what I asked a few minutes ago. When considering these heteroatoms connected to a negative charge on the carbon, am I to look for that atom that exhibits the -I effect to a larger extent or that one, which can accommodate the negative charge through resonance? Resonance effect is more important, no? But what if no resonance structures are possible?

user228700

12:44 AM

(Eg: $CCl_3^-$ vs. $CF_3^-$

user228700

Even tho $F$ exhibits the -I effect to a larger extent, $CCl_3^-$ is more stable because $Cl$ has d-orbitals, capable of "stabilizing the negative charge" but how will it be stabilized if no resonance structures are possible? )

Loong

@Kaumudi Yes, if resonance effects are possible, they are usually more important than inductive effects. However, if no resonance structures are possible, you cannot use resonance to stabilize the compound.

user228700

So what about that example that I've given?

Loong

@Kaumudi Hm, I'am not so sure whether the d-orbitals of Cl can really effectively stabilize the charge.

user228700

Without resonance, how would they be able to stabilize the charge?

Loong

12:51 AM

We have this:

5

Q: How to prove that CHCl3 is more acidic than CHF3?

Using the concept that Inductive effect becomes dominant than Resonance (mesomeric) in case of halide substituents: (1) Since both have single hydrogen, lets compare stability of carbanions $\ce{CF3-}$ and $\ce{CCl3-}$. (2) Since fluorine shows more negative inductive effect than chlorine, $\c...

However, there is no clear authoritative answer.

user32720

Then the equation would be:
PH = pKa-log [ClO2 -] / [HCl02]?

Loong

@user32720 pH = pKa + log([base]/[acid]) or pH = pKa - log([acid]/[base])

HClO2 is the acid here; ClO2^- is the base.

Mithoron

@Loong It seems your patience knows no bounds ;)

user228700

> "While in $C_Cl3^-$, chlorine has an empty d orbital thus the negative will be more dispersed into the this empty orbital hence the repulsions will be quite less as compared to $C_F3^−$"

user228700

What is this "dispersion"?

Loong

12:57 AM

6 mins ago, by Loong

@Kaumudi Hm, I'am not so sure whether the d-orbitals of Cl can really effectively stabilize the charge.

user32720

@Loong Thank you for your help

Mithoron

@Kaumudi I think you should give poor Loong a break

Loong

@user32720 ok? Can you do the rest now?

user32720

@Loong I believe so. Anything I return. All good for you!

user228700

@Loong Okay :-|

Loong

1:00 AM

@Mithoron and some acetylsalicylic acid

!!img/2-(acetyloxy)benzoic acid

user228700

@Mithoron :-P I'm sorry. I thought he/she was okay with helping me.

Chemobot

Mithoron

@Kaumudi Two help needers with different topics is quite a bit

Loong

@Kaumudi it's ok; you can always ask in chat. But don't push the other users if you don't get a quick answer. :-)

Mithoron

10

Q: Homework requests in Periodic Table chat?

I don't mind guiding users in The Periodic Table with their homework. If I get a question or two, I'll discuss it with the person. However, there have been times where users will sit in chat all night and ask question after question, seemingly completing entire assignments in chat. There have bee...

discussion chat

Beware! ;)

Also someone was quite impatient here

Loong

1:07 AM

in The h Bar, Dec 2 at 21:31, by heather

@Abcd, nope. I might point out a few rules of chat etiquette that'll help you out though. 1. No need to ask if you can ask, just ask =) 2. Don't randomly ping people; that just annoys people. 3. If some can and wants to help, they will. Good luck with your question!

@Mithoron yeah, they make the rules ;-)

Mithoron

-1

Q: Chlorous acid buffer calculation

How can I calculate this: What should be the ratio of the concentration of chlorous acid, HClO 2, and potassium chlorite, KClO 2, to give a buffer solution with pH = 3.82? Ka = 1.0x10-2. How to assemble expressions to relate substances?

homework acid-base equilibrium

Loong

@Mithoron oh, I didn't see that :-|

user228700

@Mithoron If u notice, I didn't ping anybody except when I was directly replying to Loong.

Mithoron

@user32720 Asking here after posting isn't so good

Loong

@Kaumudi don't worry, it's ok, your questions are fine

@Mithoron you summoned @Melanie :-)

user32720

1:10 AM

@Loong sorry I did not know

Mithoron

@Loong I was just writing about summoning :D

Loong

@user32720 don't worry; you are new on this site. We are here to answer your conceptual questions. However, please note that we are not a service to do your homework for you. :-)

gannex

I really really need to see a photoshop of the Insane Clown Posse showing off an atomic mass spectrometer

It's all I can think of every time I read ICP-MS

Loong

@gannex what?

gannex

https://en.wikipedia.org/wiki/Insane_Clown_Posse
https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry

Loong

1:16 AM

aha

gannex

I want a photoshop of the members of ICP holding an ICPMS and like showing it off to the crowd

user228700

This room seems to be attracting a lot more homework questions than is common in other rooms, such as The h Bar.

Loong

@gannex I always liked working with the ICP-MS. The best thing was the sound of the starting turbomolecular pump. :-)

gannex

I've never used one. I'm reading a book that really promotes it

ICPMS is like the answer to everything

Loong

@Kaumudi I think, the h bar has more questions, but they are better hidden between the discussions about sophisticated theoretical physics.

@gannex almost everything, yes

user228700

1:23 AM

Perhaps. In my experience tho, the homework questions are entertained over there because in the case of physics, (unless it's a completely numerical question) even homework questions help lead to amazing discussions about concepts.

gannex

@Loong do you know a lot about ICPMS then?

Loong

@gannex No, not a lot. I have only used one during my diploma thesis.

gannex

ah ok

I am trying to write up a procedure for an ICPMS determination

but I'll just consult my book some more

Melanie Shebel

Yes? :P

Ahem @Loong @Mithoron have you awoken a sleeping giant with homework questions?

(I'm the sleeping giant.) However, I'm neither asleep or giant. :P

Mithoron

Behold :D

Loong

1:34 AM

@MelanieShebel Hm, your profile doesn't describe you as a giant.

Melanie Shebel

No, I'm pale, awkward, and small.

Loong

@MelanieShebel You are pale? So your avatar is a colour picture? (No, please don't hurt me, dear giant!) ;-)

Mithoron

Maybe miniature giant space Melanie :D

Loong

Isoroku Yamamoto's sleeping giant quote

Isoroku Yamamoto's sleeping giant quotation is a quote by the Japanese Admiral Isoroku Yamamoto regarding the 1941 attack on Pearl Harbor by forces of Imperial Japan. The quotation is portrayed at the very end of the 1970 film Tora! Tora! Tora! as: I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve. The quotation is also featured in the 2001 film Pearl Harbor. Although the quotation may well have encapsulated many of his real feelings about the attack, there is no printed evidence to prove Yamamoto made this statement or wrote it down. == Overview == The...

Melanie Shebel

1:57 AM

I'm pretty pale. I use the lightest shade of makeup foundation they make.

Loong

@orthocresol good morning

You are here; so I can go to bed.

pentavalentcarbon

You make it sound like it's shift work.

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