The Periodic Table

CowperKettle

17:01

Can I be sure that if I ask this question on the main site it won't be downvoted?

ringo

@MAFIA36790 no kidding

@Loong and you mine. Thanks for your input

CowperKettle

Chlorine must love the most positive atoms the most.

Oh, well.

According to chemguide, we might get an acyl chloride instead.

Is the name of the acid "alpha-chlorocarboxylic acid"?

0

Q: Reaction of carboxylic acid and chlorine

From an online textbook, the first step in the preparation of an amino acid: Can we be sure that the clorine will connect exactly at that spot, in the alpha-position? Won't we get an acyl chloride instead? Or a molecule where Cl is connected in the beta-position, or further down the line?

organic-chemistry

(off to read more about amino acids)

PhMgBr

17:17

@CowperKettle Huh?

CowperKettle

@PhMgBr I'm trying to see some kind of logic in the equations, not just cram them into my brain.

PhMgBr

@CowperKettle Where else would Chlorine add?

CowperKettle

@PhMgBr chemguide.co.uk/organicprops/acids/pcl5.html

Hippalectryon

@Martin-マーチン from mafia's meta post link. It probably has mol/...

PhMgBr

@CowperKettle There's always logic if you read some reaction mechanism. If you want to make logic out of things, you should first study acids and bases, and then I'll tell you something.

Then you can study and understand mechanisms easily.

CowperKettle

17:19

I know about acids and bases.

PhMgBr

Aha, then about nucleophiles and electrophiles?

CowperKettle

I know that Chlorine is a nucleophile

PhMgBr

What are nucleophiles?

CowperKettle

species with excess negative charge seeking to grab a H(+) or something looking like that H(+)

PhMgBr

So?

What is the relationship between nucleophiles and electrophiles and acids and bases?

CowperKettle

17:22

attraction

PhMgBr

No no, I meant how are those definitions related?

What does an acid do to a nucleophile? What does an acid do to the electrophile?

CowperKettle

Acids are nucleophiles.

PhMgBr

Aha, and electrophiles are bases.

Hippalectryon

@PhMgBr O_o wat

CowperKettle

I mean, when the acid has lost its H+, it's a nucleophile

PhMgBr

17:24

But no.

@CowperKettle That's not an acid anymore. >:)

Trapped!

CowperKettle

I see.

PhMgBr

The vice versa is true @Cowp: Acids are electrophiles and bases are nucleophiles.

CowperKettle

NH3 is a base, and it attracts H+, so it's a nucleophile. Okay.

I knew that, only got my signals crossed.

PhMgBr

So, what is the difference between nucleophilicity and basicity, or electrophilicity and acidity?

I hope you don't mind my numerous questions @Cowp. It's how my awesome Chem teacher makes me understand things and it's the most effective teaching method: Interactive teaching

@CowperKettle These can always be confusing.

CowperKettle

@PhMgBr I don't mind. THe difference is that nucleophiles attract protons.

PhMgBr

17:27

@CowperKettle And what do bases do? Is it not attracting protons? :P

CowperKettle

Yes, bases do that. (0:

The alpha-C atom on the acid is closer to its acidic end.

PhMgBr

Aha

CowperKettle

But when Cl2 is split, a single Cl still has no charge.

PhMgBr

But it's a radical, and radicals are pretty reactive.

Radicals are species with an unpaired electron.

O is a radical.

CowperKettle

But they have no charge, so they can attach everywhere. They don't pick.

PhMgBr

17:31

@CowperKettle Well, won't a Cl attract H and become HCl?

Hippalectryon

@PhMgBr There are no radicals involved in acid chloride formation though ?

CowperKettle

@PhMgBr Why should it, it has no charge?

PhMgBr

@CowperKettle Because forming HCl is much more 'favorable' than being H and Cl radicals.

@Hippalectryon Cowp is talking about chlorine dissociation.

Hippalectryon

@PhMgBr Oh my bad

PhMgBr

Cl2 -> 2Cl

CowperKettle

17:34

@PhMgBr Okay. But since atomarous Cl carries no charge, it can tear off that H everywhere.

Not at some specific site.

PhMgBr

@CowperKettle Wait, we are talking about acid chloride formation?

CowperKettle

@PhMgBr Yes. But I initially wanted to know why exactly the other Cl will attach exactly in the alpha position.

I found this

chemgapedia.de/vsengine/vlu/vsc/en/ch/12/oc/vlu_organik/c_acid/…

PhMgBr

@CowperKettle Well, think of it like this.

CowperKettle

Maybe we need a special catalyst to make the halogen attach in a specific position

PhMgBr

The oxygens in carboxyl love electrons and drag the electron cloud from carbon.

CowperKettle

17:38

nods

PhMgBr

The carbon has a considerable partial charge, but it still loves electron cloud as much as the other carbon.

So it drags some of the other carbon's cloud and the other carbon gets a partial charge.

@CowperKettle They usually use SOCl2 for acid chloride synthesis.

The carboxyl atom has no space available for chlorine's attack.

But the other one does.

Hippalectryon

It's easier to use Cl^- for the mechanism though, with SOCl2 it's a bit complicated

CowperKettle

@PhMgBr Yet here this attack is described: chemguide.co.uk/organicprops/acids/pcl5.html

PhMgBr

@Hippalectryon Eh, just some extra atoms.

Hippalectryon

@PhMgBr It's quite different though, there's a cyclic intermediate and stuff

PhMgBr

17:42

It's on that page.

@Hippalectryon Sure, 'cause that's not possible with one Cl-, and well, how else are we gonna provide Cl anions?

CowperKettle

@PhMgBr Ah, so with pure single-atom Cl we get it attached in alpha-position for some reason.

Hippalectryon

@PhMgBr We'll find a way \o/ :P

PhMgBr

@CowperKettle Here's some reason: chemtube3d.com/acid_chloride_formation_thionyl_chloride.html

Hippalectryon

>Puts HCl in water
> Has Cl-
> Puts COOH
> Cries

PhMgBr

And that's Clayden guys' site.

@Hippalectryon Let's cry together

Hippalectryon

17:44

PhMgBr

OK let's talk so ^ scrolls off.

Hey @Penta

pentavalentcarbon

I am here

PhMgBr

But @here doesn't ping you

pentavalentcarbon

ohohohohoho a funny person!

CowperKettle

@PhMgBr I see. I can't believe people are able to memorize such schemes.

PhMgBr

17:52

@CowperKettle They aren't.

Hippalectryon

The internet memorizes it for us

PhMgBr

They categorize them into a few categories: Nucleophilic substitution, nucleophilic addition, aromatic electrophilic substitution etc.

CowperKettle

Sneaky chemists.

PhMgBr

In each set of mechanisms something not-so-unique happens @Cowp, and they usually only need to know that.

CowperKettle

nods

PhMgBr

17:54

That's why I'm recommending you grab a textbook on organic chemistry and start reading.

Online material like chemguide is nice, but it's not replacing a book. Never can

CowperKettle

I am reading a Russian textbook. Ending the 10th grade now.

I use online resources to get extra info.

PhMgBr

Oh noice

I can sleep well at night now @Cowp. :)

!!ice cream

Chemobot

CowperKettle

I have a couple of dozen English textbooks, but I don't know which to pick.

I thought I should first read the Russian school curriculum through.

PhMgBr

@Cowp It's always been like this for me: I end x'th grade lessons, and then some interesting askable-on-chem.SE x-2'th grade questions hit me.

CowperKettle

18:02

(0:

PhMgBr

Good questions on the site aren't necessarily touching advanced topics unlike language; they're often thought-out questions from people fluent enough in what they studied to ask them.

CowperKettle

By what mechanism would you expect to get the acid chloride? The $\sigma _{C-H}$ bond $\alpha$ to the carbonyl is going to be the weakest bond in terms of homolytic cleavage. — SendersReagent 12 mins ago

PhMgBr

Yay! The only cool comment-answers are chem's.

CowperKettle

So the H will drift away homolytically, in its non-ionic form?

Not as an H+, but just as H.

PhMgBr

Hmm, I thought it's H+

CowperKettle

18:07

But why will taht bond be the weakest?

> Irradiation will cleave the Cl−ClCl−Cl bond and yield chlorine radicals (Cl⋅)Cl⋅). These will abstract hydrogen atoms (not protons) from the carboxylic acid to form a carbon centered radical (and HClHCl).

"Carbon-centered radical"?

PhMgBr

@CowperKettle Again, like what I said, the oxygen gets a lot of electron could and carbon needs to pull some from others to satisfy it's thirst

@CowperKettle That's not HClHCl

It's HCHCl

CowperKettle

Sorry, that's a formatting mishap.

It's HCl in the text

1

A: Reaction of carboxylic acid and chlorine

Yes, we can :-D Note the $h\nu$ in the reaction. It is a radical reaction. Irradiation will cleave the $\ce{Cl-Cl}$ bond and yield chlorine radicals ($\ce{Cl*})$. These will abstract hydrogen atoms (not protons) from the carboxylic acid to form a carbon centered radical (and $\ce{HCl}$). The fa...

I feel that it must be a good answer, but I'm too dense.

PhMgBr

@CowperKettle I don't see an HClHCl

CowperKettle

> The favoured and position for this radical is the αα carbon, where the radical is stabilized by interaction with the −C=O bond.

"the favored and position"? probably "end position"? Whatever that may be.

PhMgBr

Yeah haha

CowperKettle

18:14

I write "carbon centered radical" in Google and get some very advanced sci articles, no simple explanation.

PhMgBr

Oh ahh, wait. Now I understand

I completely mixed this with some other mechanism @Cowp.

Lemme explain.

CowperKettle

nods

PhMgBr

@Cowp if there had to be grabbing the H from the carboxyl to form a carboxylate, the H would've came out as H+, not H.

CowperKettle

Sure.

PhMgBr

The reason being, that O is pretty electronegative, and RCOO- is more stable than RCOO. (Much more, because of delocalization)

CowperKettle

18:18

Than RCOOH?

PhMgBr

@CowperKettle No, than RCOO.

CowperKettle

But we don't get RCOO anyway.

PhMgBr

@CowperKettle Yes, because the more stable product will form. Lemme explain

So, we have to remove the hydrogen from a place that's most stable without it.

CowperKettle

nods

PhMgBr

We can't get it from R.

The R radicals are unstable.

user116211

18:22

That's it.... bye comrades.

CowperKettle

Shubh ratri, Mafia!

PhMgBr

@MAFIA36790 Night

So the only place that remains is the hydrogen in carbonyl

user116211

@CowperKettle I'm a Russian MAFIA, BTW ;p

CowperKettle

@PhMgBr Do they exist at all? I though a radical is a single atom.

@MAFIA36790 Then Dobroy Nochi, Mafia! (0:

PhMgBr

@CowperKettle A radical can be a single atom, and not a single atom. Yes, single atoms are radicals.

But radicals are produced in many reactions, and since they're unstable and reactive, as you say, they usually act as intermediates and react.

But that doesn't mean they don't exist.

CowperKettle

18:26

But isn't the alpha carbon part of the R group?

It will be unstable anyway then.

I see. THe "end position" is where we get the unpaired electron.

PhMgBr

@CowperKettle I meant where R is RCH2COOH

CowperKettle

And in this position, this unpaired electron is not so radical, because the C=O bond draws it towards the carbon nearby.

So this electron kinda does not stick out too much.

PhMgBr

@CowperKettle That pun! Nice

CowperKettle

Pun? Unintentional. (0:

PhMgBr

Yes, that's why it's (more) stable.

Hippalectryon

18:30

punintentional

PhMgBr

Everything again goes back to how oxygen drags the cloud from carbon @Cowp. That's always the case in carbonyl when we don't want to dig further into more advanced MO schemes and calculations.

@Hippalectryon Nah, more like, puntentional

CowperKettle

0

A: Reaction of carboxylic acid and chlorine

I am going to say, no, this does not work in practice. In theory you would say that that the α C-H bond is the weakest because the resulting radical is stabilised by conjugation into the C=O. That's all fine and dandy until you actually run the experiment. The problem is twofold. Firstly, the c...

PhMgBr

Pretty nice answer. BTW @Ortho between Clayden and Carey, which one'd you choose if you could only choose one? Should I go read Carey when I finished Clayden?

Hippalectryon

I always laugh internally when I see "The solution" in a chem answer ._.

CowperKettle

"electrophilic radical"?

PhMgBr

18:37

@CowperKettle A radical that likes electrons

Snail Mail

Quick question:

Which is more common?:

Reaction 1: Fe + CuO -> FeO + Cu or Reaction 2: 2Fe + 3CuO -> Fe2O3 + 3Cu

CowperKettle

Fe2O3 seems to be more widespread in nature, no? I don't recall exactly.

Snail Mail

Ah, essentially my question is: is FeO more common than Fe2O3?

Wikipedia: "As the mineral known as hematite, Fe2O3 is the main source of iron for the steel industry."

Wiki Answers: "Fe2O3 is more common."

I guess I've answered my question :P

@CowperKettle Thanks for your answer though

Oh sorry wait....

CowperKettle

You're welcome

Hippalectryon

Absolutely unrelated to chemistry, but just sharing that :>

Snail Mail

18:46

The question is: is FeO more likely to be produced (not found) than Fe2O3?

Or would you say that the fact it is more often found leads on to say that it is more often produced?

PhMgBr

@Cowp translating Ortho's answer, he's saying that you might think that conjugation stabilizes and the CH bond your question wanted to break is weakest, but it's not true because
1. chlorine doesn't choose its victim and
2. since it's an electrophilic radical and likes electrons, it wants a hydrogen that has some more cloud to it.

CowperKettle

@PhMgBr I'm trying to understand WHY it is an electrophilic radical.

Oh, he just expanded the answer

> On top of that, it is what we would consider as an "electrophilic radical"; it has a very low-energy SOMO, and therefore has a tendency to abstract a more electron-rich hydrogen atom. Essentially, it means that the radical behaves more like an electrophile than a nucleophile. In the transition state for hydrogen abstraction

PhMgBr

@CowperKettle Well, were you expecting it to be nucleophilic?

CowperKettle

I expected it to be neutral

No I'll need to read about MO to understand this.

PhMgBr

@Cowp it's basically the same argument you used to hear before: "halogens are electronegative and they want to gain an electron to reach stability"

But in a more chemistry, scientific way.

!!greet/@Snail

Chemobot

18:50

Welcome to The Periodic Table @Snail! Here are our chat guidelines and it's recommended that you read them. If you want to turn Mathjax on, follow the instructions in this answer. Happy chatting!

CowperKettle

nods

Snail Mail

Ah that's a cool command :P

!!greet/[someone]

Chemobot

Welcome to The Periodic Table [someone]! Here are our chat guidelines and it's recommended that you read them. If you want to turn Mathjax on, follow the instructions in this answer. Happy chatting!

Snail Mail

Woops :)

PhMgBr

@SnailMail Depends on the conditions, but in normal lab conditions with excess CuO, considering the Cu^2+/Cu E0, it will oxidize all its way to Fe2O3.

Snail Mail

18:52

@PhMgBr Thanks for the swift response :)

Have a good day

orthocresol

@PhMgBr Clayden definitely, IMO Carey/Sundberg is not a good intro. It's good if you have your basics down and want to go further then Carey/Sundberg is great but for starters you'd go for Clayden.

PhMgBr

@orthocresol Oh, so it's more ᕙ(⇀‸↼‶)ᕗ than Clayden. Noice

orthocresol

My impression is that Carey/Sundberg is a bit inconsistent in how much prerequisite knowledge it expects, so if you're confident enough then it's great (there's a lot of info in it)

CowperKettle

Basically the main take-home message for me is to read about MO theory..

orthocresol

@CowperKettle The radical is neutral, but it leans more towards an electrophile than a nucleophile. These are called "polar effects in radical reactions" - as with everything in chemistry, it is not black and white

Honestly though, at a simple level of theory, you just need to say that yes it is chlorinated at the alpha position.

PhMgBr

19:06

@CowperKettle Chemistry's pretty diverse. Even more diverse than language. We have to stick to simplifications because the more we try to explain things the more we have to know and apply different concepts, in multitudes.

Loong

19:33

@orthocresol I have used the statistical factor and mentioned the Hammond postulate in a related answer: chemistry.stackexchange.com/a/26950/7951 :-)

orthocresol

20:11

@Loong I credited you again :D

PhMgBr

Come to think of it, Clayden's pretty inconsistent with its prerequisites too @Ortho

Loong

@orthocresol thank you :-D

orthocresol

Very coincidental question because I was revising radical stuff for organic

PhMgBr

@Loong Kewl answer

Come to think of it, almost every book I've read in inconsistent with its prerequisites.

I'm such an intermediate. -___-

!!flip

Chemobot

(╯°□°）╯︵ ┻━┻

orthocresol

20:16

@PhMgBr I felt like Clayden's introductory chapters were meant to bring any reader up to the level required but I can't remember so I'm not sure. Of course the same textbook will work differently for different people too. In all honesty I haven't read Clayden for quite a while already (the main reason why I open Clayden is actually to cite stuff for answers here because I figure people will likely have access to it). Most of the suggested reading lists here only have specialised books

PhMgBr

Clayden is specialized.

In Oxford talk.

I can't help but realize that the language used in Oxford people's writing is pretty similar to one another.

For instance, I liken much of your writing to Clayden's @Ortho.

orthocresol

Clayden is from Manchester though :D

PhMgBr

Talking in a cool nerd way, with arguments resulting in "mmm, you're right"

@orthocresol Oxford affects minds

orthocresol

It's a style I picked up, I think it works quite well. Judging by the popularity of Clayden at least. I can write in the formal textbook style quite well too

PhMgBr

Note that "mmm" is pretty important and happens in all reactions.

orthocresol

20:19

@PhMgBr global.oup.com/academic/content/series/o/…; These are specialised :P

PhMgBr

Although sometimes to get a hang of what you write nicely and to understand it I have to reread what is written.

Åna

sup

PhMgBr

!!greet/@Åna

Chemobot

Welcome to The Periodic Table @Åna! Here are our chat guidelines and it's recommended that you read them. If you want to turn Mathjax on, follow the instructions in this answer. Happy chatting!

PhMgBr

@Hipp Unicode is broken ^

Åna

20:20

@Chemobot @PhMgBr I think I broke it.

PhMgBr

FIX URGANT ASAP KTHXBYE

Loong

@orthocresol oh, I have one of those

orthocresol

@Loong They cost £20 apiece... Thankfully the library has like 15 copies of every one

Åna

@Chemobot pfff, chat guidelines? Surely not. ;)

orthocresol

Loong

20:27

I have "Fractals in Chemistry".

orthocresol

Ah, that's one I've never touched

PhMgBr

Huh wait. @Åna how are you related to Art?

Are you his/her sock, or related IRL?

Åna

@PhMgBr lil sister

actually related

PhMgBr

Oh aha

Åna

He's next door right now :)

PhMgBr

20:29

ArtsOfCode have manifested SE chats. Read in cool voice. We're doomed. Maybe

ArtOfCode

That I am

(she told me to turn up here, I'm not that much of a ninja)

PhMgBr

i.imgur.com/kmAYjU0.mp4

Åna

wat

Loong

@orthocresol I used it for a poster and a talk when I was a student; that was a long while ago

Åna

Sup @skillpatrol

skill patrol

20:33

chillin, how bout you?

Åna

chattin ;)

PhMgBr

OK @Åna Just broke chat because if I type "A" her name still shows in the ping list or whatever that's called.

@Ana

^ Does that ping?

Oh it does.

Åna

Yes, yes it does

PhMgBr

If this is intentional it's pretty cool.

Åna

No, it's actually my name. I break a surprising amount of systems.

Åna

20:45

@PhMgBr watcha think of my avatar art? I may have borrowed Art's graphics tablet...

PhMgBr

It's pretty cool.

Åna

:)

PhMgBr

@Ortho editing your answer, I think 2nd class header fit in better than 1st class ones.

K now it's easier to gulp

There has never been more truth to a comic:

ringo

23:27

Casually Explained: Absolute Hot

►

Very informative

Loong

!!untable

Chemobot

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