The Periodic Table

Jan

12:03 AM

Oh noes! Plagiarism! D=

paracresol

4:30 AM

@M.A.R. Gee, how generous, but I'm afraid I must decline ;3

CowperKettle

6:32 AM

> P-epoxypiraterone

What does this letter P mean?

ah, it's beta

FineReader made a mistake

Secret

7:33 AM

Negative-X Experiment - Starting A Fire With Water

►

old news but cool

DHMO

9:35 AM

What is the lowest pH ever obtained? I have found something like -3.6 (not the pKa!)

ringo

Only -3.6?

That's surprising

I don't know why but this post that I answered isn't getting bumped to the front page :/

-4

Q: What happens to the molecules of a liquid when it evaporates?

Let's say I spill liquid on some fabric or on a impermeable material like a countertop. Eventually, the liquid stops being a liquid and we say it has "dried", but what happened to the molecules? Did they change phase? How were the conditions for phase change met? Assume we are at room temperature...

I think it's not likely to get seen if it doesn't get bumped

DHMO

9:55 AM

@ringo what is your record?

CowperKettle

10:59 AM

Can a chloride remove a hydroxy group from a molecule and attach itself in the C3 position?

My text describes an impurity molecule in a drug.

This impurity molecule can interact with other impurities

and transmute into other impurities

One of the forms that transmutes into another impurity is called [molecule name] C3 reactive species

Ah, there's a hydroxy group in position C3 in this impurity. So it's unclear how it becomes a reactive species.

DHMO

11:18 AM

@CowperKettle what is a C3?

what is the molecule?

CowperKettle

11:31 AM

@DHMO "Dehydroepiandrosterone C3 reactive species"

The text was written by Italian chemists

So it's not very clear what they mean now and then

Where is C3 on DHEA?

I dunno

The text says that DHEA C3 reactive species reacts with isopropanol

Loong

CowperKettle

@Loong thank you! That was so fast!

M.A.R.

@CowperKettle Loong knows every question you will ask in advance

He just calculates the necessity to answer you and does it

CowperKettle

Can DHEA react with isopropanol in C3 position only by forming a reactive species first?

Should DHEA undergo translation into a reactive species, and only then attach isopropanol there?

Loong

Do you have H+?

CowperKettle

11:39 AM

Do you mean "is the medium acidic"?

M.A.R.

Yes

CowperKettle

If it's acidic, the -OH group will disattach and form water?

and prasterone will be left with a 'reactive interface' sticking out in C3 position?

Loong

@CowperKettle For example. Or can H+ come from some acidic impurity?

CowperKettle

@Loong why not?

During drug manufacture, there might be some acidic impurtiy

Is this a standard way of expressing it, "C3 reactive species"?

I mean, when something has a reactive thingie in C3 position?

Loong

Ok, so R–OH is a poor leaving group, R–OH2(+) is much better.

The resulting "reactive species" is a carbocation.

CowperKettle

11:44 AM

How would we call this OH2(+) in C3 position?

Can we say "prasterone with a carbocation in C3 position"?

I'm trying to phrase this in Russian

(0:

M.A.R.

@CowperKettle Call? What do you mean? OH2 will leave, leaving the positive charge on the rest of what's left

The thing that's left has carbon, and is a cation, hence a carbocation

Loong

@CowperKettle its conjugate acid

CowperKettle

So I can't say "C3 reactive species" because the positive charge will diffuse across the whole molecule

or maybe "a reactive prasterone species with an unoccupied C3"

Loong

Реакции нуклеофильного замещения

Реакции нуклеофильного замещения (англ. nucleophilic substitution reaction) — реакции замещения, в которых атаку осуществляет нуклеофил — реагент, несущий неподеленную электронную пару. Уходящая группа в реакциях нуклеофильного замещения называется нуклеофуг. Все нуклеофилы являются основаниями Льюиса. Общий вид реакций нуклеофильного замещения: R−X + Y− → R−Y + X− (где Y− анионный нуклеофил) R−X + Y−Z → R−Y + X−Z (где Y−Z нейтральный нуклеофил) Выделяют реакции алифатического (широко распространены) и ароматического (мало распространены) нуклеофильного замещения. Реакции алифатического нуклеофильного…

M.A.R.

GAAAAA

CowperKettle

11:48 AM

@M.A.R. I see. The tiny leaving carbocation will be the reactive species, not the DHEA

M.A.R.

@CowperKettle The water is considered the thing that's leaving. The carbocation is bigger and stays behind

CowperKettle

Carbocation stays attached to the DHEA?

M.A.R.

Carbocation is DHEA's son

Well, I got here in the middle of the conversation

So probably

It's like DHEA, but without a couple of atoms

Loong

DHEA + H+ -> carbocation + H2O

(if we assume an sn1 pathway)

CowperKettle

Can we say "a carbocation is formed at the C3 position"?

Loong

11:54 AM

yes

Do you see inversion of the C3 carbon or racemization?

CowperKettle

inversion of the C3 carbon?

This is the presumed impurity formation scheme

The text says that "in order to get triflated, prasterone needs some isopropanol to be present'

I don't understand what "prasterone C-3 reactive species" is

Loong

@CowperKettle ok, you see that the C3 carbon has S stereoconfiguration in the picture

Do you really get only S or both R and S ?

CowperKettle

I don't know; the text is silent on that count

Stereochemistry

Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. An important branch of stereochemistry is the study of chiral molecules. Stereochemistry is also known as 3D chemistry because the prefix "stereo-" means "three-dimensionality". The study of stereochemistry focuses on stereoisomers and spans the entire spectrum of organic, inorganic, biological, physical and especially supramolecular chemistry. Stereochemistry includes methods for determining and describing these relationships...

Is this somehow related?

M.A.R.

Yep

Loong

If the "C3 reactive species" really is a carbocation, you should get both R and S (probably not 50:50).

CowperKettle

12:01 PM

I thought that "S configuration" can only be said in regard to the whole moleucle

I never knew a single carbon inside a large molecule can be in "S configuration"

Is "S" related to "chirality"?

Loong

yes

CowperKettle

I only had a short reading of that a year ago (0:

Is there a page describing how a single C3 carbon can have "S configuration"?

orthocresol

@ringo If a post is downvoted heavily, it won't appear on the front page.

Loong

@CowperKettle DHEA is (3S,8R,9S,10R,13S,14S)-3-hydroxy-10,13-dimethyl-1,2,3,4,7,8,9,10,11,12,13,14,15,‌16-tetradecahydro-17H-cyclopenta[a]phenanthren-17-one

So it has six stereocentres.

CowperKettle

Ah! Thank you! So relative to each stereo-centre, if will concentrate our attention on it only, we can have either an S- or an R-form of the whole molecule?

Loong

12:07 PM

Правила Кана — Ингольда — Прелога

Правила Кана — Ингольда — Прелога (иногда, правило последовательности, правила старшинства) — набор правил, регулирующих в номенклатуре ИЮПАК старшинство заместителей у хиральных атомов и двойных связей. В дальнейшем определённое старшинство заместителей используется для присвоения стереоизомерам обозначений абсолютной конфигурации: R/S- или E/Z-. Использование набора таких обозначений перед систематическим названием соединения позволяет уникальным образом описать конфигурацию его молекулы. Правила старшинства были опубликованы Р. С. Каном, К. К. Ингольдом и В. Прелогом в 1966 году. Правила Кана…

M.A.R.

@Loong No Russianing in this chat

Esp. the large scary oneboxes

Loong

@M.A.R. This ~~election~~ chat room was hacked by Russian hackers.

CowperKettle

@Loong I see! I now wonder how this relates to reactive species (0:

Loong

@CowperKettle If the "C3 reactive species" really is a carbocation at C3, it would lose the stereoconfiguration at C3.

(8R,9S,10R,13S,14S)-10,13-dimethyl-17-oxo-2,3,4,7,8,9,10,11,12,13,14,15,16,17-te‌tradecahydro-1H-cyclopenta[a]phenanthren-3-ylium

CowperKettle

@Loong because instead of the hydroxyl group there will be nothing there?

Loong

12:12 PM

yes, only a positive charge

CowperKettle

> If the "C3 reactive species" really is a carbocation, you should get both R and S (<<< because the Isopropanol will attach randomly and generate both?)

Loong

yes, so you would get (3S,8R,9S,10R,13S,14S)-3-isopropoxy-10,13-dimethyl-1,2,3,4,7,8,9,10,11,12,13,14,‌15,16-tetradecahydro-17H-cyclopenta[a]phenanthren-17-one as well as (3R,8R,9S,10R,13S,14S)-3-isopropoxy-10,13-dimethyl-1,2,3,4,7,8,9,10,11,12,13,14,‌15,16-tetradecahydro-17H-cyclopenta[a]phenanthren-17-one

CowperKettle

ah, it's so clear with these neat names!

Loong

not exactly randomly since the "reactive species" is still chiral

CowperKettle

although they look like walls of text to me (0:

Loong

12:16 PM

you only need to look at position 3

M.A.R.

@CowperKettle They're like computer 0s and 1s. There's a lot of science behind it, but merely sighting gives you nothing but BS

CowperKettle

It still could be a carbocation because the schematic of the chem reaction is given for example purposes only.

To prove that this reaction is impossible in this particular manufacturing process

Thank you for refreshing my chem knowledge somewhat

I'm still unsure how to translate the term [molecule name] C3 reactive species to Russian, which was my goal.

(0:

BBL!

DHMO

4:32 PM

9

Q: Carbometalation of alkenes

Why aren't alkenes readily carbometalated? For example, carbocupration of an alkyne produces and alkene. Why does it stop at the alkene level?

organic-chemistry reaction-mechanism transition-metals reactivity organometallic-compounds

Can anyone correct the image?

At the bottom-left corner, it should say $\ce{C2H5CuMgBr2}$ where it says $\ce{C2H9CuMgBr2}$ instead.

@orthocresol @Loong @Jan ^

Hippalectryon

5:18 PM

@DHMO done, in the edit queue

DHMO

@Hippalectryon thanks

@Hippalectryon wait, why do you have such a low rep?

I thought you're the one who made chemobot lol

Hippalectryon

I am :D

DHMO

then how come lol

Hippalectryon

I'm just not very active on the main site :-) I prefer chatting here

DHMO

I see

Hippalectryon

5:20 PM

I'm not confident enough to answer most questions

khaverim

7:23 PM

anyone here use Orca? just wondering (for now..)

DSVA

I'm using NWChem and G09 but no Orca

M.A.R.

8:27 PM

Yo @Mart the Star Wars fan starwars.com/news/…

Mithoron

9:00 PM

-5

Q: Hydrocarbons aromatic help with question stuck

hydrocarbons armomaric. Need help with a single question to move onto another lesson. Please help.

organic-chemistry

Essence of h-w dump :D

M.A.R.

@Mithoron Should we push, or pull, to un-stuck it?

I'm stuck

Mithoron

@M.A.R. Yeah, heard it already

@M.A.R. :D

Loong

And the actual question is just

I am disappointed.

Mithoron

Bwahaha :D

I didn't bother to check his link :D

BTW Last Jedi is like least original title possible for the new movie

DSVA

god, wasted a whole day because others are terriblely stupid...and I still didn't solve the problem-.-

Mithoron

9:20 PM

@DSVA What problem?

DSVA

@Mithoron we got a nice UPLC which is intended as routine instrument. But some colleagues are misusing it for stupid stuff, somehow managed to introduce a reservation system to a routine instrument and pretty much make it impossible to just get a quick MS run.

you go there, have to plug in all detectors, get rid of leaks, put in a column, wash the PDA for hours until you give up and bypass it and in the end you even notice that the water used by the system has two phases

LC, not MS, I needed just fluorescence

DHMO

11:48 PM

@orthocresol Could you tell me what is wrong with my mechanism?

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