The Periodic Table - 2016-10-19 (page 3 of 3)

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pentavalentcarbon

9:00 PM

You looking for an explanation for "more amphoteric"?

Gosh, that's starting to sound like an empty threat now.

Well, not me. Dissenter is...

pentavalentcarbon

(I know)

Amphoteric just means it possesses the ability to react as an acid and as a base...

So, "A is more amphoteric than B" is kinda ambiguous.

pentavalentcarbon

I barely remember the difference between Bronsted/Lowry and Arrhenius

One sec

Lmfao

pentavalentcarbon

9:01 PM

need to recall an example every time

Uploading image rn

!!greet/Zhe

Welcome to The Periodic Table Zhe! 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!

pentavalentcarbon

The reactions on Wikipedia are neat, but why do some of them need water when reacting with a base? Just to balance things?

In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid as well as a base. The word is derived from the Greek word amphoteroi (ἀμφότεροι) meaning "both". Many metals (such as copper, zinc, tin, lead, aluminium, and beryllium) form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation states of the oxide. Metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides. Amphoteric oxides include lead oxide and zinc oxide, among many others. One type of amphoteric species are amphiprotic molecules...

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9:03 PM

@pentavalentcarbon Ya pretty much.

pentavalentcarbon

Also I could never have predicted a lot of these, like hydroxides reacting with hydroxides...never learned that

yo. wow, this place is happening

Did we settle the score on "more amphoteric"? (I had trouble finding the chat button, and then didn't know which chat to go to...)

@Zhe Seems like you figured it out. This is the main chat room for chem.

the question in question is at the bottom of the pic i uploaded

As I said earlier this is a freshman chemistry lab

This is a very ez question /s

From the pic, it seems like it is looking for a qualitative explanation?

Mod powers. Heh

9:08 PM

@Dissenter Well, it changes the problem, sort of

pentavalentcarbon

Ok, this is a little confusing to me, but my intuition says that if one has both a larger $K_a$ and $K_b$ than the other, then it's "more amphoteric".

If I even remember what those rate constants mean

It looks like the question should be which hydroxide is easier dissolved in NaOH

Or rather dissolves in NaOH at lower concentration

You mean equilibrium constants?

@Mithoron yes, i didn't see it as that b4

QQ. It's been ages since I've done coordination chem: when you write OH_{x} twice, is this inner sphere versus outer sphere?

What do you mean when you write (OH) twice?

One of them is an (OH2) the other is (OH)

9:14 PM

Cu(OH)_{4}(OH)_{2}

Oh...

Nm then

So, so I think this is just a periodic trends problem...

The hydroxides are roughly equally basic

So, it just comes down to Lewis acidity of the metal?

Cu(OH2)_4(OH)

Cu(OH2)4(OH)2

@Dissenter I commented that your values are misleading 'cause Cu(OH)2 doesn't dissolve well in NaOH, but acidity of hydrated cation is higher

Why

My source says Cu2+ hydrated ion has a Ka of about 10^-6

I mean 10^-7

Zn2+ hydrated ion has a Ka of about 10^-10

No one wants 500 free points??

@Dissenter It only means Cu(H2O)OH+ is less basic than analogous Zn cation

pentavalentcarbon

@Dissenter I are dumb, forgive us

9:23 PM

Are you sure about the Cu2+ and Zn2+ Ka values?

Based on periodic trends, I would've guessed that the zinc hydrate is more acidic...

@Dissenter We may get to this, but you'll probably need to heavily edit your question

@Zhe Hmm, I guess it should be

I pulled the Ka values from the reference table in the lab manual

I forgive we, for us is forgiving

@Dissenter screenshot of the table?

@Zhe Is that just based on charge density?

Z_{eff}?

9:26 PM

Yeah, same thing.

You can type maths here as well, just need to put $$ around it as usual.

$Z_\mathrm{eff}$

Sweet!

Oh, I don't see it interpreted that way...

Do I need to turn on some mode?

pentavalentcarbon

Yes.

You need the ChatJax bookmarklet: gist.githubusercontent.com/berquist/…

Hello :)

Thanks penta.

@9-BBN bringing back bad memories of grad school :)

9:28 PM

Now, I'm not really paying much attention to the discussion, but are there possibly some Jahn-Teller effects going on with the Cu(II) aquo ion that affect its acidity?

You can't use charge density

pentavalentcarbon

It does love to exchange its axial ligands.

@Zhe Ugh ? sorry

@9

@9-BBN no worries. I got out :)

The book actually lecture students about the shortcomings of the charge density model in predicting the acidity of transition metal ions

pentavalentcarbon

9:29 PM

Btw @Zhe I have to go but sometime I would love to bug you about your job and location in your SE profile...

I don't understand what you mean ^^

The electostatic model fails for transition metals that are not isoelectronic with noble gas elements

@pentavalentcarbon SGTM

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Ideas ?

Acetylide

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9:32 PM

You answer faster than your shadow ^^

I would try to somehow get to cyclohexanone, then add acetylide and eliminate H2O.

@orth

@orthocresol

@9-BBN scale?

Can you do a Sonogashira coupling?

scale of what?

Scale of reaction

9:33 PM

Thanks orthocresol and dissenter

I would not attempt to do Sonogashira on like 50-g scale, but for something small...

This is only on paper to train myself but I have not always the solutions ^^

@9-BBN Based on your username, I have to recommend a cross coupling reaction :)

Sonogashira coupling

The Sonogashira reaction is a cross-coupling reaction used in organic synthesis to form carbon–carbon bonds. It employs a palladium catalyst to form a carbon–carbon bond between a terminal alkyne and an aryl or vinyl halide. R − ≡ ...

I know it, I just learnt it few days ago :)

Stille, sonogashira, ...

Many Ph.D.'s were sacrificed to bring you this chemistry

3

9:36 PM

Lol

But I used 9BBN for hydroboration in some cases if i remember well

Alchemists brought me the undergrad lab i'm teaching

I know it too

I will do Suzuki in lab experiment in a week

It will be fun ^^

The goal of the experiment is to work in group of 12 and test some parameters

The morning and do it with a lot of product with the better we found the morning on the afternoon ^^

What are you coupling?

Hum let me check

9:41 PM

Barcelona
4 - 0
Man. City

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@zhe

user image

Last four lines is what we can test

What do you think about the difference between PdOAc2 and PdCl2 ?

shrug Although I worked on cross couplings for 5 years, I never bothered to actually learn about the idiosyncracies

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Banana extract is a ligand? Wow...

@orthocresol P.R. Boruah, A.A. Ali, B. Saikia, D. Sarma Green Chem. 2015, 17, 1442

9:47 PM

You have to wonder how on earth people noticed this sort of thing.

@zhe what "idiosyncracies" are ?

@9-BBN Well, the paper says that with banana extract and Pd(OAc)2, they got 96% yield in 15 min..

Yeah and maybe 1 min with a microwave ? :P

I cannot open the file

Of the ref

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Good to see ppl are actually using microwave these days

9:50 PM

We are not at school but our teacher teach us very well and gives a lot of examples

@9-BBN catalyst counter ions, etc. Stuff-that-you-need-to-optimize-for.

This is the only intersting teacher of this semester ...

@Mithoron I think that throws my rationale out the window...

@Zhe ok but what does in means then because I just know this in theory but I don't really figure out on how it will works

And after the experiment pyrolisis to finish

@9-BBN Depending on how well expressed the coupling moieties are, you may or may not have to alter the published reaction conditions

Generally authors optimized for the examples in their table

See example from orthocresol above

9:57 PM

Yeah

But if you veer away from those substrates, you might need to do additional optimization

In general I make product that I can sell to sigma aldrich

Cool

I cannot change what there is in the pdf of experiments

Even if it is a good idea :(

Also, I only just noticed "water extract of banana" O_o

9:59 PM

Yeah pretty good

I'll do that

I eat a banana per day for years now

!!daily

daily :)

I eat a banana daily for years *

Is this better?

No, I was testing chemobot.

It turns out that the !!daily command is only for room owners, not moderators. Oops.

!!daily

OK lol

all right time to commute home. catch you all later

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Oct '1619

The Periodic Table

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