The Periodic Table

10:58 AM

0

Q: Consider the vibrational mode that corresponds to the boat-like bending of a benzene ring. Is it (i) Infrared active? (ii) Raman active?

This question was asked in an assignment in my college. So we've been taught how to distinguish functional groups by IR and nothing much. So I request someone to please explain the answer in detail.

I think that this question has great potential for a canonical answer (read: me regurgitating my notes) if it is broadened to "How can one tell if a vibrational mode is IR- or Raman-active?"

It is just a shame that it is so homework-ish right now.

I don't blame OP for it, he does not seem to have the prerequisite knowledge to determine how vibrational spectra work

We already discussed the rose bengal question in great detail.

I feel that this is really the same thing, just at a lower level, one can expect OP to search on Google (and searching for this will of course yield a lot of information) but I think it is not fair to expect them to self-study molecular symmetry if they are in high school.

and without knowledge of symmetry, most of the hits are presumably incomprehensible

I am glad that it has not been closed yet.

user116211

@orthocresol So, if you think it would be beneficial to have a canonical post on the topic, why not propose it at the meta? I'm sure the community would approve it; and then the the post can be created. It would help in the future.

orthocresol

I might edit it and post an answer if I feel up to the task

But it is dinner time now :)

user116211

@orthocresol Okayish; eat healthy ;))

orthocresol

Just rambling, really

I don't know what my point is. I think maybe the point is if we broaden homework questions some of them can be of great use

even the "trashy" "dumpy" homework questions, which this actually is

user116211

@orthocresol See, we have no problem with homework; we have problem with those which totally lacks conceptual query.

orthocresol

11:09 AM

mmhmm

user116211

But this one, I deem, might have some implicit conceptual query.

orthocresol

ye, +1 to that

user116211

Meanwhile, at Physics, there is a long on-going discussion on how to make the HW close reason more explicitly clear.

user116211

Also, we are thinking of changing the name "Homework" as it sounds ambiguous at the first place.

orthocresol

that has always been an issue here, I think

lots of comments with "Hi, please check the homework policy" are met with the "Bbbbut this isn't homework" response

user116211

11:13 AM

@orthocresol this is really bothering.

user116211

Anyways, @ortho, have your dinner; I'm going back to my studies ;)

orthocresol

I'll go and check out what you guys are discussing

Haha alright. All the best

user116211

@orthocresol Wait...then, let me link you some recent posts on this:

user116211

in The h Bar, 3 hours ago, by DanielSank

Physics - Stack Exchange is not a problem solving or review service. If you have a question about a specific problem, narrow it down to the specific concept that is giving you trouble, show effort to address the issue yourself, and ask about that. If the question can be answered by a quick Google search, it's off topic.

user116211

^^^ There is no mention of Homework.

user116211

11:19 AM

26

Q: Should we rename the homework policy?

The homework policy is a constant source of confusion for new (and sometimes established) users. We see this confusion, for example, when users respond to closures based on the homework policy by defending their post with "This is not a homework problem", or similar. Some users have even been con...

discussion tags questions homework

orthocresol

@MAFIA36790 Thanks, much appreciated.

user116211

You can also look into this:

user116211

14

Q: Replacing the homework policy 1b: what is our scope anyway?

Abstract: Analyzing the data from the last replace-the-homework-policy question was inconclusive. So back to the drawing board, or really back to our starting point: what kinds of questions do we really want to see closed? In particular, what are better ways to characterize our actual reasons for...

discussion scope homework insufficient-effort

DEAD

12:20 PM

@Loong Mhm

Loong

@DEAD, oh, you are alive :-)

@Loong I am?

@DEAD `(.•.)´

Yo, Ortho.

where have you been?

12:27 PM

It seems you have (mis)used my absence and raided the star board.

@orthocresol Tabriz

I wanted to recover after a stream of nihilism and apathy running through my veins after meta.ELL kept being meta.ELL.

orthocresol

Hehe

DEAD

Anything exciting happened while I was gone?

Well, except you and Penta conquering the star board.

getafix

@orthocresol I agree with you. I wanted to right an answer along similar lines for IR/Raman question, but held back..

P.S I think the guy is a university student..

orthocresol

@DEAD Not much, but I think the homework experiment is looking good

DEAD

Oh?

Well, I prolly gotta go. I'll take a look at the stats after coming back.

At least, there seems to be a less dramatic and more focused meta.

Oh noes! Jan has taken over the meta . . . I WANT MY META BACK

Jan

12:49 PM

@Dead you seam to have changed to some @Rubredoxin or other biology?

Welcome back. I had gotten a tad worried after I saw yesterday that you had been offline for what seemed forever. (Ten days or so.)

user34388

Hi everyone

On the following page, it is claimed that there exists a cubic metaboric acid (HBO2)n. What is its formula and structure?

Metaboric acid

Metaboric acid is the name for a family of inorganic compounds formed by the dehydration of boric acid. Metaboric acids are colourless solids with the empirical formula HBO2. There are three forms of metaboric acid, all are white solids. One form of metaboric acid is molecule, and the other forms are polymers. == Preparation == Heating of boric acid at 80-100 °C releases water to give orthorhombic metaboric acid: 3 B(OH)3 → (BOH)3O3 + 3 H2O This form is molecular, consisting of discrete trimers. This molecule has C3h symmetry and forms a sheet-like structure, similar to that of boric acid itself...

orthocresol

1:04 PM

rubisco, world's best enzyme

user34388

@orthocresol Could you help me with my answer that already got 2 downvotes?

-2

A: What is lithium pyroborate?

Lithium pyroborate ($\ce{Li2B4O7}$) is the salt of lithium ($\ce{Li}$) and pyroboric acid ($\ce{H2B4O7}$). Nomenclature The prefix ortho- designates an acid with the maximum number of hydroxyl ($\ce{OH}$) groups. For boron ($\ce{B}$), orthoboric acid is $\ce{H3BO3}$ (also written as $\ce{B(OH...

orthocresol

i can't

i know nothing about this

user34388

What do you think is missing? @orthocresol

orthocresol

appropriate references

user34388

@orthocresol right, thanks

orthocresol

1:07 PM

i cannot pass judgment on whether the structures are right or wrong

but i know that if i see that it is taken from XYZ textbook, then i will believe that it has some credibility

user34388

@orthocresol The problem is I just replaced Na+ with Li+ in some structures I find

orthocresol

then, perhaps, don't answer

if you are not sure of it

or leave it as a comment

user34388

@orthocresol I don't find any reason to assume that Na+ and Li+ would bring a different pyroborate structure...

orthocresol

"I found this structure of sodium pyroborate here: <LINK>"

Jan

Request to @RuBisCO: Please make your capitalisation appropriate 8D

user34388

1:11 PM

@orthocresol ok, thanks

Jan

@orthocresol Only because cherry trees wouldn’t blossom without it ;p

user34388

@orthocresol Is it better now?

orthocresol

not sure how reliable these are, but i did not downvote anyway

i downvote if it is wrong, but i cannot tell, i do not know much about borate structures

@Jan actually, rubisco is a really slow enzyme. the best enzyme is probably something like carbonic anhydrase :D

Jan

@orthocresol Actually, 'the best enzyme' is primarily opinion-based ;p

orthocresol

ah, but it is an opinion based on facts

Voting to reopen

user34388

1:18 PM

@orthocresol I must be stupid, lithium tetraborate is on ChemSpider

!!img/B4Li2O7

Chemobot

user34388

@orthocresol yay, the third downvote, my answer is now in grey

Jan

@Chemobot Somehow I don’t trust that structure …

user34388

@Jan Can you help me with my answer that just got its 3rd downvote?

Jan

@user34388 Delete now, and you will receive a shiny, virtual, beautiful, bronze-coloured badge!

orthocresol

1:20 PM

always a healthy dose of skepticism when it comes to borates

user34388

-3

A: What is lithium pyroborate?

Lithium pyroborate ($\ce{Li2B4O7}$) is the salt of lithium ($\ce{Li}$) and pyroboric acid ($\ce{H2B4O7}$). Nomenclature The prefix ortho- designates an acid with the maximum number of hydroxyl ($\ce{OH}$) groups [reference]. For boron ($\ce{B}$), orthoboric acid is $\ce{H3BO3}$ (also written ...

orthocresol

in fact anything with boron is just complicated rubbish

user34388

@Jan no badge received?

Jan

@user34388 I can’t, sorry. But a boron connected to only two oxygens and nothing else rings alarm bells.

user34388

@Jan so you mean both of my structures are wrong?

@Jan I think you confused it with this badge

orthocresol

1:22 PM

why would anybody be tricking you

@Jan i haven't gotten peer pressure yet..

user34388

@orthocresol Nope, when did I say that?

orthocresol

@user34388 come on, that's not cool

Jan

@user34388 No

@orthocresol Neither have I. My answers tend to never get less than -2 score, no matter what I do =C

user34388

Whatever

orthocresol

@Jan HI I AM FROM SAME CLASS, PLS ANSWER I HAVE TEST TOMORROW.

Jan

1:25 PM

I personally think the cyclic structure sounds reasonable.

user34388

@Jan do you mean both of my structures are wrong?

but the first structure is the commonly cited one

Jan

But the only boron compounds I know anything about are tetrahydridoborates and dialkylboron chlorides.

orthocresol

actually, that won't even get to -3, chances are it will be deleted before that happens

user34388

@Jan what is a tetrahydridoborate?

Jan

@user34388 $\ce{BH4-}$

user34388

1:26 PM

@Jan I thought that's a tetrahydroborate

But whatever

Now what do you think caused the -3 votes?

orthocresol

@Jan oh, you surely know more than that :) BH3 and other boranes, like 9-BBN...

Jan

@orthocresol Actually, no, I refuse to claim knowledge on boranes, except for the 2-electron-3-centre bond in B2H6. And yeah, I should have included dialkylborohydrides in the list above xD

orthocresol

:) H3B-SMe2 or OEt2

user34388

@Jan Which three centres?

Jan

@user34388 B-H-B.

user34388

1:30 PM

@Jan so it is not symmetrical?

-6

Q: Structure of dinitrogen trioxide

What is the structure of $\ce{N2O3}$ My attempt: $$O=N-O-N=O$$ Also in my structure atoms are getting octet. Then still it is not correct. Can I know where I am going wrong? What is the correct structure?

molecular-structure

This is ridiculous. Does not google and hates stack exchange for saying that.

Jan

@user34388 Yeah, it is. That’s the point.

@orthocresol The CBS-catalyst ;)

user34388

@Jan it is symmetrical??

but if one B-H-B participated in a 3c2e bond then what about the other B-H-B?

orthocresol

@Jan oh wow, that's exotic. I haven't actually learnt that.

both are 3c2e

user34388

??

alright, I'll just accept it then

Jan

@user34388 What @orthoseal said.

Loong

1:32 PM

@orthocresol The \, before dx is also mentioned in the AMS guide: ftp.ams.org/ams/author-info/documentation/howto/mit-2.pdf

user34388

@orthoseal I'll be calling you that from now on

Loong

However, I don’t link to that AMS document on meta because it contains some things that would be not correct according to international standards.

Jan

Both B-H-B fragments are 2-electron-3-centre bonds.

orthocresol

@user34388 yeah but you don't know how to ping me with that.

Jan

@user34388 You need to be cool to ping @orthoseal with that name x3

user34388

1:33 PM

@orthoseal I just did

orthocresol

Nope you didn't

@Loong I put in my \,'s religiously now!

2

user34388

@ortho seal yes I did

orthocresol

Nearly there but not quite

user34388

Hey, I did ping you. Your message is colored grey in the background when I mouseover my message.

Jan

@user34388 What was your trick? Ctrl-c, ctrl-v? x3

hBy2Py

1:37 PM

@user34388 His name is orthocresol, not orthoseal

user34388

@Jan You mean I copied from you? No, yours didn't ping

@hBy2Py it's a joke

hBy2Py

I know, but he's not gonna get pinged that way.

(I may have arrived late to this discussion... :-D)

user34388

@hBy2Py I did ping him. You can mouseover my message.

Jan

@hBy3Py yes he is =O

hBy2Py

Oh, man, really?

orthocresol

1:38 PM

@hBy2Py It does ping me, actually

hBy2Py

That works?

I don't like that

Creepy SE chat black magic.

user34388

orthocresol

@hByHiLookThisPingsYou.

hBy2Py

Indeed

user34388

@orthoseal Does this ping you?

orthocresol

1:39 PM

:)

hBy2Py

Ok, I'mma just shaddup now and leave you all to your conversation.

user34388

Strange.

orthocresol

@hBy2Py Whatcha up to?

Jan

@user34388 I just thought how f*king wide is your desktop? =O

user34388

@orthoSeal Does this ping you?

Strange.

hBy2Py

1:40 PM

@orthocresol Just getting the day started. Some COMSOL work, then probably working on a proposal.

user34388

@Jan 1600x900

orthocresol

@hBy2Py Ah, all the best, the day's actually ending soon here..

hBy2Py

@orthocresol Good day?

user34388

@hByTesting

black magic

hBy2Py

@user34388 Did ping

orthocresol

1:41 PM

@hBy2Py Goodnight :)

hBy2Py

haha

user34388

@hBy2Py alright

orthocresol

Well, not much, it is the hols now so I am just doing nothing

Jan

@hBy2Py Is it bad if I read Comsomol rather than Comsol?

hBy2Py

@Jan ... maybe?

getafix

1:46 PM

Well if you really want peer pressure that bad, right a BS answer to some random post and then get three people on the chat to downvote it and then delete it immediately

before it is removed by a mod

user34388

Would anyone want to construct a MO for diborane, lol

!!img/diborane

Chemobot

getafix

No chembot no

hBy2Py

!!doubleflip/Chemobot

getafix

@user34388 pretty sure you can find one online

Chemobot

1:47 PM

ʇoqoɯǝɥƆ︵╰(゜益゜)╯︵ Ɔɥǝɯoqoʇ

orthocresol

!!img/Rover's Dog Shampoo

Chemobot

getafix

go home chembot you're drunk

3

Jan

@getafix Nah, I want legitimate badges.

getafix

lol..then start writing shit answers lol

hBy2Py

1:48 PM

ortho-hydroxytoluene... what?!?

user34388

@hBy2Py orthocresol.

Jan

I've tried it with debateable ones, but as I said, they never exceed -2 =C

orthocresol

@hBy2Py cresol is the common name for hydroxytoluene

user34388

getafix

@Jan guess you're just that good

orthocresol

1:49 PM

@Jan Your profile doesn't seem to have anything below 0

hBy2Py

@orthocresol <smacks forehead> of course.

But why did it return that as a result from "Rover's Dog Shampoo"?

Jan

@orthocresol Not on chem, nope ;)

orthocresol

@Jan Ah, of course..

Sep 11 at 13:34, by Loong

@user34388 It's in the non-validated list for 2-Methylphenol on Chemspider http://www.chemspider.com/Chemical-Structure.13835772.html :-(

user34388

@getafix What the hell is that energy rise of a non-bonding orbital?

getafix

@user34388 what?

hBy2Py

1:52 PM

@orthocresol I ... just ... uh.

user34388

@getafix See the picture above

!!img/Franklin Cresolis

Chemobot

orthocresol

@hBy2Py It's so ridiculous it's funny...

user34388

!!img/202-423-8

Chemobot

user34388

1:54 PM

Let's use those numbers to !!img/ from now on

Chemobot

No result found.

hBy2Py

@user34388 Well, yeah, the CAS number is sensible

getafix

the cresols are taking over

orthocresol

@user34388 if you want to test out, just use this chat.stackexchange.com/rooms/38172/chemobot

user34388

!!img/1,2,3,4-tetradeuterio-5-deuteriooxy-6-(trideuteriomethyl)benzene

Chemobot

1:54 PM

user34388

@orthocresol I wasn't testing out

Can anyone explain that name to me?

Jan

@user34388 That should have been the fully deuterated cresol. I.e. D instead of H at every H.

hBy2Py

@user34388 Yeah, that figure isn't correct for that name.

user34388

@Jan right, thanks

orthocresol

shorter name: perdeuterated o-cresol..

user34388

1:57 PM

Why is this closed as homework but this not?

orthocresol

Now it is.

user34388

@orthocresol ... I was just about to answer

Jan

@user34388 Some questions just happen to have a greater experimentally measured half-life …

Loong

@user34388 This question was asked by new user; so it automatically appears in a review.

user34388

@Loong I see, thanks

Jan

2:07 PM

@Loong But even if they aren’t new, someone typically opens it, flags or votes to close, and 15 minutes after posting it appears. (My observation.)

Wow, question just posted, already upvoted =O

Also, I managed to cite ~~Cpt.~~ Barbosa =D

user34388

@Jan When I see a question posted by a high-rep I just upvote before even reading it

Loong

@Jan Some users don't flag because they want to vote in a review in order to get a badge.

And reading the title How many grams can be obtained from kg, I expected an even worse question. ;-)

3

user34388

2:52 PM

-2

A: What is lithium pyroborate?

Lithium pyroborate ($\ce{Li2B4O7}$) is the salt of lithium ($\ce{Li}$) and pyroboric acid ($\ce{H2B4O7}$). Nomenclature The prefix ortho- designates an acid with the maximum number of hydroxyl ($\ce{OH}$) groups [reference]. For boron ($\ce{B}$), orthoboric acid is $\ce{H3BO3}$ (also written ...

three downvotes and an accept mark...

By the way it is +1/-3

Jan

@Loong So did I ;)

@Loong I could stop waiting for the review queue but I didn’t … ^^'

Loong

@Jan Well, you already have your Close Votes Steward badge. ;-)

Jan

@Loong What I was implying ;)

CowperKettle

3:27 PM

Good evening all!

@Loong 1024, if you're a programmer

user34388

@Jan is there dimers of EO_x^n- which contains a O-O bond other than S2O8^2- ?

Loong

@CowperKettle 1000 ± 100 if you are an engineer

4

CowperKettle

(0:

> The development of electrospray ionization for the analysis of biological macromolecules[4] was rewarded with the attribution of the Nobel Prize in Chemistry to John Bennett Fenn in 2002. (cool)

user34388

@others you can answer my question as well

Jan

@user34388 I don’t know any off the top of my head.

user34388

3:34 PM

@Jan thanks

CowperKettle

If I'm describing an electrospray ionization unit, do I say "electrospray needle voltage is 4000 V" or "electrospray capillary tube voltage is 4000 V"?

or is it "emitter" or "tip"?

In Russian, it is "Voltage at the spraying capillary", but that might be different in English

Loong

@CowperKettle Do find anything here? dx.doi.org/10.1351/PAC-REC-06-04-06

CowperKettle

3:49 PM

@Loong Thank you!

Loong

> 159. electrospray needle, electrospray emitter

CowperKettle

Great!

Loong

> Narrow bore tube from which highly charged droplets are emitted in electrospray ionization.

CowperKettle

I thing the users would have understood even "capillary" but since "needle" is the conventional term, it's even better

That's odd

> 249,00 € / $374.00 / £187.00*

But it permitted me to download it for free

I wonder if there's a Russian translation of this glossary. That would have been ideal

CowperKettle

4:12 PM

Now my text says: "Voltage at the transporting capillary"

D'oh

The IUPAC document probably has it under some other name

CowperKettle

4:29 PM

"nebulizer capillary"?

I'm not sure

Rubisco

5:13 PM

@Jan I deliberately use wrong capitalization.

The most primary reason is to annoy you.

Another, marginal reason is to have a name-like . . . name.

user116211

@Rubisco: o/

Rubisco

Hey

CowperKettle

I wonder if there's a Wiki article on such "concentrators"

Are they widespread?

Maybe it's the "centrifugal evaporator"?

Centrifugal evaporator

A centrifugal evaporator is a device used in chemical and biochemical laboratories for the efficient and gentle evaporation of solvents from many samples at the same time, and samples contained in microtitre plates. If only one sample required evaporation then a rotary evaporator is most often used. The most advanced modern centrifugal evaporators not only concentrate many samples at the same time, they eliminate solvent bumping and can handle solvents with boiling points of up to 220 °C. This is more than adequate for the modern high throughput laboratory. == Design == A centrifugal evaporator...

Rubisco

@CowperKettle concen-what

CowperKettle

> We invented the centrifugual vacuum
concentrator and decades after this
breakthrough innovation, scientists
around the world continue to use
Thermo Scientific Savant SpeedVac
concentrators to remove solvents from
their samples.

(from the PDF)

So it must be "evaporator"

Maybe

Rubisco

5:27 PM

@CowperKettle Hey, that doesn't rhyme.

CowperKettle

@Rubisco That's PDF formatting. I'm too tired to write a poem about vacuum evaporators now

> If solvents remove from your samples you wish,
Say, some bicarbonate from your Petri dish,
Take our concentrator, don't ever be shy
[compose the rest]

Rubisco

Get some sleep, Shakespeare.

CowperKettle

No, I'll read some more

> Before applying the samples on the target .. (what is "target" in mass spectrometry? The English word must be different from the Russian one)

CowperKettle

5:58 PM

> Prior to their application to the target we added 10 µl of 1% trifluoroacetic acid solution to each sample.

How generally are those samples loaded into a mass spectometer, I wonder

Shokhet

9:08 PM

Hey. I'm working through a pre-lab in my manual right now. In the procedures, I'm told that I'll need to "gently shake the jar or stir it with a spatula before weighing," and "be prepared to explain to your instructor why this step is important." I don't recall anything from the lectures or the book about why that might be important. Unfortunately, my Googling skills are not powerful enough to solve this one :/ ...anyone have any ideas?

...also, I'm not really used to this SE site...would the above be a good question to post on the main site?

...to clarify; the above is an excerpt from the lab manual instructions for an experiment called "Separation of Mixture," where the mixture involved is NH4Cl + SiO2 + NaCl. The step I quoted from is referring to the mixture of all three items, before they're weighed on an analytical balance before we start separating things.

Buttonwood

11:04 PM

@Shokhet Likely the first thing prior to the separation of the three compounds is to set up properly the experiment. Like getting the jar for the mixture, and the three components. The experiment does not ask you "to remove a layer of NH4Cl" that is on top of a layer of SiO2 (or NaCl).

Indeed, if the three components are well mixed with each other, you'll have grains of SiO2 side by side to crystals of NaCl and NH4Cl. Then it is up to chemical or/and physical methods divide the mixture again.

In tune of sequential questions like: Is SiO2 soluble in water (think about sand, often SiO2 is a major component of sand)? Hm, no. yet the two salts. So addition of water generates a slurry, once you filter the suspension, you get the SiO2 off ( -> filtercake); the salts stay in solution ( -> filtrate).

Shokhet

11:35 PM

So what you're saying, @Buttonwood, is that it's not important to shake the mixture up before it's weighed, but the reason we need to shake it up at the beginning is to make sure that it's properly set up for the other parts of the experiment?

As an aside, I have to say I love the tags in the room description for the fun of it; the one I like best is the one that says welcome :D

pentavalentcarbon

11:48 PM

o/

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