/sci/ - Science & Math

>>1128595

http://tinyurl.com/2c6m48e 9b5023aa522990c2e70ad45ed770d5f2

Fucking unstable is what it is.

Very soon it will be carbon dioxide and formic acid, I expect.

>>1128616
thanks for clearing that up. I mean what's the name of this shit?

>>1128623

I don't know the systematic name, at a guess I'd call it formyl carbonate or something. There are sites that you can do a reverse search with a SMILES string or by drawing the structure.

>>1128599
Is thnis what you thought the last question the AS exam was? Cos it wasn't this, it was 2 c's with a double bond o on each and an OH on each

The COOH on the right is called a carboxyl group, the COH group on the left is called an aldehyde, and when joined by an O, t's called an ether. I don't know how to IUPAC this though.

>>1128646
it said suggest a structure. the Mr was 90 and the molecular formula was c2 h2 o4 so this is right too

>>1128599

Search is done, it's called carboxy formate

http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=HistorySearch&db=pccompound&query_key=1&hin
it=true

>>1128653

C2H2O4, in an AS-level exam, was probably more likely to be oxalic acid.

Sorry OP :(

Also wait a sec, if you're doing AS that means you're underage b&, get out you scoundrel

>>1128653
no C-H band, they might still let it through,I'm not sure

As far as i know this is above the level of AS chemistry.

>>1128684

Nah, this is pretty basic. The question is just testing understanding of valency.

>>1128684
They did't ask to name it in the exam, you worked out the MR, epirical formula and figured out the bonds it had with the absorption spectrum

>>1128597

http://tinyurl.com/2c6m48e bd98a35f8122c1795bb7f3a0bbd44634

>>1128705
Ahh okay, that makes more sense. Which board was it?

>>1128721
OCR

Shit, I'm now wondering if I got this right or not. Can't quite remember what I put for the final answer, but at least I got the Mr as 90, so that's a couple marks~

OP here. A lot of my friends put a di-carboxylic acid
ie an ethane molecule with two carboxylic acids on each carbon. I see no reason why this is incorrect I just didn't think of any other way of doing it at the time. Just wondered what it's called

>an ethane molecule with two carboxylic acids on each carbon

no there's not.

>>1128750
"MY FRIENDS"
my answer is in the picture

I quickly glanced at the data sheet and saw that the O-H bond was between 3200 and 3500, I didn't see the seperate O-H bond number present in Carboxylic acids. So, based on the bonds I had, I deduced it was an di-ester with two carbons.
Try making a di-ester with two carbons. try it right now.

>>1128664
Ohai. I resat this and I'm 19.

http://www.wolframalpha.com/input/?i=H2O4C2

>>1128802
no no no it definitely had an O-H in the range for those found in carboxylic acids. also a carbonyl C=O. but what was the other one they gave you? it better not be C-H

im curious, where is this test from?

i'd like to see the spectra.

>>1128838
it's an as level exam sat this morning. It won't be on the OCR website for a while

>>1128844
im sorry but i actually have no idea what AS refers to, im quite ignorant of these things.

>>1128838
A home made copy may be on the studentroom in about an hour, I'm checking it now.

>>1128817
I noticed when i came out the exam. I'm so annoyed, I thought the peak at 2800 was just a C-H bond. Argh

>>1128817
C-O
otherwise an OH attatched wouldn't make sense

>>1128852
it's the exam you sit the year before the last year of school ie year 12

>>1128866
good point cheers. just put my mind at rest

>>1128598

is u poop sausage lulz cdd79293154355ec2b4e7563886ba61c

>>1128867
Woah, i just looked at one of the past AS papers, in year twelve i would not have been able to do most of that paper.

holy crap Australia has a shitty education system, you guys learn how to read IR/ about aromatic ring activation/deactivation in year 12?

>>1128898
no I have no idea about the deactivation thing. We learn about IR spectroscopy, alcohols, alkenes, halagenoalkanes, green chemistry and other stuff

>>1128898
We didn't get taught about aromatic rings. There was about 5 marks worth on them in the exam though. Mix that with the fact that I misread the infra table and I mixed up enthalpy change for formation and combustion and I am royally fucked.
More of a biology guy anyway.

>>1128898
Nah, it's a UK exam board.

>>1128597

is u poop sausage lulz 8a64da250a9eb43b4aecf1126e635f5f

>>1128908
but one of the questions is only answerable (unless you're a lucky guess) with the knowledge that bromine is a ortho-para director, im looking at it right now, how can they expect you to know it if its something you havent been taught?

>>1128918
well if the UK teaches more shit than Australia, i'd say its a better in terms of education right off the bat.

>>1128946
you sure it's AS? I've never even heard of that. Copy the question or send me a link

>>1128955
http://www.ocr.org.uk/download/assess_mat/ocr_7769_sam_gce_unit_f324.pdf

the one with the Diazonium salt

>>1128598

http://tinyurl.com/2c6m48e epic lulz f4d65d7af5a69b95a7f4ac853ff6a1ca

>>1128962
F324 is the Upper Sixth (A2) unit.
We've just done F322 (I think that F323 is the coursework)

>>1128962
We didn't learn that unit, they may have taught it another year though.

>>1128962
nah we do nothing like that. That could be next year's exam or they've changed the syllabus since that paper

I sat this and just wrote a 3 page essay on what i'm going to do now i've failed all my A-levels... hopefully i get some sympathy marks and get an E instead of a U.

>>1128985

They changed the syllabus recently i think, last 2 years maybe..

>>1128985
>>1128979
>>1128977

and this is for like what, 16 year olds?
Good god man, the more i look at these tests the more i think Australia is the land of derpy hurr.

Unit F321 Atoms, bonds and groups jan 2010
Unit F322 - Chains, energy and resources today
Unit F324 - Rings, polymers and analysis jan 2011
Unit F325 - Equilibria, energetics and elements june 2011

Good luck guys.

>>1129005
yeh the link you sent will be the sorta thing we'll be doing next year 17/18 years old

>>1129005
It's for 17-18 year olds.

>>1129011
>analysis jan 2011
WHERE THE EXPLOSIONS AT?
I GOT TOLD THERE'D BE EXPLOSIONS. INSTEAD WE GET INFRA RED SPECTROM-SOMESHIT AND TITRATION

>>1129013
>>1129021

and this is secondary education?
I learnt this shit in Uni (tertiary, 18/19 years old), shoulda just gone to the UK and saved myself these shitty uni fees.

>>1129042
hell yeah

>>1129021
year 12 = 16/17

>>1129103
he linked an A2 paper. AS is for 16/17, but he was looking at A2 rather that AS so it's 17/18.

Fuck me, that AS this morning.

Probaby should have revised, I guessed about 80 percent of it.

In the exam, my enthalpy calculations were all over the place, I pretty much ended up doing them as if they were bond enthalpies.

Anyone get a huge number for the amount of energy produced each day?

Did the IR look like this?

>>1129184
>fuck me, That AS
>fuck me,Dat AS

>>1129205
Something like that, the peak just before 3000 is right at least.

>>1129217
yea, thats the Csp³-H oscillation...

>>1129217

That's the kind of peak that is often right when you're doing IR with organic compounds...
Thought you don't have any sp3 CH here.

>>1129238
hm.. yea there shouldn't be a band... I'll get my organic chem book...

>>1129204
yup it was something times ten to the eight

>>1129205
HAHAHA... theres no acid (2900-3200/3300cm^-1) and no carbonyl-group in there. The IR doesnt fit.

at least youre expecting an acid - group and a carbonyl (around 1730) for this structure.

>>1129204
Yeah, mine was stupidly huge. Also, wasn't really a chem question, more like physics... physics? in my chemistry paper?!

>>1129256
my book says:

2400-3200 associated O-H-valence for carboxylic acids.

>>1129274
But I got that IR from a specral data bank...
and I bet that IR is right...

>>1128661
what about simply ethandioic acid.

>>1129274
there is a carbonyl group (1692) and also an acid group (3487-3476 (OH)) and a bit under 3000.

I do IRs every day. l2interpret

>>1129280
I was sat there thinking, oh, that's a really big number, the space they've given us for the answer is fucking tiny.
Oh well, it's industry, they use a fuckton of stuff.

>>1129300
>>1129300
>>1129300
>>1129300

TEH ANSWRE WAS ETHANDIOIC ACID.
YOU MORON.

>>1129300
Yeah, that's what I had
HO        OH
     C=C
H           H

>>1129335
Too many H's not enough O's it's empirical formula was CH02 making it's actual formual C2H204

You've mixed up the H and O number in your model.

>>1129335
>>1129335
>>1129335
>>1129335

THATS NOT ETHANDIOIC ACID YOU MORON

HOOCCOOH

NOT HARD. GET OVER IT

/THREAD
>>1129335
>>1129335

>>1129354
Fuck, of course it isn't. That's not even what I put in the exam. I was thinking of something else
O         O
    C=C
HO     OH
That's what I had.

>>1128599
I'm assuming no double bond between the 2 Carbon atoms though and a double between the C's and the O's

>>1129376
Fucking hell, of course there isn't. What's wrong with me?

That's the right IR btw.
>>1129205
was with KBr disc.

you didnt have too name it suggest a formuli derp

>>1129406
yeh I know, I was wondering what it was called is all

>>1128616
>>1128616

try that again.

>>1128651
>>1128651

sp2/sp carbons bridged with an oxygen are not ethers. they are anhydrides (when both Cs are carbonyl carbons), vinylic esters (when one is a sp2 ene carbon) or acetylenic esters (when one is an sp yne carbon)

both are incredibly rare, incredibly unstable, and would never be tested or discussed in anything but a theoretical chemistry or atmospheric chemistry course.


what the fuck is ethanedioic acid?
HO-(O=C)-(C=O)-OH is called oxalic acid.

that is the only possible answer for a non-upper division university level question.


people are debating this as if it was hard, but the reality is that there are only an incredibly limited number of possible answers, and oxalic acid is the only one that would even be remotely recognizable to someone who has never seen any advanced reaction mechanisms (atmospheric chemistry)

>>1129473
thank you!
I wanted to say the same but I was too lazy...

>>1129473
ethanedioic acid is a synonym for oxalic acid...

1) IR absorption bands do not differ tremendously for organic compounds.

this is one major issue undergraduates have.

an IR peak should never vary more than about 10-20 cm-1 from reference values. if it does, you fucked up your sample prep, you have a bad calibration/instrument fuck up, or you DO NOT have what you want.


2) no one uses SP3 C-H stretches to identify a compound.

nor does anyone use a 1-2 PPM 1H NMR methylene or methyl proton shift to identify a compound.


it is very well known in synthetic organic chemistry that "grease" contaminates everything.

trace grease from the ground glass joints, grease from seals and valves in/on those metal barrels full of hexane/ethyl acetate/dichloromethane, from the ubiquitous squeeze bottles used in every organic lab, from trace plastic contaminating a barrell full of Silica, etc.

grease is everywhere, and it takes a very very small amount of grease to give you a ridiculous methyl and methylene signal.


if you tried to publish a paper in which you even mentioned those shifts/stretches in the actual main body of the work (rather than in supplemental material) you would be laughed out of academia.

>>1129473

>>1129509
>>1129509
>>1129509


even contaminated teflon (eg not fully flourinated teflon that has dissolved or been scrated off stop cocks or stir bars)

OP here.
Can someone please just name the compound in the picture?

>>1129522
>stop cocks
wtf? (germanfag here)

>>1129509
yep, also IR is the least reliable source of identification. It is nice to see if you didnt fuck up the whole reaction, but you cant see smaller amounts of byproducts or reagents.

>>1129561
>>1129561


IR is usually relegated to a tertiary analytical tool in organic chemistry, or a primary analytical tool in organometallic chemistry.


it is very very useful in identifying the type of bonding of carbonyl complexes, nitric oxide complexes, and similar simple ligand systems.

indeed, the IR shift is one of the main identifying features of a keto type carbonyl in a dinuclear vs a carbonyl type (eg bridged vs non bridged)

>>1129561
sie sind gerate fur die fliessen von Gase im Labor

>>1129579
>>1129579
>>1129579


no one uses any other name for them, though other names do apply:

spigot
valve

>>1129561
>>1129561


honestly, its much easier to take a crude NMR in carbon tet or CDCl3

crude NMR on an old 200 MHZ varian takes a total of 7 minutes, including pre and post shim, running 20-32 FIDs

>>1129579
I make a IR of every compound I do in the lab. Just today I had a perfect IR, all the bands I expected, but my H-NMR was horrible...

>>1129586
ah okay, I dont even know how they are called in german... ventil I guess (valve)

Shit's fucked up is what it is.

Has a negative vibration mode = not stable.

>>1129657
where did you find that? does it have a name?

>>1129708

I calculated it. 2 mins in Gaussian.

>>1129594
>>1129594


here is a quick bit of advice:

use more of your sample if your H1 NMR is full of noise.

people always say:

dont use more than 5-8 mg of sample.

fuck that shit bitch, use like 20 mg.

if all you care about are the shifts (not the integration) then the increased concentration will increase the relative signal of the analyte vs the noise.

>>1129739
that's good advice. My TAs (is that what you all them in englihs?) always tell me to use 5 mg...

>>1129726

Decent. What level of theory?

>>1128816

Sorry OP, can just name it in home language : /
It has aldehide, acidic and ethre groups ...and it aint oxalic acid ....
Formil acethyl ethre?