The Periodic Table

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Mithoron

12:18 AM

@lord Synchronisation :D

At least it looked like we got into chat the same moment

4 hours later…

Jan

4:12 AM

What’s our highest buzzword to content ratio in a question title yet?

samjoe

4:53 AM

Can Raney nickel directly reduce carbonyl ? I know they can be reduced by first converting them to thioketals

But can Raney Nickel directly do that

8 hours later…

Martin - マーチン

1:08 PM

@Jan I think we had one with 100%, something like chemistry question help or so... Don't remember...

Fawad

How can that be beta fructose?at its anomeric carbon OH group is down. It means it’s alpha fructose?no?

1,3-feeds

Q: Why do results become less accurate at high temperatures?

While carrying out a reaction of thiosulphate solution and hydrochloric acid to determine the rate of reaction (by timing how long it took for the solution to go cloudy), I found that my results became less accurate at higher temperatures when I plotted the Rate in s-1 against the Temperature in ...

discussion

Fawad

@secret what you say?

Secret

I don't see any problem with it. If you lookup the $\beta$ fructose and $\alpha$ glucose, they are indeed having all the OH group in the orientation shown (and one of these form the glycosidic bond)

The $\beta$ fructose is 180 rotated version of that shown in wikipedia

Fawad

1:25 PM

In sucrose it shows both OH groups are same side (downwards)

but in alpha glucose OH group is downwards and in beta fructose OH group is upward

Wait. I see numbering on fructose is in anti-clockwise. What changes will that make?

Secret

that is because the $\beta$ fructose is actually bonded upside down

Show me in your book how it draw the $\beta$ fructose all by itself, then I might be able to illustrate

Loong

Q: Why does the fructose monomer in sucrose appear different from isolated fructose?

I understood that the representation of fructose is: But during the formation of sucrose: How did fructose, whose representation is given in the first picture, turn out to be different in the second. I tried to visualize myself rotating the molecule but the position of oxygen changes and i...

organic-chemistry molecular-structure carbohydrates

Fawad

@Secret I notice now. Thanks. So by 180 you mean upside down?

Secret

yup

Fawad

@Loong meanwhile thinking I could have got those yummy 10 upvotes if I asked before him

Secret

1:31 PM

Yup, using Loong's CSE, you can draw a rotational axis passing through the O atom and then flip it

Fawad

1:47 PM

@Secret I see resemblance after flipping. But now Oxygen is not at same position.

Secret

rotate like this

Fawad

Correct? @secret

Or like this.

Got.thanks and sorry for any disturbance

Secret

Fawad

Why schools don’t use stick and balls for better visualisations :( .

Took 30 min but finally understood.

Secret

Ball and stick get cluttered very quickly for biomolecules. Sucrose is still small, but wait until you get to cellulose

Fawad

2:00 PM

1 hour later…

getafix

3:08 PM

is it sorta valid to design an experiment on the basis of a back of then envelope calculation? So I am trying to make a host-guest complex, the formation of which I am monitoring using fluorescence emission...so i did like a rough trial experiment, where the fluorescence of the host became 1/3rd of the original intensity..so i guess complexation wasn't quantitative, and 30% of the host is free (?)

So i made an order of magnitude estimate for K ( i had a 0.1 mM 1:1 mixture of the both the species) so K = 0.06/0.03*0.03 = 66.67 (order of magnitude estimate)

So i am thinking of using excess host, the amount of which i calculated as follows ..assuming 99% complexation 0.099/((x - 0.099)*(0.001)) = 60.6061 where x is the initial amount of host..i get about 1.7 mM so roughly 17 equivs

but now that I am actually about to do the experiment, my reasoning seems a bit wish washy...

Opinions?

If i assume 100% complexation the denominator becomes zero...hence i assumed 99

but then if i assume 99.9% same formula spits out 16.58 mM so..about 166 equivs.

ahh am I being stupid? I should probably just go home it is 1 AM and try on monday lol

orthocresol

3:56 PM

@getafix going home is probably a good idea. ;) But if you have chemicals to play with, why not try it out? There’s no real harm.

getafix

4:14 PM

@orthocresol don't have a lot, and synthesis is complicated so i would rather get I right in my first attempt

My supervisor said he wants me to isolate about 25 mg of the complex

I can possibly remove the host but the guest and complex are hard to separate using size exclusion chromatography (which is probably my best bet at separation I think) which is why I need near quantitative complexation

orthocresol

4:32 PM

@getafix oof. OK. Well then I guess you better discuss it with somebody in the group...

getafix

4:52 PM

Yeah should probably get some sleep anyway,

2 hours later…

Abcd

6:58 PM

Hey!

I think all the processes that we conduct in the laboratory are irreversible, aren't they? (With reference to thermodynamics)

If yes, how do I calculate the entropy change for the lab processes?

1,3-feeds

7:57 PM

Q: How can a question asking what do a group of compounds have in common be put on hold because it is "too broad"?

This old question (What is the mechanism of action of anaesthetics?) has recently been put on hold as being too broad. The grounds are, apparently, that such a diverse range of compounds acting as anaesthetics must have different mechanisms of action. So the question is too broad because it wou...