Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
 Pages:  1  ..  89    91
Author: Subject: The Short Questions Thread (4)
mackolol
National Hazard
****




Posts: 366
Registered: 26-10-2017
Location: Poland
Member Is Offline

Mood: Psychedelic

[*] posted on 20-4-2020 at 08:28


Quote: Originally posted by Sulaiman  
Apply vacuum first then heat,
if you heat first, when you apply vacuum there is a good chance of violent boiling.


But is there any other disadvantage beside too violent boiling? (maybe glassware damage)

Quote: Originally posted by fusso  
You forgot that the heat would also increase the pressure causing an explosion.


Ah, right
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 2900
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 25-4-2020 at 04:20
Has anyone checked the 'accuracy' of cheap Chinese pH papers ?






CAUTION : Hobby Chemist, not Professional or even Amateur
View user's profile View All Posts By User
mackolol
National Hazard
****




Posts: 366
Registered: 26-10-2017
Location: Poland
Member Is Offline

Mood: Psychedelic

[*] posted on 25-4-2020 at 05:36


I'm using ones and they work quite well for my purposes, but the scale isn't very precise..
View user's profile View All Posts By User
karlos³
International Hazard
*****




Posts: 790
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: verrückt & wissenschaftlich

[*] posted on 30-5-2020 at 23:33


The chemoluminescence reaction with NaBH4 and KMnO4 is known I would guess?
I would like to try it soon, but the reaction also calls for sodium hexametaphosphate which I don't have.

But why is that stuff involved?
I don't understand it, because actually, it is not really involved:
NaBH4 + Mn(III, IV or VIII)/H+→ products + Mn(II)*→ Mn(II) + light (~690nm)

What does this salt do in there? Is it needed?
Can it be replaced, if so, what can I use as replacement?
I read up on that, and besides it seems that it can be substituted with sodium orthophosphate, and that it is only in there because it affects the wavelength.

What would be a good replacement? I have no phosphorus acid, neither its salts.
chemplayer uses phosphoric acid, instead of the sulfuric, is it just for acidification used, or does it affect the wavelenght as well?
Only P-containing substance I can offer would be some sodium hypophosphite.

Can someone help? I would really love to try it, but I'm just not sure if it is even worthwhile under these circumstances.
View user's profile View All Posts By User
wg48temp9
National Hazard
****




Posts: 450
Registered: 30-12-2018
Member Is Offline


[*] posted on 31-5-2020 at 08:58


Quote: Originally posted by karlos³  
The chemoluminescence reaction with NaBH4 and KMnO4 is known I would guess?
I would like to try it soon, but the reaction also calls for sodium hexametaphosphate which I don't have.

But why is that stuff involved?
I don't understand it, because actually, it is not really involved:
NaBH4 + Mn(III, IV or VIII)/H+→ products + Mn(II)*→ Mn(II) + light (~690nm)

What does this salt do in there? Is it needed?
Can it be replaced, if so, what can I use as replacement?
I read up on that, and besides it seems that it can be substituted with sodium orthophosphate, and that it is only in there because it affects the wavelength.

What would be a good replacement? I have no phosphorus acid, neither its salts.
chemplayer uses phosphoric acid, instead of the sulfuric, is it just for acidification used, or does it affect the wavelenght as well?
Only P-containing substance I can offer would be some sodium hypophosphite.

Can someone help? I would really love to try it, but I'm just not sure if it is even worthwhile under these circumstances.


You should read the following paper:
Attachment: Mechanism-Permanganate-Chemiluminescence-hindson2010.pdf (436kB)
This file has been downloaded 34 times

Apparently polyphosphate ions complex Mn3+ which increases the chemoluminescence 50 fold. The correct ph is also required.

Interestingly phenols and ascorbic acid can be used in place of the NaBH4.




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.
View user's profile View All Posts By User
mayko
International Hazard
*****




Posts: 1052
Registered: 17-1-2013
Location: Carrboro, NC
Member Is Offline

Mood: anomalous

[*] posted on 31-5-2020 at 11:53


You might be interested in this too (same first author)


Hindson, C. M., Smith, Z. M., Barnett, N. W., Hanson, G. R., Lim, K. F., & Francis, P. S. (2013). Autocatalytic Chemiluminescence Sheds New Light on the Classic Permanganate–Oxalate Reaction. The Journal of Physical Chemistry A, 117(19), 3918–3924. https://doi.org/10.1021/jp312603m




Attachment: Hindson et al. - 2013 - Autocatalytic chemiluminescence sheds new light on the classic permanganate-oxalate reaction.pdf (1.6MB)
This file has been downloaded 38 times





al-khemie is not a terrorist organization
"Chemicals, chemicals... I need chemicals!" - George Hayduke
"Wubbalubba dub-dub!" - Rick Sanchez
View user's profile Visit user's homepage View All Posts By User
karlos³
International Hazard
*****




Posts: 790
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: verrückt & wissenschaftlich

[*] posted on 31-5-2020 at 17:26


Thank you both very much! :)
View user's profile View All Posts By User
karlos³
International Hazard
*****




Posts: 790
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: verrückt & wissenschaftlich

[*] posted on 18-6-2020 at 06:06


I need some dimethylamine freebase, and I have DMF, can I hydrolyse it with base simply at RT?0
That would be very practical for me, giving me a solution I can use directly as it is for the reductive amination I intend to use it for.
If not, I guess I have to go via the HCl hydrolysis instead.
View user's profile View All Posts By User
stoichiometric_steve
International Hazard
*****




Posts: 746
Registered: 14-12-2005
Member Is Offline

Mood: satyric

[*] posted on 18-6-2020 at 12:24


Quote: Originally posted by karlos³  
I need some dimethylamine freebase, and I have DMF, can I hydrolyse it with base simply at RT?0
That would be very practical for me, giving me a solution I can use directly as it is for the reductive amination I intend to use it for.
If not, I guess I have to go via the HCl hydrolysis instead.


Why not hydrolyze with NaOH with heating, driving off the Dimethylamine through a drying column and collecting it in chilled MeOH until saturated?
View user's profile View All Posts By User
karlos³
International Hazard
*****




Posts: 790
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: verrückt & wissenschaftlich

[*] posted on 18-6-2020 at 12:37


Because the smell lingers :D
Well guess I rather go via the HCl hydrolysis.
Its better and easier stored this way.
My ketone is a hydroxyketone as you well know, and so it will form an imine very readily and a stable one even.
View user's profile View All Posts By User
stoichiometric_steve
International Hazard
*****




Posts: 746
Registered: 14-12-2005
Member Is Offline

Mood: satyric

[*] posted on 26-6-2020 at 15:37


Quote: Originally posted by karlos³  
Because the smell lingers :D
Well guess I rather go via the HCl hydrolysis.
Its better and easier stored this way.
My ketone is a hydroxyketone as you well know, and so it will form an imine very readily and a stable one even.


You have a point there, but i think a solution in MeOH would be way more versatile, and if set up correctly, you won't even have to deal with any fumes whatsoever.
View user's profile View All Posts By User
Belowzero
Hazard to Self
**




Posts: 69
Registered: 6-5-2020
Location:                 Member Is Offline
Member Is Offline


[*] posted on 3-7-2020 at 04:48


After the whole corona thing dies down I expect the market to be flooded by used cheap plexiglass , perhaps even free.
While looking for fumehood designs I stumbled across designs that are made entirely out of plexiglass , although not the most important feat. it looks really slick.
Relatively easy material to work with and not too heavy.

Now I wonder if this material is resistant enough to withstand at least a few years of abuse?
I could coat the parts exposed to the highest airflow volume with say epoxy/paint to make it more resilliant.


[Edited on 3-7-2020 by Belowzero]
View user's profile View All Posts By User
Σldritch
Hazard to Others
***




Posts: 225
Registered: 22-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 5-7-2020 at 12:24


How much space do i need for GAMESS, macmolplt and avogadro? I want to look at orbitals of up to maybe 30 atom clusters and only have 30Gb. Do i even have enough space for all the programs?
View user's profile View All Posts By User
karlos³
International Hazard
*****




Posts: 790
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: verrückt & wissenschaftlich

[*] posted on 30-7-2020 at 14:40


How reliable is this patent regarding the reductive amination of napthylglyoxyl hydrate?
Can aldehyde hydrates be reductively aminated like this? Never saw another example of it so far.
The patent is United States Patent Office 3,463,808, like look at example 13.
Or, United States Patent Office 3,312,733, example 9.
What do you guys think? I'm trying to run a reductive amination of 2-naphthylglyoxyl hydrate right now, but I am not so confident it will work.
Still in the process of aldimine formation.
View user's profile View All Posts By User
karlos³
International Hazard
*****




Posts: 790
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: verrückt & wissenschaftlich

[*] posted on 31-7-2020 at 11:51


Sadly, it didn't seem to work so far.
I still have to work it up properly, but after an acidic quench way too much oil fell out, indicating my substrate hasn't reacted to an amine as intended.

Can someone shoot an opinion about these doubtful patents please?
View user's profile View All Posts By User
 Pages:  1  ..  89    91

  Go To Top