| Pages:
1
2
3
4
..
104 |
elementcollector1
International Hazard
Posts: 2684
Registered: 28-12-2011
Location: The Known Universe
Member Is Offline
Mood: Molten
|
|
Does Schweizer's Reagent react with red phosphorus? (I know, cook question, but I can't exactly find a reference...)
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
|
|
|
sonogashira
National Hazard
Posts: 555
Registered: 10-9-2006
Member Is Offline
Mood: No Mood
|
|
How small can the incident area of a laser beam be made, in theory and in practice?
|
|
|
elementcollector1
International Hazard
Posts: 2684
Registered: 28-12-2011
Location: The Known Universe
Member Is Offline
Mood: Molten
|
|
If I had to guess...
In theory: 1 photon wide
In practice: Microscopic (search 'optical tweezers')
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
|
|
|
confused
Hazard to Others
Posts: 244
Registered: 17-3-2013
Location: Singapore
Member Is Offline
Mood: tired
|
|
Im thinking of getting a hotplate stirrer for distillations/refluxes as its hard to get good control of temperature with an open flame...
would a maximum temperature of 350'C work for most common laboratory procedures?
is 350'C sufficent to concentrate sulfuric acid past 95% concentration?
and is there a significant diffrence between aluminium and ceramic top plates?
|
|
|
Varmint
Hazard to Others
Posts: 264
Registered: 30-5-2013
Location: Near Atlanta, GA
Member Is Offline
Mood: No Mood
|
|
sonogashira:
See the link regarding AIRY disk.
http://en.wikipedia.org/wiki/Airy_disk
In essence, the shorter the wavelength, the smaller the spot (which is why Blu-Ray holds much more data than the DVD which is written (or meant to be
read) by a red laser beam.
No matter the wavelength, a single photon sized spot is absolutely out of the question.
This has applications in the real world as well, note how even cellphone cameras are reaching very high mega-pixel counts? At some point the sensors
cannot be made any smaller because the airy disk will cover adjacent cells, rendering further increases in sensor pixel density useless.
Ergo, the sensors have a finite minimum size, after which the senor size must increase to utilize the comparatively "large" dot the airy disk
represents for small image features you wish to preserve.
DAS
[Edited on 15-8-2013 by Varmint]
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Varmint  | | At some point the sensors cannot be made any smaller because the airy disk will cover adjacent cells, rendering further increases in sensor pixel
density useless. |
This is true about geometrical optics, the model in which the Airy disc sits. It's not
quite the same with diffractive optics, or other optical models.
But if you're using an ordinary lens with its de facto aperture, I have nothing to disagree with invoking the Airy disk.
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
Nobody seems to find my questions in these threads, but I am looking to t-Butylate a primary amine (specifically GABA). Can anyone suggest reaction
conditions?
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
sonogashira
National Hazard
Posts: 555
Registered: 10-9-2006
Member Is Offline
Mood: No Mood
|
|
Thank you Varmint.
"t-Butylate a primary amine (specifically GABA)."
You may make it via THF to Cl(CH2)4OH [with HCl] to Cl(CH2)3COOH to your amine, alternatively. Or GBL to the chloride directly.
[Edited on 15-8-2013 by sonogashira]
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
| Quote: Originally posted by sonogashira |
"t-Butylate a primary amine (specifically GABA)."
You may make it via THF to Cl(CH2)4OH [with HCl] to Cl(CH2)3COOH to your amine, alternatively. Or GBL to the chloride directly.
|
Disregard the post that used to be here. Found http://www.sciencemadness.org/talk/viewthread.php?tid=8477
Get the distinct impression that it's not happening and I need an alternate route.
[Edited on 8-16-13 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
Mailinmypocket
International Hazard
Posts: 1351
Registered: 12-5-2011
Member Is Offline
Mood: No Mood
|
|
Molecular sieves?
So, being lucky enough to be a diabetic(T1) I need to use glucose test strips to determine my blood glucose levels. The manufacturer of the strips
recently changed the small vials to include a plastic capsule filled with small beads, I immediately took it apart to squirrel away these beads in
case they may be of use. My question is, what are they? I'm thinking some sort of molecular sieve (perhaps 4A?) but I'm not sure. There is sadly no
MSDS or other information available from the manufacturer either. Given the ingredients, does anyone have a clue of what these things might be?
 
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
It's a desiccant. The
ingredients on the package have nothing to do with the beads.
|
|
|
Mailinmypocket
International Hazard
Posts: 1351
Registered: 12-5-2011
Member Is Offline
Mood: No Mood
|
|
Hmm... Okay. I thought perhaps the glucose oxidase was oxygen sensitive or something. I wish I knew the composition of this stuff though.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
It might also be an oxygen scavenger, too. The most common one I've seen, though, is finely divided elemental iron.
As to what the prills are, my first guess, just from the photo, was calcium chloride. If you want to get some indirect evidence, dry them in an oven
and weigh. Put them in an "anti-desiccator" with a liquid water source to saturate the atmosphere inside. After a week, weigh them again. Since
different desiccants have different capacities to sequester water, it'll give some idea.
|
|
|
elementcollector1
International Hazard
Posts: 2684
Registered: 28-12-2011
Location: The Known Universe
Member Is Offline
Mood: Molten
|
|
Does 'cryohol' (a mixture of dry ice and ethanol) still work if you replace the ethanol with isopropanol? I think it should, but mine failed to
liquefy chlorine and it has me wondering.
EDIT: On that note, are there any alternative cryohol mixes? Dry ice is hard to come by where I am.
[Edited on 19-8-2013 by elementcollector1]
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
|
|
|
confused
Hazard to Others
Posts: 244
Registered: 17-3-2013
Location: Singapore
Member Is Offline
Mood: tired
|
|
you could try acetone if isopropanol doesn't work
It should though, according to wiki, it should reach -77'c
i would say LN2, but since dry ice is already hard to come by...
maybe you could try some form of mechanical cooling, but i doubt it will reach anywhere near dry ice would get you
http://en.wikipedia.org/wiki/List_of_cooling_baths
[Edited on 19-8-2013 by confused]
|
|
|
karlos³
International Hazard
Posts: 1520
Registered: 10-1-2011
Location: yes!
Member Is Offline
Mood: oxazolidinic 8)
|
|
Hello people,
I would like to know if an aromatic amide can in a one-pot reaction be halogenated to the N-haloamide and on the aromatic ring too?
To be specific, im talking about the hofmann rearrangement, which I want to use to make 4-chloroaniline from benzamide with TCCA in methanol, then
rearrangement with lye.
I cant find any reason why it wont work if I would just use two times the stochiometric amount of TCCA and take two times more care during addition?
There are papers out there for the use of TCCA for N-chloroamides/hofmann rearrangement, there are papers out there for aromatic halogenation, but i
cant find any thats stating this will not work, or why it is undesirable?
Or maybe its just rare someone wants to do such a thing?
I had some paper which proves my assumption it could be possible, it was stating ring-halogenation of an aromatic amide during a hofmann
rearrangement. when hypochlorite solution was used in excess, as a side product.
Seems just logical it would work, as its for both cases an electrophilic chlorination.
Can someone tell me if I missed something?
Or is it indeed possible to make 4-Chloroaniline from Benzamide in one shot?
|
|
|
sonogashira
National Hazard
Posts: 555
Registered: 10-9-2006
Member Is Offline
Mood: No Mood
|
|
If I recall correctly, you will need acidic conditions to chlorinate the benzene ring. I have some examples of NCS aromatic chlorination using
sulphuric acid, or acetic acid, so I imagine that TCCA should need similar conditions. Please post the papers that you have on TCCA aromatic
chlorination.
|
|
|
karlos³
International Hazard
Posts: 1520
Registered: 10-1-2011
Location: yes!
Member Is Offline
Mood: oxazolidinic 8)
|
|
Yes indeed, my reference use sulfuric acid as well as catalyst, forgot about the conditions needed, that wont do it.
But I got another ref, actually a bromination, with TCCA/NaBr to form tribromoisocyanuric acid/TBCA, in methanol.
Just TBCA in MeOH.
The attached reference for N-haloamide preparation uses just TCCA in MeOH.
How about now, that seems to work in theory?
Could the reaction of TBCA and benzamide lead to 4,N-dibromobenzamide?
I only post both relevant references, since i think i got them from here and dont want to waste polverones bandwidth .
Attachment: jo00828a039.pdf (149kB)
This file has been downloaded 4492 times
Attachment: A New Regioselective Bromination of Activated Aromatic Rings.pdf (69kB)
This file has been downloaded 2318 times
|
|
|
sonogashira
National Hazard
Posts: 555
Registered: 10-9-2006
Member Is Offline
Mood: No Mood
|
|
Thanks. Here's a paper for 4-chlorination of N-acetylaniline with TCCA, if it's of any use.
Attachment: 4-chloroaniline.pdf (65kB)
This file has been downloaded 1309 times
|
|
|
plante1999
International Hazard
Posts: 1936
Registered: 27-12-2010
Member Is Offline
Mood: Mad as a hatter
|
|
Does anyone have a good plating book (including chromium plating) to refer me to?
A download link would also be highly apprecied, (reference section or U2U).
I never asked for this.
|
|
|
IrC
International Hazard
Posts: 2710
Registered: 7-3-2005
Location: Eureka
Member Is Offline
Mood: Discovering
|
|
| Quote: Originally posted by plante1999 | Does anyone have a good plating book (including chromium plating) to refer me to?
A download link would also be highly apprecied, (reference section or U2U). |
Old books yet still good. Much of the reason I find old books useful is they are free, they also cover making things used in the art, many of the
procedures being old but proven are much easier for a home lab to build using available salvage.
http://archive.org/details/electroplatingtr00reet
http://archive.org/details/principleselect00fielgoog
http://archive.org/details/removalofcopperi00somm
http://archive.org/details/practicalelectro00brun
http://archive.org/details/completetreatise00langrich
http://archive.org/details/electrodepositio00languoft
http://archive.org/details/practicalelectro00bedeuoft
http://archive.org/details/acompletetreati00langgoog
http://archive.org/details/electroplatingma00harp
http://archive.org/details/structureofchrom93353kasp
http://archive.org/details/protectivevalueo13333blum
http://archive.org/details/acceleratedtests13451stra
http://archive.org/details/throwingpowerinc41271farb
http://archive.org/details/jresv43n2p101
http://archive.org/details/jresv46n6p472
http://archive.org/details/jstor-41326936
http://archive.org/details/cleaningelectrop02ream
http://archive.org/details/radiochemicalstu18rein
http://archive.org/details/practicalhandboo00trev
http://archive.org/details/bstj59-2-169
http://archive.org/details/cleaningelectrop00ream
http://archive.org/details/TheBrushElectricLightAndElectro-p...
http://archive.org/details/electroplatinga00wattgoog
http://archive.org/details/TheBrushElectricLightAndElectro-p...
http://archive.org/details/practicalelectro00bede
http://archive.org/details/electroplatingtr00barcrich
http://archive.org/details/electroplatingwi00hasl
[Edited on 9-10-2013 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
|
|
|
Variscite
Hazard to Self
Posts: 69
Registered: 21-5-2013
Member Is Offline
Mood: diffusing
|
|
What are the pros and cons of a 14/20 setup vs a 24/40 setup for the home chemist? As in learning the reactions, I know it would be fine. But what
about a reasonable amount of reagent preparation, too small to be useful?
|
|
|
roXefeller
Hazard to Others
Posts: 463
Registered: 9-9-2013
Location: 13 Colonies
Member Is Offline
Mood: 220 221 whatever it takes
|
|
methOH vs. methoxide
I've been trolling the forums for a couple years now, but this is obviously my first question: Why do many people discussing reagents abbreviate to
methOH or methoxide? I can generally study the process occuring and figure whether it is methanol (methyl with hydroxyl) or a base like NaOH
dissolved in methanol. But why would we want to default to these less exacting abbreviations in a discipline that usually requires exact naming
(nitrite v. nitrate, nitrous oxide v. nitric oxide, or the many o- m- p-1- 2- etc variations of functional groups on a benzene ring)? Thanks so much
for the forum. I'm finally able to get back to my chemistry interests after going through a mechanical eng detour.
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
This is the first I've seen "methOH." MeOH is common and acceptable. Here are a couple references you may find helpful:
<strong><a href="http://bama.ua.edu/~blacksto/SCB_page/SCB%20site/research%20handouts/joc_abbreviations.pdf" target="_blank">Standard
Abbreviations and Acronyms</a></strong> <img src="../scipics/_pdf.png" /> (The Journal of Organic Chemistry)
<strong><a href="http://www.chem.wisc.edu/areas/reich/handouts/acronyms.pdf" target="_blank">Organic Chemistry
Acronyms</a></strong> <img src="../scipics/_pdf.png" /> (UW-Madison Chem.)
<em>Welcome to [active] Science Madness!</em>
|
|
|
confused
Hazard to Others
Posts: 244
Registered: 17-3-2013
Location: Singapore
Member Is Offline
Mood: tired
|
|
Question
Hi,
what causes the errosion of carbon electrodes during electrolysis of a copper sulfate solution?
|
|
|
| Pages:
1
2
3
4
..
104 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
