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

Printable Version  
 Pages:  1  ..  14    16    18  ..  28
Author: Subject: The short questions thread (1)
appetsbud
Harmless
*




Posts: 21
Registered: 15-8-2008
Member Is Offline

Mood: No Mood

[*] posted on 8-1-2009 at 11:36


is silica gel classed as a molecular seive? and if so, what adsorbtion capability? if not, is it possible to use it as a substitute for 3A molecular seives? will it remove substances other than water from things?

thanks
View user's profile View All Posts By User
Nicodem
Super Moderator
*******




Posts: 4230
Registered: 28-12-2004
Member Is Offline

Mood: No Mood

[*] posted on 9-1-2009 at 00:40


No, neither silicagel or silica is a molecular sieve. Molecular sieves are zeolite-type materials. They are very cheap, almost as cheap as silica. Silicagel can absorb some water, but it does not do so as energetically as molecular sieves and it can therefore not be used for the same principle. Also, I never heard of silicagel being used in liquid phase, generally it is just used to maintain dry atmosphere in desiccators. As for it absorbing other things, it depends on what other thing is.
Quote:
Originally posted by UnintentionalChaos
My question is about cyanuric acid.

I've read in several places that it crystallizes from water as the dihydrate, but does anyone know how stable this hydrate is? For example, will storing over H2SO4 in a dessicator leave the anhydrous product, or will it not lose any water? I've been meaning to do some experiments, but the stoichiometry will go out the window if I don't know if it's hydrated or not. Thanks.

I think if you store it over H2SO4 it will not loose hydration water at room temperature, at least if it is a real crystal hydratation water. Hydrated cyanuric acid has the form of larger needles (it looks "crystalline", 1-2 mm needles, depending on how slowly they grew), while the anhydrous form is more fine (more powder-like). I have no idea at which temperature the hydrate starts loosing water.

[Edited on 9/1/2009 by Nicodem]
View user's profile View All Posts By User
S.C. Wack
bibliomaster
*****




Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline

Mood: Enhanced

[*] posted on 9-1-2009 at 11:03


Quote:
Originally posted by Intergalactic_Captain
Anyone familiar with the Letts Nitrile Synthesis? Ar-COOH + KSCN -> ArCN +CO2 + KSH


Quote:
Originally posted by solo
E. E. Reid, Am. Chem. J. 43, 162 (1910); G. D. van Epps, E. E. Reid, J. Am. Chem. Soc. 38, 2120 (1916)


I posted the JACS article before in a relevant thread (acetonitrile), in a zip due to the attachment size limit at the time, and have reattached it there just now.

I did this because I've been reading some lately, because the American Chemical Journal has just become available at Google Books. Including the above citation from 1910, which jogged my memory:
http://books.google.com/books?id=AcsAAAAAYAAJ&pg=PA162

This is interesting because it shows that ferrocyanide and sulfur substitute for thiocyanate, at least with metal benzoates.

It is nice to finally be able to read that journal. Unfortunately only 1880-1910 volumes are available, and only a third of those. The Big State U. down the road has it in inaccessible offsite storage, like nearly all QD journals, in favor of barren expanses of carpet. Literally half the library is empty space. The local library just down the street, which used to enable me to find many thousands of journal references, put ALL of their journals in inaccessible offsite storage a couple years ago.
View user's profile Visit user's homepage View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 9-1-2009 at 14:44


Hey, Does anybody know the percentage yield of 4-Nitrotoluene after a mono nitration?
thanks,
View user's profile View All Posts By User This user has MSN Messenger
solo
International Hazard
*****




Posts: 3869
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline

Mood: ....getting old and drowning in a sea of knowledge

[*] posted on 9-1-2009 at 14:46
Reference Information


STUDIES IN THE PREPARATION OF NITRILES. II. THE PREPARATION OF ALIPHATIC NITRILES.
G. D. van Epps, E. Emmet Reid
J. Am. Chem. Soc. 1916, 38 (10), pp 2120–2128

Attachment: STUDIES IN THE PREPARATION OF NITRILES. II. THE PREPARATION OF ALIPHATIC NITRILES.pdf (553kB)
This file has been downloaded 987 times





It's better to die on your feet, than live on your knees....Emiliano Zapata.
View user's profile View All Posts By User
not_important
International Hazard
*****




Posts: 3873
Registered: 21-7-2006
Member Is Offline

Mood: No Mood

[*] posted on 9-1-2009 at 17:40


Quote:
Originally posted by Picric-A
Hey, Does anybody know the percentage yield of 4-Nitrotoluene after a mono nitration?
thanks,


Under what conditions? Simple nitration with HNO3 gives roughly 60 o / 40 p, but I've read reports for different conditions ranging from 2.5:1 o/p to 1:4 o/p ratios.
View user's profile View All Posts By User
Squall
Harmless
*




Posts: 37
Registered: 22-8-2007
Member Is Offline

Mood: Alive

[*] posted on 9-1-2009 at 18:14
Magnesium


I am looking for a small quantity of scrap magnesium. I would appreciate any information on where to get some or if you have some to sell or give. Thanks

[Edited on 9-1-2009 by Squall]
View user's profile View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 10-1-2009 at 02:27


I was thinking a simple nitration with HNO3/H2SO4, with reflux at 50degrees C.
Do you know what the conditions are to get the 1:4 o:p ratio? seems temting...

Squall- try marine stores, they may have old magnesium sacrificial anodes, other than that any scrap metal dealer may be able to help you,

Thanks,
View user's profile View All Posts By User This user has MSN Messenger
not_important
International Hazard
*****




Posts: 3873
Registered: 21-7-2006
Member Is Offline

Mood: No Mood

[*] posted on 10-1-2009 at 03:33


Don't think you need to heat for nitrating toluene, and I'm puzzled at how you reflux that mix at 50 C .

A lot of the high ratio methods depended on using hardtogetium difficulttoobtainate, I don't remember real details. Vapour phase nitration over Zeolite H-beta at 120-140 C converts about half the toluene and 3/4 of the HNO3 to mono-nitrate with less than 1% loss to benzoic acid, ratio of p/o was around 2.6 to 2.8 to 1.
View user's profile View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 10-1-2009 at 05:34


Your right, i was confusing toluene with benzene, sorry.
I am probably going to try a normal nitration folowed by seperating the 40% P from the O.
Vapour phase nitrations are beyond my ability.
Thanks.
View user's profile View All Posts By User This user has MSN Messenger
hector2000
Hazard to Others
***




Posts: 127
Registered: 22-8-2006
Member Is Offline

Mood: Cool

[*] posted on 11-1-2009 at 01:33


this reaction is possible?





Chemistry=Chem+ is+ Try
View user's profile View All Posts By User
sparkgap
International Hazard
*****




Posts: 1234
Registered: 16-1-2005
Location: not where you think
Member Is Offline

Mood: chaotropic

[*] posted on 11-1-2009 at 02:20


No, for one thing lead tetraacetate cannot magically convert an -OH group into a -CH3 group.

sparky (~_~)




"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
View user's profile View All Posts By User
turd
International Hazard
*****




Posts: 800
Registered: 5-3-2006
Member Is Offline

Mood: No Mood

[*] posted on 11-1-2009 at 04:50


Quote:
Originally posted by sparkgap
No, for one thing lead tetraacetate cannot magically convert an -OH group into a -CH3 group.


No, not by magic: http://en.wikipedia.org/wiki/Dakin-West_reaction#General_ket...
View user's profile View All Posts By User
sparkgap
International Hazard
*****




Posts: 1234
Registered: 16-1-2005
Location: not where you think
Member Is Offline

Mood: chaotropic

[*] posted on 11-1-2009 at 05:39


And if you'll look at what turd posted, the extra carbon should have come from somewhere, acetic anhydride in the case of Dakin-West.

sparky (~_~)




"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
View user's profile View All Posts By User
turd
International Hazard
*****




Posts: 800
Registered: 5-3-2006
Member Is Offline

Mood: No Mood

[*] posted on 11-1-2009 at 07:56


Or from Pb(OAc)2 in the "lead acetate process". :)

Quote http://en.wikipedia.org/wiki/Phenylacetone:
Quote:
For example, phenylacetic acid is distilled with lead acetate to yield phenylacetone.


So the question has some merit.
View user's profile View All Posts By User
Maja
Hazard to Others
***




Posts: 143
Registered: 27-2-2006
Member Is Offline

Mood: No Mood

[*] posted on 11-1-2009 at 10:11


I have MEK/Water mix distilled from nail polish, what would be the best way to separate MEK from water ?
View user's profile View All Posts By User
solo
International Hazard
*****




Posts: 3869
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline

Mood: ....getting old and drowning in a sea of knowledge

[*] posted on 11-1-2009 at 13:58


.....try distilling it out since it goes at 80C .... or make an adduct and separate that way........solo



It's better to die on your feet, than live on your knees....Emiliano Zapata.
View user's profile View All Posts By User
solo
International Hazard
*****




Posts: 3869
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline

Mood: ....getting old and drowning in a sea of knowledge

[*] posted on 11-1-2009 at 14:08


I have recently tried reading the rotation of a sample using a polarimeter, I don't know the angle of rotation of (2S)-N-methyl-1-phenyl-propan-2-amine, because I don't know the concentration of the sample to use .....also I guess recemic (2S)-N-methyl-1-phenyl-propan-2-amine will have no rotation at all?...and so what is the l-isomer's rotation ?.... does anyone know where I might look to find this information .....solo



It's better to die on your feet, than live on your knees....Emiliano Zapata.
View user's profile View All Posts By User
DJF90
International Hazard
*****




Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline

Mood: No Mood

[*] posted on 11-1-2009 at 16:03


With angles of rotation, both isomers will rotate the same amount so long as the concentration is the same, but in opposite directions (one will be clockwise, the other is counterclockwise, but which isomer rotates in which direction is found experimentally. You are right in saying racemic mixtures have no rotation though. The wikipedia page below ought to help slightly: http://en.wikipedia.org/wiki/Specific_rotation . Where to find the specific rotation for this compound is beyond me, although I would hazard a guess and say the merck index, seeing as it has a vast quantity of data on different compounds. This page may also help: http://library.tedankara.k12.tr/carey/ch7-4.html

[Edited on 12-1-2009 by DJF90]
View user's profile View All Posts By User
solo
International Hazard
*****




Posts: 3869
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline

Mood: ....getting old and drowning in a sea of knowledge

[*] posted on 11-1-2009 at 16:47


.......`i just read my own question, `i can be so blind sometimes, hence if recemic is 0˚ rotation it would mean that the l,isomer has the same 18˚ that the d, isomer has but in the opposite direction ......what `i need to know what concentration of the material should be that i load into the vial that is used to read in the polarimeter........solo



It's better to die on your feet, than live on your knees....Emiliano Zapata.
View user's profile View All Posts By User
497
International Hazard
*****




Posts: 778
Registered: 6-10-2007
Member Is Offline

Mood: HSbF6

[*] posted on 11-1-2009 at 18:42


Will this work?

NaNO2 + Na2S2O7 -> N2O3 + Na2SO4

or..

4NaNO3 + 2Na2S2O7 -> 2N2O4 + O2 + 4Na2SO4

Specifically will it work by direct reaction of the reactants in the solid state?
View user's profile View All Posts By User
hector2000
Hazard to Others
***




Posts: 127
Registered: 22-8-2006
Member Is Offline

Mood: Cool

[*] posted on 11-1-2009 at 23:41


how much is solubility of sodium phenylacetate in acetone and ETOH?



Chemistry=Chem+ is+ Try
View user's profile View All Posts By User
Nicodem
Super Moderator
*******




Posts: 4230
Registered: 28-12-2004
Member Is Offline

Mood: No Mood

[*] posted on 12-1-2009 at 01:41


Quote:
Originally posted by solo
.......`i just read my own question, `i can be so blind sometimes, hence if recemic is 0˚ rotation it would mean that the l,isomer has the same 18˚ that the d, isomer has but in the opposite direction ......what `i need to know what concentration of the material should be that i load into the vial that is used to read in the polarimeter........solo

Literature values are always described as specific rotations, therefore it does not matter much what is the concentration of your sample, because you have to calculate the specific rotation anyway. Optical rotation is wavelength, solvent and temperature dependent, so you need to use these conditions as reported in the literature (in reality they are also concentration dependent due to molecular association, but this effect is usually minor).
http://en.wikipedia.org/wiki/Specific_rotation




…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)

Read the The ScienceMadness Guidelines!
View user's profile View All Posts By User
chemrox
International Hazard
*****




Posts: 2953
Registered: 18-1-2007
Location: UTM
Member Is Offline

Mood: LaGrangian

[*] posted on 12-1-2009 at 14:24
aniline HCl solubilities


I need an expanded list of solvents for aniline HCl..ie as many solvents as possible. Thanks, CRX



"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
View user's profile View All Posts By User
kclo4
International Hazard
*****




Posts: 915
Registered: 11-12-2004
Location:
Member Is Offline

Mood: No Mood

[*] posted on 12-1-2009 at 14:59


Quote:
Originally posted by 497
Will this work?

NaNO2 + Na2S2O7 -> N2O3 + Na2SO4

or..

4NaNO3 + 2Na2S2O7 -> 2N2O4 + O2 + 4Na2SO4

Specifically will it work by direct reaction of the reactants in the solid state?


If they were ground to a fine powder, and heated it would work. Of course, at standard pressures, they would form as the gases NO and NO2 which would then need to be condensed to form N2Ox.
View user's profile Visit user's homepage View All Posts By User
 Pages:  1  ..  14    16    18  ..  28

  Go To Top