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

Printable Version  
 Pages:  1  ..  96    98
Author: Subject: The Short Questions Thread (4)
Sulaiman
International Hazard
*****




Posts: 3231
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 21-6-2022 at 22:03


Quote: Originally posted by mayko  
I tried to grow some rochelle's salt crystals.

The salt is deliquescent so I GUESS that some sort of dessicator is required.

Edit : just checked.. <30% RH to dessicate.

Also, decomposes above 55C

[Edited on 22-6-2022 by Sulaiman]




CAUTION : Hobby Chemist, not Professional or even Amateur
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 6-7-2022 at 08:16


Quote: Originally posted by AvBaeyer  
Dry, very dry.

AvB


thank you , but tell me this in many of the articles read and videos viewed , the topic of the reaction being anhydrous only shows up when using NaH as a base but otherewise nothing in the use of the bases methoxide or ethoxide....why is that? Is it something one should know from the start .....I had my sample of 4-amina acetophenone analysed , and it turns out to be benzocaine and benzoic acid.....is it that the amine reacted with the enol or the base....quite confused ....I'm currently on test #13 and the same results even though i introduce the ethyl ethoxide last slowly with an excess of benzocaine ....but the results are the same once i add the HCl to keep the reaction to the right.....then heated to decarboxylate.......any hints , and yes i've run the reaction with anhydrous reagents, but the results seems to be the same.......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
mayko
International Hazard
*****




Posts: 1137
Registered: 17-1-2013
Location: Carrboro, NC
Member Is Offline

Mood: anomalous (Euclid class)

[*] posted on 6-7-2022 at 20:30


Quote: Originally posted by Sulaiman  
Quote: Originally posted by mayko  
I tried to grow some rochelle's salt crystals.

The salt is deliquescent so I GUESS that some sort of dessicator is required.

Edit : just checked.. <30% RH to dessicate.

Also, decomposes above 55C

[Edited on 22-6-2022 by Sulaiman]


Where are you getting this? I've never heard of any special drying apparatus being necessary. Wikipedia gives a melting point of 75C, a dehydration point of 130C, and a decomposition point of 220C so I don't feel too bad about heating the aqueous solutions.

I poked and prodded the syrup, dripped ethanol and acetone on the surface, smeared a thin layer on the side of the beaker, left a toothpick in... nothing. I would have thrown it out except I got lazy cleaning and then after many weeks of sitting I thought I saw mold in it... no, the syrup was crystallizing in a couple points! Within a day or so it was solid throughout. I saved a bit, redissolved the crystallized mass, and then used the residue as a seed. I now have a jumble of fat needles, not really the blocks I expect but I'm going to use them to reseed another round and see how that goes.




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
clearly_not_atara
International Hazard
*****




Posts: 2333
Registered: 3-11-2013
Member Is Offline

Mood: Big

[*] posted on 7-7-2022 at 07:46


It's on Wikipedia.

Quote:
Rochelle salt crystals will begin to dehydrate when the relative humidity drops to about 30 per cent and will begin to dissolve at relative humidities above 84 per cent.




[Edited on 04-20-1969 by clearly_not_atara]
View user's profile View All Posts By User
mayko
International Hazard
*****




Posts: 1137
Registered: 17-1-2013
Location: Carrboro, NC
Member Is Offline

Mood: anomalous (Euclid class)

[*] posted on 7-7-2022 at 11:04


"dehydrate" in that passage refers to the loss of water of crystallization, not crystallization from solution.



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
karlos┬│
International Hazard
*****




Posts: 1517
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: oxazolidinic 8)

[*] posted on 8-7-2022 at 19:09


The benzylic bromination of 2-methylnaphthalene, using NBS, is ideally done in presence of a radical initiator, benzoyl peroxide is usually used for that purpose.
With such a radical initiator, I could use a number of solvents, as the benzylic bromination will in that case be the main- and not side reaction.

Tried it once without, solventless, 20h in a melt, and the yield was(side reaction aromatic bromination) just a third of the theoretical yield.

So, here is the question: can I use the 2,4-dichlorobenzoylperoxide(50% under some silicon oil, because explosive :o) as alternative radical initiator?
I expect the answer to be "of course", but I figured it won't hurt to ask.




verr├╝ckt und wissenschaftlich
View user's profile View All Posts By User
Tsjerk
International Hazard
*****




Posts: 2784
Registered: 20-4-2005
Location: Netherlands
Member Is Offline

Mood: Mood

[*] posted on 9-7-2022 at 09:56


I'm making 5-formyl vanillyl and after reacting vanillyl and hexamine, and adding HCl I dumped the reaction on ice. The reaction contains 55 grams water, 55 grams acetic acid, 50 ml 30% HCl, and about 50 grams organics. I dumped this hot mixture on 400 grams of ice of approximately 0 degrees.

Now what I didn't expect was this mixture to go below 0 degrees, but it went all the way down to -7 degrees. Why is that? What endothermic process is going on here?
View user's profile View All Posts By User
DraconicAcid
International Hazard
*****




Posts: 3949
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline

Mood: Semi-victorious.

[*] posted on 9-7-2022 at 10:20


Quote: Originally posted by Tsjerk  
I'm making 5-formyl vanillyl and after reacting vanillyl and hexamine, and adding HCl I dumped the reaction on ice. The reaction contains 55 grams water, 55 grams acetic acid, 50 ml 30% HCl, and about 50 grams organics. I dumped this hot mixture on 400 grams of ice of approximately 0 degrees.

Now what I didn't expect was this mixture to go below 0 degrees, but it went all the way down to -7 degrees. Why is that? What endothermic process is going on here?

Ice melting is endothermic. Because you've got a lot of acid, that lowers the melting point just like salt would.




Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
View user's profile View All Posts By User
mayko
International Hazard
*****




Posts: 1137
Registered: 17-1-2013
Location: Carrboro, NC
Member Is Offline

Mood: anomalous (Euclid class)

[*] posted on 28-7-2022 at 20:06


when nitrosyl chloride reacts with limonene, why does it add only to the cyclohexene double bond, and not to the 2-propene side chain?



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
Fery
International Hazard
*****




Posts: 715
Registered: 27-8-2019
Location: Czechoslovakia
Member Is Offline


[*] posted on 28-7-2022 at 22:55


Quote: Originally posted by Tsjerk  
... adding HCl I dumped the reaction on ice... what I didn't expect was this mixture to go below 0 degrees, but it went all the way down to -7 degrees. Why is that? What endothermic process is going on here?
IIRC the mixture of ice and concentrated HCl solution produces quite low temperatures, you diluted HCl in other reagents but anyway you still observed the endothermic process



If there is a heaven, it seems not to be materially based. Does chemistry exist there and if yes, how does it look like? Are there good souls well supplied with laboratory equipment, glass, chemicals and information?
View user's profile Visit user's homepage View All Posts By User
Fery
International Hazard
*****




Posts: 715
Registered: 27-8-2019
Location: Czechoslovakia
Member Is Offline


[*] posted on 28-7-2022 at 23:01


Quote: Originally posted by mayko  
when nitrosyl chloride reacts with limonene, why does it add only to the cyclohexene double bond, and not to the 2-propene side chain?
Mayko that's true, but I do not know why. I'm not too much skilled in theory, I like practical chemistry more. Anyway it is nice experiment https://www.sciencemadness.org/whisper/viewthread.php?tid=15...



If there is a heaven, it seems not to be materially based. Does chemistry exist there and if yes, how does it look like? Are there good souls well supplied with laboratory equipment, glass, chemicals and information?
View user's profile Visit user's homepage View All Posts By User
mayko
International Hazard
*****




Posts: 1137
Registered: 17-1-2013
Location: Carrboro, NC
Member Is Offline

Mood: anomalous (Euclid class)

[*] posted on 29-7-2022 at 05:46


Yep, I've been wanting to try the limonene to carvone conversion for a while, finally getting set up and want to understand more about the mechanisms



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
 Pages:  1  ..  96    98

  Go To Top