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ketel-one
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Short question, I know it's very beginnerish
When you cleave an ether R1-O-R2 with boiling HI, you get R1-OH and R2-I, right? If you got R1-OH and R2-OH it probably would just be called
hydrolysis. And can you use HI3 instead of HI?
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kclo4
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I assume HI3 is a mix of HI and I2, and is used to increase the solubility of I2 in solution?
I don't think it would be wise to use..
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ketel-one
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Alright I suppose I'd bubble some hydrogen through it to make more HI, I don't exactly have any H2S
And forget about the first question I've figured out already you do get R1-OH + R2-I
http://www.brainmass.com/homework-help/chemistry/organic-che...
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not_important
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That will give you hydrogen gas containing a bit of elemental iodine, the reaction is very slow without a catalyst.
You can use iodine, water, and H2S, which give aqueous HI and elemental sulfur; iodine, water, and SO2, which gives you aqueous HI and H2SO4; or I2,
H2O, and red phosphorous, the favorite of meth makers.
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kclo4
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Sulfur is easy to get, and you can make H2S easily from it by heating it with wax.
SO2 can obviously be made by burning the sulfur.
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ketel-one
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Oh right I just remembered a good way to get sulfur... Lots of matches in HCl, i believe last time I tried it it also made Cl2O or something... I
forget it was a couple years ago.
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dann2
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Hello,
How do you do that. Simply heat Sulphur and candle wax together?
Dann2
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woelen
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Yes, simply heat a mix of sulphur and paraffin. Use excess paraffin. If you buy white candles, then try to find the paraffin ones. There also are
stearin-based candles and these may react in a different way. Paraffin can also be purchased from eBay as a pure chemical, it just is an alkane with
many C-atoms in a chain (IIRC numbers of C atoms is more than 20).
When the mix of sulphur and paraffin is heated, then the paraffin melts, the sulphur also melts, but somewhat later. On stronger heating the mix
starts fuming and bubbling. The fume is due to evaporation and recondensation of paraffin, the bubbles you obtain consist of H2S gas. Purification can
be achieved by bubbling through paraffin oil (which also is a mix of alkanes, but with somewhat lower number of C-atoms). The paraffin fumes dissolve
in the paraffin oil, the H2S bubbles through the oil. Try to pass large bubbles of gas through a tall column, otherwise you will suffer from excessive
foaming.
Be warned though, that this procedure is very messy. Your reaction vessel is covered by a gummy very hard to remove material which has a terrible
smell. I once did the experiment in a large and wide test tube. I decided to discard that tube, it simply appeared impossible to make it clean again.
Also keep in mind that H2S is very toxic, one of the members of this forum almost passed out after inhaling too much H2S. The sense of smell is
deadened by high concentrations of H2S, this introduces an additional safety risk.
[Edited on 9-9-09 by woelen]
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Klute
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I really advise against using H2S, even in a sealed apparatus. The event of a leak is just too dangerous. I was thinking I could handle it with a good
scrubber, but didn't realize that even after gas generation has finished the sludge still contains enough H2S to kill someone. I had a very bad and
frightening experience with it. Certainly not something for newbees or even intermediates..
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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ketel-one
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Right I guess that's my que.
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entropy51
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And here you are crapping all over another thread.
They're just BS'ing you man. H2S isn't poisonous. Make all you want.
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JohnWW
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Oh yeah? Besides being smelly, the stuff is DEADLY poisonous, being comparable to HCN or (CN)2, HOCN, CO, CH2N2, PH3, and HN3, as gases or vapors, and
their salts, which have a similar mode of action entailing preferential bonding to the Fe atom in hemoglobin in place of O2. There are some people
here who apparently do not want to see you back, so you could oblige them by making and breathing in a large enough amount of the stuff.
P.S. If your statement was intended as a joke, there are, unfortunately, those naïve enough to take it literally.
[Edited on 9-9-09 by JohnWW]
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entropy51
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Thank you, John for ruining my joke.
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watson.fawkes
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Quote: Originally posted by Klute  | | I really advise against using H2S, even in a sealed apparatus. The event of a leak is just too dangerous. |
I'll second this, not from experience, because I don't intend to have any with this. Don't make H2S in a sealed apparatus made out
of iron pipe, even. H2S causes sulfide embrittlement in iron and steel, causing cracking from the inside that leads to a sudden rupture visible from
the outside. Industrially, when significant quantities of H2S are present, various high-nickel alloys are specified, such as the Hastelloy series, and
those are pricey. This is even something to worry about with ordinary sulfur, as moisture + sulfur + heat makes non-trivial amounts of H2S.
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Formula409
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Can brominated bicyclic molecules be used as alkylating agents? For example, 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptane (i.e. borneol [alcohol of
camphor] brominated at the OH):
Many thanks!
Formula409.
[Edited on 10-9-2009 by Formula409]
[Edited on 10-9-2009 by Formula409]
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Formatik
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What liquid substance will dissolve the most substances at room temperature? Water? DMSO?
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Paddywhacker
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| Quote: Originally posted by Formula409 | Can brominated bicyclic molecules be used as alkylating agents? For example, 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptane (i.e. borneol [alcohol of
camphor] brominated at the OH):
Many thanks!
Formula409.
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In what way ... Friedel-Crafts? I doubt it.
But it should react with a Grignard, and should form a Grignard, and alkylate that way.
This compound can be made, I think, from alpha pinene and dry HBr. Any reason why it wouldn't react as I suggest?
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DJF90
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I suspect making the grignard reagent will work oks. Also the alkyllithium, possibly by lithium-bromine exchange with MeLi or the likes. You havent
staed as to whether the bromine substituent is endo or exo, and suspect that only the endo-isomer (I hope I've got this right) will react in any form
of Sn2 (albeint probably poorly) with nucleophilic reagents as there is too much steric hindrance for the approach of the nucleophile in the exo
isomer (and this may be the case with the endo isomer too...)
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JohnWW
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Yes, a secondary bromide like that one could be made into a Grignard reagent, for introduction of a 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptanyl
group into another alkyl or aryl halide, substituting for the halogen. In addition, that secondary bromide would show some dissociation into a
carbocation in a polar aprotic solvent, enabling it to be used for electrophilic addition reactions, e.g. to amines to make substituted amine salts,
or to alcohols or ketones or aldehydes to make ethers, or possibly under some conditions to ethers to make oxonium salts.
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Nicodem
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I don't know exactly which compound Formula409 is asking about (the structure is ambiguous) since the bromination of borneol can give two compounds,
bornyl bromide or isobornyl bromide, or a mixture of two, depending on the method used. The examples in the literature use some pretty hard to obtain
reagents. Therefore, I have no idea how Formula409 intents to obtain (iso)bornyl bromide except maybe from HBr addition on pinene like Paddywhacker
suggested (described in Journal of Organic Chemistry, 51, 4947-4953).
In any case an SN2 substitution is nearly impossible on the two bornyl bromides, because it is a stericaly hindered, bridged, cyclic and secondary
bromide (each of these factors is deactivating for SN2 mechanism). It might be possible with S-nucleophiles or other extremely strong and not too
basic nucleophiles. Under basic conditions only an E2 mechanism can result. An SN1 would most likely give a rearrangement product(s) and in any case
is only possible in an acidic media so the choice of nucleophiles (which Formula409 failed to specify) is very limited. There are examples of some SET
based nucleophilic substitutions on such systems described in the literature (for example the mechanistical study in Tetrahedron Letters, 30,
493-496), but I doubt this is relevant.
JohnWW, aliphatic secondary alkyl bromides do not dissociate to carbocations just like that, certainly not in absence of any acid! There is no way you
can get an SN1 substitution with amines on normal secondary alkyl halides and I wish you could provide a reference if you know about any such example.
Only tertiary alkyl halides and some alkyls stabilized by resonance can participate in SN1 reactions in neutral or basic media. You would need the
presence of a very strong acid, AlBr3 for example, to get something resembling a carbocation, but only transiently resembling. And obviously this is
not possible in the presence of such nucleophiles like the amines because they are too basic. I could find no examples for your suggestion of using
(iso)bornyl bromide derived Grignards in a Kumada coupling, but there are some examples of Kumada, Suzuki and Stille couplings using Grignard reagents
on norbornyl bromides (that is similar, but in the reversed role of reaction partners, from what you proposed).
…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!
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JohnWW
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| Quote: Originally posted by Nicodem | | (cut)JohnWW, aliphatic secondary alkyl bromides do not dissociate to carbocations just like that, certainly not in absence of any acid! There is no
way you can get an SN1 substitution with amines on normal secondary alkyl halides and I wish you could provide a reference if you know about any such
example. Only tertiary alkyl halides and some alkyls stabilized by resonance can participate in SN1 reactions in neutral or basic media. You would
need the presence of a very strong acid, AlBr3 for example, to get something resembling a carbocation, but only transiently resembling. And obviously
this is not possible in the presence of such nucleophiles like the amines because they are too basic. I could find no examples for your suggestion of
using (iso)bornyl bromide derived Grignards in a Kumada coupling, but there are some examples of Kumada, Suzuki and Stille couplings using Grignard
reagents on norbornyl bromides (that is similar, but in the reversed role of reaction partners, from what you proposed). |
I am sorry to disappoint you, Nicodem, but I must believe the evidence before my eyes, in the form of the authoritative organic textbooks, such as
Solomons, McMurry, Morrison & Boyd, Bruice, etc., that I have before me. Aliphatic secondary halides, especially bromides of a fairly large
structure like that one in question which provide some steric support for dissociation, DO undergo slight dissociation to form carbocations in aprotic
polar solvents in equilibrium with the undissociated form, although of course the degree of dissociation is much less than that of tertiary halides
(especially tertiary halides in which the resulting positive charge is delocalized by resonance as in triphenylmethyl(+)). And, moreover, the same
textbooks indicate that the degree of dissociation, though small, IS quite sufficient, by shifting the equilibrium, for the resulting carbocations to
quantitatively bond by electrophilic addition to the N atoms of amines to form substituted amine halide salts. I simply cannot understand why you
should think otherwise. The same would apply to electrophilic addition to oxo-compounds to result in oxonium salts, and similarly sulfonium salts. The
equilibria in favor of carbocation formation, and hence reaction rates, can be improved by catalytic use of Lewis acids such as AlBr3 or FeBr3.
BTW the C atom to which the Br atom is bonded in 2-bromo-1,7,7-trimethylbicyclo[2.2.1]heptane is, as in borneol, asymmetric (chiral) and optically
active; and it is not clear from the illustration provided which enantiomer is the one in question. The one in which the dimethylated bridge is closer
to the Br atom would undergo the greater degree of dissociation, and thereby react faster.
[Edited on 11-9-09 by JohnWW]
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Nicodem
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| Quote: Originally posted by JohnWW |
And, moreover, the same textbooks indicate that the degree of dissociation, though small, IS quite sufficient, by shifting the equilibrium, for the
resulting carbocations to quantitatively bond by electrophilic addition to the N atoms of amines to form substituted amine halide salts. I simply
cannot understand why you should think otherwise. The same would apply to electrophilic addition to oxo-compounds to result in oxonium salts, and
similarly sulfonium salts. The equilibria in favor of carbocation formation, and hence reaction rates, can be improved by catalytic use of Lewis acids
such as AlBr3 or FeBr3. |
I'm not saying that SN1 based reactions on bornyl bromide is not possible. Like I already said, they could (and actually should) be possible but only
under acidic conditions. It is true that the bornyl carbocation is somewhat more stabilized than a normal secondary carbocation (due to
hyperconjugation over the ring structure), but still not as much as tert-carbocations are. I searched CA and Beilstein and could find no reactions of
bornyl halides&alcohols&esters with amines. The only SN1 based reactions with N-nucleophiles found, were several examples of the Ritter
reaction on bornyl alcohols (which are often acompanied by rearrangement to camphene system) and the reactions of bornyl alchols&chlorides with a
mixture of aniline&aniline salts. Both are reactions in acidic media. The reaction or bornyl alcohols and bornyl chlorides with anilines is low
yielding and also gives a large amount of camphene and tricyclene as side product, thus indisputibly indicating an SN1 mechanism (ref: Journal
fuer Praktische Chemie, 322, 423-428; Chemische Berichte, 43, 3204; DE205850). However, I could find absolutely no examples of SN1 based
reactions in basic media. So I still say that the reaction of bornyl bromides with amines can not give bornyl amines because the SN2 mechanism is
practicaly unavailable due to deactivating factors, while the SN1 mechanism requires acidic media in which aliphatic amines are not nucleophilic any
more (and is thus limited to anilines and perhaps some other amines of low basicity, the salts of which are acidic enough to catalyse the reaction).
The topic of SN1 based reactions in neutral and basic media trully interests me and my request for an example of a reaction of the type you describe
is still valid. I searched for almost an hour and could find none.
…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!
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Sedit
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Can anyone suggest a method of deploymerizing PVC or CPVC to yeild Vinylchloride or much better yet 1-2-Dichloroethane since that will be the target
compound anyway. I have been reading up but as of yet all I have found it methods that require supercritical water and/or strange conditions of high
heats and pressure.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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JohnWW
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Depolymerization - in general, this is difficult, if not impossible, given that most polymerization reactions are exothermic and
probably also involve an increase in entropy. However, those that involve acid or alkaline hydrolysis of polyesters (including polycarbonates) or
polyamides (including nylons and proteins), in which strongly polar groups provide the linkages, are quite feasible. But such methods would generally
not apply to other types of polymers formed in different types of reactions such as condensations of unsaturated monomers or free-radical reactions,
e.g. polyethylene, or related polymers of other monomers derived from ethylene or acetylene, such as those of propylene, vinyl chloride or fluoride or
acetate, or tetrafluoroethylene.
The methods described for the latter types of polymers in http://en.wikipedia.org/wiki/Thermal_depolymerization generally involve hydrous anaerobic pyrolysis; and the products are not the original
monomers but instead simply substances of lower molecular weight - oligomers, like light crude oil.
[Edited on 12-9-09 by JohnWW]
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entropy51
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Polystyrene and Polymethylmethacrylate can be decomposed by pyrolysis and the monomer distilled out.
Better to remain silent and appear a fool than to open your mouth and remove all doubt.
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