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Nicodem
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Only few imines of the most electrophylic carbonyl compounds (formaldehyde, some benzaldehydes, etc.), or the ones that are additionally stabilized by
hydrogen bonds, or endocyclic imines, or certain groups at the amine part, are stable enough for isolations involving extractions from aq. phases.
Others hydrolyse very rapidly even in neutral pH, and about immediately in acidic aq. media.
PS1: I don't want to see any more drug cooks acronyms like P2P, MDP2P or similar! This is a forum for amateur science, so use chemical names.
PS2: The condensation Intergalactic_Captain was inquiring was the Knoevenagel condensation between substituted benzaldehydes and nitromethane. He is not asking about any Henry reaction, just about the
applicability of that method at Org. Synth. for substituted benzaldehydes.
…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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hector2000
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what is d-tartaric acid?
(L-(+)-tartaric acid) or(D-( − )-tartaric acid)?
[Edited on 16-2-2009 by hector2000]
Chemistry=Chem+ is+ Try
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Nicodem
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http://en.wikipedia.org/wiki/Tartaric_acid
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hector2000
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yes before i read it but i am confused
always d isomer is + and l isomer is - but tartaric acid has diffrent
d is - and l is +
d-tartaric acd is dextro tartaric acid or is d(-)tartarc acid?
Chemistry=Chem+ is+ Try
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sparkgap
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The Small-type Capitalized D and L and the small d and l are two different things. See this.
Another reason to be careful with capitalization!
sparky (~_~)
"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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hector2000
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yes you say true
my question is this:
d-tartaric acd is dextro tartaric acid or is D(-)tartarc acid?
i want to Resolution of Racemates
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Nicodem
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The prefix (+)- means dextrorotatory, (-)- is levorotatory. Read the wikipedia entry I linked above and the one Sparkgap provided to figure out which
configuration of tartaric acid corresponds to which optical activity. Nobody here can answer your question but yourself since you do not use the
prefixes correctly. For example, your name "d(-)tartarc acid" makes no sense whatsoever since "d-" is the prefix for dextrorotatory while
"(-)-" is the prefix for levorotatory (you can not have a "dextrolevorotatory" compound  ). Make up your mind or correct your capitalisation. It is quite probable you confused D- with d- and L- with l-, two
things that have nothing in common.
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Baphomet
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I think he just got the dash '-' mixed up with the negative sign '-'
Indeed on some keyboards these are even the same key 
\"Who ARE you? You\'re like the drummer from REO Speedwagon - nobody knows who you are\" from \'Employee of the Month\'
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hector2000
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@nicodem i know that and also i am confused about that
for example see these componet:
L(+)-tartaric acid merck number:100804
D(-)-tartaric acid merck number:800799
really which one is d-tartaric acid(dextrotartaric acid)
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sparkgap
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The "+" in L(+)-tartaric acid would imply that that is the dextrorotatory enantiomer.
sparky (~_~)
"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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497
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Extra short and easy question for you:
If you monomethylate (say with MeOH/H2SO4) an alkyl hydroquinone, will it methylate the OH ortho to the alkyl group or meta to the alkyl group? For
example, would it form 2-ethyl-4-methoxyphenol or 3-ethyl-4-methoxyphenol or, god forbid, a mixture of the two?
Thanks.
[Edited on 17-2-2009 by 497]
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chemrox
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alkyl are o,p directing so I would say the major product would be ortho but you'd get 3-5% of the meta as well
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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497
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But it's not actually methylating on the ring, so does that still apply?
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not_important
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You'll get a mix, more para than ortho if the alkyl group crowds the ortho HO- enough. You may find you get some C-methylation as well, primarily at
the C-O positions but possibly at the C-alkyl as well; for most substrates this happens to only a small degree if at all.
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Nicodem
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| Quote: | Originally posted by chemrox
alkyl are o,p directing so I would say the major product would be ortho but you'd get 3-5% of the meta as well |
497 is asking about O-methylation, I guess with dimethyl sulfate or methyl hydrogensulfate, because "MeOH/H2SO4" does not makes much sense,
unless he is talking about the benzoquinone catalysed monoalkylation of hydroquinones with alcohols which is however a different thing altogether...
In any case electrophilic aromatic substitution has nothing to do with this.
| Quote: | Originally posted by 497
But it's not actually methylating on the ring, so does that still apply? |
With a methylating reagent, a mixture of all mono- and dimethylation products would be obtained, with the ratio depending on the reaction conditions,
but never selectively only one product.
With the benzoquinone catalysed alkylation with MeOH you would obtain a mixture of both possible monomethylated products in a ratio approaching 1 : 1,
but not exactly such. Electronic effects should in my opinion somewhat favour the formation of 2-ethyl-4-methoxyphenol due to the higher basicity of
the carbonyl group distant from the alkyl in the benzoquinoid intermediate. But then again, this is hard to predict unless you use the DFT theory and
do some computational chemistry.
To not_important: Concurrent C-alkylation of the phenoxides generally occurs <5% extent in most phenols, with some
electrophiles more than others (allyl bromide is one such, but still ~5%), at least in my experience. Yet there are phenols that will give a much
larger proportion of C-alkylation, for example resorcinol and some others. This is a topic that interest me quite a lot. If you happen to
have a reference or a review paper discussing the topic, I would appreciate if you could share it.
[Edited on 18/2/2009 by Nicodem]
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497
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Thank you Nicodem, that was exactly what I wanted to know. Although not the answer I was hoping to hear  . I think I've found a way around that problem anyhow.
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Ebao-lu
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Did any one come accross a picture of JWH-018 binding to the CB receptor(of any kind), or any other 1-alkyl-3-aroylindole binding? I mean, which atoms
are relevant for binding, and the alkyl chain disposition while binding. If possible, gei me a link, or tell where can i find a picture(i want just in
brief for JWH018, not to study all the cannabinoid family)..
[Edited on 18-2-2009 by Ebao-lu]
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Nicodem
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If by "picture" you mean crystallographic data then the answer is negative since both CB receptors are transmembrane receptors and thus have not been
crystallized (with or without a ligand) yet (I think rhodopsin is the only transmembrane protein ever crystalized up to now and of which the
crystallographic data is available).
On the other hand, if by "picture" you mean a hypothetical model of interaction, then you better start looking for review papers on the topic as
surely some model was described (if not graphically, at least by describing the interactions of the pharmacophore).
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Ebao-lu
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Yes, of course i mean a model of interaction. My main interest is the position of alkyl "tail" there - is it directed to fill the space between N and
naphtoyl, or it is directed perpendicularry to the indole ring, or any other way...
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Intergalactic_Captain
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Nicodem - Thanks for pointing that out. I should have recognized the confusion earlier on, but I figured the members here with experience in the
matter would know what I was asking.
Another unrelated question - I need a small amount of n-pentanol, and it doesn't appear to be a particularly common ingredient in anything.
Hydrolysis of amyl acetate first came to mind, but the stuff's expensive and most likely iso-amyl acetate (the more commonly used banana/"juicy fruit"
flavoring). Right now I'm thinking this - Baeyer-villiger oxidation of cyclopentanone (from pvc solvents) to caprolactone, hydrolysis to 6-HO-caproic
acid, and then decarboxylation to the one-carbon shorter n-pentanol.
Anyone ever tried to decarboxylate an aliphatic substance? Would the hydroxyl group interfere in any way in a simple benzoic acid style carboxylation
(add a base and heat)? The reason I ask is related to biodiesel - It seems that if decarboxylation of fatty acids was particularly easy, the market
would be flooded with plant-derived gasolines rather than methyl-esters. Once again, maybe I'm not being clear in illustrating my confusion, but
that's the parallel that's got me wondering.
...and, completely unrelated once again, anyone have any experience with organocadmium reagents? I found a couple papers on their ketone-forming and
other reactions and have been completely fascinated for a few days now.
If you see me running, try to keep up.
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superman1451
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Question,
when decomposing ammonium dichromate why does it seem like there is way more product than reactant after the reaction has finished?
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DJF90
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The chromium (III) oxide is produced is very voluminous compared to the ammonium dichromate.
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not_important
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| Quote: | Originally posted by Intergalactic_Captain
Anyone ever tried to decarboxylate an aliphatic substance? |
Most don't decarboxylate very well, it takes electron withdrawing groups nearby, preferably alpha. Thus malonic acid, acetoacetic acid, Cl3CCO2H, and
so on, all lose CO2 fairly readily.
| Quote: | | Would the hydroxyl group interfere in any way in a simple benzoic acid style carboxylation (add a base and heat)? |
I suggest reading the history of polymer chemistry, in particular the work of Wallace Carothers, and you may wish to reflect on the term
polyester.
| Quote: | | The reason I ask is related to biodiesel - It seems that if decarboxylation of fatty acids was particularly easy, the market would be flooded with
plant-derived gasolines rather than methyl-esters. |
You got that right, babe. There have been a number of schemes for thermal decomposition of waste biological materials, many of which were to produce
significant quantities of alkanes. To date none have been particularly successful, see Wiki on "thermal depolymerization".
| Quote: | | ...and, completely unrelated once again, anyone have any experience with organocadmium reagents? I found a couple papers on their ketone-forming and
other reactions and have been completely fascinated for a few days now. |
Yes. Sensitive to moisture, oxygen, light, sometimes to the phase of the Moon, and occasionally to the existence of space-time. Toxic, if ignited
have the delightful property of forming finely divided CdO smoke which is known to be a human carcinogen and has other interesting effects on health.
To some extent replaced by organocopper compounds, but still interesting chemistry. To get some useful details on the use of organocadmium compounds,
you may wish to read this http://pubs.acs.org/doi/abs/10.1021/cr60315a001
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497
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| Quote: | Originally posted by Ullmann
And about the sodium methoxide : it can easily be done from a methanolic NaOH solution (3 molar) by addition of one equivalent of 3A molecular sieves,
which can be obtained OTC for conservation of artcraft... also Na2CO3 in MeOH can be use to form it... |
Is this true? I'm skeptical because I've never seen it mentioned anywhere else, always that you have to have Na metal to make NaOMe...
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manimal
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| Quote: | Originally posted by Formula409
Actually, I was planning on exploring whether thiourea dioxide (http://www.sciencemadness.org/talk/viewthread.php?tid=11785) is suitable for performing the reduction, naturally I will need some sort of way of
quantitatively measuring yield, so the reduction procedures detailed on Rhodium are unsuitable for research.
Formula409.
[Edited on 16-2-2009 by Formula409] |
Rhodium has a procedure for the reduction of imines with sodium dithionite. It calls for forming the imine first in DMF by combining the ketone and
amine, then adding the dithionite, Na2CO3 and water.
An adaptation using thiourea dioxide should adhere to the same general outline of forming the imine in the usual way and then adding to it the
reducer, a base and water. Note the funky cosolvent used, which I think should be replaced with isopropanol or ethanol.
See here:
| Quote: | To a solution of the imine (30 mmol), either preformed or prepared in situ from the amine (30 mmol) and the carbonyl compound (30 mmol), in
dimethy1formamide (70 ml) at 110ｰC under nitrogen was added solid sodium hydrogen carbonate (120 mmol). The mixture was stirred vigorously;
solid sodium dithionite (60 mmol) was added, followed immediately by water (30 ml). Gas evolution took place some minutes after the addition of the
water. Stirring was continued at 110ｰC for 30 min; the reaction-mixture was allowed to cool to room temperature and then poured into water (300
ml). The aqueous solution was extracted with ether (4x75 ml) which was in turn washed with water (4x50 ml) and saturated brine (50 ml). The ethereal
extract was dried and evaporated to give the amine. The product was purified by distillation or through the hydrochloride.
The amine hydrochlorides were prepared by adding a slight excess of 5 M hydrochloric acid to the neat amine. The mixture was stirred and the solid
product was collected by filtration. |
http://www.erowid.org/archive/rhodium/chemistry/redamin.dith...
[Edited on 21-2-2009 by manimal]
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